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Author SHA1 Message Date
Niels Lohmann c637e73bea Remove unreachable branches from the binary writer
Coverage reported conditions in the binary writer that can never be
false, and marked the code behind them with LCOV_EXCL. Remove them
instead of excluding them:

- CBOR writes the length of a string, binary value, array, or object
  exactly like an unsigned integer, only with another major type. One
  function, write_cbor_head(), now writes both, so the integer tests
  cover every width and the four excluded 64-bit length branches are
  gone.
- A last `else if` whose condition holds for every remaining value
  (an unsigned value at most UINT64_MAX, a signed one in the range of
  int64_t) is now a plain `else`.
- Whether a signed integer fits into an int64 for UBJSON and BJData is
  decided by its type at compile time. Only an integer type wider than
  64 bits gets a range check and the high-precision fallback.
- The private get_impl(boolean_t*) was never called.

The UBJSON type prefix 'H' of an optimized container of unsigned
integers beyond the range of int64 was reachable although excluded; it
is tested now.

The output is unchanged.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-25 22:10:59 +02:00
5 changed files with 571 additions and 1417 deletions
+110 -219
View File
@@ -168,92 +168,20 @@ class binary_writer
if (j.m_data.m_value.number_integer >= 0)
{
// CBOR does not differentiate between positive signed
// integers and unsigned integers. Therefore, we used the
// code from the value_t::number_unsigned case here.
if (j.m_data.m_value.number_integer <= 0x17)
{
write_number(static_cast<std::uint8_t>(j.m_data.m_value.number_integer));
}
else if (j.m_data.m_value.number_integer <= (std::numeric_limits<std::uint8_t>::max)())
{
oa.write_character(to_char_type(0x18));
write_number(static_cast<std::uint8_t>(j.m_data.m_value.number_integer));
}
else if (j.m_data.m_value.number_integer <= (std::numeric_limits<std::uint16_t>::max)())
{
oa.write_character(to_char_type(0x19));
write_number(static_cast<std::uint16_t>(j.m_data.m_value.number_integer));
}
else if (j.m_data.m_value.number_integer <= (std::numeric_limits<std::uint32_t>::max)())
{
oa.write_character(to_char_type(0x1A));
write_number(static_cast<std::uint32_t>(j.m_data.m_value.number_integer));
}
else
{
oa.write_character(to_char_type(0x1B));
write_number(static_cast<std::uint64_t>(j.m_data.m_value.number_integer));
}
// integers and unsigned integers
write_cbor_head(0x00, static_cast<std::uint64_t>(j.m_data.m_value.number_integer));
}
else
{
// The conversions below encode the sign in the first
// byte, and the value is converted to a positive number.
const auto positive_number = -1 - j.m_data.m_value.number_integer;
if (j.m_data.m_value.number_integer >= -24)
{
write_number(static_cast<std::uint8_t>(0x20 + positive_number));
}
else if (positive_number <= (std::numeric_limits<std::uint8_t>::max)())
{
oa.write_character(to_char_type(0x38));
write_number(static_cast<std::uint8_t>(positive_number));
}
else if (positive_number <= (std::numeric_limits<std::uint16_t>::max)())
{
oa.write_character(to_char_type(0x39));
write_number(static_cast<std::uint16_t>(positive_number));
}
else if (positive_number <= (std::numeric_limits<std::uint32_t>::max)())
{
oa.write_character(to_char_type(0x3A));
write_number(static_cast<std::uint32_t>(positive_number));
}
else
{
oa.write_character(to_char_type(0x3B));
write_number(static_cast<std::uint64_t>(positive_number));
}
// a negative integer n is encoded as -1 - n
write_cbor_head(0x20, static_cast<std::uint64_t>(-1 - j.m_data.m_value.number_integer));
}
break;
}
case value_t::number_unsigned:
{
if (j.m_data.m_value.number_unsigned <= 0x17)
{
write_number(static_cast<std::uint8_t>(j.m_data.m_value.number_unsigned));
}
else if (j.m_data.m_value.number_unsigned <= (std::numeric_limits<std::uint8_t>::max)())
{
oa.write_character(to_char_type(0x18));
write_number(static_cast<std::uint8_t>(j.m_data.m_value.number_unsigned));
}
else if (j.m_data.m_value.number_unsigned <= (std::numeric_limits<std::uint16_t>::max)())
{
oa.write_character(to_char_type(0x19));
write_number(static_cast<std::uint16_t>(j.m_data.m_value.number_unsigned));
}
else if (j.m_data.m_value.number_unsigned <= (std::numeric_limits<std::uint32_t>::max)())
{
oa.write_character(to_char_type(0x1A));
write_number(static_cast<std::uint32_t>(j.m_data.m_value.number_unsigned));
}
else
{
oa.write_character(to_char_type(0x1B));
write_number(static_cast<std::uint64_t>(j.m_data.m_value.number_unsigned));
}
write_cbor_head(0x00, j.m_data.m_value.number_unsigned);
break;
}
@@ -283,33 +211,7 @@ class binary_writer
case value_t::string:
{
// step 1: write control byte and the string length
const auto N = j.m_data.m_value.string->size();
if (N <= 0x17)
{
write_number(static_cast<std::uint8_t>(0x60 + N));
}
else if (N <= (std::numeric_limits<std::uint8_t>::max)())
{
oa.write_character(to_char_type(0x78));
