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Commits
| Author | SHA1 | Message | Date | |
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 Niels Lohmann
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e9970066c5 |
Scan strings with SSE2, SSSE3, or NEON (#5853)
* Scan strings with SSE2, SSSE3, or NEON The string fast path found the end of a run of plain characters 8 bytes at a time (SWAR) and validated non-ASCII text one sequence at a time, calling validate_one_utf8() out of line for each. The vector code of json_view's scanner, in the new shared header detail/input/simd_scan.hpp, now does both 16 bytes at a time: SSE2 finds the end of a run on x86-64, and the UTF-8 check of Keiser and Lemire runs with NEON on AArch64 and with SSSE3 on x86-64. SSSE3 is not part of x86-64, so the check is compiled for it with a function attribute and used when the CPU has it (cached in a constant-initialized atomic), else the scalar check; code compiled with -mssse3 skips the CPU check. The first word of a run is still checked with SWAR (the first four with NEON, where a vector mask costs more), as most keys and short values end there, and the scalar helpers are always inlined. On anything else, the scalar code is unchanged. The new macro JSON_NO_SIMD selects the portable code everywhere, including the SSE2/NEON digit formatting of the floating-point writer. The lexer tests now also run with JSON_NO_SIMD and, on x86-64, with -mssse3, and a new test places every byte that ends a run at each offset across several 16-byte blocks, after ASCII and after CJK text. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Keep the string scan from slowing down short strings and dump() on Arm Three benchmarks were 7-9% slower than develop on Apple M1 (Apple Clang, -O3 -flto): Accept/jeopardy, Dump/citm_catalog, and Dump/jeopardy. - dump(): the serializer passes a string without its closing quote, so plain_run_end() ran out of input and called the out-of-line NEON loop for every string, with fewer than 16 bytes left. The loop is now only called for 16 bytes or more. - accept(): no string of jeopardy.json reaches the vector UTF-8 check, yet compiling it into the lexer's scan function made it 5% slower: the function runs once per token and now saved more registers and kept a stack slot. lexer_string_bulk_run() checks the first four words inline and continues out of line, and the serializer keeps string_bulk_run() inline, which is faster there. - The byte that ends a run is read from the scanned buffer instead of through get(), which Apple Clang merged with the other get() calls that load the read position again right after it was stored (3%). Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Define string_bulk_run_from() only where lexer_string_bulk_run() calls it With NEON and simdutf in C++17, lexer_string_bulk_run() takes the string_bulk_run() path, so the out-of-line helper was unused. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Do not dispatch the SSSE3 string scan with GCC's C++20 modules GCC does not keep the target("ssse3") attribute on functions it reads back from a module interface, so the module build (ci_module_cpp20, gcc:latest) rejected the intrinsics in vector_utf8_run() with "needs isa option -mssse3". With __cpp_modules, GCC now uses the portable UTF-8 check like other compilers without the target attribute; the SSE2 scan stays, and -mssse3 or more still compiles the SSSE3 check directly. Clang is not affected. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Include <cpuid.h> only once when json.hpp and json_view.hpp are both used The SSSE3 dispatch of the string scan and the one of json_view each include <cpuid.h>. Before GCC 11 the header has no include guard, so a translation unit that includes both headers fails with GCC 10: "redefinition of 'unsigned int __get_cpuid_max(unsigned int, unsigned int*)'". Guard both includes with NLOHMANN_JSON_CPUID_INCLUDED. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Add an ABI tag for JSON_NO_SIMD JSON_NO_SIMD selects between two definitions of the internal scanning and formatting functions. Like JSON_VIEW_NO_SIMD (_vns), it now appends _ns to the inline namespace, so translation units built with and without it can be linked into one program without ODR violations. Signed-off-by: Niels Lohmann <mail@nlohmann.me> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me> |
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Niels Lohmann
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4da932f518 |
Make parsing from std::istream and FILE* fast (#5828)
* Make parsing from std::istream and FILE* fast
Squashed onto develop
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Niels Lohmann
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63c10a51fc |
Review and extend the documentation, and check it in CI (#5638)
* Review and extend the documentation, and check it in CI A review of all documentation pages found factual errors, dead links, missing cross-references, and gaps in examples. This fixes them and adds checks so the same problems are caught automatically. Fixes: - wrong signatures and version histories (operator!= C++20 member, binary() subtype type, get<PointerType>(), JSON_NO_THREAD_LOCAL, ...) - stale descriptions (number parsing since #5283, UBJSON table, SAX example that no longer compiled, tsl::ordered_map advice) - dead internal and external links; repology.org badges (the domain is suspended) replaced by badges that query the registries directly - deprecation notes link the migration guide; the guide itself fixed Additions: - "See also" sections, cross-references, 25 runnable examples, 12 Mermaid diagrams, new API pages for json_pointer::operator<=> and byte_container_with_subtype::operator==/!