dump() writes doubles with the conversion of Zmij by Victor Zverovich
(https://github.com/vitaut/zmij, MIT), ported to C++11 in
detail/conversions/zmij.hpp: the shortest decimal in the rounding
interval, the closest one if there are several. Grisu2 does not always
find the shortest digits; about 0.14% of random doubles are now written
differently (0.08% with fewer digits, 0.06% with the closest last
digit); short decimals such as 0.1 or 2555.56 are not affected. float
keeps Grisu2.
The layout of doubles is unchanged, but written differently: the digits
are converted eight at a time (the BCD conversion of Xiang JunBo, as in
Zmij) and stored with one byte swap per eight digits; leading and
trailing zeros are counted from those bytes; and the layouts of
format_buffer() are written with fixed-size moves instead of per-digit
loops and moves of the buffer (to_chars() uses a local buffer if the
caller's is shorter than the 41 bytes this may write).
The powers of ten come from the table for number parsing, adjusted
where it holds them rounded up, and from the compressed tables of Zmij
beyond 10^308. json::dump() gets faster on floats: canada -53%,
numbers -46%, mesh -37%, marine_ik -30%.
Tests: the powers of ten recomputed with a small big-integer; for random
doubles, all powers of two and of ten and their neighbors, and boundary
values: the output reads back as the same value, no decimal with one
digit fewer does, the layout equals that of format_buffer() for the same
digits, and (C++17) the digits equal those of std::to_chars.
The size ratios of canada.json in unit-binary_formats.cpp and one
expectation in unit-to_chars.cpp change with the shorter output.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Add BON8 support
Add to_bon8/from_bon8 and input_format_t::bon8 for BON8, a binary format
that uses the byte values that cannot begin a UTF-8 character as type
markers, so strings need no length prefix. It is the most compact of the
supported binary formats on the benchmark files.
The reader is non-recursive like the other binary readers. A string ends
at the first byte that cannot continue it, so the reader hands the one or
two bytes it reads past a string back to the value that follows. The
writer produces the canonical representation of the specification, except
for NFC normalization; its output is identical to that of the reference
implementation (HikoGUI) on all files of the test data.
The round-trip tests need the .bon8 files of json_test_data 3.2.0.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Address review comments
- Reuse detail::validate_one_utf8 to check strings in to_bon8; the error
now names the first byte of the invalid sequence.
- Document that to_bon8 leaves bytes in the output adapter on an
exception, and that string_open is only an output of write_bon8_marker.
- Explain why the pushback buffer of the BON8 reader cannot overflow.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Select the BON8 float prefix by type
get_bon8_float_prefix only depends on the type of its argument, so make
the type a template parameter instead of passing an unused value.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Rename a test variable that Flawfinder mistakes for read()
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix the BON8 CI failures
- compare the float in write_bon8_float with number_float_t constants,
so GCC does not warn about a float-to-double conversion
- mark check_bon8_utf8's context as used when exceptions are disabled
- choose the compact float prefix in a helper rather than with nested
conditional operators (clang-tidy)
- use auto for the cast in the BON8 integer reader (clang-tidy)
- write the int32 minimum test values as long long literals (MSVC C4146)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Amalgamate
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Read BON8 strings in bulk from contiguous input
- copy the valid UTF-8 of a string in one step when the input is
contiguous (twitter.json is read in 1.68 instead of 2.52 ms,
jeopardy.json in 196 instead of 297 ms, close to CBOR and MessagePack)
- share the new valid_utf8_prefix() with the writer's UTF-8 check, which
now skips ASCII 8 bytes at a time
- let the fuzzer check that contiguous and stream input give the same
value or error, and test both paths in the unit tests
- clarify that a second 0xFF after a string is an empty string
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Link the BON8 functions from the other binary format pages
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Name the bulk scan flag after the input, not BON8
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Read BSON keys in bulk from contiguous input
BSON keys (and array indices) are C-style strings, which were read byte
by byte. For contiguous input they are now read up to their \x00-byte in
one step, using the same bulk_scan flag as BON8 strings: twitter.json is
read in 1.46 instead of 2.01 ms, citm_catalog.json in 2.93 instead of
3.33 ms, jeopardy.json in 182 instead of 207 ms. canada.json, whose keys
are almost all one-digit array indices, takes 2 % longer.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix the BON8 CI failures of the bulk-read tests
- skip the contiguous-versus-stream tests of BON8 strings and BSON keys
when exceptions are disabled: they catch the parse errors of invalid
input, and without exceptions the library aborts instead
- use static_cast for the int64 test value (google-readability-casting)
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Move the explicit basic_json instantiation into its own test file
Linking test-regression3_cpp20 with clang and MinGW failed with
"relocation truncated to fit: IMAGE_REL_AMD64_REL32 against `.rdata'",
as test-regression2 did before #5511. The explicit instantiation of
basic_json<> for #4825 compiles every member function, including the
BON8 reader and writer, into that object, and it was already close to
the limit (2,226,104 bytes on develop, 2,234,960 with BON8; clang -O1,
C++20).
Give the instantiation a file of its own: unit-regression3 is now
1,594,736 bytes and unit-explicit_instantiation 1,095,064. The new file
mentions JSON_HAS_CPP_17 and JSON_HAS_CPP_20 so it keeps being built
for the C++17 standard the regression was about.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Convert the bytes of the BON8 test strings explicitly
The str() helper constructed a std::string from a byte range, which
converts each unsigned char implicitly; -fsanitize=integer reports that
for bytes of 0x80 and above (ci_test_clang_sanitizer).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