write_number(static_cast<std::uint8_t>(N));
}
else if (N <= (std::numeric_limits<std::uint16_t>::max)())
{
oa.write_character(to_char_type(0x79));
write_number(static_cast<std::uint16_t>(N));
}
else if (N <= (std::numeric_limits<std::uint32_t>::max)())
{
oa.write_character(to_char_type(0x7A));
write_number(static_cast<std::uint32_t>(N));
}
// LCOV_EXCL_START
else if (N <= (std::numeric_limits<std::uint64_t>::max)())
{
oa.write_character(to_char_type(0x7B));
write_number(static_cast<std::uint64_t>(N));
}
// LCOV_EXCL_STOP
write_cbor_head(0x60, j.m_data.m_value.string->size());
// step 2: write the string
oa.write_characters(
@@ -321,33 +223,7 @@ class binary_writer
case value_t::array:
{
// step 1: write control byte and the array size
const auto N = j.m_data.m_value.array->size();
if (N <= 0x17)
{
write_number(static_cast<std::uint8_t>(0x80 + N));
}
else if (N <= (std::numeric_limits<std::uint8_t>::max)())
{
oa.write_character(to_char_type(0x98));
write_number(static_cast<std::uint8_t>(N));
}
else if (N <= (std::numeric_limits<std::uint16_t>::max)())
{
oa.write_character(to_char_type(0x99));
write_number(static_cast<std::uint16_t>(N));
}
else if (N <= (std::numeric_limits<std::uint32_t>::max)())
{
oa.write_character(to_char_type(0x9A));
write_number(static_cast<std::uint32_t>(N));
}
// LCOV_EXCL_START
else if (N <= (std::numeric_limits<std::uint64_t>::max)())
{
oa.write_character(to_char_type(0x9B));
write_number(static_cast<std::uint64_t>(N));
}
// LCOV_EXCL_STOP
write_cbor_head(0x80, j.m_data.m_value.array->size());
// step 2: write each element
for (const auto& el : *j.m_data.m_value.array)
@@ -376,7 +252,7 @@ class binary_writer
write_number(static_cast<std::uint8_t>(0xda));
write_number(static_cast<std::uint32_t>(j.m_data.m_value.binary->subtype()));
}
else if (j.m_data.m_value.binary->subtype() <= (std::numeric_limits<std::uint64_t>::max)())
else
{
write_number(static_cast<std::uint8_t>(0xdb));
write_number(static_cast<std::uint64_t>(j.m_data.m_value.binary->subtype()));
@@ -385,32 +261,7 @@ class binary_writer
// step 1: write control byte and the binary array size
const auto N = j.m_data.m_value.binary->size();
if (N <= 0x17)
{
write_number(static_cast<std::uint8_t>(0x40 + N));
}
else if (N <= (std::numeric_limits<std::uint8_t>::max)())
{
oa.write_character(to_char_type(0x58));
write_number(static_cast<std::uint8_t>(N));
}
else if (N <= (std::numeric_limits<std::uint16_t>::max)())
{
oa.write_character(to_char_type(0x59));
write_number(static_cast<std::uint16_t>(N));
}
else if (N <= (std::numeric_limits<std::uint32_t>::max)())
{
oa.write_character(to_char_type(0x5A));
write_number(static_cast<std::uint32_t>(N));
}
// LCOV_EXCL_START
else if (N <= (std::numeric_limits<std::uint64_t>::max)())
{
oa.write_character(to_char_type(0x5B));
write_number(static_cast<std::uint64_t>(N));
}
// LCOV_EXCL_STOP
write_cbor_head(0x40, N);
// step 2: write each element
oa.write_characters(
@@ -423,33 +274,7 @@ class binary_writer
case value_t::object:
{
// step 1: write control byte and the object size
const auto N = j.m_data.m_value.object->size();
if (N <= 0x17)
{
write_number(static_cast<std::uint8_t>(0xA0 + N));
}
else if (N <= (std::numeric_limits<std::uint8_t>::max)())
{
oa.write_character(to_char_type(0xB8));
write_number(static_cast<std::uint8_t>(N));
}
else if (N <= (std::numeric_limits<std::uint16_t>::max)())
{
oa.write_character(to_char_type(0xB9));
write_number(static_cast<std::uint16_t>(N));
}
else if (N <= (std::numeric_limits<std::uint32_t>::max)())
{
oa.write_character(to_char_type(0xBA));
write_number(static_cast<std::uint32_t>(N));
}
// LCOV_EXCL_START
else if (N <= (std::numeric_limits<std::uint64_t>::max)())
{
oa.write_character(to_char_type(0xBB));
write_number(static_cast<std::uint64_t>(N));
}
// LCOV_EXCL_STOP
write_cbor_head(0xA0, j.m_data.m_value.object->size());
// step 2: write each element
for (const auto& el : *j.m_data.m_value.object)
@@ -517,7 +342,7 @@ class binary_writer
oa.write_character(to_char_type(0xCE));
write_number(static_cast<std::uint32_t>(j.m_data.m_value.number_integer));
}
else if (j.m_data.m_value.number_unsigned <= (std::numeric_limits<std::uint64_t>::max)())
else
{
// uint 64
oa.write_character(to_char_type(0xCF));
@@ -552,8 +377,7 @@ class binary_writer
oa.write_character(to_char_type(0xD2));
write_number(static_cast<std::int32_t>(j.m_data.m_value.number_integer));
}
else if (j.m_data.m_value.number_integer >= (std::numeric_limits<std::int64_t>::min)() &&
j.m_data.m_value.number_integer <= (std::numeric_limits<std::int64_t>::max)())
else
{
// int 64
oa.write_character(to_char_type(0xD3));
@@ -588,7 +412,7 @@ class binary_writer
oa.write_character(to_char_type(0xCE));
write_number(static_cast<std::uint32_t>(j.m_data.m_value.number_integer));
}
else if (j.m_data.m_value.number_unsigned <= (std::numeric_limits<std::uint64_t>::max)())
else
{
// uint 64
oa.write_character(to_char_type(0xCF));
@@ -1526,6 +1350,46 @@ class binary_writer
// CBOR //
//////////
/*!
