Compare commits

..
Author SHA1 Message Date
Claude 675f914725 Add review-like-gregmarr Claude skill
Distilled from gregmarr's inline review and conversation comments on
nlohmann/json: checklist of recurring review topics and his review voice.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N5NasBGrV1SGwx7n1eo75g
2026-10-30 23:26:28 +00:00
7 changed files with 884 additions and 2060 deletions

No files matched your search

@@ -0,0 +1,194 @@
---
name: review-like-gregmarr
description: Review a diff, branch, or PR of nlohmann/json the way long-time contributor gregmarr does — a line-by-line read focused on C++11 correctness, reference invalidation, backward/source compatibility, ODR/ABI, duplicated logic, hidden costs, repo conventions (amalgamation, astyle, macros) and precise docs, phrased as short courteous questions. Use when asked to "review like Greg", "gregmarr review", or for a careful maintainer-style review of changes to this library.
---
# Review like gregmarr
Distilled from ~1,400 inline review comments and ~1,300 issue/PR comments by
@gregmarr on nlohmann/json. He is a careful, courteous, line-by-line reviewer
who ("just a contributor") defers final decisions to @nlohmann.
## Workflow
1. Determine the target: a PR number (`gh pr diff <n>`), a branch
(`git diff $(git merge-base HEAD develop)...HEAD`), or the working tree
(`git diff`). Read the full diff, and open surrounding code in `include/nlohmann/`
whenever a hunk's context is not enough to judge it.
2. Walk the diff **file by file, hunk by hunk**, applying the checklist below.
Comment on specific lines; don't write a big essay.
3. Write the review in his voice (see "Voice"). Group nothing artificially —
emit one comment per location, in file/line order, with `path:line`.
4. If the same issue repeats, comment fully once, then "As above" /
"Same here (and N other places in this file)."
5. End with a 1–3 line summary only if useful (e.g. "Just this remaining and
then LGTM." or "@nlohmann thoughts on the naming?"). Don't post to GitHub
unless the user asks.
## Checklist (roughly in order of how often he raises them)
### Duplication and simplification (most frequent)
- Copy-pasted bodies, duplicated `#if/#elif` blocks, or "a copy of this function
that can get out of sync" → propose a shared helper or alias, with a code sketch.
- **Diverging limits/constants**: a new depth/recursion limit or magic number
where one already exists → "Should this reuse the existing recursion limit?
Different limits per operation invites them to diverge over time."
- Unneeded variables, parameters that can be deduced, values passed to a
function that the constructor already has, output parameter == return value.
- Verbose type spellings → `using` alias / alias template; `decltype()` where the
type is known.
- Disabling a lint warning instead of fixing the code ("why not just add the parens?").
### Lifetime, invalidation, UB
- A reference/pointer/iterator into a container (`stack.back()`,
`container_stack.back()`, `ordered_map` elements) held across `push_back`,
`pop_back`, `emplace`, or reallocation → "This invalidates `top`." Prefer a
`const` copy, or at least a comment warning future editors.
- Dangling refs from rvalue arguments stored in adapters; views outliving documents.
- Wrong logic operators (`&&` vs `||`), lost `!`, unreachable code, `continue`
that should be `break`, missing `return`, off-by-one in counters
(`chars_read` incremented twice).
- Uninitialized members → default member initializers; parameters that
"should not have a default so it's never left off by accident".
- Exception safety: leaks when `to_json` is called on a non-null value, partial
state, destructors that allocate, swallowed exceptions (`noexcept` that hides
throws — "The library shouldn't try to swallow the exception").
- Thread-unsafe calls (`setlocale`), specializations that redefine `std::` things
(ODR / UB).
- Narrowing/truncation: `static_cast<std::make_unsigned<...>>`, signed/unsigned
`char` cases, `n == 0` edge cases, buffer overruns guarded only by `JSON_ASSERT`.
### C++11 floor and portability
- The library requires only **C++11**: flag `if constexpr`, C++14 generic
lambdas/variable templates, `std::clamp`, C++17 library features, etc. unless
gated.
- Gate on the library's macros (`JSON_HAS_CPP_17`, `JSON_HAS_CPP_20`,
`JSON_HAS_THREE_WAY_COMPARISON`, `JSON_HAS_FILESYSTEM`) or feature-test macros
with `defined()` checks and exact values
(`#if defined(__cpp_lib_char8_t) && __cpp_lib_char8_t >= 201811`), not raw
`__cplusplus`. Don't silently disable a feature for an existing config.
- User-overridable macros: if externally defined, leave as-is — never clobber to
`1` (breaks `#define X 0`). `#if X` vs `#ifdef X` must match the convention.
- New macros start with `JSON_` / `NLOHMANN_JSON_` consistently with neighbors.
- `throw` must be `JSON_THROW` (and `try/catch` → `JSON_TRY/JSON_CATCH`) so
`JSON_NOEXCEPTION` builds work.
- `(std::min)(a, b)` / `(std::max)` for Windows macros; MSVC warnings (C4100
etc.); `string_t` not being `std::string`/`char`.
- Code relying on operations not required of user-supplied `array_t`/`object_t`
(range ctor, `emplace_hint`, allocator) → ask whether that's allowed.
- Does it work with `JSON_USE_IMPLICIT_CONVERSIONS=0`? With `JSON_DIAGNOSTICS`?
### Compatibility, ABI, API design
- Behavior changes to existing APIs/macros (e.g. `NLOHMANN_DEFINE_TYPE_*`,
released in 3.11.0) are breaking → needs opt-in macro or wait for 4.0; must be
prominently documented in release notes. Cite when the behavior shipped.
- Header-only: source compatibility matters, binary doesn't — adding a
**defaulted** parameter is fine; new overloads add ambiguity risk.
- Anything that changes layout or semantics per-config → should it be part of the
ABI tag (`json_abi_diag...`)? Mismatched config macros across TUs = ODR violation.
- Brand-new API shouldn't be added as deprecated — use `= delete` or omit.
- Naming consistency with existing options (`ignore_trailing_commas` vs
`ignore_comments`; singular "diagnostic"); names that read like functions;
single-letter or inconsistently `m_`-prefixed members.
- Prefer a type-safe template over passing a `value_t` that could be invalid.
- "Why would this belong in this library?" for very niche features.
### Hidden costs
- Extra copies (lost `std::move`, removed C++17 path), temporaries
(`push_back(std::string(...))` vs two `push_back`s), repeated `.back()` calls,
casting more than once, `reserve()` inside loops, quadratic recomputation for
deep nesting, dynamic allocation replacing stack allocation.
- `push_back` → `emplace_back`; `rbegin()`, `.data()`, `std::array`, `pop_back()`
to keep counters in sync.
- Struct member order/padding (put `bool` after `int`; "store value before type"),
`sizeof(basic_json)` growth, per-node pointer cost. "Don't pay for what you
don't use."
- Compile-time impact of new includes/templates.
- Ask for measurement instead of asserting a win.
### Style and repo conventions
- Formatting must match `make pretty` (astyle): spaced `template <`, `!` in traits
→ suggest `detail::negation<>`; 4-space indents; brace style; blank lines.
- Redundant keywords: `inline` inside class bodies or on templates (full
specializations do need it), `noexcept` on destructors, `public` in `struct`,
`{}` after defaulted init, C-style casts → `static_cast`.
- Sorted includes (cpplint: system before others), sorted lists in docs/CMake.
- **Amalgamation**: changes must be in `include/nlohmann/...` and
`single_include/` regenerated via `make amalgamate` — flag edits made only in
`single_include`, or amalgamated output that doesn't match / contains unrelated
changes.
- Merge debris, stray files at repo root, accidental changes to vendored files
(doctest.h), Makefile tweaks from local testing, missing trailing newline,
whitespace churn mixed with real changes ("separate commit or PR?").
- Comments: explain non-obvious code ("Comment about why this iterates
backwards?"); no change-log wording like "still" in live code; comment
blocks must stay attached to their function.
### Docs (`docs/mkdocs/docs/...`, README)
- Typos as `s/varry/vary/` or "typo: interal".
- Accuracy vs. actual behavior; state preconditions ("array is not empty"),
costs (one pointer per value with `JSON_DIAGNOSTICS`), defaults, which overloads
a sentence applies to, version numbers ("3.13.0").
- Consistency with sibling pages; unexplained claims ("Why is that a problem?
It's not obvious here."); markdown table column alignment.
- New macros/features need a docs page and an example.
### Tests
- Not his main focus, but: new macro/feature needs tests in `tests/src/unit-*.cpp`
that always build with the option (coverage build); test both with and
without the option; tests should use different values than the
initial ones; put tests in the existing file instead of duplicating a SAX class;
static_asserts where possible.
### Usually NOT commented on
Commit messages/PR titles, licensing, local variable naming bikeshedding,
demanding benchmarks, rejecting the overall feature idea. CI YAML gets
comments only for merge debris.
## Voice
- **Mostly questions**: "Is there a reason…?", "Should this…?", "Would it make
sense to…?", "Why not…?", "Any reason not to…?", "Is this needed?",
"Intentional?"
- **Flat statements only for clear bugs**, with the reason: "This `if` will
never be true. You want `||` not `&&`." "Remove the noexcept. The library
shouldn't try to swallow the exception."
- **Terse when trivial**: "`emplace_back`", "typo: alse", "astyle, negation",
"as above", "Lost a blank line here."
- **Concrete sketches** in plain fenced code blocks introduced with "Maybe like
this?" / "Something like this:" / "Untested:". Rarely ```suggestion blocks.
- **Hedge taste**: "minor nit:", "Personally I prefer…", "I'm on the fence…",
"not something for which I would hold up the PR", "(If this was just moved,
ignore this.)", "not the fault of this PR".
- Cite evidence: cppreference, godbolt, the standard, related issues/PRs by
number, existing code ("see `NLOHMANN_JSON_ABI_TAG_DIAGNOSTICS`").
- Light humor allowed sparingly (":)", "astyle strikes again", "Ugh").
- Praise is rare and short ("Good change.", "Looks reasonable.").
- Defer design calls: "@nlohmann has the final say here."
- Never invent facts about the code: if unsure, phrase it as a question rather than a claim.
## Example output
```
include/nlohmann/detail/input/parser.hpp:212
This invalidates `top`. Make it a `const` copy so it can't be read after the
`push_back` by a future change?
include/nlohmann/detail/input/parser.hpp:240
Should this reuse the existing recursion limit rather than adding a new one?
Different limits per operation invites them to diverge over time.
include/nlohmann/detail/macro_scope.hpp:88
If this has been externally defined, we should leave it as-is. This will break
if someone has `#define JSON_HAS_FOO 0`.
include/nlohmann/json.hpp:1534
`throw` → `JSON_THROW`, or this can't be used by people that disable exceptions.
single_include/nlohmann/json.hpp:9001
Looks like this was edited directly. Changes go in `include/` and then
`make amalgamate`.
docs/mkdocs/docs/api/basic_json/back.md:12
Should this list the precondition that the array is not empty?
```
+8 -163
View File
@@ -19,7 +19,6 @@
#include <nlohmann/detail/view/macro_scope.hpp>
#include <nlohmann/detail/view/node.hpp>
#include <nlohmann/detail/view/scan.hpp>
#include <nlohmann/detail/view/simd.hpp>
NLOHMANN_JSON_NAMESPACE_BEGIN
namespace detail
@@ -104,56 +103,12 @@ NLOHMANN_VIEW_NOINLINE FloatType float_value(const char* first, const node& n)
return convert_float<FloatType>(first, last, dot, mantissa_end);
}
#if NLOHMANN_VIEW_VECTOR
/*!
@brief the value of the first 16 digits of a run of digits with a point after
int_digits of them (or none, if int_digits >= 16)
The 17 bytes at p are read at once: the bytes after the point move down by one,
then pairs, quadruples, and octets of digits are combined by multiplications
(after simdjson). The bytes [p, p + 32) must be readable. Bytes that are not
digits (only in a damaged image loaded with image_check::bounds) give a wrong
value, but no undefined behavior.
*/
NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t sixteen_digits(const unsigned char* p, unsigned int_digits) noexcept
{
#if NLOHMANN_VIEW_NEON
const uint8x16_t low = vld1q_u8(p);
const uint8x16_t index = vcombine_u8(vcreate_u8(0x0706050403020100u), vcreate_u8(0x0F0E0D0C0B0A0908u));
const uint8x16_t before_point = vcltq_u8(index, vdupq_n_u8(static_cast<std::uint8_t>(int_digits)));
const uint8x16_t digits = vsubq_u8(vbslq_u8(before_point, low, vextq_u8(low, vld1q_u8(p + 16), 1)), vdupq_n_u8('0'));
const uint16x8_t twos = vpaddlq_u8(vmulq_u8(digits, vreinterpretq_u8_u16(vdupq_n_u16(0x010A))));
const uint32x4_t fours = vpaddlq_u16(vmulq_u16(twos, vreinterpretq_u16_u32(vdupq_n_u32(0x00010064))));
const uint64x2_t eights = vpaddlq_u32(vmulq_u32(fours, vreinterpretq_u32_u64(vdupq_n_u64(0x0000000100002710u))));
return (vgetq_lane_u64(eights, 0) * 100000000u) + vgetq_lane_u64(eights, 1);
#else
// NOLINTBEGIN(portability-simd-intrinsics)
const __m128i low = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(p))); // NOLINT(bugprone-casting-through-void)
const __m128i high = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(p + 16))); // NOLINT(bugprone-casting-through-void)
const __m128i before_point = _mm_cmpgt_epi8(_mm_set1_epi8(static_cast<char>(int_digits)), _mm_setr_epi8(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15));
const __m128i moved = _mm_or_si128(_mm_srli_si128(low, 1), _mm_slli_si128(high, 15));
const __m128i digits = _mm_sub_epi8(_mm_or_si128(_mm_and_si128(before_point, low), _mm_andnot_si128(before_point, moved)), _mm_set1_epi8('0'));
// (16-bit lanes: SSE2 has no multiply-add of bytes)
const __m128i tens = _mm_setr_epi16(10, 1, 10, 1, 10, 1, 10, 1);
const __m128i twos = _mm_packs_epi32(_mm_madd_epi16(_mm_unpacklo_epi8(digits, _mm_setzero_si128()), tens),
_mm_madd_epi16(_mm_unpackhi_epi8(digits, _mm_setzero_si128()), tens));
const __m128i fours = _mm_madd_epi16(twos, _mm_setr_epi16(100, 1, 100, 1, 100, 1, 100, 1));
const __m128i eights = _mm_madd_epi16(_mm_packs_epi32(fours, fours), _mm_setr_epi16(10000, 1, 10000, 1, 10000, 1, 10000, 1));
const auto upper = static_cast<std::uint32_t>(_mm_cvtsi128_si32(eights));
const auto lower = static_cast<std::uint32_t>(_mm_cvtsi128_si32(_mm_srli_si128(eights, 4)));
// NOLINTEND(portability-simd-intrinsics)
return (std::uint64_t{upper} * 100000000u) + lower;
#endif
}
#endif
/*!
@brief the digits of a float token with at most 19 digits, from its layout
The digit layout recorded while parsing says where the integer digits, the
fraction digits, and the exponent are, so the digits are read eight at a
time without scanning (with SIMD, a token of 16 to 19 digits sixteen at a
time).
time without scanning.
@param[in] p first character of the token
@param[in] e end of the token
@@ -163,34 +118,15 @@ NLOHMANN_VIEW_ALWAYS_INLINE float_significand layout_decimal(const unsigned char
{
const bool negative = *p == '-';
p += negative ? 1 : 0;
std::uint64_t w = 0;
std::uint64_t w = parse_upto19(p, int_digits, limit);
p += int_digits;
std::int64_t q = 0;
#if NLOHMANN_VIEW_VECTOR
const unsigned count = int_digits + frac_digits;
if (count >= 16 && limit - p >= 32)
if (frac_digits != 0)
{
// (the point, if any, follows the integer digits; the digits after
// the first 16 are at most three)
w = sixteen_digits(p, int_digits);
for (unsigned i = 16; i < count; ++i)
{
w = (w * 10) + static_cast<std::uint64_t>(p[i + (i >= int_digits ? 1 : 0)] - '0');
}
p += count + (frac_digits != 0 ? 1 : 0);
w = (w * int_pow10(frac_digits)) + parse_upto19(p + 1, frac_digits, limit);
p += 1 + frac_digits;
q = -static_cast<std::int64_t>(frac_digits);
}
else /* NOLINT(readability/braces) */
#endif
{
w = parse_upto19(p, int_digits, limit);
p += int_digits;
if (frac_digits != 0)
{
w = (w * int_pow10(frac_digits)) + parse_upto19(p + 1, frac_digits, limit);
p += 1 + frac_digits;
q = -static_cast<std::int64_t>(frac_digits);
}
}
if (p != e)
{
// [eE][+-]digits; huge exponents saturate (the parser rejected
@@ -225,22 +161,12 @@ NLOHMANN_VIEW_ALWAYS_INLINE float_significand layout_decimal(const unsigned char
The result is correctly rounded by the lexer's conversion
(detail::decimal_to_float(): Clinger's fast path where both operands are
exact, else the Eisel-Lemire algorithm, which needs no fallback for up to 19
digits), so it is the value parse() produces. Tokens of 16 or more digits go
to Eisel-Lemire directly: the fast path takes few of them (none of 17 digits),
and its check is a branch that data like GeoJSON coordinates mispredicts.
digits), so it is the value parse() produces.
