Commit Graph
6 Commits
Author SHA1 Message Date
Niels Lohmann ea03d601af json_view: comparison without temporaries and a faster image float check (#5890)
* Compare json_view values without a vector per container and a basic_json per number

operator== of views (view/view, view/json, and editable documents) built two
vectors of members for every object it entered, sorted them with stable_sort
for every object, and converted each number to a basic_json value. It now:

- keeps the members of all open objects in one vector (reserved with
  geometric growth, so that nested objects do not reallocate), and orders
  them by insertion sort for up to 16 members, or not at all when the keys
  ascend already;
- compares numbers of one type directly, and builds a basic_json only for
  numbers of different types;
- compares short texts (keys, numbers, most strings) with two overlapping
  loads (bytes_equal(), in node.hpp);
- first walks both documents in lockstep, in the order of their text, which
  finds most pairs of equal values without the work of the comparison. The
  walk only enters an object if the comparison would visit its members in the
  same order (the object type keeps the order, the keys ascend, or all values
  are scalars), so a difference is never found later than before, and it
  records the containers it found different, so that the comparison does not
  walk them again;
- rejects values of different types and arrays of different sizes before any
  of this, and, for an object type that keeps the order, objects whose first
  (up to four) members have different keys, which ends a comparison that
  differs near the start without preparing the members.

Results are unchanged: numbers compare by value across types, duplicate keys
resolve as parse() resolves them, and objects compare in document order for
ordered_json and by key otherwise.

Instructions of one comparison of a document with an equal copy, macOS arm64
(develop -> now), json_document / ordered_json_document / editable:

  twitter    16.1M -> 7.0M   17.7M -> 1.5M    16.6M -> 7.3M
  citm       45.0M -> 3.4M   47.0M -> 3.2M    45.7M -> 4.3M
  canada    111.4M -> 13.7M  111.4M -> 13.7M  113.3M -> 15.0M
  jeopardy   26.2M -> 3.7M   27.3M -> 3.7M    26.6M -> 12.1M

and of a view with a basic_json value:

  twitter    11.4M -> 5.9M   11.2M -> 7.3M    11.6M -> 5.9M
  citm       33.9M -> 9.7M   32.6M -> 9.1M    34.6M -> 9.8M
  canada     92.9M -> 32.1M  92.9M -> 32.1M   93.9M -> 32.8M

and Linux instruction counts (GCC 13 / Clang 18) of the same comparisons:

  document with an equal copy   json_document     ordered_json_document   editable
    twitter                     -49 % / -52 %     -89 % / -89 %           -48 % / -50 %
    citm                        -90 % / -89 %     -91 % / -90 %           -88 % / -87 %
    jeopardy (4,000 questions)  -85 % / -85 %     -86 % / -86 %           -46 % / -49 %
  view with a basic_json value
    twitter                     -41 % / -45 %     -28 % / -35 %           -45 % / -44 %
    citm                        -63 % / -65 %     -63 % / -66 %           -65 % / -64 %
    jeopardy                    -39 % / -43 %     -14 % / -24 %           -44 % / -43 %

A sweep that places one difference at about 2,100 positions of eight
documents (a token at an even spacing, the first and last tokens, the first,
middle and last member of the root removed, one appended, the document
wrapped) in five kinds of comparison (view/view of read-only and of editable
documents, view/json, json_document, editable/view) finds the same results as
before and no placement slower on the Mac (Clang); on Linux no placement is
slower than 3 % (Clang and GCC).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Check the float tokens of a json_document image without a sort and a scan of every character

load(image_check::full) checked every float token of an image by sorting
the token ranges, scanning the token character by character, and comparing
the digit layout with the node's. Now:

- the ranges are sorted only if they are not sorted already (save() writes
  them in the order of the nodes, so they are);
- a token of the shape [-]digits.digits whose digit counts are the ones the
  node records (nearly all of them) is accepted by checking its digits eight
  at a time, without the general scan;
- the general scan skips runs of digits eight at a time.

Damaged tokens are still rejected as before: the check accepts exactly the
tokens that the general scan accepts.