@brief write the head of a CBOR data item
The head is the major type in the upper three bits of the first byte and
an argument - an unsigned integer, the length of a string, the number of
elements of a container - in the shortest of its encodings: in the lower
five bits of the first byte itself if it is at most 23, otherwise in the
1, 2, 4, or 8 bytes that follow (RFC 8949, section 3).
@param[in] major_type the major type, shifted into the upper three bits
@param[in] argument the argument of the data item
*/
void write_cbor_head(const std::uint8_t major_type, const std::uint64_t argument)
{
if (argument <= 0x17)
{
write_number(static_cast<std::uint8_t>(major_type + argument));
}
else if (argument <= (std::numeric_limits<std::uint8_t>::max)())
{
oa.write_character(to_char_type(static_cast<std::uint8_t>(major_type + 0x18)));
write_number(static_cast<std::uint8_t>(argument));
}
else if (argument <= (std::numeric_limits<std::uint16_t>::max)())
{
oa.write_character(to_char_type(static_cast<std::uint8_t>(major_type + 0x19)));
write_number(static_cast<std::uint16_t>(argument));
}
else if (argument <= (std::numeric_limits<std::uint32_t>::max)())
{
oa.write_character(to_char_type(static_cast<std::uint8_t>(major_type + 0x1A)));
write_number(static_cast<std::uint32_t>(argument));
}
else
{
oa.write_character(to_char_type(static_cast<std::uint8_t>(major_type + 0x1B)));
write_number(argument);
}
}
static constexpr CharType get_cbor_float_prefix(float /*unused*/)
{
return to_char_type(0xFA); // Single-Precision Float
@@ -1631,7 +1495,7 @@ class binary_writer
}
write_number(static_cast<std::int64_t>(n), use_bjdata);
}
else if (use_bjdata && n <= (std::numeric_limits<uint64_t>::max)())
else if (use_bjdata)
{
if (add_prefix)
{
@@ -1711,30 +1575,59 @@ class binary_writer
}
write_number(static_cast<uint32_t>(n), use_bjdata);
}
else if ((std::numeric_limits<std::int64_t>::min)() <= n && n <= (std::numeric_limits<std::int64_t>::max)())
{
if (add_prefix)
{
oa.write_character(to_char_type('L')); // int64
}
write_number(static_cast<std::int64_t>(n), use_bjdata);
}
// LCOV_EXCL_START
else
{
if (add_prefix)
{
oa.write_character(to_char_type('H')); // high-precision number
}
const auto number = BasicJsonType(n).dump();
write_number_with_ubjson_prefix(number.size(), true, use_bjdata);
for (std::size_t i = 0; i < number.size(); ++i)
{
oa.write_character(to_char_type(static_cast<std::uint8_t>(number[i])));
}
// every value of an integer type of at most 64 bits fits into an
// int64; only a wider type needs a range check
write_ubjson_int64_or_high_precision(n, add_prefix, use_bjdata,
std::integral_constant < bool, std::numeric_limits<NumberType>::digits <= std::numeric_limits<std::int64_t>::digits > {});
}
// LCOV_EXCL_STOP
}
template<typename NumberType>
void write_ubjson_int64_or_high_precision(const NumberType n, const bool add_prefix, const bool use_bjdata, std::true_type /*fits_int64*/)
{
if (add_prefix)
{
oa.write_character(to_char_type('L')); // int64
}
write_number(static_cast<std::int64_t>(n), use_bjdata);
}
template<typename NumberType>
void write_ubjson_int64_or_high_precision(const NumberType n, const bool add_prefix, const bool use_bjdata, std::false_type /*fits_int64*/)
{
if ((std::numeric_limits<std::int64_t>::min)() <= n && n <= (std::numeric_limits<std::int64_t>::max)())
{
write_ubjson_int64_or_high_precision(n, add_prefix, use_bjdata, std::true_type {});
return;
}
if (add_prefix)
{
oa.write_character(to_char_type('H')); // high-precision number
}
const auto number = BasicJsonType(n).dump();
write_number_with_ubjson_prefix(number.size(), true, use_bjdata);
for (std::size_t i = 0; i < number.size(); ++i)
{
oa.write_character(to_char_type(static_cast<std::uint8_t>(number[i])));
}
}
template<typename NumberType>
static constexpr CharType ubjson_int64_or_high_precision_prefix(const NumberType /*n*/, std::true_type /*fits_int64*/) noexcept
{
return 'L';
}
template<typename NumberType>
static CharType ubjson_int64_or_high_precision_prefix(const NumberType n, std::false_type /*fits_int64*/) noexcept
{
// anything outside of the range of an int64 is treated as a
// high-precision number
return ((std::numeric_limits<std::int64_t>::min)() <= n && n <= (std::numeric_limits<std::int64_t>::max)()) ? 'L' : 'H';
}
/*!