*/
template<typename FloatType>
NLOHMANN_VIEW_ALWAYS_INLINE FloatType layout_float(const unsigned char* p, const unsigned char* e, unsigned int_digits, unsigned frac_digits, const unsigned char* limit) noexcept
{
const float_significand d = layout_decimal(p, e, int_digits, frac_digits, limit);
if (int_digits + frac_digits >= 16)
{
using format = ieee_binary_format<std::numeric_limits<FloatType>::digits>;
native_float_t<FloatType> value{};
float_from_bits(eisel_lemire<format>(d.exponent, d.w) | (d.negative ? (std::uint64_t{1} << format::sign_bit()) : 0u), value);
return value;
}
return decimal_to_float<FloatType>(d);
return decimal_to_float<FloatType>(layout_decimal(p, e, int_digits, frac_digits, limit));
}
/// the value of a float set by an edit: its token (the shortest round-trip
@@ -259,80 +185,6 @@ NLOHMANN_VIEW_NOINLINE FloatType edited_float(const char* token, const node& n)
return float_value<FloatType>(token, n);
}
#if NLOHMANN_VIEW_VECTOR
/// eisel_lemire() for the token w * 10^q of coordinate_float()
template<typename Format>
NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t coordinate_bits(std::int64_t q, std::uint64_t w, Format /*format*/) noexcept
{
return eisel_lemire<Format>(q, w);
}
/*!
@brief (binary64) eisel_lemire() without the cases that tokens of 16 or 17
digits with 5 or more after the point cannot reach: a value of 0, a
subnormal, an infinity, or a tie (q < -4)
*/
NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t coordinate_bits(std::int64_t q, std::uint64_t w, ieee_binary_format<53> format) noexcept
{
if (NLOHMANN_VIEW_UNLIKELY(w == 0 || q > -5))
{
return eisel_lemire<ieee_binary_format<53>>(q, w);
}
static_cast<void>(format);
const int lz = count_leading_zeros(w);
const std::uint64_t normalized = w << static_cast<unsigned>(lz);
const auto index = static_cast<std::size_t>(2 * (q - pow5_128_smallest_power));
const uint128_parts product = full_multiplication(normalized, pow5_128()[index]);
std::uint64_t high = product.high;
if (NLOHMANN_VIEW_UNLIKELY((high & 0x1FFu) == 0x1FFu))
{
// (the lower bits may carry into the result)
const std::uint64_t second = full_multiplication(normalized, pow5_128()[index + 1]).high;
high += product.low + second < product.low ? 1u : 0u;
}
const auto upperbit = static_cast<unsigned>(high >> 63u);
std::uint64_t mantissa = high >> (upperbit + 9);
auto power2 = static_cast<std::uint64_t>(((217706 * q) >> 16) + 63 + static_cast<std::int64_t>(upperbit) - lz + 1023);
mantissa = (mantissa + (mantissa & 1u)) >> 1u;
const bool carry = mantissa >= (std::uint64_t{2} << 52u);
mantissa = carry ? (std::uint64_t{1} << 52u) : mantissa;
power2 += carry ? 1u : 0u;
return (mantissa & ~(std::uint64_t{1} << 52u)) | (power2 << 52u);
}
/*!
@brief (binary32 and binary64) the value of a float token of the source with
16 or 17 digits, a point, and no exponent, the shape of most coordinates
written with full precision; whether the token of n has this shape
These tokens skip the general layout of layout_decimal(): no digits beyond
the 17th, no exponent (and Eisel-Lemire directly, as in layout_float()).
*/
template<typename FloatType>
NLOHMANN_VIEW_ALWAYS_INLINE bool coordinate_float(const document_data& d, const node& n, FloatType& value) noexcept
{
const unsigned int_digits = n.extra & 0xFFu;
const unsigned frac_digits = n.extra >> 8u;
const unsigned count = int_digits + frac_digits;
const auto* const first = reinterpret_cast<const unsigned char*>(d.src + n.off); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
const unsigned negative = first[0] == '-' ? 1u : 0u;
if (count - 16u > 1u || frac_digits == 0 || n.len != negative + count + 1 || d.size - n.off < 33)
{
return false;
}
const unsigned char* const digits = first + negative;
const std::uint64_t w = sixteen_digits(digits, int_digits);
// (the 17th digit follows the point)
const std::uint64_t w17 = (w * 10) + static_cast<std::uint64_t>(digits[17] - '0');
using format = ieee_binary_format<std::numeric_limits<FloatType>::digits>;
native_float_t<FloatType> result{};
float_from_bits(coordinate_bits(-static_cast<std::int64_t>(frac_digits), count == 17 ? w17 : w, format{}) | (static_cast<std::uint64_t>(negative) << format::sign_bit()), result);
value = result;
return true;
}
#endif
/// the value of the float token of a node, as parse() converts it; floats and
/// doubles with at most 19 digits are converted from the digit layout
template<typename FloatType>
@@ -348,13 +200,6 @@ FloatType float_value(const document_data& d, const node& n)
template<typename FloatType>
FloatType float_value(const document_data& d, const node& n, std::true_type /*binary32 or binary64*/)
{
#if NLOHMANN_VIEW_VECTOR
FloatType value {};
if (coordinate_float(d, n, value))
{
return value;
}
#endif
const unsigned int_digits = n.extra & 0xFFu;
const unsigned frac_digits = n.extra >> 8u;
if (NLOHMANN_VIEW_LIKELY(int_digits + frac_digits <= 19)) // (255 marks "many")
+1 -403
View File
@@ -14,9 +14,7 @@
#include <cstddef> // size_t
#include <cstdint> // uint8_t, uint32_t
#include <cstring> // memcpy, memset
#include <functional> // less
#include <limits> // numeric_limits
#include <memory> // unique_ptr
#include <type_traits> // integral_constant
#include <vector> // vector
@@ -386,143 +384,6 @@ struct depth_counter<false>
}
};
/*!
@brief where the double x nearest to a token w * 10^q lies, for 10^15 <= w <
10^17 and -17 <= q <= -1 (Eisel-Lemire, then a fixed-point position)
dump() writes the shortest decimal in the rounding interval of x (the closest
one if there are several, see zmij::to_shortest()). Its digits are those of a
multiple of 10^g of the token's last digit, with g = dec_exp + 1 - q for x's
decimal exponent dec_exp: the multiple of 10^g nearest to x if it lies in the
interval (at most one does), else the multiple of 10^(g - 1) nearest to x
(see token_digits_1() and token_digits_2()). For g <= 0, the token itself is
in the interval.
The position is exact in a 64-bit fixed-point number with 56 bits after the
point (of the token's last digit): x / 10^q = 2c * 5^-q / 2^t for x = c * 2^e2
and t = q + 1 - e2, with at most 56 bits after the point here, and |x / 10^q -
w| is at most half the spacing of the doubles, below 12 units. So only the low
64 bits of 2c * 5^-q are needed. c and e2 come from Eisel-Lemire's product
directly (as eisel_lemire() rounds it: no tie is possible for q < -4, and its
second product is added where it can carry into the result).
@param[out] offset x / 10^q - w + 32, with 56 bits after the point
@param[out] radius half the spacing of the doubles at x, likewise (+ 1 if
the interval is closed)
@return g; 3 if the digits are not decided here (a power of two, whose
interval is not symmetric, or out of range)
*/
NLOHMANN_VIEW_ALWAYS_INLINE int locate_token(std::uint64_t w, int q, std::uint64_t& offset, std::uint64_t& radius) noexcept
{
const int lz = count_leading_zeros(w);
const std::uint64_t normalized = w << static_cast<unsigned>(lz);
const auto index = static_cast<std::size_t>(2 * (q - pow5_128_smallest_power));
const uint128_parts product = full_multiplication(normalized, pow5_128()[index]);
std::uint64_t high = product.high;
if (NLOHMANN_VIEW_UNLIKELY((high & 0x1FFu) == 0x1FFu))
{
// (as eisel_lemire(): the lower bits may carry into the result)
const std::uint64_t second = full_multiplication(normalized, pow5_128()[index + 1]).high;
high += product.low + second < product.low ? 1u : 0u;
}
const auto upperbit = static_cast<unsigned>(high >> 63u);
const std::uint64_t mantissa = high >> (upperbit + 9);
const std::uint64_t c = (mantissa + (mantissa & 1u)) >> 1u;
// e2 as eisel_lemire() computes the exponent (log2(10) ~ 217706 / 2^16)
const int e2 = static_cast<int>((217706 * static_cast<std::int64_t>(q)) >> 16) + 63 + static_cast<int>(upperbit) - lz - 52;
const int t = q + 1 - e2;
const int g = ((e2 * 315653) >> 20) + 1 - q; // (dec_exp as in zmij::to_shortest(), for a regular x)
static const std::array<std::uint64_t, 17> fives = {{1u, 5u, 25u, 125u, 625u, 3125u, 15625u, 78125u, 390625u, 1953125u, 9765625u, 48828125u, 244140625u, 1220703125u, 6103515625u, 30517578125u, 152587890625u}};
const std::uint64_t five = fives[static_cast<std::size_t>(-q)]; // 5^-q
const unsigned s = static_cast<unsigned>(56 - t) & 63u;
offset = ((2 * c * five) << s) - (w << 56u) + (std::uint64_t{32} << 56u);
radius = (five << s) + ((c & 1u) == 0 ? 1u : 0u);
// (c = 2^52: a power of two; c = 2^53: rounded up to one. With 8 to 16
// fraction digits, as the batch's tokens have, t is in [15, 40] and g at
// most 2. x lies halfway between two candidates only if its distance from
// the token is a whole unit (g == 2) or a half (g == 1): such tokens are
// left to the full conversion)
const bool decided = c - ((std::uint64_t{1} << 52u) + 1) < (std::uint64_t{1} << 52u) - 1
&& (offset & ((std::uint64_t{1} << 55u) - 1)) != 0;
return decided ? g : 3;
}
/// all bits set if b, else none
NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t mask_if(bool b) noexcept
{
return std::uint64_t{0} - static_cast<std::uint64_t>(b);
}
/// a if b, else c, without a branch (the conditions of token_digits_1/2() are
/// as good as random, and GCC compiled their ?: as branches: one misprediction
/// per float of canada.json on x86-64)
NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t select_if(bool b, std::uint64_t a, std::uint64_t c) noexcept
{
return c ^ ((a ^ c) & mask_if(b));
}
/// the distance of a position (see locate_token()) from the biased point 32
NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t biased_distance(std::uint64_t position) noexcept
{
constexpr std::uint64_t center = std::uint64_t{32} << 56u;
// |position - center|, without a branch: negated (complemented, plus 1) if below
const std::uint64_t below = mask_if(position < center);
return ((position - center) ^ below) - below;
}
/*!
@brief (g == 1) the digits dump() writes for a token, from the position of its
double (see locate_token()): the multiple of 10 nearest to x if it is in the
interval, else w rounded to x (an exact tie between two candidates, like
754570942.33984373, whose double is 754570942.33984375, is excluded by
locate_token())
With |x - w| at most the radius, which is below half the spacing of the
candidates, the multiple of 10 nearest to x is w - r10 or the one above it.
*/
NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t token_digits_1(std::uint64_t w, std::uint64_t offset, std::uint64_t radius, std::uint64_t r10) noexcept
{
constexpr std::uint64_t one = std::uint64_t{1} << 56u;
const std::uint64_t from = offset + (r10 * one); // x - (w - r10) (+ 32)
const bool up = from > 37 * one; // (nearer to the multiple above)
const bool shorter = biased_distance(from - (mask_if(up) & (10 * one))) < radius;
const std::uint64_t a = w - r10 + (mask_if(up) & 10u);
const std::uint64_t b = w + ((offset + (one / 2)) >> 56u) - 32; // w rounded to x
return select_if(shorter, a, b);
}
/*!
@brief (g == 2) the digits dump() writes for a token, as token_digits_1(): the
multiple of 100 nearest to x if it is in the interval, else the multiple of 10
nearest to x
*/
NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t token_digits_2(std::uint64_t w, std::uint64_t offset, std::uint64_t radius, std::uint64_t r10, std::uint64_t r100) noexcept
{
constexpr std::uint64_t one = std::uint64_t{1} << 56u;
const std::uint64_t from = offset + (r100 * one);
const bool up = from > 82 * one;
const bool shorter = biased_distance(from - (mask_if(up) & (100 * one))) < radius;
const std::uint64_t a = w - r100 + (mask_if(up) & 100u);
// x - (w - r10), in [-12, 21]: the multiple of 10 nearest to x is that one,
// or one or two above, or one below
const std::uint64_t y = offset + (r10 * one);
const std::uint64_t steps = static_cast<std::uint64_t>(y > 37 * one) + static_cast<std::uint64_t>(y > 47 * one);
const bool down = y < 27 * one;
const std::uint64_t b = w - r10 + (10 * steps) - (mask_if(down) & 10u);
return select_if(shorter, a, b);
}
/// the four ASCII digits of x < 10^4, the first in the lowest byte (as
/// little-endian memory holds them)
NLOHMANN_VIEW_ALWAYS_INLINE std::uint32_t four_digit_text(std::uint32_t x) noexcept
{
const std::uint32_t ab = (x * 5243u) >> 19u; // x / 100
std::uint32_t v = ab | ((x - (ab * 100u)) << 16u);
const std::uint32_t a = ((v * 103u) >> 10u) & 0x000F000Fu; // / 10 per 16-bit lane
v = a | ((v - (a * 10u)) << 8u);
return v + 0x30303030u;
}
/// how the view's dump() writes a value
struct dump_style
{
@@ -850,7 +711,6 @@ class view_serializer
std::array<frame, 32> buffer; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
std::vector<frame> heap;
small_stack<frame> stack(buffer.data(), buffer.size(), heap);
float_batch batch;
const char* const src = m_doc.src;
const char* const src_end = src + m_doc.size;
char* w = m_out.cursor();
@@ -990,7 +850,7 @@ class view_serializer
else if (enabled(fast_double::value))
{
room(64);
w = write_double_ahead(w, src, n, batch);
w = write_double_at(w, *n);
}
else
{
@@ -1015,20 +875,6 @@ class view_serializer
case value_t::array:
{
const bool object = n->kind == node_kind::object;
// (read-only documents, compact output) a pair of floats,
// like the coordinates of GeoJSON, without a frame
if (enabled(!Editable && !Pretty && !SourceNumbers && fast_double::value) && n->next == 3 && n->len == 2
&& n[1].kind == node_kind::number_float && n[2].kind == node_kind::number_float)
{
room(2 * 64);
*w++ = '[';
w = write_double_ahead(w, src, n + 1, batch);
*w++ = ',';
w = write_double_ahead(w, src, n + 2, batch);
*w++ = ']';
n += 2; // (the element before the next node)
break;
}
room(8);
if (n->len == 0)
{
@@ -1138,254 +984,6 @@ class view_serializer
}
}
/// (float_batch) the mark of digits whose rounding carried beyond the
/// token's last four (see mark())
static constexpr std::uint64_t carried() noexcept
{
return std::uint64_t{1} << 63u;
}
/// floats of 16 or 17 digits ahead of the walk, converted together (see
/// convert_ahead()), with their digits as mark() keeps them
struct float_batch
{
static constexpr std::size_t capacity() noexcept
{
return 256;
}
/// (on the heap, allocated by the first conversion: a frame of more
/// than a page made every dump of a small document slower)
struct entries
{
std::array<const node*, 256> at; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
std::array<std::uint64_t, 256> digits; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
};
std::unique_ptr<entries> storage{};
const node** at = nullptr;
std::uint64_t* digits = nullptr;
std::size_t count = 0;
std::size_t next = 0;
const node* scanned = nullptr; ///< where the last scan of the node array ended
};
/// (doubles) the float at n as dump() writes it, at w (64 bytes of room):
/// from the batch if it holds n
NLOHMANN_VIEW_ALWAYS_INLINE char* write_double_ahead(char* w, const char* src, const node* n, float_batch& batch)
{
#if NLOHMANN_VIEW_VECTOR && NLOHMANN_VIEW_LITTLE_ENDIAN
// (digits 0: not written by the batch; carried(): rounding carried
// beyond the last four digits)
if (batch.next != batch.count && batch.at[batch.next] == n && batch.digits[batch.next] - 1 < carried() - 1)
{
return write_token_digits(w, src, *n, batch.digits[batch.next++]);
}
return write_double_beside(w, n, batch);
#else
static_cast<void>(src);
static_cast<void>(batch);
return write_double_at(w, *n);
#endif
}
#if NLOHMANN_VIEW_VECTOR && NLOHMANN_VIEW_LITTLE_ENDIAN
/// write_double_ahead() for a float that is not the batch's next one (out
/// of line: the walk is faster with less code in its loop)
NLOHMANN_VIEW_NOINLINE char* write_double_beside(char* w, const node* n, float_batch& batch)
{
// (an editable document's walk can skip nodes of the array)
const std::less<const node*> before{}; // NOLINT(modernize-use-transparent-functors) C++11 has no std::less<>
while (batch.next != batch.count && before(batch.at[batch.next], n))
{
++batch.next;
}
if ((batch.next != batch.count && batch.at[batch.next] == n) || convert_ahead(n, batch))
{
const std::uint64_t digits = batch.digits[batch.next++];
if ((digits & carried()) != 0)
{
return write_carried_digits(w, *n, digits & ~carried());
}
if (digits != 0)
{
return write_token_digits(w, m_doc.src, *n, digits);
}
}
return write_double_at(w, *n);
}
/*!