Instructions of load(image_check::full) (develop -> now):

  macOS arm64        canada 44.6M -> 30.9M (-31 %), jeopardy 11.3M -> 10.7M,
                     citm 10.4M -> 10.0M, twitter 5.06M -> 4.94M
  Linux GCC 13       canada -50 %, jeopardy -43 %, twitter -31 %, citm -28 %
  Linux Clang 18     canada -42 %, jeopardy -48 %, twitter -35 %, citm -32 %

image_check::bounds is unchanged (within 0.4 %).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Rename names that Flawfinder takes for the file function open()

The comparison cursors' open() is now enter(), and a test's open and
close strings are head and tail.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix the compiler and lint failures of the json_view comparison

- all_digits(): the lambda declares its constant itself; MSVC does not
  let a lambda without captures read a constexpr local of the function
- equal(): the frame's "in document order" index is a namespace-scope
  constant (document_order); the local constexpr npos in the default
  member initializers of the local struct crashed GCC 9 and MinGW GCC
  and was not found by MSVC
- keys_differ_early() keeps the first keys in std::arrays (cpplint:
  variable-length arrays; clang-tidy: C arrays), and the basic_json
  side's first_keys() is not noexcept (key() may throw)
- the numbers of one type are compared in an if chain instead of a
  nested conditional operator
- the dump test avoids C arrays and temporary string concatenations

View comparison instructions are unchanged (Apple clang, twitter, citm,
canada: -0.1 % to +0.1 %).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Keep the byte comparison helpers in compare.hpp

Address review comments: bytes_equal() and bytes_less() move from node.hpp
to compare.hpp, their only user; key_less() no longer splits the comment of
resolve_indices() from its function; and the loop counters of bytes_equal()
and all_digits() are scoped to their loops.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Dispatch on the compile-time conditions of the json_view comparison

MSVC (/W4 /WX) reported C4127 (conditional expression is constant) for
the template parameter EA and the object type's ordering in an if
condition; both are now tag-dispatched.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Remove a nested duplicate guard from the json_view image test

clang-tidy reported the inner #if !defined(JSON_NOEXCEPTION) as
redundant (the test case is in the same #if) and a find() != npos, which
gets the NOLINT the other tests use.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Mark Infer's null dereference in materialize() as a false positive

Infer (ci_infer, also red on develop since #5882) reports a null
dereference in json_sax_dom_parser::null() called from materialize(). The
member pointer the parser stores a value of an object in is set by the
key() before it, so it is not null there.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Move the json_view comparison tests into their own file

With the tests this branch adds, the object file of unit-json_view_dump.cpp
got too large for the MinGW x64 assembler ("file too big"). The test case
"json_view comparison" is now unit-json_view_compare.cpp, unchanged and
also built with C++17.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Build the DOM parser with Visual Studio 2015 again

Since #5882, the three VS 2015 jobs of AppVeyor fail on develop:
- the detection of keys that can be indexed instantiated std::hash for
  every string type, which VS 2015 rejects with a static_assert for a type
  it does not hash (alt_string): std::hash is now looked at only for
  objects in a vector
- the frame stack copied its frames with std::copy to a raw pointer, which
  VS 2015 reports as unsafe (C4996, an error with /WX): a loop now

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* json_view: no per-object allocations in ordered_json comparisons

For an object type that keeps the order of its members (ordered_json),
resolve_indices() allocated a vector per compared object, and
resolve_members() two. They now use one working vector owned by equal(),
whose capacity is reused, and resolve_indices() needs none when the keys
are unique. resolve_members() sorts small objects by insertion, as the
other paths do.

Instructions per comparison (callgrind, GCC 13 and clang 18, x86-64):
twitter, ordered_json view == ordered_json: 0.939 / 0.941; 20000 small
objects with a duplicate key: 0.741-0.768; all other rows (json,
citm_catalog, canada, view == view) within 0.988-1.003.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-30 15:19:42 +01:00
Niels Lohmann 54f6b3ef06 json_view: source positions in materialize() with JSON_DIAGNOSTIC_POSITIONS (#5945)
* json_view: source positions in materialize() with JSON_DIAGNOSTIC_POSITIONS

With JSON_DIAGNOSTIC_POSITIONS, materialize() now gives every value the
start_pos()/end_pos() that basic_json::parse() would give it, so exceptions
about materialized values name the same bytes (#5864).

