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Author SHA1 Message Date
Niels Lohmann 9222763ab9 Merge branch 'develop' into claude/todo-191-plan-508110
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-21 10:51:41 +02:00
Niels Lohmann d13c9e7212 Fix links to moved API pages in the API changes page
mkdocs --strict rejects links to pages that only exist as redirects.
Also link operator<< to operator_ltlt.md and operator>> to
operator_gtgt.md instead of the other way round.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-10 07:42:37 +02:00
Niels Lohmann 522e7465b0 Merge branch 'develop' into claude/todo-191-plan-508110
Regenerate tools/api_checker/api_surface.json with the CI libclang
(18.1.1 on Linux) and point the new ordered_map links in
features/performance.md to api/ordered_map/index.md.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-10 04:01:42 +02:00
Niels Lohmann fe4e78e867 Merge branch 'develop' into claude/todo-191-plan-508110
- ordered_map.hpp: develop's refactored members, with this branch's
  @sa links on every public member
- byte_container_with_subtype operator==/!= and ordered_map docs:
  develop's reviewed text (#5638); drop the now unreferenced examples
- basic_json.md: keep both version-history additions
- add the docset entries that develop's style check now requires for the
  25 API pages this branch adds
- regenerate tools/api_checker/api_surface.json for develop's API

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-04 17:35:55 +02:00
Niels Lohmann 9196e92520 Merge branch 'develop' into claude/todo-191-plan-508110
Conflicts: none textual. Follow-up fixes for develop's changes:
- docs/mkdocs/docs/api/ordered_map/index.md: develop's new paragraph
  (#5609) was written for api/ordered_map.md; fixed its relative
  ordered_json.md link for the page's new location, plus two
  pre-existing links from an earlier merge (ordered_json.md,
  features/object_order.md)
- tools/api_checker/api_surface.json: regenerated with libclang 18.1.1
  on Linux (swap() noexcept now includes json_base_class_t; new
  integral-key contains/count/find/value overloads)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-30 20:36:12 +02:00
Niels Lohmann 7d22d865dd Merge branch 'develop' into claude/todo-191-plan-508110
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-28 22:22:46 +02:00
Niels Lohmann 4c73319d3b Use one-line module docstrings in the API checker scripts
Codacy runs two docstring checkers with opposite rules for module
docstrings: with the summary on the first line it reported D213, with
the summary on the second line it reports D212. A one-line docstring
satisfies both. Keep the summary as the docstring and move the details
into a comment below it; nothing reads the module docstrings.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-28 18:42:34 +02:00
Niels Lohmann da5097abcd Restore the CI spelling of json_pointer's operator string_t in the API surface
The develop merge regenerated api_surface.json on macOS, whose libclang
spells the name of the deprecated conversion operator as
"operator nlohmann::json_pointer::string_t_helper<...>::type". CI's
pinned libclang 18.1.1 on Linux spells it
"operator typename string_t_helper<...>::type", so check_api_docs
reported the file as out of date. This restores CI's spelling, which is
byte-identical to the file CI regenerated.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-27 21:37:14 +02:00
Niels Lohmann 2319f6e6f9 Address Codacy findings in the API checker scripts
Put multi-line docstring summaries on their own line, as a single
sentence followed by a blank line (pydocstyle D205, D209, D213, D415).

Annotate the subprocess import and calls with nosec: they only run
fixed argument lists, never through a shell (Bandit B404, B603, B607).
Do the same for the three broad except clauses in extract_api.py,
which deliberately fall through to the next libclang candidate or skip
an unresolvable alias (Bandit B110, B112).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-27 18:09:03 +02:00
Niels Lohmann 9a0d1c0c47 Merge branch 'develop' into claude/todo-191-plan-508110
Resolve the conflict in docs/mkdocs/docs/home/architecture.md by taking
develop's rewritten page and pointing its ordered_map links at the moved
api/ordered_map/index.md. Also update the ordered_map.md links develop
added in ordered_json.md, object_order.md, and template_parameters.md.