@brief convert the floats of 16 or 17 digits among the next nodes of the
array at once; whether n is the first of them
Such tokens (like the coordinates of GeoJSON, written with 17 digits) are
written as the token with its last four digits replaced
(write_token_digits()). Each step (the digits, locate_token(),
token_digits_1/2()) is a long chain of dependent operations; one loop per
step over many floats lets the processor overlap the floats, which it does
not across the steps of one float (on Apple M1, one loop for the digits and
locate_token() made the dump of canada.json 12 % slower). Each node of the array
is scanned once; a node that the walk does not reach in order (in an
editable document) is written without the batch.
*/
NLOHMANN_VIEW_NOINLINE bool convert_ahead(const node* n, float_batch& batch)
{
const std::less<const node*> before{}; // NOLINT(modernize-use-transparent-functors) C++11 has no std::less<>
const node* const last = m_doc.nodes + m_doc.node_count;
if (before(n, batch.scanned) || before(n, m_doc.nodes) || !before(n, last))
{
return false;
}
const char* const src = m_doc.src;
const char* const src_end = src + m_doc.size;
const node* const stop = last - n > 1024 ? n + 1024 : last;
batch.count = 0;
batch.next = 0;
// the digits of each token (and its last four from the text)
std::array<std::uint64_t, 256> digits; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
std::array<int, 256> exponent; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
std::array<std::uint32_t, 256> last_four; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
const node* p = n;
if (!batch.storage)
{
batch.storage.reset(new typename float_batch::entries); // NOLINT(cppcoreguidelines-owning-memory,modernize-make-unique): C++11
batch.at = batch.storage->at.data();
batch.digits = batch.storage->digits.data();
}
for (; p != stop && batch.count != float_batch::capacity(); ++p)
{
// a token of the source: 16 or 17 digits, at least 8 after the
// point, no exponent, 32 bytes to read
const unsigned frac_digits = p->extra >> 8u;
const unsigned int_digits = p->extra & 0xFFu;
const unsigned count = int_digits + frac_digits;
if (p->kind == node_kind::number_float && (p->flags & node_flags::storage) == 0
&& count - 16u <= 1u && frac_digits >= 8 && src_end - (src + p->off) >= 33)
{
const auto* const token = reinterpret_cast<const unsigned char*>(src + p->off); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
const unsigned sign = token[0] == '-' ? 1 : 0;
const unsigned char* const first = token + sign;
const std::uint64_t w = sixteen_digits(first, int_digits);
// (the 17th digit follows the point; a token with an exponent
// gets digits outside the range of locate_token(), and is not
// written by the batch. A token 0.xxx with 16 significant
// digits is: its double is written as "0." and its digits too)
const std::uint64_t w17 = (w * 10) + static_cast<std::uint64_t>(first[17] - '0');
const std::size_t i = batch.count++;
batch.at[i] = p;
if (p->len != sign + count + 1)
{
digits[i] = 0;
}
else
{
digits[i] = count == 17 ? w17 : w;
}
exponent[i] = -static_cast<int>(frac_digits);
// (byte 0: the last digit, byte 1: the last two, bits 16-29: the last four)
std::uint32_t four = 0;
std::memcpy(&four, token + p->len - 4, 4);
four -= 0x30303030u;
const std::uint32_t pairs = ((four & 0x0F0F0F0Fu) * 2561u) >> 8u; // (byte 0, 2: the pairs)
last_four[i] = (four >> 24u) | ((pairs >> 16u & 0xFFu) << 8u) | ((((pairs & 0x00FF00FFu) * 6553601u) >> 16u) << 16u);
}
}
batch.scanned = p;
// the position of each double, and the floats of either kind
std::array<std::uint64_t, 256> offset; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
std::array<std::uint64_t, 256> radius; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
std::array<std::uint8_t, 256> kind_1; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
std::array<std::uint8_t, 256> kind_2; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
std::size_t count_1 = 0;
std::size_t count_2 = 0;
for (std::size_t i = 0; i != batch.count; ++i)
{
const std::uint64_t w = digits[i];
// (the range excludes the values of bytes that are not digits, only
// in a damaged image loaded with image_check::bounds)
const int g = w - 1000000000000000u < 99000000000000000u ? locate_token(w, exponent[i], offset[i], radius[i]) : 3;
batch.digits[i] = mask_if(g <= 0) & ((last_four[i] >> 16u) + 1);
kind_1[count_1] = static_cast<std::uint8_t>(i);
count_1 += static_cast<std::size_t>(g == 1);
kind_2[count_2] = static_cast<std::uint8_t>(i);
count_2 += static_cast<std::size_t>(g == 2);
}
// the digits to write, in one loop per kind (see mark())
for (std::size_t k = 0; k != count_1; ++k)
{
const std::size_t i = kind_1[k];
const std::uint64_t s = token_digits_1(digits[i], offset[i], radius[i], last_four[i] & 0xFFu);
batch.digits[i] = mark(digits[i], s, last_four[i] >> 16u);
}
for (std::size_t k = 0; k != count_2; ++k)
{
const std::size_t i = kind_2[k];
const std::uint64_t s = token_digits_2(digits[i], offset[i], radius[i], last_four[i] & 0xFFu, (last_four[i] >> 8u) & 0xFFu);
batch.digits[i] = mark(digits[i], s, last_four[i] >> 16u);
}
return batch.count != 0 && batch.at[0] == n;
}
/*!
@brief a float token of 16 or 17 digits as dump() writes it, at w (64 bytes
of room), from the digits of its double (see locate_token()) whose
rounding carried beyond the token's last four digits
(like 43.42027299999999 -> 43.420273): the digits go to the writer of
Zmij's results as its 15 or 16 leading digits and one more, which omits
the trailing zeros.
*/
NLOHMANN_VIEW_NOINLINE char* write_carried_digits(char* w, const node& n, std::uint64_t digits) const noexcept
{
const int exponent = -(n.extra >> 8u);
const std::uint64_t leading = digits / 10;
const auto last = static_cast<unsigned char>(digits - (leading * 10));
const bool seventeen = digits >= 10000000000000000u;
*w = '-';
w += m_doc.src[n.off] == '-' ? 1 : 0;
return ::nlohmann::detail::dtoa_impl::write_shortest(w, seventeen ? ::nlohmann::detail::zmij::shortest_decimal{leading, exponent, last, last != 0}
: ::nlohmann::detail::zmij::shortest_decimal{digits, exponent - 1, 0, false});
}
/// the digits s of a token with the digits w and the last four digits
/// r4, as the batch keeps them: the new last four digits + 1 (only those
/// are written over the token's), or s marked if it differs from w beyond
/// them (0 stays for a float the batch does not write)
static std::uint64_t mark(std::uint64_t w, std::uint64_t s, std::uint64_t r4) noexcept
{
const std::uint64_t last = s - (w - r4);
return last < 10000 ? last + 1 : s | carried();
}
/*!
@brief a float token of 16 or 17 digits as dump() writes it, at w (64 bytes
of room): the token with its last four digits replaced by digits - 1 (see
mark(); the others are the token's), and without trailing zeros after the
point, but one
*/
char* write_token_digits(char* w, const char* src, const node& n, std::uint64_t digits)
{
const char* const token = src + n.off;
std::memcpy(w, token, 32);
char* const end = w + n.len;
const std::uint32_t last = four_digit_text(static_cast<std::uint32_t>(digits - 1));
std::memcpy(end - 4, &last, 4);
// (the token's text before the new digits, from the source: reading
// the output back would wait for the stores)
std::uint64_t before = 0;
std::memcpy(&before, token + n.len - 12, 8);
const std::uint32_t last_zeros = last ^ 0x30303030u;
const std::uint64_t before_zeros = before ^ 0x3030303030303030u;
if (NLOHMANN_VIEW_UNLIKELY(last_zeros == 0 && before_zeros == 0))
{
return write_double_at(w, n); // (twelve or more trailing zeros)
}
const unsigned zeros = last_zeros != 0 ? (static_cast<unsigned>(count_leading_zeros(last_zeros)) / 8) - 4
: 4 + (static_cast<unsigned>(count_leading_zeros(before_zeros)) / 8);
const unsigned frac_digits = n.extra >> 8u;
return end - (zeros < frac_digits ? zeros : frac_digits - 1);
}
#endif
/// a float node as dump() writes it
void write_float_node(const node& n)
{
+9 -567
View File
@@ -2522,8 +2522,6 @@ NLOHMANN_JSON_NAMESPACE_END
// #include <nlohmann/detail/view/scan.hpp>
// #include <nlohmann/detail/view/simd.hpp>
NLOHMANN_JSON_NAMESPACE_BEGIN
namespace detail
@@ -2608,56 +2606,12 @@ NLOHMANN_VIEW_NOINLINE FloatType float_value(const char* first, const node& n)
return convert_float<FloatType>(first, last, dot, mantissa_end);
}
#if NLOHMANN_VIEW_VECTOR
/*!
@brief the value of the first 16 digits of a run of digits with a point after
int_digits of them (or none, if int_digits >= 16)
The 17 bytes at p are read at once: the bytes after the point move down by one,
then pairs, quadruples, and octets of digits are combined by multiplications
(after simdjson). The bytes [p, p + 32) must be readable. Bytes that are not
digits (only in a damaged image loaded with image_check::bounds) give a wrong
value, but no undefined behavior.
*/
NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t sixteen_digits(const unsigned char* p, unsigned int_digits) noexcept
{
#if NLOHMANN_VIEW_NEON
const uint8x16_t low = vld1q_u8(p);
const uint8x16_t index = vcombine_u8(vcreate_u8(0x0706050403020100u), vcreate_u8(0x0F0E0D0C0B0A0908u));
const uint8x16_t before_point = vcltq_u8(index, vdupq_n_u8(static_cast<std::uint8_t>(int_digits)));
const uint8x16_t digits = vsubq_u8(vbslq_u8(before_point, low, vextq_u8(low, vld1q_u8(p + 16), 1)), vdupq_n_u8('0'));
const uint16x8_t twos = vpaddlq_u8(vmulq_u8(digits, vreinterpretq_u8_u16(vdupq_n_u16(0x010A))));
const uint32x4_t fours = vpaddlq_u16(vmulq_u16(twos, vreinterpretq_u16_u32(vdupq_n_u32(0x00010064))));
const uint64x2_t eights = vpaddlq_u32(vmulq_u32(fours, vreinterpretq_u32_u64(vdupq_n_u64(0x0000000100002710u))));
return (vgetq_lane_u64(eights, 0) * 100000000u) + vgetq_lane_u64(eights, 1);
#else
// NOLINTBEGIN(portability-simd-intrinsics)
const __m128i low = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(p))); // NOLINT(bugprone-casting-through-void)
const __m128i high = _mm_loadu_si128(static_cast<const __m128i*>(static_cast<const void*>(p + 16))); // NOLINT(bugprone-casting-through-void)
const __m128i before_point = _mm_cmpgt_epi8(_mm_set1_epi8(static_cast<char>(int_digits)), _mm_setr_epi8(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15));
const __m128i moved = _mm_or_si128(_mm_srli_si128(low, 1), _mm_slli_si128(high, 15));
const __m128i digits = _mm_sub_epi8(_mm_or_si128(_mm_and_si128(before_point, low), _mm_andnot_si128(before_point, moved)), _mm_set1_epi8('0'));
// (16-bit lanes: SSE2 has no multiply-add of bytes)
const __m128i tens = _mm_setr_epi16(10, 1, 10, 1, 10, 1, 10, 1);
const __m128i twos = _mm_packs_epi32(_mm_madd_epi16(_mm_unpacklo_epi8(digits, _mm_setzero_si128()), tens),
_mm_madd_epi16(_mm_unpackhi_epi8(digits, _mm_setzero_si128()), tens));
const __m128i fours = _mm_madd_epi16(twos, _mm_setr_epi16(100, 1, 100, 1, 100, 1, 100, 1));
const __m128i eights = _mm_madd_epi16(_mm_packs_epi32(fours, fours), _mm_setr_epi16(10000, 1, 10000, 1, 10000, 1, 10000, 1));
const auto upper = static_cast<std::uint32_t>(_mm_cvtsi128_si32(eights));
const auto lower = static_cast<std::uint32_t>(_mm_cvtsi128_si32(_mm_srli_si128(eights, 4)));
// NOLINTEND(portability-simd-intrinsics)
return (std::uint64_t{upper} * 100000000u) + lower;
#endif
}
#endif
/*!
@brief the digits of a float token with at most 19 digits, from its layout
The digit layout recorded while parsing says where the integer digits, the
fraction digits, and the exponent are, so the digits are read eight at a
time without scanning (with SIMD, a token of 16 to 19 digits sixteen at a
time).
time without scanning.
@param[in] p first character of the token
@param[in] e end of the token
@@ -2667,34 +2621,15 @@ NLOHMANN_VIEW_ALWAYS_INLINE float_significand layout_decimal(const unsigned char
{
const bool negative = *p == '-';
p += negative ? 1 : 0;
std::uint64_t w = 0;
std::uint64_t w = parse_upto19(p, int_digits, limit);
p += int_digits;
std::int64_t q = 0;
#if NLOHMANN_VIEW_VECTOR
const unsigned count = int_digits + frac_digits;
if (count >= 16 && limit - p >= 32)
if (frac_digits != 0)
{
// (the point, if any, follows the integer digits; the digits after
// the first 16 are at most three)
w = sixteen_digits(p, int_digits);
for (unsigned i = 16; i < count; ++i)
{
w = (w * 10) + static_cast<std::uint64_t>(p[i + (i >= int_digits ? 1 : 0)] - '0');
}
p += count + (frac_digits != 0 ? 1 : 0);
w = (w * int_pow10(frac_digits)) + parse_upto19(p + 1, frac_digits, limit);
p += 1 + frac_digits;
q = -static_cast<std::int64_t>(frac_digits);
}
else /* NOLINT(readability/braces) */
#endif
{
w = parse_upto19(p, int_digits, limit);
p += int_digits;
if (frac_digits != 0)
{
w = (w * int_pow10(frac_digits)) + parse_upto19(p + 1, frac_digits, limit);
p += 1 + frac_digits;
q = -static_cast<std::int64_t>(frac_digits);
}
}
if (p != e)
{
// [eE][+-]digits; huge exponents saturate (the parser rejected
@@ -2729,22 +2664,12 @@ NLOHMANN_VIEW_ALWAYS_INLINE float_significand layout_decimal(const unsigned char
The result is correctly rounded by the lexer's conversion
(detail::decimal_to_float(): Clinger's fast path where both operands are
exact, else the Eisel-Lemire algorithm, which needs no fallback for up to 19
digits), so it is the value parse() produces. Tokens of 16 or more digits go
to Eisel-Lemire directly: the fast path takes few of them (none of 17 digits),
and its check is a branch that data like GeoJSON coordinates mispredicts.
digits), so it is the value parse() produces.
*/
template<typename FloatType>
NLOHMANN_VIEW_ALWAYS_INLINE FloatType layout_float(const unsigned char* p, const unsigned char* e, unsigned int_digits, unsigned frac_digits, const unsigned char* limit) noexcept
{
const float_significand d = layout_decimal(p, e, int_digits, frac_digits, limit);
if (int_digits + frac_digits >= 16)
{
using format = ieee_binary_format<std::numeric_limits<FloatType>::digits>;
native_float_t<FloatType> value{};
float_from_bits(eisel_lemire<format>(d.exponent, d.w) | (d.negative ? (std::uint64_t{1} << format::sign_bit()) : 0u), value);
return value;
}
return decimal_to_float<FloatType>(d);
return decimal_to_float<FloatType>(layout_decimal(p, e, int_digits, frac_digits, limit));
}
/// the value of a float set by an edit: its token (the shortest round-trip
@@ -2763,80 +2688,6 @@ NLOHMANN_VIEW_NOINLINE FloatType edited_float(const char* token, const node& n)
return float_value<FloatType>(token, n);
}
#if NLOHMANN_VIEW_VECTOR
/// eisel_lemire() for the token w * 10^q of coordinate_float()
template<typename Format>
NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t coordinate_bits(std::int64_t q, std::uint64_t w, Format /*format*/) noexcept
{
return eisel_lemire<Format>(q, w);
}
/*!