- json_sax_dom_parser takes the lexer type as a defaulted template
  parameter; materialize() passes position_source, which reports the
  positions it derives from the index. diagnostic_positions treats npos as
  "no position" and keeps ranges all-or-nothing.
- Strings with escapes keep the offset of their opening quote plus one in
  `next` (only with the macro); materialize() scans from there to the closing
  quote. The end of an array or object is found by scanning from the end of
  its last element over whitespace, comments and a trailing comma.
- In editable documents, values written by edits, arrays and objects whose
  elements changed, and containers whose last element has no position get
  none. Images keep the flag is_new, and load() checks that `next` of a
  string is within the text.

Nothing changes on the parse path without the macro. The view's own
exceptions still carry no byte range, so the tests that compare them with
those of materialized values skip it under the macro, as they skip the path
under JSON_DIAGNOSTICS.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Indent comment in unit-json_view_from_json.cpp

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Address review: clearer position code and docs

- position_source gets clear(); set_scalar() returns early for new values,
  switches on node_kind, and uses no local copies; the one position_source
  per materialize() call is documented
- no npos + 1 for containers without a position; a comment on why the end
  of a container is reported as its closing bracket
- less duplication under #if in materialize() and the builder
- diagnostic_positions sets npos explicitly
- docs: positions of basic_json values after changes, positions in images
  depend on how the document was parsed, when next is set, and the cost of
  positions while parsing

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Share the comment scanners of the view builder with materialize()

skip_line_comment() and find_block_comment_end() in scan.hpp are used by
the builder's comment() and by position_source::container_end(), which
had its own copy.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Address review: if/else for container positions, clearer next field

- the opening bracket of a container sets positions with an if/else instead
  of a ternary, and the frame takes its start from positions
- the closing bracket of a container is found in nested if/else; the parent's
  last_end is taken from positions, so it is npos whenever no range is set
- architecture.md: the next field reads "or 0 if it was not; all other
  values: 0" instead of "else 0; otherwise 0"

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix GCC unused-result and clang-tidy raw-string findings in unit-json_view_positions.cpp

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-28 20:24:49 +01:00
Niels Lohmann 4cdfa6d0f4 json_view: no save() and load() on big-endian targets (#5920)
The image format is little-endian only. Instead of throwing
type_error.320 at runtime, save_image(), load_image() and the members
save() and load() do not exist on a big-endian target, so a call fails to
compile, like set() on a read-only document. type_error.320 remains for
saving a discarded document.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-26 20:13:30 +01:00
Niels Lohmann 731f1b5bfb json_view: view_mode enum instead of bool Editable, node_kind for node::kind (#5919)
* json_view: view_mode enum instead of bool Editable, node_kind for node::kind

basic_json_document and basic_json_view take a view_mode (read_only, the
default, or editable) instead of a bool: basic_json_document<json, true>
did not say what true means. The shortcut aliases are unchanged.

The kind of a node is a node_kind (the value_t values plus link, 10 as
before), which removes the static_cast<std::uint8_t>(value_t::...) of
every comparison. The node and image layouts are unchanged.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* json_view: node_kind in the node writers, spell out read_only, comment fixes

The builder and the edit functions take and store a node_kind instead of
casting a value_t; the numbering assertions and the comments now speak of
node_kind, and the link kind notes that it follows value_t::discarded.
The read-only aliases name view_mode::read_only like the editable ones.
view_mode.md says the mode is a compile-time property of the type.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* json_view: views of read-only documents convert to editable views

A read-only document has no edits, so a view of it reads correctly as a
view of an editable document before its first edit. The implicit
conversion lets a function taking a json_editable_view accept the views
of both modes. There is no conversion the other way: a read-only view of
an editable document would read wrong values after the next edit.

The mode comparisons in the cross-mode operator==/!= use an
is_other_mode trait, which astyle keeps compact.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-26 20:13:30 +01:00
Niels Lohmann fe5e401870 Consolidate duplicated detail helpers and bodies (#5891) (#5901)
* Add shared detail helpers for the #5891 cleanup

Add detail::is_primitive(value_t), detail::hex4_lower(), detail::utf8_shape(),
detail::input_format_name(), detail::empty_input_message(), the exception ids
116, 319, 320 and 416 to detail::exception_id, and make
detail::is_ascii_copyable() constexpr. Later commits switch the duplicated
code over to them.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 1.4: BSON writers share one write-pass UTF-8 sanitizer (#5891)

write_bson_entry_header and write_bson_string re-derived the error-handler
policy differently. Both now use sanitize_utf8_for_bson_write, which treats
strict like keep (the size pass already validated) and sanitizes replace/ignore
into the bytes the size pass measured. No context plumbing is needed.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.1.1: one MessagePack container prefix helper (#5891)