= - landing page, guides for untrusted input and performance - "unreleased" badge after versions newer than the latest release Checks: - strict documentation build (broken links/anchors fail it); CI and the publish workflow fetch the full history the build needs - weekly external link check, Mermaid syntax check in CI - check_structure.py: example titles, heading levels, alt texts, header links, docset index coverage; its unused-example check works again - all examples produce the same output on every platform Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Keep the customer links that could not be fixed A dead link on the customers page is still the evidence of where the use of the library was documented. Keep the original URLs of the entries without a working replacement (Marne, Cisco Webex Desk Camera, Philips Hue, CyberArk) and exclude exactly these URLs from the link check. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Correct the duplicate-key recipe's claim about SAX positions The SAX interface's key() receives no position either; only parse_error() does. Also note that the recipe does not report the path to the repeated key (see discussion #5085). Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Say the library is available as a single header and mention json_fwd.hpp Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Correct documentation errors found while hunting for bugs - patch/patch_inplace: list the JSON pointer errors parse_error.106-109 and out_of_range.402/404, and quote the actual parse_error.105 message. - unflatten: list parse_error.106/107/108 and out_of_range.404. - to_bson: list out_of_range.415 (binary subtype above 255) and note that 412 and 415 are new in 3.13.0. - to_string: state that string_t must be convertible to std::string, also in the StringType requirements table. - JSON Lines: a `while (input >> j)` loop also throws after the last value for concatenated JSON values; show a loop that works for both. - BON8: a string gets 0xFF only if nothing follows it in the message; a string at the end of an array or object is ended by 0xFE. - custom_string_type.hpp: add operator+=(char), which the "Always required" list asks for (json_pointer::to_string, flatten, unflatten, and diff did not compile), and an ADL int_to_string for diff and items. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Cache the release headers with functools.lru_cache Codacy (Pylint) flagged the mutable default argument that header() used as its cache. functools.lru_cache keeps the same memoization without it. The script's output is unchanged. Signed-off-by: Niels Lohmann <mail@nlohmann.me> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me> |
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Niels Lohmann
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abbe52d6de |
Add JSON_PRECISE_STREAM_POSITION to leave the character that terminates a number in the stream (#5344)
* docs: qualify the operator>> stream positioning guarantee operator>>'s notes state that it leaves the stream positioned right after the parsed value, so that concatenated JSON values can be read back to back. That does not hold when the value is a number: a number is only terminated by the character that follows it, and the lexer's unget() is simulated (it rewinds only the lexer's own bookkeeping), so that character stays consumed from the stream. Document the actual behaviour: the guarantee holds for all value types except numbers, which must be followed by whitespace. Also qualify the cross-reference on the JSON Lines page, which repeated the unqualified claim. Documentation only; the behaviour itself is tracked in #5340. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * fix: restore the character that terminates a number (#5340) operator>> is documented to leave the stream positioned right after the parsed value, so that concatenated JSON values can be read back to back. That did not hold for numbers: a number is only terminated by the character following it, and lexer::scan_number() reads that character and calls unget() -- which is simulated and rewinds only the lexer's own bookkeeping. input_stream_adapter consumes via sbumpc() with no matching sungetc(), so the terminating character stayed consumed and the next extraction started one byte too late ('1true' left the stream at 'rue'). Propagating unget() to the adapter directly does not work: next_unget makes the following get() replay the cached character, so the terminator would be delivered twice. Instead, restore the still-pending character once at the end of a non-strict parse, where the input is handed back to the caller: - input_stream_adapter gains unget_character() (sungetc()) and advertises it via supports_unget, detected the same way as supports_seek. - lexer::restore_pending_unget() turns a pending simulated unget of a real (non-EOF) character into a real one and clears next_unget so the character is not also replayed. It is a no-op for adapters that cannot unget, and reports failure when sungetc() fails, in which case the input is left as it was before. - parser calls it on the three non-strict paths, i.e. for operator>> and sax_parse(strict = false). Strict parse()/accept() are unaffected: they require the input to end after the value, so the character is consumed by the end-of-input check anyway. Parse error messages and reported positions are unchanged. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * tests: fix CI failures in the #5340 test helpers Four CI failures, all in the new test code: - GCC (-Werror=useless-cast): drop the `json(...)` wrapper around `json::parse(...)