@brief (binary64) eisel_lemire() without the cases that tokens of 16 or 17
digits with 5 or more after the point cannot reach: a value of 0, a
subnormal, an infinity, or a tie (q < -4)
*/
NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t coordinate_bits(std::int64_t q, std::uint64_t w, ieee_binary_format<53> format) noexcept
{
if (NLOHMANN_VIEW_UNLIKELY(w == 0 || q > -5))
{
return eisel_lemire<ieee_binary_format<53>>(q, w);
}
static_cast<void>(format);
const int lz = count_leading_zeros(w);
const std::uint64_t normalized = w << static_cast<unsigned>(lz);
const auto index = static_cast<std::size_t>(2 * (q - pow5_128_smallest_power));
const uint128_parts product = full_multiplication(normalized, pow5_128()[index]);
std::uint64_t high = product.high;
if (NLOHMANN_VIEW_UNLIKELY((high & 0x1FFu) == 0x1FFu))
{
// (the lower bits may carry into the result)
const std::uint64_t second = full_multiplication(normalized, pow5_128()[index + 1]).high;
high += product.low + second < product.low ? 1u : 0u;
}
const auto upperbit = static_cast<unsigned>(high >> 63u);
std::uint64_t mantissa = high >> (upperbit + 9);
auto power2 = static_cast<std::uint64_t>(((217706 * q) >> 16) + 63 + static_cast<std::int64_t>(upperbit) - lz + 1023);
mantissa = (mantissa + (mantissa & 1u)) >> 1u;
const bool carry = mantissa >= (std::uint64_t{2} << 52u);
mantissa = carry ? (std::uint64_t{1} << 52u) : mantissa;
power2 += carry ? 1u : 0u;
return (mantissa & ~(std::uint64_t{1} << 52u)) | (power2 << 52u);
}
/*!
@brief (binary32 and binary64) the value of a float token of the source with
16 or 17 digits, a point, and no exponent, the shape of most coordinates
written with full precision; whether the token of n has this shape
These tokens skip the general layout of layout_decimal(): no digits beyond
the 17th, no exponent (and Eisel-Lemire directly, as in layout_float()).
*/
template<typename FloatType>
NLOHMANN_VIEW_ALWAYS_INLINE bool coordinate_float(const document_data& d, const node& n, FloatType& value) noexcept
{
const unsigned int_digits = n.extra & 0xFFu;
const unsigned frac_digits = n.extra >> 8u;
const unsigned count = int_digits + frac_digits;
const auto* const first = reinterpret_cast<const unsigned char*>(d.src + n.off); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
const unsigned negative = first[0] == '-' ? 1u : 0u;
if (count - 16u > 1u || frac_digits == 0 || n.len != negative + count + 1 || d.size - n.off < 33)
{
return false;
}
const unsigned char* const digits = first + negative;
const std::uint64_t w = sixteen_digits(digits, int_digits);
// (the 17th digit follows the point)
const std::uint64_t w17 = (w * 10) + static_cast<std::uint64_t>(digits[17] - '0');
using format = ieee_binary_format<std::numeric_limits<FloatType>::digits>;
native_float_t<FloatType> result{};
float_from_bits(coordinate_bits(-static_cast<std::int64_t>(frac_digits), count == 17 ? w17 : w, format{}) | (static_cast<std::uint64_t>(negative) << format::sign_bit()), result);
value = result;
return true;
}
#endif
/// the value of the float token of a node, as parse() converts it; floats and
/// doubles with at most 19 digits are converted from the digit layout
template<typename FloatType>
@@ -2852,13 +2703,6 @@ FloatType float_value(const document_data& d, const node& n)
template<typename FloatType>
FloatType float_value(const document_data& d, const node& n, std::true_type /*binary32 or binary64*/)
{
#if NLOHMANN_VIEW_VECTOR
FloatType value {};
if (coordinate_float(d, n, value))
{
return value;
}
#endif
const unsigned int_digits = n.extra & 0xFFu;
const unsigned frac_digits = n.extra >> 8u;
if (NLOHMANN_VIEW_LIKELY(int_digits + frac_digits <= 19)) // (255 marks "many")
@@ -7978,9 +7822,7 @@ NLOHMANN_JSON_NAMESPACE_END
#include <cstddef> // size_t
#include <cstdint> // uint8_t, uint32_t
#include <cstring> // memcpy, memset
#include <functional> // less
#include <limits> // numeric_limits
#include <memory> // unique_ptr
#include <type_traits> // integral_constant
#include <vector> // vector
@@ -8355,143 +8197,6 @@ struct depth_counter<false>
}
};
/*!
@brief where the double x nearest to a token w * 10^q lies, for 10^15 <= w <
10^17 and -17 <= q <= -1 (Eisel-Lemire, then a fixed-point position)
dump() writes the shortest decimal in the rounding interval of x (the closest
one if there are several, see zmij::to_shortest()). Its digits are those of a
multiple of 10^g of the token's last digit, with g = dec_exp + 1 - q for x's
decimal exponent dec_exp: the multiple of 10^g nearest to x if it lies in the
interval (at most one does), else the multiple of 10^(g - 1) nearest to x
(see token_digits_1() and token_digits_2()). For g <= 0, the token itself is
in the interval.
The position is exact in a 64-bit fixed-point number with 56 bits after the
point (of the token's last digit): x / 10^q = 2c * 5^-q / 2^t for x = c * 2^e2
and t = q + 1 - e2, with at most 56 bits after the point here, and |x / 10^q -
w| is at most half the spacing of the doubles, below 12 units. So only the low
64 bits of 2c * 5^-q are needed. c and e2 come from Eisel-Lemire's product
directly (as eisel_lemire() rounds it: no tie is possible for q < -4, and its
second product is added where it can carry into the result).
@param[out] offset x / 10^q - w + 32, with 56 bits after the point
@param[out] radius half the spacing of the doubles at x, likewise (+ 1 if
the interval is closed)
@return g; 3 if the digits are not decided here (a power of two, whose
interval is not symmetric, or out of range)
*/
NLOHMANN_VIEW_ALWAYS_INLINE int locate_token(std::uint64_t w, int q, std::uint64_t& offset, std::uint64_t& radius) noexcept
{
const int lz = count_leading_zeros(w);
const std::uint64_t normalized = w << static_cast<unsigned>(lz);
const auto index = static_cast<std::size_t>(2 * (q - pow5_128_smallest_power));
const uint128_parts product = full_multiplication(normalized, pow5_128()[index]);
std::uint64_t high = product.high;
if (NLOHMANN_VIEW_UNLIKELY((high & 0x1FFu) == 0x1FFu))
{
// (as eisel_lemire(): the lower bits may carry into the result)
const std::uint64_t second = full_multiplication(normalized, pow5_128()[index + 1]).high;
high += product.low + second < product.low ? 1u : 0u;
}
const auto upperbit = static_cast<unsigned>(high >> 63u);
const std::uint64_t mantissa = high >> (upperbit + 9);
const std::uint64_t c = (mantissa + (mantissa & 1u)) >> 1u;
// e2 as eisel_lemire() computes the exponent (log2(10) ~ 217706 / 2^16)
const int e2 = static_cast<int>((217706 * static_cast<std::int64_t>(q)) >> 16) + 63 + static_cast<int>(upperbit) - lz - 52;
const int t = q + 1 - e2;
const int g = ((e2 * 315653) >> 20) + 1 - q; // (dec_exp as in zmij::to_shortest(), for a regular x)
static const std::array<std::uint64_t, 17> fives = {{1u, 5u, 25u, 125u, 625u, 3125u, 15625u, 78125u, 390625u, 1953125u, 9765625u, 48828125u, 244140625u, 1220703125u, 6103515625u, 30517578125u, 152587890625u}};
const std::uint64_t five = fives[static_cast<std::size_t>(-q)]; // 5^-q
const unsigned s = static_cast<unsigned>(56 - t) & 63u;
offset = ((2 * c * five) << s) - (w << 56u) + (std::uint64_t{32} << 56u);
radius = (five << s) + ((c & 1u) == 0 ? 1u : 0u);
// (c = 2^52: a power of two; c = 2^53: rounded up to one. With 8 to 16
// fraction digits, as the batch's tokens have, t is in [15, 40] and g at
// most 2. x lies halfway between two candidates only if its distance from
// the token is a whole unit (g == 2) or a half (g == 1): such tokens are
// left to the full conversion)
const bool decided = c - ((std::uint64_t{1} << 52u) + 1) < (std::uint64_t{1} << 52u) - 1
&& (offset & ((std::uint64_t{1} << 55u) - 1)) != 0;
return decided ? g : 3;
}
/// all bits set if b, else none
NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t mask_if(bool b) noexcept
{
return std::uint64_t{0} - static_cast<std::uint64_t>(b);
}
/// a if b, else c, without a branch (the conditions of token_digits_1/2() are
/// as good as random, and GCC compiled their ?: as branches: one misprediction
/// per float of canada.json on x86-64)
NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t select_if(bool b, std::uint64_t a, std::uint64_t c) noexcept
{
return c ^ ((a ^ c) & mask_if(b));
}
/// the distance of a position (see locate_token()) from the biased point 32
NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t biased_distance(std::uint64_t position) noexcept
{
constexpr std::uint64_t center = std::uint64_t{32} << 56u;
// |position - center|, without a branch: negated (complemented, plus 1) if below
const std::uint64_t below = mask_if(position < center);
return ((position - center) ^ below) - below;
}
/*!
@brief (g == 1) the digits dump() writes for a token, from the position of its
double (see locate_token()): the multiple of 10 nearest to x if it is in the
interval, else w rounded to x (an exact tie between two candidates, like
754570942.33984373, whose double is 754570942.33984375, is excluded by
locate_token())
With |x - w| at most the radius, which is below half the spacing of the
candidates, the multiple of 10 nearest to x is w - r10 or the one above it.
*/
NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t token_digits_1(std::uint64_t w, std::uint64_t offset, std::uint64_t radius, std::uint64_t r10) noexcept
{
constexpr std::uint64_t one = std::uint64_t{1} << 56u;
const std::uint64_t from = offset + (r10 * one); // x - (w - r10) (+ 32)
const bool up = from > 37 * one; // (nearer to the multiple above)
const bool shorter = biased_distance(from - (mask_if(up) & (10 * one))) < radius;
const std::uint64_t a = w - r10 + (mask_if(up) & 10u);
const std::uint64_t b = w + ((offset + (one / 2)) >> 56u) - 32; // w rounded to x
return select_if(shorter, a, b);
}
/*!
@brief (g == 2) the digits dump() writes for a token, as token_digits_1(): the
multiple of 100 nearest to x if it is in the interval, else the multiple of 10
nearest to x
*/
NLOHMANN_VIEW_ALWAYS_INLINE std::uint64_t token_digits_2(std::uint64_t w, std::uint64_t offset, std::uint64_t radius, std::uint64_t r10, std::uint64_t r100) noexcept
{
constexpr std::uint64_t one = std::uint64_t{1} << 56u;
const std::uint64_t from = offset + (r100 * one);
const bool up = from > 82 * one;
const bool shorter = biased_distance(from - (mask_if(up) & (100 * one))) < radius;
const std::uint64_t a = w - r100 + (mask_if(up) & 100u);
// x - (w - r10), in [-12, 21]: the multiple of 10 nearest to x is that one,
// or one or two above, or one below
const std::uint64_t y = offset + (r10 * one);
const std::uint64_t steps = static_cast<std::uint64_t>(y > 37 * one) + static_cast<std::uint64_t>(y > 47 * one);
const bool down = y < 27 * one;
const std::uint64_t b = w - r10 + (10 * steps) - (mask_if(down) & 10u);
return select_if(shorter, a, b);
}
/// the four ASCII digits of x < 10^4, the first in the lowest byte (as
/// little-endian memory holds them)
NLOHMANN_VIEW_ALWAYS_INLINE std::uint32_t four_digit_text(std::uint32_t x) noexcept
{
const std::uint32_t ab = (x * 5243u) >> 19u; // x / 100
std::uint32_t v = ab | ((x - (ab * 100u)) << 16u);
const std::uint32_t a = ((v * 103u) >> 10u) & 0x000F000Fu; // / 10 per 16-bit lane
v = a | ((v - (a * 10u)) << 8u);
return v + 0x30303030u;
}
/// how the view's dump() writes a value
struct dump_style
{
@@ -8819,7 +8524,6 @@ class view_serializer
std::array<frame, 32> buffer; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
std::vector<frame> heap;
small_stack<frame> stack(buffer.data(), buffer.size(), heap);
float_batch batch;
const char* const src = m_doc.src;
const char* const src_end = src + m_doc.size;
char* w = m_out.cursor();
@@ -8959,7 +8663,7 @@ class view_serializer
else if (enabled(fast_double::value))
{
room(64);
w = write_double_ahead(w, src, n, batch);
w = write_double_at(w, *n);
}
else
{
@@ -8984,20 +8688,6 @@ class view_serializer
case value_t::array:
{
const bool object = n->kind == node_kind::object;
// (read-only documents, compact output) a pair of floats,
// like the coordinates of GeoJSON, without a frame
if (enabled(!Editable && !Pretty && !SourceNumbers && fast_double::value) && n->next == 3 && n->len == 2
&& n[1].kind == node_kind::number_float && n[2].kind == node_kind::number_float)
{
room(2 * 64);
*w++ = '[';
w = write_double_ahead(w, src, n + 1, batch);
*w++ = ',';
w = write_double_ahead(w, src, n + 2, batch);
*w++ = ']';
n += 2; // (the element before the next node)
break;
}
room(8);
if (n->len == 0)
{
@@ -9107,254 +8797,6 @@ class view_serializer
}
}
/// (float_batch) the mark of digits whose rounding carried beyond the
/// token's last four (see mark())
static constexpr std::uint64_t carried() noexcept
{
return std::uint64_t{1} << 63u;
}
/// floats of 16 or 17 digits ahead of the walk, converted together (see
/// convert_ahead()), with their digits as mark() keeps them
struct float_batch
{
static constexpr std::size_t capacity() noexcept
{
return 256;
}
/// (on the heap, allocated by the first conversion: a frame of more
/// than a page made every dump of a small document slower)
struct entries
{
std::array<const node*, 256> at; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
std::array<std::uint64_t, 256> digits; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
};
std::unique_ptr<entries> storage{};
const node** at = nullptr;
std::uint64_t* digits = nullptr;
std::size_t count = 0;
std::size_t next = 0;
const node* scanned = nullptr; ///< where the last scan of the node array ended
};
/// (doubles) the float at n as dump() writes it, at w (64 bytes of room):
/// from the batch if it holds n
NLOHMANN_VIEW_ALWAYS_INLINE char* write_double_ahead(char* w, const char* src, const node* n, float_batch& batch)
{
#if NLOHMANN_VIEW_VECTOR && NLOHMANN_VIEW_LITTLE_ENDIAN
// (digits 0: not written by the batch; carried(): rounding carried
// beyond the last four digits)
if (batch.next != batch.count && batch.at[batch.next] == n && batch.digits[batch.next] - 1 < carried() - 1)
{
return write_token_digits(w, src, *n, batch.digits[batch.next++]);
}
return write_double_beside(w, n, batch);
#else
static_cast<void>(src);
static_cast<void>(batch);
return write_double_at(w, *n);
#endif
}
#if NLOHMANN_VIEW_VECTOR && NLOHMANN_VIEW_LITTLE_ENDIAN
/// write_double_ahead() for a float that is not the batch's next one (out
/// of line: the walk is faster with less code in its loop)
NLOHMANN_VIEW_NOINLINE char* write_double_beside(char* w, const node* n, float_batch& batch)
{
// (an editable document's walk can skip nodes of the array)
const std::less<const node*> before{}; // NOLINT(modernize-use-transparent-functors) C++11 has no std::less<>
while (batch.next != batch.count && before(batch.at[batch.next], n))
{
++batch.next;
}
if ((batch.next != batch.count && batch.at[batch.next] == n) || convert_ahead(n, batch))
{
const std::uint64_t digits = batch.digits[batch.next++];
if ((digits & carried()) != 0)
{
return write_carried_digits(w, *n, digits & ~carried());
}
if (digits != 0)
{
return write_token_digits(w, m_doc.src, *n, digits);
}
}
return write_double_at(w, *n);
}
/*!
@brief convert the floats of 16 or 17 digits among the next nodes of the
array at once; whether n is the first of them
Such tokens (like the coordinates of GeoJSON, written with 17 digits) are
written as the token with its last four digits replaced
(write_token_digits()). Each step (the digits, locate_token(),
token_digits_1/2()) is a long chain of dependent operations; one loop per
step over many floats lets the processor overlap the floats, which it does
not across the steps of one float (on Apple M1, one loop for the digits and
locate_token() made the dump of canada.json 12 % slower). Each node of the array
is scanned once; a node that the walk does not reach in order (in an
editable document) is written without the batch.