Array and object prefixes differed only in the fix marker and the 16/32-bit
markers; both now delegate to write_msgpack_container_prefix. Output is
byte-identical.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.1.2: one iterative walker for CBOR and MessagePack (#5891)

write_cbor_iterative and write_msgpack_iterative (and their *_value_or_push
helpers) were identical but for the head, scalar, and key writers. They are now
one template over a small policy struct, so everything inlines. BON8 keeps its
own walker (open string run, closing marker), noted in a comment.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.1.3, 2.1.8: one UBJSON container start helper, shared frame base (#5891)

write_ubjson_start_array/_object are now write_ubjson_start_container<IsArray>,
keeping the array-only begin()+1 scan and excessive_valueless rule.
ubjson_frame derives from binary_container_frame instead of duplicating it.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.1.4: write_bytes helper for the byte-string write sites (#5891)

The 13 oa.write_characters(reinterpret_cast<const CharType*>(x.data()), n)
sites now call write_bytes(const void*, size_t); copy_characters sites and the
buffer-based writes are untouched.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.1.5: shared object-key writer for CBOR and MessagePack (#5891)

write_cbor_key and write_msgpack_key were the same SFINAE pair apart from the
string/scalar writers; both now delegate to write_object_key<Walk>. UBJSON key
and to_format_length stay as they are.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.3.10: writer-side format names from input_format_name (#5891)

The CBOR/MessagePack/UBJSON/BSON/BJData/BON8 literals in throw_on_discarded and
throw_integer_out_of_range calls now come from detail::input_format_name; the
texts are identical, and UBJSON vs BJData still follows use_bjdata.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* serializer: constexpr ascii table, hex4_lower, dedupe helpers (#5891)

1.1: build ascii_copyable() at compile time from is_ascii_copyable and
test find_ascii_copyable_run against it for every byte. 1.2/2.5.4: use
detail::hex4_lower in both \uXXXX writers. 2.1.6: factor the repeated
flush/emit blocks in dump_escaped_impl into always-inline helpers.
2.1.7: comment why the escape copy does not use put_buffer.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 1.6: use string_t-aware to_string/concat in meta() (#5891)

Replaces the four std::to_string sites; rendered text unchanged.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 1.7: use detail::is_primitive in json.hpp switches (#5891)

has_no_children, set_parents, max_size and the two diff walkers.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.2.1: factor insert()/iterator throw helpers (#5891)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.2.2: share swap() overloads via swap_impl (#5891)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.2.4: factor primitive reset and range check in erase()/range ctor (#5891)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.2.6: share push_back array bodies via push_back_array_impl (#5891)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.2.7: route parse/accept/sax_parse through *_impl helpers (#5891)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.2.8: share the vector-returning to_* bodies via to_binary_vector (#5891)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.2.10: merge destroy_string/destroy_binary into destroy_pointer (#5891)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.4.1/1.7: exceptions: share what_impl, flatten diagnostics switch (#5891)

The four create() bodies build their message through one protected
static helper; the diagnostics parent walk handles array/object and
ignores all other types.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.4.2/2.4.3/1.7: json_pointer: share slash and escape checks, drop primitive case lists (#5891)

The leading-slash and invalid '~' escape checks are shared helpers; the
reference-token walks test object and array first and treat everything
else as primitive.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 1.7/2.4.9: iter_impl, iteration_proxy: drop primitive case lists, share compare preamble (#5891)

Object and array stay the first branches; everything else is the
primitive case. operator== and operator< share the different-container
check.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.4.5/2.4.6: from_json: share get_number_value and reserve_if_possible (#5891)

The three number cases of get_arithmetic_value and the arithmetic
from_json share one helper (boolean stays accepted only by the latter);
the array and object reserve overload pairs become one.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.4.8: ordered_map: share erase_impl between the key erase overloads (#5891)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 1.7: json_pointer: flatten walk drops the primitive case list (#5891)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 1.2/1.3/1.5/2.5.1/2.5.2/2.5.5: share helpers in the view code (#5891)