Regenerate api_surface.json for the new BON8 functions and the changed
comparison operator. Restrict the documented_non_public leak check to
@sa URLs into json.nlohmann.me: develop now uses @sa to link GitHub
issues from private members such as copy_structured, which is not a
documentation leak.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-27 18:07:00 +02:00
Niels Lohmann 1bbb5d400a Regenerate api_surface.json after merging develop
develop added JSON_HEDLEY_WARN_UNUSED_RESULT to a number of basic_json
members (#5520) and reworked operator<<'s output adapter, so the
committed API surface no longer matched what extract_api.py produces and
the "Check for uncommitted API surface changes" step failed.

This is the patch the workflow itself uploads for that purpose; the
changes are limited to recorded signatures plus the way libclang spells
json_pointer's conversion operator.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-09-15 10:06:55 +02:00
Niels Lohmann 08d18d5a82 Merge remote-tracking branch 'origin/develop' into HEAD 2026-09-14 21:26:29 +02:00
Niels LohmannandClaude Sonnet 5 a27065bd12 Regenerate api_surface.json after merging develop
develop gained iterator+sentinel support for accept()/parse()/sax_parse()/
from_cbor()/from_msgpack()/from_ubjson()/from_bjdata()/from_bson() (#5205)
since this branch was created, which check_api_docs.yml's drift check caught
immediately: GitHub's pull_request trigger checks out the PR-vs-base merge
commit, not the PR branch in isolation, so CI was comparing the committed
api_surface.json (generated before that upstream change existed) against a
fresh extraction of a json.hpp that already had it.

This superseded an earlier, incorrect diagnosis of the same symptom (a
JSON_HAS_RANGES cross-environment pin) -- that fix remains in place since it's
still a real, independent determinism improvement for three other
JSON_HAS_RANGES-gated locations in type_traits.hpp, but it wasn't the actual
cause of this particular mismatch: these new overloads turned out to be
unconditional (SFINAE-gated via can_compare_ne, not preprocessor-gated), so
no environment-detection difference was involved here at all.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-07-11 23:45:46 +02:00
Niels Lohmann 3940f4b730 Merge remote-tracking branch 'origin/develop' into claude/todo-191-plan-508110 2026-07-11 23:43:30 +02:00
Niels LohmannandClaude Sonnet 5 0663907b68 Fix cross-environment API-surface drift and lint findings from CI
extract_api.py's own extraction wasn't deterministic across machines, which
CI's drift check caught immediately: JSON_HAS_RANGES auto-detects via the
standard library's __cpp_lib_ranges feature-test macro, which isn't reliably
gated to C++20 mode by every stdlib -- undefined under -std=c++17 with macOS's
libc++, but defined under the identical flag with the Ubuntu stdlib CI uses,
so parse()/accept()/from_*() extracted different signatures purely depending
on which machine ran the extraction. Pinned to -DJSON_HAS_RANGES=0: the
deterministic and safe choice, since pinning to 1 was tried first and found to
fail to parse on a stdlib without full <ranges> support even when the macro
claims otherwise.

Also found and fixed a second, independent source of the same class of drift:
get_identity_name() used cursor.spelling verbatim for CONVERSION_FUNCTION
cursors, which libclang renders as its own internally-canonicalized form of
the return type rather than what's literally written. Confirmed for
json_pointer::operator string_t() spelling differently on two machines
pinned to the identical libclang==18.1.1 wheel, with the JSON_HAS_RANGES fix
above ruled out as the cause. Now derived from the cursor's own raw source
text instead, immune to libclang's dependent-type resolution differences and
incidentally more readable than the libclang-internal forms it replaces.

Bumped SURFACE_FORMAT_VERSION to 3 and regenerated all 27 history snapshots
and the committed api_surface.json; both fixes are documented in
tools/api_checker/history/README.md's format-history log.