@@ -1776,12 +1669,10 @@ class binary_writer
{
return 'm';
}
if ((std::numeric_limits<std::int64_t>::min)() <= j.m_data.m_value.number_integer && j.m_data.m_value.number_integer <= (std::numeric_limits<std::int64_t>::max)())
{
return 'L';
}
// anything else is treated as a high-precision number
return 'H'; // LCOV_EXCL_LINE
// every value of an integer type of at most 64 bits fits into
// an int64; only a wider type needs a range check
return ubjson_int64_or_high_precision_prefix(j.m_data.m_value.number_integer,
std::integral_constant < bool, std::numeric_limits<typename BasicJsonType::number_integer_t>::digits <= std::numeric_limits<std::int64_t>::digits > {});
}
case value_t::number_unsigned:
@@ -1814,12 +1705,12 @@ class binary_writer
{
return 'L';
}
if (use_bjdata && j.m_data.m_value.number_unsigned <= (std::numeric_limits<std::uint64_t>::max)())
if (use_bjdata)
{
return 'M';
}
// anything else is treated as a high-precision number
return 'H'; // LCOV_EXCL_LINE
return 'H';
}
case value_t::number_float:
+168 -413
View File
@@ -2157,17 +2157,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
// value access //
//////////////////
/// get a boolean (explicit)
boolean_t get_impl(boolean_t* /*unused*/) const
{
if (JSON_HEDLEY_LIKELY(is_boolean()))
{
return m_data.m_value.boolean;
}
JSON_THROW(type_error::create(302, detail::concat("type must be boolean, but is ", type_name()), this));
}
/// get a pointer to the value (object)
object_t* get_impl_ptr(object_t* /*unused*/) noexcept
{
@@ -5996,240 +5985,21 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
{
// the patch
basic_json result(value_t::array);
diff_recursively(result, source, target, path, 0);
return result;
}
private:
/// @brief two arrays or two objects @ref diff_iteratively is diffing
struct diff_frame
{
diff_frame(const basic_json* source_, const basic_json* target_, const std::size_t path_length_) noexcept
: source(source_), target(target_), path_length(path_length_)
{}
// declared for GCC's -Weffc++, which asks for them in a class with
// pointer members and a non-trivial destructor; the exception
// specifications are left implicit, as GCC 4.8 rejects explicit ones
// that differ from them
diff_frame(const diff_frame&) = default;
diff_frame(diff_frame&&) = default;
diff_frame& operator=(const diff_frame&) = default;
diff_frame& operator=(diff_frame&&) = default;
~diff_frame() = default;
/// the values being diffed, both arrays or both objects
const basic_json* source;
const basic_json* target;
/// the length of their path in `current_path`
std::size_t path_length;
/// arrays: the next index to diff
std::size_t index = 0;
/// objects: the next member of source to look at
const_iterator member{}; // NOLINT(readability-redundant-member-init)
/// objects: the keys common to both, in source's order
std::vector<typename object_t::key_type> common_keys{}; // NOLINT(readability-redundant-member-init)
/// objects: the next entry of common_keys
std::size_t next_common = 0;
/// objects: the "add" operations for keys only target has
basic_json added_ops{}; // NOLINT(readability-redundant-member-init)
};
// The operations of a diff are built by the functions below rather than
// where they are needed: building one takes several temporaries, and
// unoptimized builds give each temporary a stack slot of its own in the
// function it appears in. In diff_recursively, which is on the call stack
// once per nesting level, that made every level cost kilobytes of stack.
/// @brief append a "replace" operation for @a path with @a value to @a result
static void diff_replace(basic_json& result, const string_t& path, const basic_json& value)
{
result.push_back(
{
{"op", "replace"}, {"path", path}, {"value", value}
});
}
/// @brief append a "remove" operation for @a path to @a result
static void diff_remove(basic_json& result, const string_t& path)
{
result.push_back(object(
{
{"op", "remove"}, {"path", path}
}));
}
/// @brief append an "add" operation for @a path with @a value to @a result
static void diff_add(basic_json& result, const string_t& path, const basic_json& value)
{
result.push_back(
{
{"op", "add"}, {"path", path}, {"value", value}
});
}
/// @brief append the "remove" operations for the elements of array
/// @a source from @a index on, and the "add" operations for the
/// elements of array @a target from source's size on, to @a result
static void diff_array_tails(basic_json& result, const basic_json& source, const basic_json& target,
const string_t& path, const std::size_t index)
{
// remove my remaining elements, highest index first; appending
// in that order avoids the quadratic reinsertion done before
for (std::size_t j = source.size(); j > index; --j)
{
diff_remove(result, detail::concat<string_t>(path, '/', detail::to_string<string_t>(j - 1)));
}
// add other remaining elements
for (std::size_t i = source.size(); i < target.size(); ++i)
{
diff_add(result, detail::concat<string_t>(path, "/-"), target[i]);
}
}
/*!
@brief compare the keys of objects @a source and @a target
If the keys both objects have are in the same order in both, and the keys
only @a target has come after them, stores the keys common to both in
source's order in @a common_keys, stores the "add" operations for the keys
only @a target has in @a added_ops, and returns true: the caller then diffs
the objects member by member. Otherwise, appends operations that remove
every member of @a source and add every member of @a target to @a result,
and returns false.