*/
NLOHMANN_VIEW_NOINLINE bool convert_ahead(const node* n, float_batch& batch)
{
const std::less<const node*> before{}; // NOLINT(modernize-use-transparent-functors) C++11 has no std::less<>
const node* const last = m_doc.nodes + m_doc.node_count;
if (before(n, batch.scanned) || before(n, m_doc.nodes) || !before(n, last))
{
return false;
}
const char* const src = m_doc.src;
const char* const src_end = src + m_doc.size;
const node* const stop = last - n > 1024 ? n + 1024 : last;
batch.count = 0;
batch.next = 0;
// the digits of each token (and its last four from the text)
std::array<std::uint64_t, 256> digits; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
std::array<int, 256> exponent; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
std::array<std::uint32_t, 256> last_four; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
const node* p = n;
if (!batch.storage)
{
batch.storage.reset(new typename float_batch::entries); // NOLINT(cppcoreguidelines-owning-memory,modernize-make-unique): C++11
batch.at = batch.storage->at.data();
batch.digits = batch.storage->digits.data();
}
for (; p != stop && batch.count != float_batch::capacity(); ++p)
{
// a token of the source: 16 or 17 digits, at least 8 after the
// point, no exponent, 32 bytes to read
const unsigned frac_digits = p->extra >> 8u;
const unsigned int_digits = p->extra & 0xFFu;
const unsigned count = int_digits + frac_digits;
if (p->kind == node_kind::number_float && (p->flags & node_flags::storage) == 0
&& count - 16u <= 1u && frac_digits >= 8 && src_end - (src + p->off) >= 33)
{
const auto* const token = reinterpret_cast<const unsigned char*>(src + p->off); // NOLINT(cppcoreguidelines-pro-type-reinterpret-cast)
const unsigned sign = token[0] == '-' ? 1 : 0;
const unsigned char* const first = token + sign;
const std::uint64_t w = sixteen_digits(first, int_digits);
// (the 17th digit follows the point; a token with an exponent
// gets digits outside the range of locate_token(), and is not
// written by the batch. A token 0.xxx with 16 significant
// digits is: its double is written as "0." and its digits too)
const std::uint64_t w17 = (w * 10) + static_cast<std::uint64_t>(first[17] - '0');
const std::size_t i = batch.count++;
batch.at[i] = p;
if (p->len != sign + count + 1)
{
digits[i] = 0;
}
else
{
digits[i] = count == 17 ? w17 : w;
}
exponent[i] = -static_cast<int>(frac_digits);
// (byte 0: the last digit, byte 1: the last two, bits 16-29: the last four)
std::uint32_t four = 0;
std::memcpy(&four, token + p->len - 4, 4);
four -= 0x30303030u;
const std::uint32_t pairs = ((four & 0x0F0F0F0Fu) * 2561u) >> 8u; // (byte 0, 2: the pairs)
last_four[i] = (four >> 24u) | ((pairs >> 16u & 0xFFu) << 8u) | ((((pairs & 0x00FF00FFu) * 6553601u) >> 16u) << 16u);
}
}
batch.scanned = p;
// the position of each double, and the floats of either kind
std::array<std::uint64_t, 256> offset; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
std::array<std::uint64_t, 256> radius; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
std::array<std::uint8_t, 256> kind_1; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
std::array<std::uint8_t, 256> kind_2; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): written before read
std::size_t count_1 = 0;
std::size_t count_2 = 0;
for (std::size_t i = 0; i != batch.count; ++i)
{
const std::uint64_t w = digits[i];
// (the range excludes the values of bytes that are not digits, only
// in a damaged image loaded with image_check::bounds)
const int g = w - 1000000000000000u < 99000000000000000u ? locate_token(w, exponent[i], offset[i], radius[i]) : 3;
batch.digits[i] = mask_if(g <= 0) & ((last_four[i] >> 16u) + 1);
kind_1[count_1] = static_cast<std::uint8_t>(i);
count_1 += static_cast<std::size_t>(g == 1);
kind_2[count_2] = static_cast<std::uint8_t>(i);
count_2 += static_cast<std::size_t>(g == 2);
}
// the digits to write, in one loop per kind (see mark())
for (std::size_t k = 0; k != count_1; ++k)
{
const std::size_t i = kind_1[k];
const std::uint64_t s = token_digits_1(digits[i], offset[i], radius[i], last_four[i] & 0xFFu);
batch.digits[i] = mark(digits[i], s, last_four[i] >> 16u);
}
for (std::size_t k = 0; k != count_2; ++k)
{
const std::size_t i = kind_2[k];
const std::uint64_t s = token_digits_2(digits[i], offset[i], radius[i], last_four[i] & 0xFFu, (last_four[i] >> 8u) & 0xFFu);
batch.digits[i] = mark(digits[i], s, last_four[i] >> 16u);
}
return batch.count != 0 && batch.at[0] == n;
}
/*!
@brief a float token of 16 or 17 digits as dump() writes it, at w (64 bytes
of room), from the digits of its double (see locate_token()) whose
rounding carried beyond the token's last four digits
(like 43.42027299999999 -> 43.420273): the digits go to the writer of
Zmij's results as its 15 or 16 leading digits and one more, which omits
the trailing zeros.
*/
NLOHMANN_VIEW_NOINLINE char* write_carried_digits(char* w, const node& n, std::uint64_t digits) const noexcept
{
const int exponent = -(n.extra >> 8u);
const std::uint64_t leading = digits / 10;
const auto last = static_cast<unsigned char>(digits - (leading * 10));
const bool seventeen = digits >= 10000000000000000u;
*w = '-';
w += m_doc.src[n.off] == '-' ? 1 : 0;
return ::nlohmann::detail::dtoa_impl::write_shortest(w, seventeen ? ::nlohmann::detail::zmij::shortest_decimal{leading, exponent, last, last != 0}
: ::nlohmann::detail::zmij::shortest_decimal{digits, exponent - 1, 0, false});
}
/// the digits s of a token with the digits w and the last four digits
/// r4, as the batch keeps them: the new last four digits + 1 (only those
/// are written over the token's), or s marked if it differs from w beyond
/// them (0 stays for a float the batch does not write)
static std::uint64_t mark(std::uint64_t w, std::uint64_t s, std::uint64_t r4) noexcept
{
const std::uint64_t last = s - (w - r4);
return last < 10000 ? last + 1 : s | carried();
}
/*!
@brief a float token of 16 or 17 digits as dump() writes it, at w (64 bytes
of room): the token with its last four digits replaced by digits - 1 (see
mark(); the others are the token's), and without trailing zeros after the
point, but one
*/
char* write_token_digits(char* w, const char* src, const node& n, std::uint64_t digits)
{
const char* const token = src + n.off;
std::memcpy(w, token, 32);
char* const end = w + n.len;
const std::uint32_t last = four_digit_text(static_cast<std::uint32_t>(digits - 1));
std::memcpy(end - 4, &last, 4);
// (the token's text before the new digits, from the source: reading
// the output back would wait for the stores)
std::uint64_t before = 0;
std::memcpy(&before, token + n.len - 12, 8);
const std::uint32_t last_zeros = last ^ 0x30303030u;
const std::uint64_t before_zeros = before ^ 0x3030303030303030u;
if (NLOHMANN_VIEW_UNLIKELY(last_zeros == 0 && before_zeros == 0))
{
return write_double_at(w, n); // (twelve or more trailing zeros)
}
const unsigned zeros = last_zeros != 0 ? (static_cast<unsigned>(count_leading_zeros(last_zeros)) / 8) - 4
: 4 + (static_cast<unsigned>(count_leading_zeros(before_zeros)) / 8);
const unsigned frac_digits = n.extra >> 8u;
return end - (zeros < frac_digits ? zeros : frac_digits - 1);
}
#endif
/// a float node as dump() writes it
void write_float_node(const node& n)
{
+672 -85
View File
@@ -35,9 +35,9 @@ using json_view_test::has_duplicate_keys;
#include <string>
#include <vector>
// These tests were split off unit-json_view.cpp, whose object file got too large for the MinGW
// linker (see json_view_test_helpers.hpp). Like that file, this one is also built
// with C++17, as it mentions JSON_HAS_CPP_17.
// These tests were split off unit-json_view.cpp, whose object file got too large
// for the MinGW linker (see json_view_test_helpers.hpp). Like that file, this one
// is also built with C++17, as it mentions JSON_HAS_CPP_17.
TEST_CASE("json_view dump")
{
@@ -150,88 +150,6 @@ TEST_CASE("json_view dump")
CHECK(many_doc.root().dump() == json::parse(many_tokens).dump());
}
// tokens of 16 and 17 digits without an exponent (like GeoJSON
// coordinates), which dump() converts in batches: doubles exactly
// halfway between two candidates for the shortest digits, random
// digits, and digits near a shorter decimal (...99999997,
// ...00000003), whose rounding carries; in pairs and among other
// values, so that the batches are interrupted; the last token near the
// end of the text
{
std::mt19937_64 tokens(5627); // NOLINT(cert-msc32-c,cert-msc51-cpp,bugprone-random-generator-seed)
const auto draw = [&tokens](std::size_t n)
{
const std::uint64_t r = tokens() % n;
return static_cast<std::size_t>(r);
};
std::string coordinates = "[754570942.33984373,257769445.56835938,858106901.94921875,97944964.876953125,"
"[0.5,1e-7],[1.5,-0.0,2.5],[1E2,12.5,0.1,3.25,4.5,5.75,6.125,7.0,8.5],[],[1.5],[1,2.5],[2.5,\"x\"],[[1.5],2.5],";
for (int i = 0; i < 20000; ++i)
{
const std::size_t length = 16 + draw(2);
std::string digits(1, static_cast<char>('1' + draw(9)));
const std::size_t kept = draw(3) == 0 ? length : 2 + draw(length - 3);
for (std::size_t k = 1; k < kept; ++k)
{
digits += static_cast<char>('0' + draw(10));
}
digits += std::string(length - kept, draw(2) == 0 ? '9' : '0');
digits.back() = static_cast<char>('0' + draw(10));
const std::size_t point = 1 + draw(9);
const std::string token = (draw(2) == 0 ? "-" : "") + digits.substr(0, point) + "." + digits.substr(point);
if (i != 0)
{
coordinates += ',';
}
if (draw(8) == 0)
{
coordinates += R"({"x":)";
coordinates += token;
coordinates += R"(,"s":"a"})";
}
else
{
coordinates += '[';
coordinates += token;
coordinates += ',';
coordinates += token;
coordinates += ']';
}
}
coordinates += ",-65.613616999999977]";
const json_document parsed = json_document::parse(coordinates);
const ordered_json j = ordered_json::parse(coordinates);
CHECK(parsed.root().dump() == j.dump());
CHECK(parsed.root().dump(1) == j.dump(1));
CHECK(parsed.root().dump(-1, ' ', true) == j.dump(-1, ' ', true));
CHECK(parsed.root().back().get<double>() == j.back().get<double>());
CHECK(parsed.root().back().dump() == "-65.61361699999998");
std::size_t i = 0;
for (const json_view v : parsed.root())
{
const ordered_json& e = j[i++];
CHECK(v.dump() == e.dump());
if (v.is_array() && !v.empty() && v[0].is_number())
{
CHECK(v[0].get<double>() == e[0].get<double>());
}
}
// an editable document: edits move some arrays, so that the walk
// leaves the order of the parsed nodes
ordered_json_editable_document editable = ordered_json_editable_document::parse(coordinates);
ordered_json expected = j;
for (std::size_t k = 0; k < 20000; k += 97)
{
if (expected[k].is_array())
{
editable.push_back(editable.root()[k], ordered_json(1.5));
expected[k].push_back(1.5);
}
}
CHECK(editable.root().dump() == expected.dump());
}
// random doubles, written as parse() and dump() would
std::mt19937_64 rng(1170); // NOLINT(cert-msc32-c,cert-msc51-cpp,bugprone-random-generator-seed)
std::string many = "[";
@@ -253,4 +171,673 @@ TEST_CASE("json_view dump")
const nlohmann::basic_json_document<json_float> float_document = nlohmann::basic_json_document<json_float>::parse("[0.1, 1.5e10, 3.4028235e38]");
CHECK(float_document.root().dump() == json_float::parse("[0.1, 1.5e10, 3.4028235e38]").dump());
}
SECTION("members in document order, all of them")
{
const json_document d = json_document::parse(R"({"b": 1, "a": 2, "b": 3})");
CHECK(d.root().dump() == R"({"b":1,"a":2,"b":3})");
CHECK(d.root().dump(1) == "{\n \"b\": 1,\n \"a\": 2,\n \"b\": 3\n}");
// dump() writes all members, though the lookup finds the first
CHECK(d.root()["b"].dump() == "1");
}
SECTION("deep nesting")
{
const std::string deep = std::string(100000, '[') + std::string(100000, ']');
const json_document deep_document = json_document::parse(deep);
CHECK(deep_document.root().dump() == deep);
}
SECTION("ensure_ascii: a character that needs an escape at each position of a string")
{
// string lengths around the width of the vector steps, in a string value, a key, and a value near the end of the text
for (const char* const special :
{
"\xC3\xA9", "\xE4\xB8\xAD", "\xF0\x9F\x98\x80", "\x7F", "\\n", "\\u0001", "\\\"", "\\\\"
})
{
for (std::size_t length = 0; length <= 40; ++length)
{
for (std::size_t position = 0; position <= length; ++position)
{
std::string content(length, 'a');
content.insert(position, special);
const std::array<std::string, 3> texts =
{
{
"\"" + content + "\"",
"[\"" + content + "\"]",
"{\"" + content + "\":1}",
}
};
for (const std::string& text : texts)
{
CAPTURE(text)
const ordered_json_document d = ordered_json_document::parse(text);
const ordered_json j = ordered_json::parse(text);
CHECK(d.root().dump(-1, ' ', true) == j.dump(-1, ' ', true));
CHECK(d.root().dump(2, ' ', true) == j.dump(2, ' ', true));
CHECK(d.root().dump() == j.dump());
}
}
}
}
}
SECTION("ensure_ascii: every character of the Basic Multilingual Plane and some beyond")
{
// (the two- and three-byte sequences, including the ranges that need a check: E0, ED, EF BF BF)
std::string text = "[";
std::size_t in_chunk = 0;
const auto append = [&](std::uint32_t cp)
{
if (cp < 0x80)
{
if (cp < 0x20 || cp == '"' || cp == '\\')
{
return;
}
text += static_cast<char>(cp);
}
else if (cp < 0x800)
{
text += static_cast<char>(0xC0 | (cp >> 6));
text += static_cast<char>(0x80 | (cp & 0x3F));
}
else if (cp < 0x10000)
{
text += static_cast<char>(0xE0 | (cp >> 12));
text += static_cast<char>(0x80 | ((cp >> 6) & 0x3F));
text += static_cast<char>(0x80 | (cp & 0x3F));
}
else
{
text += static_cast<char>(0xF0 | (cp >> 18));
text += static_cast<char>(0x80 | ((cp >> 12) & 0x3F));
text += static_cast<char>(0x80 | ((cp >> 6) & 0x3F));
text += static_cast<char>(0x80 | (cp & 0x3F));
}
};
for (std::uint32_t cp = 0x20; cp < 0x10400; ++cp)
{
if (cp >= 0xD800 && cp < 0xE000)
{
continue;
}
if (in_chunk == 0)
{
text += text.size() > 1 ? ",\"" : "\"";
}
append(cp);
if (++in_chunk == 37)
{
text += "\"";
in_chunk = 0;
}
}
text += in_chunk != 0 ? "\"]" : "]";
const ordered_json_document d = ordered_json_document::parse(text);
const ordered_json j = ordered_json::parse(text);
CHECK(d.root().dump(-1, ' ', true) == j.dump(-1, ' ', true));
CHECK(d.root().dump(2, ' ', true) == j.dump(2, ' ', true));
CHECK(d.root().dump() == j.dump());
CHECK(d.root().dump(2) == j.dump(2));
}
SECTION("deep nesting, indented")
{
// indentations of up to and beyond the width of the writer's fixed-size copy
for (const int depth :
{
1, 5, 20, 70, 300
})
{
std::string text;
for (int i = 0; i < depth; ++i)
{
text += i % 2 == 0 ? "[1," : R"({"k":2,"\u00e9":)";
}
text += "[]";
for (int i = depth - 1; i >= 0; --i)
{
text += i % 2 == 0 ? "]" : "}";
}
const ordered_json_document d = ordered_json_document::parse(text);
const ordered_json j = ordered_json::parse(text);
for (const int indent :
{
0, 1, 2, 3, 8
})
{