`, which already returns a `json`. - GCC (-Werror=unused-result): assign the discarded `json::parse()` result to a dummy, the idiom used elsewhere in the test suite, and catch `json::parse_error&` for consistency. - clang-tidy (google-default-arguments): remove the default argument from the `pbackfail()` override; `sungetc()` supplies the base declaration's default. - MSVC (bad allocation): `no_putback_streambuf::underflow()` set a one-character get area without advancing `m_pos`, so an implementation whose `istream::get` peeks before it bumps re-read the same character forever. Keep no get area at all: `underflow()` peeks, `uflow()` consumes, and `sungetc()` still always lands in `pbackfail()`, which is what the test needs. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * fix: leave the character that terminates a number in the input Read the character following a number without consuming it, instead of consuming it and putting it back. input_stream_adapter now peeks with sgetc() and only steps over the character when the next one is requested or when the adapter is destroyed, so releasing it cannot fail - no putback position is required from the streambuf. Suggested by gregmarr in #5344. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * docs: match the version history wording to the peek-based fix Signed-off-by: Niels Lohmann <mail@nlohmann.me> * docs: drop the whitespace-separator caveat from the parsing pages The caveat added in #5343 describes the behavior this branch fixes: a number no longer consumes the character that terminates it, so concatenated values need no separator. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * refactor: split the strict and non-strict paths in parser Folding the release_lookahead() call into the existing strict check left the "in strict mode" comment on an else-if branch, and made the strict condition in sax_parse() redundant with the branch it followed. Signed-off-by: Niels Lohmann <mail@nlohmann.me> * Put the stream position fix behind JSON_PRECISE_STREAM_POSITION Leaving the character that terminates a number in the stream is observable: reading "1,2,3" with repeated operator>> works today only because the comma after each number is swallowed, and std::getline after a number skips the line break. Both break with the fix, so make it opt-in for 3.x, as suggested by @gregmarr in the review. - JSON_PRECISE_STREAM_POSITION (default 0) selects the peek-based input_stream_adapter. Without it, the adapter is the consuming one from develop and has no supports_lookahead, so lexer::release_lookahead() and the parser's calls to it compile to nothing. - The macro changes input_stream_adapter's layout and member functions, so it gets the ABI tag _psp, after _bics. The ABI config tests, the natvis generator, and nlohmann_json.natvis (regenerated) know the tag. - The tests for the fix move to unit-precise-stream-position.cpp, which defines the macro itself and runs in every build, and gain the two cases above. unit-deserialization.cpp pins the default behavior instead. - The docs describe the default behavior again and point to the new macro page; version history says "added in 3.13.0, planned default in 4.0.0". Signed-off-by: Niels Lohmann <mail@nlohmann.me> --------- Signed-off-by: Niels Lohmann <mail@nlohmann.me> |
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  KBSandmanon
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78821cd9c2 |
docs: document standards compliance and parse() vs operator>> strictness (#5326)
* docs: document RFC 8259 / JSONTestSuite compliance and parse() vs operator>> strictness The compliance story lived only in tests/src/unit-testsuites.cpp, so drive-by comparisons kept claiming the library "does not fully pass JSONTestSuite". Make it discoverable: - README: add a "Standards compliance" note stating that both nst JSONTestSuite revisions run in CI, that all mandatory y_/n_ cases pass through the strict parse() entry point, and listing the deliberate implementation-defined i_ choices (unbounded nesting, silent BOM stripping, noncharacters forwarded, strict rejection of invalid UTF-8 and lone surrogates, out_of_range.406 on numeric overflow). - features/parsing: add a "Strictness and trailing data" section documenting that parse() is strict and rejects trailing data while operator>> follows relaxed iostream semantics (parses one value and leaves the stream positioned after it) -- the single place a naive test yields a "non-compliant" result. Documentation only; no parser behavior change. Closes #5290. Signed-off-by: manon <youdie006@users.noreply.github.com> * docs: correct test-data vendoring and parse()/operator>> claims per review - README: the JSONTestSuite data is downloaded from nlohmann/json_test_data at configure time, not vendored/committed; say so. - README: only the updated suite runs y_ and n_ cases through strict parse(); the original suite's y_ cases go through operator>>. Narrow the claim. - parsing/index.md and operator_gtgt.md: note that operator>> consumes a number's terminating byte, so concatenated numbers must be whitespace-separated (1 2 works, 1true does not); structural and literal values are unaffected. Signed-off-by: manon <youdie006@users.noreply.github.com> --------- Signed-off-by: manon <youdie006@users.noreply.github.com> Co-authored-by: manon <youdie006@users.noreply.github.com> |
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Niels Lohmann
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c034480c22 |
📝 add more docs (#5231)
Signed-off-by: Niels Lohmann <mail@nlohmann.me> |
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Niels Lohmann
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b21c345179 |
Reorganize directories (#3462)
* 🚚 move files * 🚚 rename doc folder to docs * 🚚 rename test folder to tests |