*/
static bool diff_object_keys(basic_json& result, const basic_json& source, const basic_json& target,
const string_t& path, std::vector<typename object_t::key_type>& common_keys,
basic_json& added_ops)
{
// first pass: record, for every source key, whether it is
// common to both objects (in source's iteration order) or
// was deleted (i.e., in source but not in target) -- this is
// a by-product of the target.find() call already needed to
// tell the two cases apart, so it adds no extra lookups. The
// "remove" ops themselves are emitted later, interleaved
// with the per-key diffs in the caller's fast path, to match
// source's original iteration order (as the original,
// pre-reordering-aware implementation did) instead of
// grouping all removes before all per-key diffs.
std::vector<typename object_t::key_type> common_keys_source_order;
for (auto it = source.cbegin(); it != source.cend(); ++it)
{
if (target.find(it.key()) != target.end())
{
common_keys_source_order.push_back(it.key());
}
}
// second pass: find keys that were added (i.e., in target but
// not in source), and record the keys common to both, in
// target's iteration order -- again a by-product of the
// source.find() call already needed to detect added keys. At
// the same time, determine whether every added key comes
// after every common key in target's order (a precondition
// for the fast path, which only ever appends new keys
// at the very end): for an object_t whose iteration order is
// a pure function of the key set (e.g. the default std::map,
// which always iterates in sorted key order), the order
// check further below is always true and this whole
// mechanism is effectively a no-op; it only matters for a
// reorderable object_t such as the one backing `ordered_json`.
// The patch ops for keys that were added (i.e., in target but not
// in source) are built here so the fast path can reuse
// them without a second source.find() per target key. Only
// used by the fast path -- the slow (reordering) path
// rebuilds "add" ops for every key itself.
std::vector<typename object_t::key_type> common_keys_target_order;
bool new_keys_form_suffix = true;
bool seen_new_key = false;
for (auto it = target.cbegin(); it != target.cend(); ++it)
{
if (source.find(it.key()) == source.end())
{
seen_new_key = true;
diff_add(added_ops, detail::concat<string_t>(path, '/', detail::escape(it.key())), it.value());
}
else
{
common_keys_target_order.push_back(it.key());
if (seen_new_key)
{
new_keys_form_suffix = false;
}
}
}
if (common_keys_source_order == common_keys_target_order && new_keys_form_suffix)
{
// fast path: order of common keys already matches (or the
// object_t's iteration order does not depend on
// insertion history), so a plain per-key diff is correct
// and minimal, as before
common_keys = std::move(common_keys_source_order);
return true;
}
// slow path: the common keys are in a different relative
// order in source and target (only possible for a
// reorderable object_t like ordered_map). Building a
// minimal reordering patch is a nontrivial (LCS-like)
// problem; instead, remove every source key -- both
// deleted keys (which must be removed regardless) and
// common keys (removed so they can be re-added in
// target's order) -- and re-add every key that should
// remain, with its final target value, in target's
// order. basic_json::patch()'s "add" operation on an
// object uses operator[], which appends at the end for a
// vector-backed insertion-ordered map when the key does
// not already exist -- so removing a key and then adding
// it moves it to the end, fixing its position.
for (auto it = source.cbegin(); it != source.cend(); ++it)
{
diff_remove(result, detail::concat<string_t>(path, '/', detail::escape(it.key())));
}
// add every key that is either common (just removed
// above) or brand new, in target's iteration order, so
// that the final order after applying the patch matches
// target exactly
for (auto it = target.cbegin(); it != target.cend(); ++it)
{
diff_add(result, detail::concat<string_t>(path, '/', detail::escape(it.key())), it.value());
}
return false;
}
/*!
@brief @ref diff, for values at nesting level @a depth, appending the
operations to @a result
Diffing two arrays or objects calls this function again, once per nesting
level, so values nested deeply enough used to exhaust the call stack and
terminate the process. The descent is bounded here: once @ref
detail::recursion_depth_limit levels have been entered, @ref
diff_iteratively diffs what is left without the call stack.
*/
static void diff_recursively(basic_json& result, const basic_json& source, const basic_json& target,
const string_t& path, const std::size_t depth)
{
// if the values are the same, there is nothing to do
// if the values are the same, return an empty patch
if (source == target)
{
return;
}
if (JSON_HEDLEY_UNLIKELY(depth >= detail::recursion_depth_limit()))
{
diff_iteratively(result, source, target, path);
return;
return result;
}
if (source.type() != target.type())
{
// different types: replace value
diff_replace(result, path, target);
return;
result.push_back(
{
{"op", "replace"}, {"path", path}, {"value", target}
});
return result;
}
switch (source.type())
@@ -6241,50 +6011,185 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
while (i < source.size() && i < target.size())
{
// recursive call to compare array values at index i
diff_recursively(result, source[i], target[i], detail::concat<string_t>(path, '/', detail::to_string<string_t>(i)), depth + 1);
auto temp_diff = diff(source[i], target[i], detail::concat<string_t>(path, '/', detail::to_string<string_t>(i)));
result.insert(result.end(), temp_diff.begin(), temp_diff.end());
++i;
}
// We now reached the end of at least one array
// in a second pass, traverse the remaining elements
diff_array_tails(result, source, target, path, i);
// remove my remaining elements, highest index first; appending
// in that order avoids the quadratic reinsertion done before
for (std::size_t j = source.size(); j > i; --j)
{
result.push_back(object(
{
{"op", "remove"},
{"path", detail::concat<string_t>(path, '/', detail::to_string<string_t>(j - 1))}
}));
}
i = source.size();
// add other remaining elements
while (i < target.size())
{
result.push_back(
{
{"op", "add"},
{"path", detail::concat<string_t>(path, "/-")},
{"value", target[i]}
});
++i;
}
break;
}
case value_t::object:
{
std::vector<typename object_t::key_type> common_keys;
basic_json added_ops(value_t::array);
if (diff_object_keys(result, source, target, path, common_keys, added_ops))
// first pass: record, for every source key, whether it is
// common to both objects (in source's iteration order) or
// was deleted (i.e., in source but not in target) -- this is
// a by-product of the target.find() call already needed to
// tell the two cases apart, so it adds no extra lookups. The
// "remove" ops themselves are emitted later, interleaved
// with the recursive per-key diffs in the fast path below,
// to match source's original iteration order (as the
// original, pre-reordering-aware implementation did) instead
// of grouping all removes before all recursive diffs.