CHECK(d.root().dump(indent) == j.dump(indent));
CHECK(d.root().dump(indent, '\t') == j.dump(indent, '\t'));
}
}
}
SECTION("the output buffer of a small value is small")
{
// an escaped key after the value: its node lies in the arena, so the
// source extent of the value cannot be read from the next node
const std::string big(100000, 'a');
const std::string text = R"({"small":1,"list":[1,2,3],"k\n":")" + big + R"("})";
const json_document d = json_document::parse(text);
const auto small = d.root()["small"].dump();
CHECK(small == "1");
CHECK(small.capacity() < 4096);
const auto list = d.root()["list"].dump();
CHECK(list == "[1,2,3]");
CHECK(list.capacity() < 4096);
CHECK(d.root()["list"].dump(2).capacity() < 4096);
// the whole document and the large value are unaffected
CHECK(d.root().dump() == ordered_json::parse(text).dump());
CHECK(d.root()["k\n"].dump() == "\"" + big + "\"");
}
SECTION("output that outgrows the estimate")
{
// ensure_ascii writes six bytes for each two-byte character
std::string chars;
for (int i = 0; i < 5000; ++i)
{
chars += "\xC3\xA9";
}
const json_document d = json_document::parse(R"({"a":")" + chars + R"(","k\n":1})");
const json expected = json::parse("\"" + chars + "\"");
CHECK(d.root()["a"].dump(-1, ' ', true) == expected.dump(-1, ' ', true));
CHECK(d.root()["a"].dump(-1, ' ', true).size() == 2 + (5000 * 6));
}
SECTION("ensure_ascii with strings of the source, decoded strings, and edited strings")
{
// plain ASCII, non-ASCII, escaped (decoded), and mixed strings, as values and as keys;
// the second text has a DEL, which ensure_ascii writes as an escape
for (const char* const del :
{"", "\x7F"
})
{
const std::string text = std::string("{\"plain\":\"abc\",\"caf\xC3\xA9\":\"\xC3\xA9\xE2\x82\xAC\xF0\x9F\x98\x80\",")
+ "\"esc\\n\\\"\":\"a\\tb\\u00e4\\ud83d\\ude00\",\"del\":\"a" + del + "b\",\"\":\"\"," // NOLINT(modernize-raw-string-literal)
+ "\"list\":[\"x\",\"\xC3\xBC\",\"\\\\\",\"long ASCII string with more than thirty-two bytes in it\","
+ "\"long string with more than thirty-two bytes and one non-ASCII byte \xC3\xB6\"],"
+ "\"n\":[1,2.5,-0,true,null]}";
const ordered_json j = ordered_json::parse(text);
const ordered_json_document d = ordered_json_document::parse(text);
CHECK(d.root().dump(-1, ' ', true) == j.dump(-1, ' ', true));
CHECK(d.root().dump(4, ' ', true) == j.dump(4, ' ', true));
CHECK(d.root().dump() == j.dump());
CHECK(d.root()["list"].dump(-1, ' ', true) == j["list"].dump(-1, ' ', true));
CHECK(d.root()["del"].dump(-1, ' ', true) == j["del"].dump(-1, ' ', true));
// strings that an edit wrote (the source strings that they replace were plain)
ordered_json_editable_document e = ordered_json_editable_document::parse(text);
ordered_json k = j;
e.set(e.root()["plain"], std::string("\xC3\xA4gypten"));
k["plain"] = "\xC3\xA4gypten";
e.set(e.root()["list"][0], std::string("ascii after edit"));
k["list"][0] = "ascii after edit";
e.set(e.root()["list"][1], std::string("\xC3\xA4"));
k["list"][1] = "\xC3\xA4";
e.set(e.root()["del"], std::string("tab\there"));
k["del"] = "tab\there";
CHECK(e.root().dump(-1, ' ', true) == k.dump(-1, ' ', true));
CHECK(e.root().dump(2, ' ', true) == k.dump(2, ' ', true));
CHECK(e.root().dump() == k.dump());
// strings that were edited from or to ASCII text
e.set(e.root()["list"][2], std::string("\xC3\xA4"));
k["list"][2] = "\xC3\xA4";
e.set(e.root()["list"][4], std::string("plain again"));
k["list"][4] = "plain again";
CHECK(e.root().dump(-1, ' ', true) == k.dump(-1, ' ', true));
}
}
SECTION("ensure_ascii with DEL or a non-ASCII character at every position")
{
// the check whether a string of the source has no byte >= 0x7F reads
// eight bytes at a time and then the rest one by one
for (std::size_t length = 1; length <= 20; ++length)
{
for (std::size_t pos = 0; pos < length; ++pos)
{
for (const char* const c :
{
"\x7F", "\x7E", "\xC3\xA4", "\xC3\xBF" // NOLINT(modernize-raw-string-literal)
})
{
const std::string s = std::string(pos, 'a') + c + std::string(length - pos - 1, 'b');
std::string text = "[\"";
text.append(s).append("\",{\"").append(s).append("\":1}]");
const json_document d = json_document::parse(text);
const json j = json::parse(text);
CHECK(d.root().dump(-1, ' ', true) == j.dump(-1, ' ', true));
CHECK(d.root().dump(1, ' ', true) == j.dump(1, ' ', true));
}
}
}
}
SECTION("streams and discarded views")
{
const json_document d = json_document::parse(R"({"a": [1, 2]})");
std::ostringstream compact;
compact << d.root();
CHECK(compact.str() == R"({"a":[1,2]})");
std::ostringstream pretty;
pretty << std::setw(2) << std::setfill('.') << d.root() << d.root()["a"];
CHECK(pretty.str() == "{\n..\"a\": [\n....1,\n....2\n..]\n}[1,2]");
CHECK(json_view().dump() == json(json::value_t::discarded).dump());
}
}
TEST_CASE("json_view large objects")
{
// objects with 128 members or more are looked up with a hash index
for (const std::size_t members :
{
127u, 128u, 129u, 10000u
})
{
CAPTURE(members)
std::string text = "{";
for (std::size_t i = 0; i < members; ++i)
{
text += (i != 0 ? ",\"" : "\"") + std::string(i % 23, 'k') + std::to_string(i) + (i % 7 == 0 ? "\\n" : "") + "\":" + std::to_string(i);
}
text += R"(,"":"empty key","k1":"a duplicate of an earlier key"})";
const json_document d = json_document::parse(text);
const json_view v = d.root();
const json j = json::parse(text);
for (std::size_t i = 0; i < members; ++i)
{
const std::string key = std::string(i % 23, 'k') + std::to_string(i) + (i % 7 == 0 ? "\n" : "");
CHECK(v[key].get<std::size_t>() == i);
CHECK(v.contains(key));
CHECK(v.find(key).key() == key);
CHECK(v.at(key).get<std::size_t>() == i);
CHECK(!v.contains(key + "x"));
}
CHECK(v[""].get_string() == "empty key");
CHECK(v["k1"].get<int>() == 1); // the first of duplicate keys, as for small objects
CHECK(!v.contains("missing"));
CHECK_THROWS_WITH_AS(v.at("missing"), "[json.exception.out_of_range.403] key 'missing' not found", json::out_of_range&);
CHECK(v == j);
CHECK(v.materialize() == j);
}
SECTION("duplicate keys: the first member wins, with and without a table")
{
// an object of `total` members: the keys "k0".."k<n-1>" in order, then
// three keys repeated twice more (one copy in the middle, one at the
// end), and two keys repeated once; the value of a member is its
// position, so that the first member of a key can be told apart
struct member
{
std::string key;
std::size_t position;
};
const auto make_members = [](std::size_t total)
{
std::vector<std::string> keys;
for (std::size_t i = 0; i + 8 < total; ++i)
{
keys.push_back("k" + std::to_string(i));
}
const std::size_t n = keys.size();
const std::array<std::size_t, 3> triple = {{3, 17, n - 1}};
const std::array<std::size_t, 2> twice = {{5, n / 2}};
std::vector<std::string> ordered = keys;
for (const std::size_t i : triple)
{
ordered.insert(ordered.begin() + static_cast<std::ptrdiff_t>(ordered.size() / 2), keys[i]);
}
for (const std::size_t i : twice)
{
ordered.insert(ordered.begin() + static_cast<std::ptrdiff_t>(ordered.size() / 3), keys[i]);
}
for (const std::size_t i : triple)
{
ordered.push_back(keys[i]);
}
std::vector<member> result;
result.reserve(ordered.size());
for (std::size_t i = 0; i < ordered.size(); ++i)
{
result.push_back({ordered[i], i});
}
return result;
};
// 100 and 127 members: no table; 128 members and more: a table
for (const std::size_t total :
{
100u, 127u, 128u, 200u, 5000u
})
{
CAPTURE(total)
const std::vector<member> members = make_members(total);
REQUIRE(members.size() >= total);
REQUIRE(members.size() >= 100);
std::string text = "{";
std::map<std::string, std::size_t> first;
std::map<std::string, std::size_t> last;
std::map<std::string, std::size_t> occurrences;
for (const member& m : members)
{
text += (text.size() > 1 ? ",\"" : "\"") + m.key + "\":" + std::to_string(m.position);
first.insert({m.key, m.position});
last[m.key] = m.position;
++occurrences[m.key];
}
text += '}';
REQUIRE(first.size() < members.size());
const json_document d = json_document::parse(text);
const json_view v = d.root();
const json j = json::parse(text);
CHECK(v.size() == members.size()); // every occurrence is visited
const json m = v.materialize();
for (const auto& entry : first)
{
CAPTURE(entry.first)
const std::size_t expected = entry.second;
CHECK(v[entry.first].get<std::size_t>() == expected);
CHECK(v.at(entry.first).get<std::size_t>() == expected);
CHECK(v.find(entry.first).value().get<std::size_t>() == expected);
CHECK(v.value(entry.first, std::size_t{0}) == expected);
CHECK(v.contains(entry.first));
CHECK(v.count(entry.first) == occurrences[entry.first]);
const std::string pointer = "/" + entry.first;
CHECK(v[json::json_pointer(pointer)].get<std::size_t>() == expected);
CHECK(v.at(json::json_pointer(pointer)).get<std::size_t>() == expected);
CHECK(v.value(json::json_pointer(pointer), std::size_t{0}) == expected);
CHECK(v.contains(json::json_pointer(pointer)));
// materialize() and parse() keep the last value instead
CHECK(j[entry.first].get<std::size_t>() == last.at(entry.first));
CHECK(m[entry.first].get<std::size_t>() == last.at(entry.first));
}
CHECK(!v.contains("k"));
CHECK(v["missing"].is_discarded());
CHECK(v.materialize() == j);
CHECK(v == j);
}
}
SECTION("colliding keys")
{
// the hash is not seeded, so keys that all land in one place must not
// make the table build quadratic: such an object gets no table and is
// searched linearly
constexpr std::size_t members = 300;
constexpr std::size_t table_size = 1024; // the table size for 300 members: the next power of two >= 600
std::vector<std::string> colliding;
std::vector<std::string> spread;
for (std::uint64_t counter = 0; colliding.size() < members || spread.size() < members; ++counter)
{
std::string key(8, 'a');
std::uint64_t x = counter;
for (std::size_t i = 0; i < 8; ++i, x /= 26)
{
key[i] = static_cast<char>('a' + (x % 26));
}
const bool lands_in_slot_zero = (nlohmann::detail::view::key_hash(key.data(), key.size()) & (table_size - 1)) == 0;
if (lands_in_slot_zero && colliding.size() < members)
{
colliding.push_back(key);
}
else if (!lands_in_slot_zero && spread.size() < members)
{
spread.push_back(key);
}
}
const auto make_text = [](const std::vector<std::string>& keys)
{
std::string text = "{";
for (std::size_t i = 0; i < keys.size(); ++i)
{
text += (i != 0 ? ",\"" : "\"") + keys[i] + "\":" + std::to_string(i % 10);
}
return text + "}";
};
const std::string colliding_text = make_text(colliding);
const std::string spread_text = make_text(spread);
json_document with_collisions = json_document::parse(colliding_text);
json_document without_collisions = json_document::parse(spread_text);
for (const auto* pair :
{
&colliding, &spread
})
{
const json_view v = (pair == &colliding ? with_collisions : without_collisions).root();
for (std::size_t i = 0; i < members; ++i)
{
CAPTURE(i)
CHECK(v[(*pair)[i]].get<std::size_t>() == i % 10);
CHECK(v.at((*pair)[i]).get<std::size_t>() == i % 10);
CHECK(v.find((*pair)[i]).key() == (*pair)[i]);
CHECK(!v.contains((*pair)[i] + "x"));
}
CHECK(!v.contains("missing"));
}
CHECK(with_collisions.root() == json::parse(colliding_text));
// only the object with the spread keys got a table (both texts have the
// same length, so the tables are the only difference)
with_collisions.shrink_to_fit();
without_collisions.shrink_to_fit();
CHECK(without_collisions.memory_usage() >= with_collisions.memory_usage() + (table_size * sizeof(std::uint32_t)));
}
SECTION("keys that differ in their last bytes are spread over the table")
{
// The hash must spread the usual families of keys (numbered names, hex
// strings, dates, short names): a key farther than index_max_displacement
// from its home slot would leave the object without a table. The keys
// are placed with linear probing, as the table does.
const auto max_displacement = [](const std::vector<std::string>& keys)
{
std::size_t slots = 16;
while (slots < 2 * keys.size())
{
slots *= 2;
}
std::vector<bool> used(slots, false);
std::size_t farthest = 0;
for (const std::string& key : keys)
{
std::size_t i = nlohmann::detail::conditional_static_cast<std::size_t>(nlohmann::detail::view::key_hash(key.data(), key.size())) & (slots - 1);
std::size_t distance = 0;
while (used[i])
{
i = (i + 1) & (slots - 1);
++distance;
}
used[i] = true;
farthest = (std::max)(farthest, distance);
}
return farthest;
};
// the keys of a printf-like pattern with one %d, %0Nd or %0Nx, formatted with a stream
// (a format string that is not a literal is a Flawfinder error)
const auto numbered = [](const char* format, int count, int step)
{
const std::string pattern(format);
const std::size_t percent = pattern.find('%');
std::size_t conversion = percent + 1;
std::size_t width = 0;
while (pattern[conversion] >= '0' && pattern[conversion] <= '9')
{
width = (width * 10) + static_cast<std::size_t>(pattern[conversion] - '0');
++conversion;
}
const bool hex = pattern[conversion] == 'x';
std::vector<std::string> keys;
for (int i = 0; i < count; ++i)
{
std::ostringstream key;
key << pattern.substr(0, percent) << std::setfill('0') << std::setw(static_cast<int>(width))
<< (hex ? std::hex : std::dec) << (i * step) << pattern.substr(conversion + 1);
keys.push_back(key.str());
}
return keys;
};
for (const char* format :
{"key%d", "%d", "item_%04d", "a%05d", "%03dxyz", "id%d", "user_%d", "%d_suffix", "0x%04x", "A%07d", "12345678%d", "1234567%d", "123456789%d",
"configuration_parameter_value_%04d_extra", "2026-01-%02dT00:00:00Z"
})
{
CAPTURE(format)
CHECK(max_displacement(numbered(format, std::string(format).find("%02d") != std::string::npos ? 60 : 1000, 1)) < nlohmann::detail::view::index_max_displacement); // NOLINT(abseil-string-find-str-contains)
CHECK(max_displacement(numbered(format, 600, 7)) < nlohmann::detail::view::index_max_displacement);
}
std::mt19937_64 rng(7); // NOLINT(cert-msc32-c,cert-msc51-cpp,bugprone-random-generator-seed)
for (const std::size_t length :
{
std::size_t{1}, std::size_t{2}, std::size_t{3}, std::size_t{5}, std::size_t{7}, std::size_t{8}, std::size_t{9}, std::size_t{12}, std::size_t{16}, std::size_t{17}, std::size_t{33}
})
{
CAPTURE(length)
std::set<std::string> distinct;
// (there are 26 and 676 keys of one and two letters)
std::size_t wanted = 700;
if (length == 1)
{
wanted = 26;
}
else if (length == 2)
{
wanted = 500;
}
while (distinct.size() < wanted)
{
std::string key(length, 'a');
for (char& c : key)
{
c = static_cast<char>('a' + (rng() % 26));
}
distinct.insert(key);
}
CHECK(max_displacement(std::vector<std::string>(distinct.begin(), distinct.end())) < nlohmann::detail::view::index_max_displacement);
}
}
SECTION("keys of every length that differ in one byte")
{
// In a large object, a key is found by comparing its bytes with those of the member the
// table points to: up to 16 bytes as two overlapping words, longer ones with memcmp.
