* Write json_view's dump() without a call or conversion per token
The default dump() (no indentation, no ensure_ascii) gets its own
writer that makes the same walk and produces the same output:
- the write position stays in a local variable instead of a
member, so the compiler keeps it in a register across stores
through aliasing char pointers;
- strings and number tokens are copied with fixed-size 32-byte
moves wherever enough source bytes remain, instead of one
memcpy call per token;
- the innermost open container lives in local variables; a stack
that starts as a local array of 32 entries holds the rest;
- unedited documents are walked through the node array in order,
and integer tokens are read from the source directly.
On top of that, float tokens of at most 15 significant digits are
written straight from their digits via zmij::to_shortest() and
write_shortest(), without converting to a double and back: such
decimals are farther apart than a double's rounding interval, so
the token's digits are the double's shortest digits. Tokens of
16+ digits, or edited values, still go through decimal_to_float().
The view's own NEON write_decimal() is removed in favor of the
shared writer, and the dump output now grows in 64 KiB steps
instead of being resized to its estimate at once.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix MSVC C4127 and Infer finding in the view serializer
Test the template options through enabled() so that conditions combined
with them are not constant, and mark the nav::value() null dereference
as a false positive like materialize.hpp does.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix out-of-bounds read when dumping a float token of an unchecked image
A float node of an image loaded with image_check::bounds can hold a
token whose bytes are not digits, so its value need not have the digit
count recorded in the node. write_double_at() passed that count to
write_short_decimal(), which indexes its table of powers of ten by it:
an assertion failure in debug builds, an out-of-bounds read in release
builds. Use the counted overload only if the value has exactly that many
digits, otherwise count them.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Tidy the view serializer: doxygen block placement, enabled() for a constant
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Use a named document in the dump test: root() of a temporary does not compile
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Test write_short_decimal and powers_of_ten_16 against to_chars
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix clang-tidy 22 findings in unit-to_chars.cpp
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Write doubles from their bits only where double is IEEE 754 binary64
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Split the value and pointer edit tests off unit-json_view_edit.cpp
The MinGW linker of the Windows clang jobs cannot link object files with more
than 32767 sections ("relocation truncated to fit: IMAGE_REL_AMD64_REL32
against `.rdata'"). unit-json_view_edit.cpp has 35409 sections since the fast
dump instantiates more code for editable documents, so its test cases "views
and values", "deeply nested values", "pointers below a null value", and
"strings of other documents are checked" move into
unit-json_view_edit_values.cpp. The helper exception_of_call() that both
files use moves into json_view_test_helpers.hpp.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Move the dump tests of this branch to unit-json_view_dump.cpp
The dump and comparison tests moved to their own file in the dump pull
request; the tests of the fast dump() join them there.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Regenerate the amalgamated headers
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Address review: one powers-of-ten table, literal sizes from the type
- dtoa_impl::powers_of_ten() (10^0 to 10^19, one entry per line)
replaces powers_of_ten_16() and the table of int_pow10()
- put_literal() takes the length of a string literal from its type
- small_stack holds the heap vector by reference
- the growth step of the output buffer is written in hex
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Explain why the growth of the dump's stack is static
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Regenerate the amalgamated headers
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
MSVC 2015 warns C4554 on the shifts with casts in the fractional part
of zmij::to_shortest despite the parentheses; with /WX every target
fails to build. Name the shift amounts as constants instead.
The shortest-digits test built the candidates with one digit fewer via
a stream with std::setprecision(digits.size() - 2); the standard library
of MSVC 2017 ignores a precision of 0, so for two-digit values the
"shorter" candidates were the value itself. Truncate the digits
instead: the value lies within half a unit of the last digit, so the
truncated digits and their successor are the closest candidates.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Write doubles with the shortest digits (Żmij), digits in registers
Write doubles with the conversion of Zmij by Victor Zverovich (MIT),
ported to C++11 (detail/conversions/zmij.hpp). It finds the
shortest decimal that reads back as the same double, and the
closest one if there are several. Grisu2, used until now, is fast
but not always shortest: it sometimes writes a 17th digit where 16
suffice, or a last digit that is not the closest. The layout is
unchanged (1.5, 100.0, 1e+100, -0.0); float keeps Grisu2.
Digits are converted eight at a time with the BCD conversion of
Xiang JunBo, as in Zmij, and written with one byte swap per eight
digits and fixed-size moves instead of per-digit loops. Leading and
trailing zeros are counted from those bytes. to_chars() uses a
local buffer when the caller's is shorter than the 41 bytes this
may write. The powers of ten come from the number-parsing table,
adjusted where it holds values rounded up, and extended with Zmij's
compressed tables beyond 10^308.
write_shortest() converts its 16 digits in one vector register
(SSE2 on x86-64, NEON on 64-bit Arm, both baseline) and inserts the
decimal point inside the register, avoiding a store-forwarding
stall that cost about 25% of the time to write a double. dump()
writes floats and integers straight into the serializer's write
buffer instead of copying them from a member buffer, and small
integers eight digits at a time. read_eight_bytes() and
parse_eight_digits() are marked always-inline, which GCC had been
calling out of line in the number-parsing loops.
Of one million random doubles, about 0.14% are now written with
different digits, always to a value that still reads back as the
same double.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix CI findings in the Zmij writer and its tests
- bit_ops.hpp: include macro_scope.hpp (JSON_HEDLEY_ALWAYS_INLINE); fixes IWYU
- to_chars.hpp: C4100 for the unused parameter in release builds, clang-tidy
sign comparison, cpplint runtime/int, GCC -Wstrict-overflow (unsigned abs)
- unit-to_chars.cpp: parse with the library instead of strtod (MinGW's strtod
rounds some 16/17 digit inputs wrongly); no floating-point std::to_chars
with icpc
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Select the Zmij conversion by a trait, not by the double overload
The non-template overloads for double asserted binary64 doubles wherever json.hpp was included, so the library no longer compiled where double is not IEEE 754 binary64 (AVR, -fshort-double). A trait now picks Zmij for any binary64 type, including a long double of that format (MSVC, Apple Arm), and Grisu2 for the others. Remove the unused write_short_decimal, powers_of_ten_16, zmij::decimal, zmij::to_decimal, and shortest_digits(double).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Credit Zmij's authors in to_chars.hpp, the README, and the license page
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Silence MSVC C4127 for a platform-constant check in the to_chars test
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Regenerate the amalgamated headers
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---------
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Niels Lohmann