Also fixes diff_api.py's format_version guard, which only compared the two
loaded surfaces against each other and never against SURFACE_FORMAT_VERSION
(what this build actually understands) -- two surfaces on the same,
newer-than-expected format_version would have silently passed the guard.

Remaining fixes are the concretely actionable findings from Codacy's review
of the new tools/api_checker/ files: unused imports/variables, a stray
f-string with no placeholders. Left the docstring-formatting nitpicks
(pydocstyle D2xx/D4xx) and generic subprocess-usage notices alone -- the
former has no established convention elsewhere in this codebase's Python
tooling to conform to, and the latter are inherent to a dev tool that shells
out to git/clang with developer-controlled arguments, not user input.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-07-11 18:59:19 +02:00
Niels LohmannandClaude Sonnet 5 f23b3c63a2 Add AST-based public API checker and fix documentation gaps it found (#3691)
Adds tools/api_checker/: extract_api.py derives the public API surface directly
from the libclang AST (independent of documentation status), check_docs.py flags
public entries missing @sa links (and @sa on non-public ones), diff_api.py does
an overload-aware breaking/feature diff between two refs, check_macros.py cross-
checks documented macros against #define sites, and snapshot_release.py backfills
immutable per-release surface snapshots into tools/api_checker/history/ (v3.1.0
through v3.12.0) so diff_api.py can compare releases without live extraction.
POLICY.md documents what counts as public API and what stability is guaranteed.

Running this tooling against the current tree found and fixed a real documentation
backlog: ~25 new API doc pages (ordered_map's methods, json_sax's ctor/dtor/
operator=, byte_container_with_subtype's comparison operators, several orphaned
type aliases), each with a compiled and output-verified example, plus missing
@sa comments and stale/incorrect Version History entries on several existing
pages (found by diffing consecutive release pairs and checking whether the
resulting change was actually reflected in the target page's history section).

Also adds docs/home/api_changes.md, a per-release, per-function reference of
public API changes (v3.1.0 through v3.12.0) generated from the history/
snapshots, complementing (not replacing) the existing release notes.

Along the way, found and fixed several extractor bugs by testing against real
release tags rather than trusting the algorithm in isolation -- most notably an
identity-key scheme based on libclang's USR that encoded the enclosing class
template's own arity, and a since-renamed ABI inline-namespace pattern
(json_v3_11_0 vs. today's json_abi_v3_11_2) that neither of two earlier regex
attempts stripped correctly. Both are documented in extract_api.py's docstrings
and tools/api_checker/history/README.md so the failure mode doesn't recur
silently.

.github/workflows/check_api_docs.yml runs extract_api.py + check_docs.py in CI,
advisory-only for now (documented backlog may not be at zero for entities this
PR didn't touch), plus a blocking drift check on the committed
tools/api_checker/api_surface.json.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-07-11 18:59:00 +02:00
357 changed files with 673692 additions and 26194 deletions