- detail::exception_id at every numeric id; throw_* helpers take it
- hex_byte, hex4_lower, utf8_shape replace local hex/table code
- throw_array_index_out_of_range/_past_end, throw_key_not_found
- has_native_float_format replaces the hand-written IEEE check
No change of messages, ids or output.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 1.5: use utf8_shape in get_bon8_string, add exhaustive UTF-8 validator test (#5891)

get_bon8_string takes the valid range of the second byte from utf8_shape()
(0xF5..0xF7 stay errors, unget behavior unchanged). validate_one_utf8 keeps its
if-chain (hot bulk path); the new test checks decode, validate_one_utf8,
utf8_shape, json::accept and the BON8 reader against each other for every lead
and second byte.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.3.1: get_cbor_sized_bytes for the CBOR chunk getters (#5891)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.3.2: get_string_with_length for the plain-order string sites (#5891)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.3.3, 2.3.4, 2.3.10: unsupported_key_type, empty_input_message, input_format_name in the readers (#5891)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.3.7, 2.3.9: read_object_key and leave_container_and_check for CBOR/MessagePack/BON8 (#5891)

UBJSON keys (different getter signature) and its container tail stay as is.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.3.5: json_sax_dom_error_state base for the DOM SAX parsers (#5891)

Holds errored, allow_exceptions, parse_error() and is_errored(). The scalar
handlers stay in each class (parse hot path).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.3.6: table of control-character messages in the lexer (#5891)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.3.8: finish_input helper for the strict-EOF block in the parser (#5891)

sax_parse keeps its if (result) guard and return value. Also adds the
clang-tidy NOLINT for the 2.3.6 message table.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.5.7: share parse_array_index between json_pointer and json_view (#5891)

Move json_pointer::parse_array_index() and its status enum to namespace detail
(json_pointer keeps a forwarding member), and let the json_view pointer
resolution use it instead of its own copy of the RFC 6901 index grammar. Both
accepted the same tokens with the same outcome. Also update the comment on
detail::decode(), which listed four of the five UTF-8 validators and now points
to the test that keeps them in sync.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Amalgamate (#5891)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.4.5: keep the inlined number cases in from_json(ArithmeticType&) (#5891)

Calling get_number_value() from from_json(ArithmeticType&) made
GetArray<std::array<int, 1000>> 2.4x slower (it changes the inlining of the
std::array conversion), so that overload keeps its own switch, with a comment.
get_arithmetic_value() still uses the shared helper.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 2.5.7: force-inline detail::parse_array_index (#5891)

Moving parse_array_index out of json_pointer stopped clang from inlining it
into the pointer resolution (JsonPointerAt/citm_catalog +17%,
JsonPointerAt/twitter +8%); JSON_HEDLEY_ALWAYS_INLINE restores the baseline.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 1.5: keep get_bon8_string's own UTF-8 ranges (#5891)

Taking the second-byte range from utf8_shape() made BON8 decoding 2-3% slower
(FromBinaryShape/scalars, FromBinaryBuffer, alignment-pinned builds), so the byte
path keeps its hand-written ranges. The exhaustive validator test still checks
that it accepts the same sequences as the other validators.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Amalgamate (#5891)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix CI failures: constexpr, NRVO, cppcheck, IWYU (#5891)

- json_sax_dom_error_state::is_errored() cannot be constexpr: the class
  is not a literal type (GCC 4.8, GCC -Wpedantic, Clang 3.5).
- to_binary_vector: destroy the vector writer before returning, as the
  output_vector_sink sets the size of the vector in its destructor.
  Without NRVO (MSVC Debug in C++14 mode), the vector was moved out
  before it was resized.
- parser::sax_parse: return false instead of result after the early exit
  (cppcheck identicalConditionAfterEarlyExit).
- json.hpp: export detail/exceptions.hpp for IWYU, so json_view.hpp can
  name exception_id without including a detail header.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Address review: throw helpers take input_format_t, simpler type checks

- throw_on_discarded() and throw_integer_out_of_range() take an
  input_format_t and call input_format_name() themselves
- has_no_children(), set_parents() and max_size() check array, then
  object, instead of calling is_primitive() first
- parse_impl() chains like accept_impl(); sax_parse_impl() uses if/else
- std::array for the control character messages; negation<> in
  write_object_key(); clarify the is_primitive() comment