std::vector<typename object_t::key_type> common_keys_source_order;
for (auto it = source.cbegin(); it != source.cend(); ++it)
{
// fast path: common_keys is, by construction, the
// subsequence of source's keys that are common to both
// objects, in source's iteration order -- so it can be
// walked in lockstep with `source` using a cheap key
// comparison instead of another lookup. Deleted keys
// (those source keys not in common_keys) are interleaved
// here too, in source's original order, to match the
// historical (pre-reordering-aware) output order.
auto common_it = common_keys.cbegin();
if (target.find(it.key()) != target.end())
{
common_keys_source_order.push_back(it.key());
}
}
// second pass: find keys that were added (i.e., in target but
// not in source), and record the keys common to both, in
// target's iteration order -- again a by-product of the
// source.find() call already needed to detect added keys. At
// the same time, determine whether every added key comes
// after every common key in target's order (a precondition
// for the fast path below, which only ever appends new keys
// at the very end): for an object_t whose iteration order is
// a pure function of the key set (e.g. the default std::map,
// which always iterates in sorted key order), the order
// check further below is always true and this whole
// mechanism is effectively a no-op; it only matters for a
// reorderable object_t such as the one backing `ordered_json`.
// patch ops for keys that were added (i.e., in target but not
// in source); built here so the fast path below can reuse
// them without a second source.find() per target key. Only
// used by the fast path -- the slow (reordering) path
// rebuilds "add" ops for every key itself.
std::vector<typename object_t::key_type> common_keys_target_order;
basic_json added_ops(value_t::array);
bool new_keys_form_suffix = true;
bool seen_new_key = false;
for (auto it = target.cbegin(); it != target.cend(); ++it)
{
if (source.find(it.key()) == source.end())
{
seen_new_key = true;
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
added_ops.push_back(
{
{"op", "add"}, {"path", path_key},
{"value", it.value()}
});
}
else
{
common_keys_target_order.push_back(it.key());
if (seen_new_key)
{
new_keys_form_suffix = false;
}
}
}
if (common_keys_source_order == common_keys_target_order && new_keys_form_suffix)
{
// fast path: order of common keys already matches (or the
// object_t's iteration order does not depend on
// insertion history), so a plain per-key recursive diff
// is correct and minimal, as before. common_keys_source_order
// is, by construction, the subsequence of source's keys
// that are common to both objects, in source's iteration
// order -- so it can be walked in lockstep with `source`
// using a cheap key comparison instead of another lookup.
// Deleted keys (those source keys not in common_keys_source_order)
// are interleaved here too, in source's original order, to
// match the historical (pre-reordering-aware) output order.
auto common_it = common_keys_source_order.cbegin();
for (auto it = source.cbegin(); it != source.cend(); ++it)
{
if (common_it != common_keys.cend() && it.key() == *common_it)
if (common_it != common_keys_source_order.cend() && it.key() == *common_it)
{
diff_recursively(result, it.value(), target[it.key()], detail::concat<string_t>(path, '/', detail::escape(it.key())), depth + 1);
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
auto temp_diff = diff(it.value(), target[it.key()], path_key);
result.insert(result.end(), temp_diff.begin(), temp_diff.end());
++common_it;
}
else
{
// found a key that is not in target -> remove it
diff_remove(result, detail::concat<string_t>(path, '/', detail::escape(it.key())));
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
result.push_back(object(
{
{"op", "remove"}, {"path", path_key}
}));
}
}
// append the "add" ops for brand-new keys collected by
// diff_object_keys -- no second source.find() per target
// key needed
// append the "add" ops for brand-new keys collected above
// during the pass over target -- no second source.find()
// per target key needed
result.insert(result.end(), added_ops.begin(), added_ops.end());
}
else
{
// slow path: the common keys are in a different relative
// order in source and target (only possible for a
// reorderable object_t like ordered_map). Building a
// minimal reordering patch is a nontrivial (LCS-like)
// problem; instead, remove every source key -- both
// deleted keys (which must be removed regardless) and
// common keys (removed so they can be re-added in
// target's order) -- and re-add every key that should
// remain, with its final target value, in target's
// order. basic_json::patch()'s "add" operation on an
// object uses operator[], which appends at the end for a
// vector-backed insertion-ordered map when the key does
// not already exist -- so removing a key and then adding
// it moves it to the end, fixing its position.
for (auto it = source.cbegin(); it != source.cend(); ++it)
{
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
result.push_back(object(
{
{"op", "remove"}, {"path", path_key}
}));
}
// add every key that is either common (just removed
// above) or brand new, in target's iteration order, so
// that the final order after applying the patch matches
// target exactly
for (auto it = target.cbegin(); it != target.cend(); ++it)
{
const auto path_key = detail::concat<string_t>(path, '/', detail::escape(it.key()));
result.push_back(
{
{"op", "add"}, {"path", path_key},
{"value", it.value()}
});
}
}
break;
}
@@ -6299,166 +6204,16 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
default:
{
// both primitive types: replace value
diff_replace(result, path, target);
result.push_back(
{
{"op", "replace"}, {"path", path}, {"value", target}
});
break;
}
}
return result;
}
/*!