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+2 -9
View File
@@ -18,8 +18,7 @@ environment:
matrix:
# The Visual Studio 2017 jobs compile everything with /std:c++17, so they
# only build the C++17 variant of each test, split into two jobs each to
# stay below AppVeyor's 60-minute limit per job. The Visual Studio 2019
# job builds the tests for all standards and is split for the same reason.
# stay below AppVeyor's 60-minute limit per job.
- APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
configuration: Debug
platform: x86
@@ -51,13 +50,7 @@ environment:
configuration: Release
platform: x86
CXX_FLAGS: "/W4 /WX"
CMAKE_OPTIONS: "-DJSON_ImplicitConversions=OFF -DJSON_TestShard=0/2"
GENERATOR: Visual Studio 16 2019
- APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
configuration: Release
platform: x86
CXX_FLAGS: "/W4 /WX"
CMAKE_OPTIONS: "-DJSON_ImplicitConversions=OFF -DJSON_TestShard=1/2"
CMAKE_OPTIONS: "-DJSON_ImplicitConversions=OFF"
GENERATOR: Visual Studio 16 2019
- APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
-1
View File
@@ -64,7 +64,6 @@ labels:
- "tests/src/unit-json_view.*"
- "tests/src/json_view_test_helpers\\.hpp"
- "tests/src/fuzzer-(parse_json_view|json_view_image)\\.cpp"
- "tests/benchmarks/json_view/.*"
- "tools/amalgamate/config_json_view\\.json"
- "docs/mkdocs/docs/features/json_view\\.md"
- "docs/mkdocs/docs/api/basic_json_(document|view)/.*"
-22
View File
@@ -154,28 +154,6 @@ jobs:
# PR content in a job without credentials.
python3 tools/generate_natvis/generate_natvis.py $MAIN_DIR
- name: Check the nlohmann_json.natvis generator options
run: |
cd $MAIN_DIR
# The options for configurations outside the checked-in file write
# to a temporary file, so they do not affect the diff below.
GENERATOR=tools/generate_natvis/generate_natvis.py
python3 $GENERATOR --list-tags
TAG_COUNT=$(python3 $GENERATOR --list-tags | wc -l)
python3 $GENERATOR --abi-tags diag,_dp,_vns --abi-tags _diag --output $RUNNER_TEMP/abi_tags.natvis
grep -q '<!-- Namespace nlohmann::json_abi_diag_dp_vns -->' $RUNNER_TEMP/abi_tags.natvis
grep -q '<!-- Namespace nlohmann::json_abi_diag_dp_vns_v[0-9_]* -->' $RUNNER_TEMP/abi_tags.natvis
test $(grep -c '<!-- Namespace ' $RUNNER_TEMP/abi_tags.natvis) -eq $(( $(grep -c '<!-- Namespace ' nlohmann_json.natvis) + 2 ))
python3 $GENERATOR --all --output $RUNNER_TEMP/all.natvis
test $(grep -c '<!-- Namespace ' $RUNNER_TEMP/all.natvis) -eq $(( (1 << TAG_COUNT) * 2 + 1 ))
if python3 $GENERATOR --abi-tags _unknown --output $RUNNER_TEMP/unknown.natvis; then
echo "generate_natvis.py accepted an unknown ABI tag"
exit 1
fi
- name: Build patch and check for differences
id: diff
run: |
+81
View File
@@ -0,0 +1,81 @@
name: "Check API documentation"
on:
pull_request:
permissions:
contents: read
jobs:
check_api_docs:
runs-on: ubuntu-latest
steps:
- name: Harden Runner
uses: step-security/harden-runner@bf7454d06d71f1098171f2acdf0cd4708d7b5920 # v2.20.0
with:
egress-policy: audit
- name: Checkout pull request
uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
- name: Install clang
# Used only as a subprocess for `clang++ -E -v` system-include-path discovery in
# extract_api.py; it does not need to version-match the pinned libclang pip wheel
# below, which does the actual AST parsing. Do not "fix" this to be version-matched.
run: sudo apt-get update && sudo apt-get install -y clang
- name: Install Python dependencies
run: pip install -r tools/api_checker/requirements.txt
- name: Extract API and regenerate the committed surface file
run: |
python3 tools/api_checker/extract_api.py \