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* json_view: use exception_id in the value() overloads

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* json_sax: assert the invariant of place_container for the static analyzer

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

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Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-25 06:17:50 +01:00
Niels Lohmann 4971200b54 Add images of json_documents: save() and load() (#5632)
* Add images of json_documents: save() and load()

An image is a document stored so that loading it needs no
parsing: save() writes the node index, the text and the decoded
strings; the static load() reads an image written by save().

load() takes a pointer and size, a borrowed vector, or an owned
rvalue vector; the nodes are copied so they are aligned and can
be edited, while the text and decoded strings stay in the image.

image_check controls how much load() trusts the input: full
checks structure, bounds, strings and numbers, the parser's own
guarantees; bounds checks structure and bounds only; none skips
all checks, for images from a trusted source.

Layout is little-endian only ("NJVI" header, nodes, text, decoded
strings), following the idea of zero-copy formats such as
FlatBuffers and YaFF; the check follows FlatBuffers' Verifier.

New errors: parse_error.116 for a malformed image or a failed
check, type_error.320 for a discarded document or a big-endian
target.

A dedicated fuzzer and 6,000 seeded corruptions, checked under
ASan/UBSan, found and fixed two gaps: unchecked reserved header
fields, and unbounded null/boolean offsets that could make
dump() throw std::length_error.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix MSVC errors in image test and add image_check doc anchor

Move the raw string literal out of the CHECK macro (MSVC preprocessor),
cast 64-bit header fields to std::size_t (C4244 on 32-bit), and give the
image_check section in load.md a real anchor for the mkdocs strict build.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Check each distinct string and float range once in the full image check

The full check scanned the contents of every string node and every float token over its own range, so many nodes pointing to one large range made load() quadratic. The structural walk now only collects the ranges; after it, each kind is sorted and checked once per distinct range. Ranges of one kind that overlap without being identical are rejected, as save() never writes them (nodes that share a value share the whole range). The cost is linear in the size of the image plus sorting the ranges.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Adapt the image tests to named documents and last-wins lookups

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Test that the targets of links never reach an image

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Test lookups in loaded images with duplicate and colliding keys

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Release the list of large objects once load() has built the indexes

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Test that invalid UTF-8 of a loaded image is not copied into an editable document

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Document that editable documents refuse invalid UTF-8 copied from a loaded image

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Expect first-wins lookups in the image tests

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Avoid useless casts of header fields in the image tests

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix clang-tidy 22 findings in unit-json_view_image.cpp and image.hpp

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix MSVC C4244 and C2017 in the image test

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix the indentation of a loop in the image test

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Make json_view.hpp pass include-what-you-use

ci_single_binaries runs IWYU with --error on every header. For json_view.hpp
it suggested adding <array> (std::array is used), the headers that json.hpp
already provides (abi_config, abi_macros, input_adapters, json_pointer,
cpp_future, string_concat, value_t, json_fwd), and <version> for
std::nullptr_t, and removing <cstddef>.

- include <array>
- keep <cstddef> (nullptr_t, size_t; IWYU attributes them to <version> and <cstring>)
- tell IWYU not to suggest the headers that json.hpp provides: the amalgamated
  json_view.hpp only includes json.hpp, so including them here would duplicate
  their definitions
- drop edit_storage.hpp, which edit.hpp includes

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Silence a clang-tidy C++17 finding in the image test

bugprone-suspicious-stringview-data-usage flags data() of the source view
under C++17, although the length is passed and checked by the REQUIRE
before it.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Build the image link test without exceptions

load_result() exists only with exceptions; with JSON_NOEXCEPTION the test
loads the image with the check directly (a failed check aborts).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Regenerate the amalgamated headers

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Follow the renames from the review of the view builder

The review of #5620 renamed document_data's tape/tape_size/tape_cap to
nodes/node_count/node_capacity and made the decode arena a
std::vector<char>; adapt the code of this change to it.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Rename the emit lambda in the image writer for Qt compatibility

Qt defines emit as an empty macro, so a Qt header included before
json_view.hpp broke the lambda's declaration (see #5865). The slots
variables in the image tests are renamed as well.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Address the review of json_document images

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Regenerate the amalgamated headers

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

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Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-21 10:21:29 +02:00