// Keys of every length from 0 to 40, and keys that differ from them in one byte.
std::mt19937_64 rng(2026); // NOLINT(cert-msc32-c,cert-msc51-cpp,bugprone-random-generator-seed)
std::vector<std::string> keys;
std::set<std::string> distinct;
for (std::size_t length = 0; length <= 40; ++length)
{
for (int copy = 0; copy < 5; ++copy)
{
std::string key(length, 'a');
for (char& c : key)
{
c = static_cast<char>('a' + (rng() % 26));
}
if (distinct.insert(key).second)
{
keys.push_back(key);
}
}
}
std::string text = "{";
for (std::size_t i = 0; i < keys.size(); ++i)
{
text += (i != 0 ? ",\"" : "\"") + keys[i] + "\":" + std::to_string(i);
}
text += "}";
REQUIRE(keys.size() >= 128); // (a table is built for 128 members)
const json_document d = json_document::parse(text);
const json_view v = d.root();
for (std::size_t i = 0; i < keys.size(); ++i)
{
CAPTURE(keys[i])
CHECK(v[keys[i]].get<std::size_t>() == i);
CHECK(v.at(keys[i]).get<std::size_t>() == i);
CHECK(v.contains(keys[i]));
for (std::size_t at = 0; at < keys[i].size(); ++at)
{
std::string other = keys[i];
other[at] = other[at] == 'z' ? 'y' : 'z';
CAPTURE(other)
CHECK(v.contains(other) == (distinct.count(other) != 0));
}
CHECK(v.contains(keys[i] + "a") == (distinct.count(keys[i] + "a") != 0));
if (!keys[i].empty())
{
CHECK(v.contains(keys[i].substr(1)) == (distinct.count(keys[i].substr(1)) != 0));
}
}
}
SECTION("shrink_to_fit releases the tables' spare capacity")
{
const auto make_text = [](int objects, int members)
{
std::string text = "[";
for (int object = 0; object < objects; ++object)
{
text += object != 0 ? ",{" : "{";
for (int i = 0, n = members + object; i < n; ++i)
{
text += (i != 0 ? ",\"" : "\"") + std::to_string(i) + "\":" + std::to_string(i);
}
text += '}';
}
return text + "]";
};
const std::string small_text = make_text(5, 150);
const std::string big_text = make_text(40, 400);
// reading a big text, and then a small one, leaves the spare capacity
// of the big one: shrink_to_fit() brings the document to the size of
// one parsed from the small text alone
json_document d = json_document::parse(big_text);
const std::size_t big = d.memory_usage();
d.read(small_text);
CHECK(d.memory_usage() >= big);
d.shrink_to_fit();
json_document fresh = json_document::parse(small_text);
fresh.shrink_to_fit();
CHECK(d.memory_usage() == fresh.memory_usage());
CHECK(d.memory_usage() < big / 2);
CHECK(d.root() == json::parse(small_text));
for (int object = 0; object < 5; ++object)
{
const json_view v = d.root()[static_cast<std::size_t>(object)];
for (int i = 0, n = 150 + object; i < n; ++i)
{
CHECK(v[std::to_string(i)].get<int>() == i);
}
}
}
SECTION("nested, reused, and in arrays")
{
std::string inner = "{";
for (int i = 0; i < 300; ++i)
{
inner += (i != 0 ? ",\"m" : "\"m") + std::to_string(i) + "\":" + std::to_string(i);
}
inner += '}';
const std::string text = "[" + inner + ",{\"x\":" + inner + "}," + inner + "]";
json_document d = json_document::parse(text);
CHECK(d.root()[0]["m299"].get<int>() == 299);
CHECK(d.root()[1]["x"]["m150"].get<int>() == 150);
CHECK(d.root()[2]["m0"].get<int>() == 0);
const std::size_t with_index = d.memory_usage();
d.read(std::string("{\"small\": 1}"));
CHECK(d.root()["small"].get<int>() == 1);
d.read(text);
CHECK(d.root()[2]["m7"].get<int>() == 7);
CHECK(d.memory_usage() >= with_index / 2);
}
}
-298
View File
@@ -1,298 +0,0 @@
// __ _____ _____ _____
// __| | __| | | | JSON for Modern C++ (supporting code)
// | | |__ | | | | | | version 3.12.0
// |_____|_____|_____|_|___| https://github.com/nlohmann/json
//
// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
// SPDX-License-Identifier: MIT
#include "doctest_compatibility.h"
#include <nlohmann/json_view.hpp>
using nlohmann::json;
using nlohmann::ordered_json;
using nlohmann::json_document;
using nlohmann::ordered_json_editable_document;
using nlohmann::json_view;
using nlohmann::ordered_json_document;
using nlohmann::ordered_json_view;
#include <algorithm>
#include <array>
#include <cmath>
#include <cstddef>
#include <cstdint>
#include <cstring>
#include <iomanip>
#include <map>
#include <random>
#include <set>
#include <sstream>
#include <string>
#include <vector>
// These tests were split off unit-json_view_dump.cpp, whose object file got too large for the MinGW
// linker (see json_view_test_helpers.hpp). Like that file, this one is also built
// with C++17, as it mentions JSON_HAS_CPP_17.
TEST_CASE("json_view dump: escaping, nesting, and output buffers")
{
SECTION("members in document order, all of them")
{
const json_document d = json_document::parse(R"({"b": 1, "a": 2, "b": 3})");
CHECK(d.root().dump() == R"({"b":1,"a":2,"b":3})");
CHECK(d.root().dump(1) == "{\n \"b\": 1,\n \"a\": 2,\n \"b\": 3\n}");
// dump() writes all members, though the lookup finds the first
CHECK(d.root()["b"].dump() == "1");
}
SECTION("deep nesting")
{
const std::string deep = std::string(100000, '[') + std::string(100000, ']');
const json_document deep_document = json_document::parse(deep);
CHECK(deep_document.root().dump() == deep);
}
SECTION("ensure_ascii: a character that needs an escape at each position of a string")
{
// string lengths around the width of the vector steps, in a string value, a key, and a value near the end of the text
for (const char* const special :
{
"\xC3\xA9", "\xE4\xB8\xAD", "\xF0\x9F\x98\x80", "\x7F", "\\n", "\\u0001", "\\\"", "\\\\"
})
{
for (std::size_t length = 0; length <= 40; ++length)
{
for (std::size_t position = 0; position <= length; ++position)
{
std::string content(length, 'a');
content.insert(position, special);
const std::array<std::string, 3> texts =
{
{
"\"" + content + "\"",
"[\"" + content + "\"]",
"{\"" + content + "\":1}",
}
};
for (const std::string& text : texts)
{
CAPTURE(text)
const ordered_json_document d = ordered_json_document::parse(text);
const ordered_json j = ordered_json::parse(text);
CHECK(d.root().dump(-1, ' ', true) == j.dump(-1, ' ', true));
CHECK(d.root().dump(2, ' ', true) == j.dump(2, ' ', true));
CHECK(d.root().dump() == j.dump());
}
}
}
}
}
SECTION("ensure_ascii: every character of the Basic Multilingual Plane and some beyond")
{
// (the two- and three-byte sequences, including the ranges that need a check: E0, ED, EF BF BF)
std::string text = "[";
std::size_t in_chunk = 0;
const auto append = [&](std::uint32_t cp)
{
if (cp < 0x80)
{
if (cp < 0x20 || cp == '"' || cp == '\\')
{
return;
}
text += static_cast<char>(cp);
}
else if (cp < 0x800)
{
text += static_cast<char>(0xC0 | (cp >> 6));
text += static_cast<char>(0x80 | (cp & 0x3F));
}
else if (cp < 0x10000)
{
text += static_cast<char>(0xE0 | (cp >> 12));
text += static_cast<char>(0x80 | ((cp >> 6) & 0x3F));
text += static_cast<char>(0x80 | (cp & 0x3F));
}
else
{
text += static_cast<char>(0xF0 | (cp >> 18));
text += static_cast<char>(0x80 | ((cp >> 12) & 0x3F));
text += static_cast<char>(0x80 | ((cp >> 6) & 0x3F));
text += static_cast<char>(0x80 | (cp & 0x3F));
}
};
for (std::uint32_t cp = 0x20; cp < 0x10400; ++cp)
{
if (cp >= 0xD800 && cp < 0xE000)
{
continue;
}
if (in_chunk == 0)
{
text += text.size() > 1 ? ",\"" : "\"";
}
append(cp);
if (++in_chunk == 37)
{
text += "\"";
in_chunk = 0;
}
}
text += in_chunk != 0 ? "\"]" : "]";
const ordered_json_document d = ordered_json_document::parse(text);
const ordered_json j = ordered_json::parse(text);
CHECK(d.root().dump(-1, ' ', true) == j.dump(-1, ' ', true));
CHECK(d.root().dump(2, ' ', true) == j.dump(2, ' ', true));
CHECK(d.root().dump() == j.dump());
CHECK(d.root().dump(2) == j.dump(2));
}
SECTION("deep nesting, indented")
{
// indentations of up to and beyond the width of the writer's fixed-size copy
for (const int depth :
{
1, 5, 20, 70, 300
})
{
std::string text;
for (int i = 0; i < depth; ++i)
{
text += i % 2 == 0 ? "[1," : R"({"k":2,"\u00e9":)";
}
text += "[]";
for (int i = depth - 1; i >= 0; --i)
{
text += i % 2 == 0 ? "]" : "}";
}
const ordered_json_document d = ordered_json_document::parse(text);
const ordered_json j = ordered_json::parse(text);
for (const int indent :
{
0, 1, 2, 3, 8
})
{
CHECK(d.root().dump(indent) == j.dump(indent));
CHECK(d.root().dump(indent, '\t') == j.dump(indent, '\t'));
}
}
}
SECTION("the output buffer of a small value is small")
{
// an escaped key after the value: its node lies in the arena, so the
// source extent of the value cannot be read from the next node
const std::string big(100000, 'a');
const std::string text = R"({"small":1,"list":[1,2,3],"k\n":")" + big + R"("})";
const json_document d = json_document::parse(text);
const auto small = d.root()["small"].dump();
CHECK(small == "1");
CHECK(small.capacity() < 4096);
const auto list = d.root()["list"].dump();
CHECK(list == "[1,2,3]");
CHECK(list.capacity() < 4096);
CHECK(d.root()["list"].dump(2).capacity() < 4096);
// the whole document and the large value are unaffected
CHECK(d.root().dump() == ordered_json::parse(text).dump());
CHECK(d.root()["k\n"].dump() == "\"" + big + "\"");
}
SECTION("output that outgrows the estimate")
{
// ensure_ascii writes six bytes for each two-byte character
std::string chars;
for (int i = 0; i < 5000; ++i)
{
chars += "\xC3\xA9";
}
const json_document d = json_document::parse(R"({"a":")" + chars + R"(","k\n":1})");
const json expected = json::parse("\"" + chars + "\"");
CHECK(d.root()["a"].dump(-1, ' ', true) == expected.dump(-1, ' ', true));
CHECK(d.root()["a"].dump(-1, ' ', true).size() == 2 + (5000 * 6));
}
SECTION("ensure_ascii with strings of the source, decoded strings, and edited strings")
{
// plain ASCII, non-ASCII, escaped (decoded), and mixed strings, as values and as keys;
// the second text has a DEL, which ensure_ascii writes as an escape
for (const char* const del :
{"", "\x7F"
})
{
const std::string text = std::string("{\"plain\":\"abc\",\"caf\xC3\xA9\":\"\xC3\xA9\xE2\x82\xAC\xF0\x9F\x98\x80\",")
+ "\"esc\\n\\\"\":\"a\\tb\\u00e4\\ud83d\\ude00\",\"del\":\"a" + del + "b\",\"\":\"\"," // NOLINT(modernize-raw-string-literal)
+ "\"list\":[\"x\",\"\xC3\xBC\",\"\\\\\",\"long ASCII string with more than thirty-two bytes in it\","
+ "\"long string with more than thirty-two bytes and one non-ASCII byte \xC3\xB6\"],"
+ "\"n\":[1,2.5,-0,true,null]}";
const ordered_json j = ordered_json::parse(text);
const ordered_json_document d = ordered_json_document::parse(text);
CHECK(d.root().dump(-1, ' ', true) == j.dump(-1, ' ', true));
CHECK(d.root().dump(4, ' ', true) == j.dump(4, ' ', true));
CHECK(d.root().dump() == j.dump());
CHECK(d.root()["list"].dump(-1, ' ', true) == j["list"].dump(-1, ' ', true));
CHECK(d.root()["del"].dump(-1, ' ', true) == j["del"].dump(-1, ' ', true));
// strings that an edit wrote (the source strings that they replace were plain)
ordered_json_editable_document e = ordered_json_editable_document::parse(text);
ordered_json k = j;
e.set(e.root()["plain"], std::string("\xC3\xA4gypten"));
k["plain"] = "\xC3\xA4gypten";
e.set(e.root()["list"][0], std::string("ascii after edit"));
k["list"][0] = "ascii after edit";
e.set(e.root()["list"][1], std::string("\xC3\xA4"));
k["list"][1] = "\xC3\xA4";
e.set(e.root()["del"], std::string("tab\there"));
k["del"] = "tab\there";
CHECK(e.root().dump(-1, ' ', true) == k.dump(-1, ' ', true));
CHECK(e.root().dump(2, ' ', true) == k.dump(2, ' ', true));
CHECK(e.root().dump() == k.dump());
// strings that were edited from or to ASCII text
e.set(e.root()["list"][2], std::string("\xC3\xA4"));
k["list"][2] = "\xC3\xA4";
e.set(e.root()["list"][4], std::string("plain again"));
k["list"][4] = "plain again";
CHECK(e.root().dump(-1, ' ', true) == k.dump(-1, ' ', true));
}
}
SECTION("ensure_ascii with DEL or a non-ASCII character at every position")
{
// the check whether a string of the source has no byte >= 0x7F reads
// eight bytes at a time and then the rest one by one
for (std::size_t length = 1; length <= 20; ++length)
{
for (std::size_t pos = 0; pos < length; ++pos)
{
for (const char* const c :
{
"\x7F", "\x7E", "\xC3\xA4", "\xC3\xBF" // NOLINT(modernize-raw-string-literal)
})
{
const std::string s = std::string(pos, 'a') + c + std::string(length - pos - 1, 'b');
std::string text = "[\"";
text.append(s).append("\",{\"").append(s).append("\":1}]");
const json_document d = json_document::parse(text);
const json j = json::parse(text);
CHECK(d.root().dump(-1, ' ', true) == j.dump(-1, ' ', true));
CHECK(d.root().dump(1, ' ', true) == j.dump(1, ' ', true));
}
}
}
}
SECTION("streams and discarded views")
{
const json_document d = json_document::parse(R"({"a": [1, 2]})");
std::ostringstream compact;
compact << d.root();
CHECK(compact.str() == R"({"a":[1,2]})");
std::ostringstream pretty;
pretty << std::setw(2) << std::setfill('.') << d.root() << d.root()["a"];
CHECK(pretty.str() == "{\n..\"a\": [\n....1,\n....2\n..]\n}[1,2]");
CHECK(json_view().dump() == json(json::value_t::discarded).dump());
}
}
-544
View File
@@ -1,544 +0,0 @@
// __ _____ _____ _____
// __| | __| | | | JSON for Modern C++ (supporting code)
// | | |__ | | | | | | version 3.12.0
// |_____|_____|_____|_|___| https://github.com/nlohmann/json
//
// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
// SPDX-License-Identifier: MIT
#include "doctest_compatibility.h"
#include <nlohmann/json_view.hpp>
using nlohmann::json;
using nlohmann::ordered_json;
using nlohmann::json_document;
using nlohmann::ordered_json_editable_document;
using nlohmann::json_view;
using nlohmann::ordered_json_document;
using nlohmann::ordered_json_view;
#include "json_view_test_helpers.hpp"
using json_view_test::generator;
#include <algorithm>
#include <array>
#include <cmath>
#include <cstddef>
#include <cstdint>
#include <cstring>
#include <iomanip>
#include <map>
#include <random>
#include <set>
#include <sstream>
#include <string>
#include <vector>
// These tests were split off unit-json_view_dump.cpp, whose object file got too large for the MinGW
// linker (see json_view_test_helpers.hpp). Like that file, this one is also built
// with C++17, as it mentions JSON_HAS_CPP_17.