--header include/nlohmann/json.hpp \
--include include \
--output /tmp/api_snapshot.json \
--surface-output tools/api_checker/api_surface.json
- name: "Check API documentation (Phase 1: advisory)"
# Surfaces missing/broken @sa links without failing the job while the backlog from the
# initial AST-based rollout is burned down. See tools/api_checker/POLICY.md and the PR
# that introduced this workflow for the two-phase rollout plan.
continue-on-error: true
run: |
python3 tools/api_checker/check_docs.py \
--snapshot /tmp/api_snapshot.json
- name: Check macro documentation (advisory only)
# Cross-checks docs/mkdocs/docs/api/macros/ pages against #define sites. Only checks the
# documented-macro-still-exists direction; never blocks CI. See POLICY.md.
run: python3 tools/api_checker/check_macros.py
- name: Check for uncommitted API surface changes
id: diff
run: |
mkdir -p ${{ github.workspace }}/patch
git diff --patch --no-color -- tools/api_checker/api_surface.json > ${{ github.workspace }}/patch/api_surface.patch
if [ -s ${{ github.workspace }}/patch/api_surface.patch ]; then
echo "tools/api_checker/api_surface.json is out of date. Diff:"
cat ${{ github.workspace }}/patch/api_surface.patch
echo "has_diff=true" >> "$GITHUB_OUTPUT"
else
echo "has_diff=false" >> "$GITHUB_OUTPUT"
fi
# Uploaded so contributors can fix their PR with `git apply api_surface.patch`
# instead of installing libclang locally.
- name: Upload patch
if: steps.diff.outputs.has_diff == 'true'
uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
with:
name: api-surface-patch
path: patch/api_surface.patch
- name: Fail if API surface file is not up to date
# Unlike the doc-backlog check above, this is purely mechanical regeneration with no
# backlog to phase in -- blocking from the start, matching check_amalgamation.yml's
# precedent. Contributors who add/remove/rename public API must regenerate and commit
# tools/api_checker/api_surface.json as part of their PR.
if: steps.diff.outputs.has_diff == 'true'
run: exit 1
+3 -3
View File
@@ -38,14 +38,14 @@ jobs:
# Initializes the CodeQL tools for scanning.
- name: Initialize CodeQL
uses: github/codeql-action/init@6f2ac81f5cd81fe351a197ba0b00d91d03cd2aee # v4.39.0
uses: github/codeql-action/init@24c54180a607b1449ed407dd24f251e4e9147c8d # v4.38.3
with:
languages: c-cpp
# Autobuild attempts to build any compiled languages (C/C++, C#, or Java).
# If this step fails, then you should remove it and run the build manually (see below)
- name: Autobuild
uses: github/codeql-action/autobuild@6f2ac81f5cd81fe351a197ba0b00d91d03cd2aee # v4.39.0
uses: github/codeql-action/autobuild@24c54180a607b1449ed407dd24f251e4e9147c8d # v4.38.3
- name: Perform CodeQL Analysis
uses: github/codeql-action/analyze@6f2ac81f5cd81fe351a197ba0b00d91d03cd2aee # v4.39.0
uses: github/codeql-action/analyze@24c54180a607b1449ed407dd24f251e4e9147c8d # v4.38.3
@@ -37,14 +37,6 @@ jobs:
var matchArtifact = artifacts.data.artifacts.filter((artifact) => {
return artifact.name == "pr"
})[0];
// a run that failed before its jobs started (e.g. a stale queued
// run cancelled long after its push) has no artifact to report on
if (!matchArtifact) {
core.notice('Run ${{ github.event.workflow_run.id }} has no "pr" artifact; nothing to comment on.');
core.setOutput('found', 'false');
return;
}
core.setOutput('found', 'true');
var download = await github.rest.actions.downloadArtifact({
owner: context.repo.owner,
repo: context.repo.repo,
@@ -59,11 +51,9 @@ jobs:
# Extract the untrusted PR artifact into a dedicated empty directory and
# read only the two expected files by fixed path afterwards. This avoids a
# malicious archive overwriting workspace files or escaping via ../ paths.
- if: steps.download.outputs.found == 'true'
run: unzip -o pr.zip -d ./pr_artifact
- run: unzip -o pr.zip -d ./pr_artifact
- name: 'Comment on PR'
if: steps.download.outputs.found == 'true'
uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
with:
github-token: ${{ secrets.GITHUB_TOKEN }}
+1 -1
View File
@@ -47,6 +47,6 @@ jobs:
output: 'flawfinder_results.sarif'
- name: Upload analysis results to GitHub Security tab
uses: github/codeql-action/upload-sarif@6f2ac81f5cd81fe351a197ba0b00d91d03cd2aee # v4.39.0
uses: github/codeql-action/upload-sarif@24c54180a607b1449ed407dd24f251e4e9147c8d # v4.38.3
with:
sarif_file: ${{github.workspace}}/flawfinder_results.sarif
@@ -1,84 +0,0 @@
name: "json_view benchmarks"
# On demand only: runs the comparison of json_view with yyjson, simdjson, and
# Boost.JSON (tests/benchmarks/json_view/compare.py) on GitHub-hosted runners,
# for numbers from x86-64 and AArch64 Linux. It runs when started by hand, or
# when a pull request gets the label "benchmark" (on both architectures, with
# GCC and the default settings). Shared runners are noisy: the results show
# where json_view stands, but published numbers need a quiet machine (see
# tests/benchmarks/json_view/README.md).
on:
pull_request:
types: [labeled]
workflow_dispatch:
inputs:
runner:
description: "Runner image"
type: choice
options:
- ubuntu-24.04
- ubuntu-24.04-arm
default: ubuntu-24.04
compiler:
description: "Compiler"
type: choice
options:
- g++
- clang++
default: g++
native:
description: "Compile for the runner's CPU (-march=native)"
type: boolean
default: false
rounds:
description: "Rounds of bench_view"
type: number
default: 30
permissions:
contents: read
concurrency:
# (the label is part of the group: adding an unrelated label must not cancel a running benchmark)
group: json-view-benchmarks-${{ github.workflow }}-${{ github.ref }}-${{ github.event.label.name }}
cancel-in-progress: true
jobs:
compare:
if: github.event_name == 'workflow_dispatch' || github.event.label.name == 'benchmark'
strategy:
matrix:
runner: ${{ fromJSON(github.event_name == 'workflow_dispatch' && format('["{0}"]', inputs.runner) || '["ubuntu-24.04", "ubuntu-24.04-arm"]') }}
runs-on: ${{ matrix.runner }}
timeout-minutes: 60
steps:
- name: Harden Runner
uses: step-security/harden-runner@ccd8616d44fd3846e67624a50d5aad6d37bf2d25 # v2.22.1
with:
egress-policy: audit
- uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
with:
persist-credentials: false
- name: Download test data
run: |
cmake -S . -B build -DJSON_BuildTests=On
cmake --build build --target download_test_data
- name: Run the comparison
env:
CXX: ${{ inputs.compiler || 'g++' }}
CC: ${{ inputs.compiler == 'clang++' && 'clang' || 'gcc' }}
ROUNDS: ${{ inputs.rounds || 30 }}
NATIVE: ${{ inputs.native && '--native' || '' }}
run: python3 tests/benchmarks/json_view/compare.py --data build/test_files --download --rounds "$ROUNDS" $NATIVE
- name: Summary
run: cat tests/benchmarks/json_view/results/*.md >> "$GITHUB_STEP_SUMMARY"
- uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
with:
name: json_view-benchmarks-${{ matrix.runner }}-${{ inputs.compiler || 'g++' }}
path: tests/benchmarks/json_view/results/
+1 -1
View File
@@ -80,6 +80,6 @@ jobs:
# Upload the results to GitHub's code scanning dashboard.
- name: "Upload to code-scanning"
uses: github/codeql-action/upload-sarif@6f2ac81f5cd81fe351a197ba0b00d91d03cd2aee # v4.39.0
uses: github/codeql-action/upload-sarif@24c54180a607b1449ed407dd24f251e4e9147c8d # v4.38.3