@brief @ref diff without the call stack, appending the operations to
@a result
Produces the same operations as @ref diff_recursively. Only reached for
values nested more deeply than @ref detail::recursion_depth_limit.
*/
static void diff_iteratively(basic_json& result, const basic_json& source, const basic_json& target,
const string_t& path)
{
// The arrays and objects being diffed are kept on an explicit stack,
// and every pair of elements is still diffed completely before the
// next one, so the operations come out in the same order as in
// diff_recursively. The path of the values being diffed is kept in
// one buffer that grows and shrinks with the stack, rather than in a
// new string per level.
std::vector<diff_frame> stack;
string_t current_path = path;
// diff `s` against `t`, whose path is current_path: primitives,
// values of different types, and objects whose members were reordered
// are handled right away; arrays and other objects get a frame
const auto enter = [&result, &stack, &current_path](const basic_json & s, const basic_json & t)
{
// if the values are the same, there is nothing to do. Arrays and
// objects are not compared up front: comparing them visits
// everything below them, so doing that at every level would take
// quadratic time in the nesting depth - equal ones yield no
// operations anyway.
if ((!s.is_structured() || !t.is_structured()) && s == t)
{
return;
}
if (s.type() != t.type())
{
// different types: replace value
diff_replace(result, current_path, t);
return;
}
switch (s.type())
{
case value_t::array:
{
stack.emplace_back(&s, &t, current_path.size());
return;
}
case value_t::object:
{
std::vector<typename object_t::key_type> common_keys;
basic_json added_ops(value_t::array);
if (diff_object_keys(result, s, t, current_path, common_keys, added_ops))
{
// fast path: the frame walks source in lockstep with
// common_keys, as diff_recursively does, and appends
// added_ops once all members are done
stack.emplace_back(&s, &t, current_path.size());
stack.back().member = s.cbegin();
stack.back().common_keys = std::move(common_keys);
stack.back().added_ops = std::move(added_ops);
}
return;
}
case value_t::null:
case value_t::string:
case value_t::boolean:
case value_t::number_integer:
case value_t::number_unsigned:
case value_t::number_float:
case value_t::binary:
case value_t::discarded:
default:
{
// both primitive types: replace value
diff_replace(result, current_path, t);
return;
}
}
};
enter(source, target);
while (!stack.empty())
{
// invalidated when enter() pushes a frame and by the pop_back()
// at the end, so not used after either
diff_frame& frame = stack.back();
const std::size_t path_length = frame.path_length;
const std::size_t depth = stack.size();
if (frame.source->is_array())
{
const auto& source_array = *frame.source->m_data.m_value.array;
const auto& target_array = *frame.target->m_data.m_value.array;
// first pass: traverse common elements
if (frame.index < source_array.size() && frame.index < target_array.size())
{
const std::size_t i = frame.index++;
detail::concat_into(current_path, '/', detail::to_string<string_t>(i));
enter(source_array[i], target_array[i]); // may push, which invalidates `frame`
if (stack.size() == depth)
{
current_path.resize(path_length);
}
continue;
}
// We now reached the end of at least one array
// in a second pass, traverse the remaining elements
diff_array_tails(result, *frame.source, *frame.target, current_path, frame.index);
}
else
{
if (frame.member != frame.source->cend())
{
const const_iterator it = frame.member;
++frame.member;
if (frame.next_common < frame.common_keys.size() && it.key() == frame.common_keys[frame.next_common])
{
++frame.next_common;
const basic_json& target_value = (*frame.target)[it.key()];
detail::concat_into(current_path, '/', detail::escape(it.key()));
enter(it.value(), target_value); // may push, which invalidates `frame`
if (stack.size() == depth)
{
current_path.resize(path_length);
}
}
else
{
// found a key that is not in target -> remove it
diff_remove(result, detail::concat<string_t>(current_path, '/', detail::escape(it.key())));
}
continue;
}
// append the "add" ops for brand-new keys collected when the
// object was entered
result.insert(result.end(), frame.added_ops.begin(), frame.added_ops.end());
}
// this array or object is done: continue with the one it is in
stack.pop_back();
if (!stack.empty())
{
current_path.resize(stack.back().path_length);
}
}
}
public:
/// @}
////////////////////////////////
File diff suppressed because it is too large Load Diff
-153
View File
@@ -15,65 +15,8 @@ using nlohmann::json;
#endif
#include <fstream>
#include <string>
#include <vector>
#include "make_test_data_available.hpp"
namespace
{
// alternating objects and arrays nested `depth` levels deep, with members that