TEST_CASE("json_view comparison")
{
SECTION("equality of the values parse() produces")
{
generator g;
std::vector<std::string> texts;
for (int i = 0; i < 600; ++i)
{
std::string text;
g.value(text, 0);
texts.push_back(text);
// the same value written differently: sorted keys, canonical numbers
texts.push_back(json::parse(text).dump(1));
}
for (std::size_t i = 0; i + 2 < texts.size(); ++i)
{
for (std::size_t k = i; k < i + 3; ++k)
{
CAPTURE(texts[i])
CAPTURE(texts[k])
const json_document a = json_document::parse(texts[i]);
const json_document b = json_document::parse(texts[k]);
const json ja = json::parse(texts[i]);
const json jb = json::parse(texts[k]);
CHECK((a.root() == b.root()) == (ja == jb));
CHECK((a.root() != b.root()) == (ja != jb));
CHECK((a.root() == jb) == (ja == jb));
CHECK((jb == a.root()) == (ja == jb));
CHECK((a.root() != jb) == (ja != jb));
CHECK((jb != a.root()) == (ja != jb));
// ordered_json compares members in order
const ordered_json_document oa = ordered_json_document::parse(texts[i]);
const ordered_json_document ob = ordered_json_document::parse(texts[k]);
const ordered_json oja = ordered_json::parse(texts[i]);
const ordered_json ojb = ordered_json::parse(texts[k]);
CHECK((oa.root() == ob.root()) == (oja == ojb));
CHECK((oa.root() == ojb) == (oja == ojb));
}
}
}
SECTION("numbers, duplicate keys, member order")
{
const auto same = [](const char* x, const char* y)
{
const json_document dx = json_document::parse(x);
const json_document dy = json_document::parse(y);
return dx.root() == dy.root();
};
CHECK(same("1", "1.0"));
CHECK(same("[1, -1, 2.5]", "[1.0, -1.0, 25e-1]"));
CHECK(!same("1", "1.5"));
CHECK(same("18446744073709551615", "18446744073709551615"));
CHECK(same(R"({"a": 1, "a": 2})", R"({"a": 2})"));
CHECK(!same(R"({"a": 1, "a": 2})", R"({"a": 1})"));
CHECK(same(R"({"a": 1, "b": 2})", R"({"b": 2, "a": 1})"));
CHECK(!same(R"({"a": 1})", R"({"a": 1, "b": 2})"));
CHECK(!same("[1, 2]", "[2, 1]"));
CHECK(!same("\"a\"", "\"b\""));
CHECK(same("\"\\u00e9\"", "\"\xc3\xa9\""));
CHECK(!same("null", "false"));
CHECK(!same("[]", "{}"));
const ordered_json_document dup = ordered_json_document::parse(R"({"a": 1, "b": 2, "a": 3})");
const ordered_json_document last = ordered_json_document::parse(R"({"a": 3, "b": 2})");
CHECK(dup.root() == last.root());
// (== compares as parse() resolves duplicates, a lookup finds the first)
CHECK(dup.root()["a"].materialize() == 1);
CHECK(dup.root()["a"] != last.root()["a"]);
const ordered_json_document ab = ordered_json_document::parse(R"({"a": 1, "b": 2})");
const ordered_json_document ba = ordered_json_document::parse(R"({"b": 2, "a": 1})");
CHECK(ab.root() != ba.root());
// discarded values compare as basic_json's do
const json discarded(json::value_t::discarded);
CHECK((json_view() == json_view()) == (discarded == discarded)); // NOLINT(readability-container-size-empty): operator== is tested
CHECK((json_view() == discarded) == (discarded == discarded)); // NOLINT(readability-container-size-empty)
const json_document null_document = json_document::parse("null");
CHECK(!(json_view() == null_document.root())); // NOLINT(readability-container-size-empty)
CHECK(!(null_document.root() == discarded));
}
SECTION("deep nesting")
{
const std::string deep = std::string(100000, '[') + std::string(100000, ']');
const json_document a = json_document::parse(deep);
const json_document b = json_document::parse(deep);
CHECK(a.root() == b.root());
CHECK(a.root() == json::parse(deep));
const std::string other = std::string(100000, '[') + "1" + std::string(100000, ']');
const json_document c = json_document::parse(other);
CHECK(a.root() != c.root());
}
}
TEST_CASE("json_view large objects")
{
// objects with 128 members or more are looked up with a hash index
for (const std::size_t members :
{
127u, 128u, 129u, 10000u
})
{
CAPTURE(members)
std::string text = "{";
for (std::size_t i = 0; i < members; ++i)
{
text += (i != 0 ? ",\"" : "\"") + std::string(i % 23, 'k') + std::to_string(i) + (i % 7 == 0 ? "\\n" : "") + "\":" + std::to_string(i);
}
text += R"(,"":"empty key","k1":"a duplicate of an earlier key"})";
const json_document d = json_document::parse(text);
const json_view v = d.root();
const json j = json::parse(text);
for (std::size_t i = 0; i < members; ++i)
{
const std::string key = std::string(i % 23, 'k') + std::to_string(i) + (i % 7 == 0 ? "\n" : "");
CHECK(v[key].get<std::size_t>() == i);
CHECK(v.contains(key));
CHECK(v.find(key).key() == key);
CHECK(v.at(key).get<std::size_t>() == i);
CHECK(!v.contains(key + "x"));
}
CHECK(v[""].get_string() == "empty key");
CHECK(v["k1"].get<int>() == 1); // the first of duplicate keys, as for small objects
CHECK(!v.contains("missing"));
CHECK_THROWS_WITH_AS(v.at("missing"), "[json.exception.out_of_range.403] key 'missing' not found", json::out_of_range&);
CHECK(v == j);
CHECK(v.materialize() == j);
}
SECTION("duplicate keys: the first member wins, with and without a table")
{
// an object of `total` members: the keys "k0".."k<n-1>" in order, then
// three keys repeated twice more (one copy in the middle, one at the
// end), and two keys repeated once; the value of a member is its
// position, so that the first member of a key can be told apart
struct member
{
std::string key;
std::size_t position;
};
const auto make_members = [](std::size_t total)
{
std::vector<std::string> keys;
for (std::size_t i = 0; i + 8 < total; ++i)
{
keys.push_back("k" + std::to_string(i));
}
const std::size_t n = keys.size();
const std::array<std::size_t, 3> triple = {{3, 17, n - 1}};
const std::array<std::size_t, 2> twice = {{5, n / 2}};
std::vector<std::string> ordered = keys;
for (const std::size_t i : triple)
{
ordered.insert(ordered.begin() + static_cast<std::ptrdiff_t>(ordered.size() / 2), keys[i]);
}
for (const std::size_t i : twice)
{
ordered.insert(ordered.begin() + static_cast<std::ptrdiff_t>(ordered.size() / 3), keys[i]);
}
for (const std::size_t i : triple)
{
ordered.push_back(keys[i]);
}
std::vector<member> result;
result.reserve(ordered.size());
for (std::size_t i = 0; i < ordered.size(); ++i)
{
result.push_back({ordered[i], i});
}
return result;
};
// 100 and 127 members: no table; 128 members and more: a table
for (const std::size_t total :
{
100u, 127u, 128u, 200u, 5000u
})
{
CAPTURE(total)
const std::vector<member> members = make_members(total);
REQUIRE(members.size() >= total);
REQUIRE(members.size() >= 100);
std::string text = "{";
std::map<std::string, std::size_t> first;
std::map<std::string, std::size_t> last;
std::map<std::string, std::size_t> occurrences;
for (const member& m : members)
{
text += (text.size() > 1 ? ",\"" : "\"") + m.key + "\":" + std::to_string(m.position);
first.insert({m.key, m.position});
last[m.key] = m.position;
++occurrences[m.key];
}
text += '}';
REQUIRE(first.size() < members.size());
const json_document d = json_document::parse(text);
const json_view v = d.root();
const json j = json::parse(text);
CHECK(v.size() == members.size()); // every occurrence is visited
const json m = v.materialize();
for (const auto& entry : first)
{
CAPTURE(entry.first)
const std::size_t expected = entry.second;
CHECK(v[entry.first].get<std::size_t>() == expected);
CHECK(v.at(entry.first).get<std::size_t>() == expected);
CHECK(v.find(entry.first).value().get<std::size_t>() == expected);
CHECK(v.value(entry.first, std::size_t{0}) == expected);
CHECK(v.contains(entry.first));
CHECK(v.count(entry.first) == occurrences[entry.first]);
const std::string pointer = "/" + entry.first;
CHECK(v[json::json_pointer(pointer)].get<std::size_t>() == expected);
CHECK(v.at(json::json_pointer(pointer)).get<std::size_t>() == expected);
CHECK(v.value(json::json_pointer(pointer), std::size_t{0}) == expected);
CHECK(v.contains(json::json_pointer(pointer)));
// materialize() and parse() keep the last value instead
CHECK(j[entry.first].get<std::size_t>() == last.at(entry.first));
CHECK(m[entry.first].get<std::size_t>() == last.at(entry.first));
}
CHECK(!v.contains("k"));
CHECK(v["missing"].is_discarded());
CHECK(v.materialize() == j);
CHECK(v == j);
}
}
SECTION("colliding keys")
{
// the hash is not seeded, so keys that all land in one place must not
// make the table build quadratic: such an object gets no table and is
// searched linearly
constexpr std::size_t members = 300;
constexpr std::size_t table_size = 1024; // the table size for 300 members: the next power of two >= 600
std::vector<std::string> colliding;
std::vector<std::string> spread;
for (std::uint64_t counter = 0; colliding.size() < members || spread.size() < members; ++counter)
{
std::string key(8, 'a');
std::uint64_t x = counter;
for (std::size_t i = 0; i < 8; ++i, x /= 26)
{
key[i] = static_cast<char>('a' + (x % 26));
}
const bool lands_in_slot_zero = (nlohmann::detail::view::key_hash(key.data(), key.size()) & (table_size - 1)) == 0;
if (lands_in_slot_zero && colliding.size() < members)
{
colliding.push_back(key);
}
else if (!lands_in_slot_zero && spread.size() < members)
{
spread.push_back(key);
}
}
const auto make_text = [](const std::vector<std::string>& keys)
{
std::string text = "{";
for (std::size_t i = 0; i < keys.size(); ++i)
{
text += (i != 0 ? ",\"" : "\"") + keys[i] + "\":" + std::to_string(i % 10);
}
return text + "}";
};
const std::string colliding_text = make_text(colliding);
const std::string spread_text = make_text(spread);
json_document with_collisions = json_document::parse(colliding_text);
json_document without_collisions = json_document::parse(spread_text);
for (const auto* pair :
{
&colliding, &spread
})
{
const json_view v = (pair == &colliding ? with_collisions : without_collisions).root();
for (std::size_t i = 0; i < members; ++i)
{
CAPTURE(i)
CHECK(v[(*pair)[i]].get<std::size_t>() == i % 10);
CHECK(v.at((*pair)[i]).get<std::size_t>() == i % 10);
CHECK(v.find((*pair)[i]).key() == (*pair)[i]);
CHECK(!v.contains((*pair)[i] + "x"));
}
CHECK(!v.contains("missing"));
}
CHECK(with_collisions.root() == json::parse(colliding_text));
// only the object with the spread keys got a table (both texts have the
// same length, so the tables are the only difference)
with_collisions.shrink_to_fit();
without_collisions.shrink_to_fit();
CHECK(without_collisions.memory_usage() >= with_collisions.memory_usage() + (table_size * sizeof(std::uint32_t)));
}
SECTION("keys that differ in their last bytes are spread over the table")
{
// The hash must spread the usual families of keys (numbered names, hex
// strings, dates, short names): a key farther than index_max_displacement
// from its home slot would leave the object without a table. The keys
// are placed with linear probing, as the table does.
const auto max_displacement = [](const std::vector<std::string>& keys)
{
std::size_t slots = 16;
while (slots < 2 * keys.size())
{
slots *= 2;
}
std::vector<bool> used(slots, false);
std::size_t farthest = 0;
for (const std::string& key : keys)
{
std::size_t i = nlohmann::detail::conditional_static_cast<std::size_t>(nlohmann::detail::view::key_hash(key.data(), key.size())) & (slots - 1);
std::size_t distance = 0;
while (used[i])
{
i = (i + 1) & (slots - 1);
++distance;
}
used[i] = true;
farthest = (std::max)(farthest, distance);
}
return farthest;
};
// the keys of a printf-like pattern with one %d, %0Nd or %0Nx, formatted with a stream
// (a format string that is not a literal is a Flawfinder error)
const auto numbered = [](const char* format, int count, int step)
{
const std::string pattern(format);
const std::size_t percent = pattern.find('%');
std::size_t conversion = percent + 1;
std::size_t width = 0;
while (pattern[conversion] >= '0' && pattern[conversion] <= '9')
{
width = (width * 10) + static_cast<std::size_t>(pattern[conversion] - '0');
++conversion;
}
const bool hex = pattern[conversion] == 'x';
std::vector<std::string> keys;
for (int i = 0; i < count; ++i)
{
std::ostringstream key;
key << pattern.substr(0, percent) << std::setfill('0') << std::setw(static_cast<int>(width))
<< (hex ? std::hex : std::dec) << (i * step) << pattern.substr(conversion + 1);
keys.push_back(key.str());
}
return keys;
};
for (const char* format :
{"key%d", "%d", "item_%04d", "a%05d", "%03dxyz", "id%d", "user_%d", "%d_suffix", "0x%04x", "A%07d", "12345678%d", "1234567%d", "123456789%d",
"configuration_parameter_value_%04d_extra", "2026-01-%02dT00:00:00Z"
})
{
CAPTURE(format)
CHECK(max_displacement(numbered(format, std::string(format).find("%02d") != std::string::npos ? 60 : 1000, 1)) < nlohmann::detail::view::index_max_displacement); // NOLINT(abseil-string-find-str-contains)
CHECK(max_displacement(numbered(format, 600, 7)) < nlohmann::detail::view::index_max_displacement);
}
std::mt19937_64 rng(7); // NOLINT(cert-msc32-c,cert-msc51-cpp,bugprone-random-generator-seed)
for (const std::size_t length :
{
std::size_t{1}, std::size_t{2}, std::size_t{3}, std::size_t{5}, std::size_t{7}, std::size_t{8}, std::size_t{9}, std::size_t{12}, std::size_t{16}, std::size_t{17}, std::size_t{33}
})
{
CAPTURE(length)
std::set<std::string> distinct;
// (there are 26 and 676 keys of one and two letters)
std::size_t wanted = 700;
if (length == 1)
{
wanted = 26;
}
else if (length == 2)
{
wanted = 500;
}
while (distinct.size() < wanted)
{
std::string key(length, 'a');
for (char& c : key)
{
c = static_cast<char>('a' + (rng() % 26));
}
distinct.insert(key);
}
CHECK(max_displacement(std::vector<std::string>(distinct.begin(), distinct.end())) < nlohmann::detail::view::index_max_displacement);
}
}
SECTION("keys of every length that differ in one byte")
{
// In a large object, a key is found by comparing its bytes with those of the member the
// table points to: up to 16 bytes as two overlapping words, longer ones with memcmp.
// Keys of every length from 0 to 40, and keys that differ from them in one byte.
std::mt19937_64 rng(2026); // NOLINT(cert-msc32-c,cert-msc51-cpp,bugprone-random-generator-seed)
std::vector<std::string> keys;
std::set<std::string> distinct;
for (std::size_t length = 0; length <= 40; ++length)
{
for (int copy = 0; copy < 5; ++copy)
{
std::string key(length, 'a');
for (char& c : key)
{
c = static_cast<char>('a' + (rng() % 26));
}
if (distinct.insert(key).second)
{
keys.push_back(key);
}
}
}
std::string text = "{";
for (std::size_t i = 0; i < keys.size(); ++i)
{
text += (i != 0 ? ",\"" : "\"") + keys[i] + "\":" + std::to_string(i);
}
text += "}";
REQUIRE(keys.size() >= 128); // (a table is built for 128 members)
const json_document d = json_document::parse(text);
const json_view v = d.root();
for (std::size_t i = 0; i < keys.size(); ++i)
{
CAPTURE(keys[i])
CHECK(v[keys[i]].get<std::size_t>() == i);
CHECK(v.at(keys[i]).get<std::size_t>() == i);
CHECK(v.contains(keys[i]));
for (std::size_t at = 0; at < keys[i].size(); ++at)
{
std::string other = keys[i];
other[at] = other[at] == 'z' ? 'y' : 'z';
CAPTURE(other)
CHECK(v.contains(other) == (distinct.count(other) != 0));
}
CHECK(v.contains(keys[i] + "a") == (distinct.count(keys[i] + "a") != 0));
if (!keys[i].empty())
{
CHECK(v.contains(keys[i].substr(1)) == (distinct.count(keys[i].substr(1)) != 0));
}
}
}
SECTION("shrink_to_fit releases the tables' spare capacity")
{
const auto make_text = [](int objects, int members)
{
std::string text = "[";
for (int object = 0; object < objects; ++object)
{
text += object != 0 ? ",{" : "{";
for (int i = 0, n = members + object; i < n; ++i)
{
text += (i != 0 ? ",\"" : "\"") + std::to_string(i) + "\":" + std::to_string(i);
}
text += '}';
}
return text + "]";
};
const std::string small_text = make_text(5, 150);
const std::string big_text = make_text(40, 400);
// reading a big text, and then a small one, leaves the spare capacity
// of the big one: shrink_to_fit() brings the document to the size of
// one parsed from the small text alone
json_document d = json_document::parse(big_text);
const std::size_t big = d.memory_usage();
d.read(small_text);
CHECK(d.memory_usage() >= big);
d.shrink_to_fit();
json_document fresh = json_document::parse(small_text);
fresh.shrink_to_fit();
CHECK(d.memory_usage() == fresh.memory_usage());
CHECK(d.memory_usage() < big / 2);
CHECK(d.root() == json::parse(small_text));
for (int object = 0; object < 5; ++object)
{
const json_view v = d.root()[static_cast<std::size_t>(object)];
for (int i = 0, n = 150 + object; i < n; ++i)
{
CHECK(v[std::to_string(i)].get<int>() == i);
}
}
}
SECTION("nested, reused, and in arrays")
{
std::string inner = "{";
for (int i = 0; i < 300; ++i)
{
inner += (i != 0 ? ",\"m" : "\"m") + std::to_string(i) + "\":" + std::to_string(i);
}
inner += '}';
const std::string text = "[" + inner + ",{\"x\":" + inner + "}," + inner + "]";
json_document d = json_document::parse(text);
CHECK(d.root()[0]["m299"].get<int>() == 299);
CHECK(d.root()[1]["x"]["m150"].get<int>() == 150);
CHECK(d.root()[2]["m0"].get<int>() == 0);
const std::size_t with_index = d.memory_usage();
d.read(std::string("{\"small\": 1}"));
CHECK(d.root()["small"].get<int>() == 1);
d.read(text);
CHECK(d.root()[2]["m7"].get<int>() == 7);
CHECK(d.memory_usage() >= with_index / 2);
}
}