// depend on `variant` at some levels, so diffing two variants yields
// operations on many levels: replacing the innermost value, adding, removing,
// and (for ordered_json) reordering members, and changing array lengths
template<typename BasicJsonType>
BasicJsonType nested(const std::size_t depth, const int variant)
{
BasicJsonType value = variant;
for (std::size_t i = 0; i < depth; ++i)
{
if (i % 2 == 0)
{
BasicJsonType object = BasicJsonType::object();
if ((i + static_cast<std::size_t>(variant)) % 7 == 0)
{
object["x"] = i;
}
if (variant == 2 && i % 11 == 0)
{
object["z"] = "z";
}
object["a"] = std::move(value);
if (variant == 1 && i % 5 == 0)
{
object["y"] = 1;
}
value = std::move(object);
}
else
{
BasicJsonType array = BasicJsonType::array({std::move(value)});
if ((i + static_cast<std::size_t>(variant)) % 3 == 0)
{
array.push_back(i);
}
value = std::move(array);
}
}
return value;
}
// a path of `depth` reference tokens, as nested() nests its values
std::string nested_path(const std::size_t depth)
{
std::string path;
for (std::size_t i = depth; i > 0; --i)
{
path += (i - 1) % 2 == 0 ? "/a" : "/0";
}
return path;
}
} // namespace
TEST_CASE("JSON patch")
{
SECTION("examples from RFC 6902")
@@ -1808,99 +1751,3 @@ TEST_CASE("JSON patch - diff emits array removals in descending index order")
CHECK(source.patch(patch) == target);
}
}
TEST_CASE("JSON patch: diff of deeply nested values")
{
SECTION("the diff reproduces the target at every depth")
{
// depths on either side of the nesting depth up to which diff()
// recurses (detail::recursion_depth_limit(), 128); not every depth up
// to 300, as the test would then time out under Valgrind
std::vector<std::size_t> depths;
for (std::size_t depth = 0; depth <= 16; ++depth)
{
depths.push_back(depth);
}
for (std::size_t depth = 120; depth <= 136; ++depth)
{
depths.push_back(depth);
}
depths.push_back(300);
for (const auto depth : depths)
{
CAPTURE(depth);
for (int from = 0; from < 3; ++from)
{
for (int to = 0; to < 3; ++to)
{
CAPTURE(from);
CAPTURE(to);
const auto source = nested<json>(depth, from);
const auto target = nested<json>(depth, to);
const auto patch = json::diff(source, target);
CHECK(source.patch(patch) == target);
CHECK(patch.empty() == (from == to));
const auto ordered_source = nested<nlohmann::ordered_json>(depth, from);
const auto ordered_target = nested<nlohmann::ordered_json>(depth, to);
CHECK(ordered_source.patch(nlohmann::ordered_json::diff(ordered_source, ordered_target)) == ordered_target);
}
}
}
}
SECTION("a difference only in the innermost value is one replace operation")
{
for (std::size_t depth = 0; depth <= 300; ++depth)
{
CAPTURE(depth);
json source = 1;
json target = 2;
for (std::size_t i = 0; i < depth; ++i)
{
source = i % 2 == 0 ? json::object({{"a", std::move(source)}}) : json::array({std::move(source)});
target = i % 2 == 0 ? json::object({{"a", std::move(target)}}) : json::array({std::move(target)});
}
CHECK(json::diff(source, target, "/root") == json::array({{{"op", "replace"}, {"path", "/root" + nested_path(depth)}, {"value", 2}}}));
}
}
SECTION("values nested too deeply for the call stack (#5393)")
{
// diff() used to recurse once per nesting level, and compared the
// values with operator== on every level. The values are only
// parsed and diffed, never copied or compared, since those recurse
// too.
const std::size_t depth = 100000;
for (const bool objects :
{
false, true
})
{
CAPTURE(objects);
std::string source_text;
std::string target_text;
std::string equal_text;
std::string path;
for (std::size_t i = 0; i < depth; ++i)
{
source_text += objects ? "{\"a\":" : "[";
path += objects ? "/a" : "/0";
}
target_text = source_text + "2";
equal_text = source_text + "1";
source_text += "1";
const std::string closing(depth, objects ? '}' : ']');
const auto source = json::parse(source_text + closing);
const auto patch = json::diff(source, json::parse(target_text + closing));
REQUIRE(patch.size() == 1);
CHECK(patch[0]["op"] == "replace");
CHECK(patch[0]["path"] == path);
CHECK(patch[0]["value"] == 2);
CHECK(json::diff(source, json::parse(equal_text + closing)).empty());
}
}
}
+15
View File
@@ -2981,3 +2981,18 @@ TEST_CASE("UBJSON roundtrips" * doctest::skip())
}
}
}
TEST_CASE("UBJSON optimized array of unsigned integers beyond int64")
{
// UBJSON has no unsigned 64-bit type, so such values are written as
// high-precision numbers - also as the type of an optimized container
const json j = {18446744073709551615ULL, 9223372036854775808ULL};
const std::vector<std::uint8_t> expected =
{
'[', '$', 'H', '#', 'i', 2,
'i', 20, '1', '8', '4', '4', '6', '7', '4', '4', '0', '7', '3', '7', '0', '9', '5', '5', '1', '6', '1', '5',
'i', 19, '9', '2', '2', '3', '3', '7', '2', '0', '3', '6', '8', '5', '4', '7', '7', '5', '8', '0', '8'
};
CHECK(json::to_ubjson(j, true, true) == expected);
CHECK(json::from_ubjson(expected) == j);
}