with:
sarif_file: results.sarif
+1 -1
View File
@@ -65,7 +65,7 @@ jobs:
# Upload SARIF file generated in previous step
- name: Upload SARIF file
uses: github/codeql-action/upload-sarif@6f2ac81f5cd81fe351a197ba0b00d91d03cd2aee # v4.39.0
uses: github/codeql-action/upload-sarif@24c54180a607b1449ed407dd24f251e4e9147c8d # v4.38.3
with:
sarif_file: semgrep.sarif
if: always()
+5
View File
@@ -3,6 +3,7 @@
*.gcno
*.gcda
.DS_Store
__pycache__/
/.idea
/cmake-build-*
@@ -44,6 +45,10 @@ venv
nlohmann_json.spdx
# api_checker: ephemeral, location/doc-status-sensitive working file (not the committed
# release-tracking artifact -- see tools/api_checker/api_surface.json for that)
/tools/api_checker/api_snapshot.json
# Bazel-related
MODULE.bazel.lock
-2
View File
@@ -37,7 +37,6 @@ cc_library(
"include/nlohmann/detail/input/parser.hpp",
"include/nlohmann/detail/input/position_t.hpp",
"include/nlohmann/detail/input/pow5_table.hpp",
"include/nlohmann/detail/input/simd_scan.hpp",
"include/nlohmann/detail/input/string_scan.hpp",
"include/nlohmann/detail/iterators/internal_iterator.hpp",
"include/nlohmann/detail/iterators/iter_impl.hpp",
@@ -90,7 +89,6 @@ cc_library(
"include/nlohmann/detail/view/simd.hpp",
"include/nlohmann/detail/view/string_ref.hpp",
"include/nlohmann/detail/view/value.hpp",
"include/nlohmann/detail/view/view_mode.hpp",
"include/nlohmann/json.hpp",
"include/nlohmann/json_fwd.hpp",
"include/nlohmann/json_literals.hpp",
-27
View File
@@ -6,7 +6,6 @@ This file describes the source for supporting files; that is, files that are not
- [GitHub](#github)
- [REUSE](#reuse)
- [Package Managers](#package-managers)
- [Debugging](#debugging)
## Continuous Integration
@@ -290,29 +289,3 @@ The module definition for [Bazel](https://bazel.build)'s [Bzlmod](https://bazel.
Further documentation:
- [Bazel modules](https://bazel.build/external/module)
## Debugging
### `nlohmann_json.natvis`
The [Natvis](https://learn.microsoft.com/en-us/visualstudio/debugger/create-custom-views-of-native-objects) file that
gives `json` values a friendly view in the Visual Studio debugger. The file is generated by
`tools/generate_natvis/generate_natvis.py` from the template `tools/generate_natvis/nlohmann_json.natvis.j2` and the ABI
tags and version in `include/nlohmann/detail/abi_macros.hpp`; change the script or the template rather than editing
the file by hand. The file can be updated by calling
```shell
make natvis
```
The "Check amalgamation" workflow fails if the file is out of date.
The file covers the namespace variants with up to two ABI tags. A Natvis file for other configurations can be
generated with the `--abi-tags` or `--all` options, for example
`make natvis NATVIS_ARGS="--abi-tags _diag,_dp,_vns --output my_nlohmann_json.natvis"`; see
[`tools/generate_natvis`](tools/generate_natvis/README.md). With MSVC, CMake adds the file to the `nlohmann_json`
target and installs it.
Further documentation:
- [Create custom views of C++ objects in the debugger using the Natvis framework](https://learn.microsoft.com/en-us/visualstudio/debugger/create-custom-views-of-native-objects)
+2 -4
View File
@@ -46,7 +46,7 @@ all:
@echo "clean - remove built files"
@echo "(fuzzers) - see tests/fuzzing.md, or run 'make -C tests fuzzers' to build the AFL fuzzers"
@echo "macro_builder_check - check that macro_scope.hpp matches tools/macro_builder's output"
@echo "natvis - regenerate nlohmann_json.natvis from the current ABI tags and version (pass generator options via NATVIS_ARGS, see tools/generate_natvis/README.md)"
@echo "natvis - regenerate nlohmann_json.natvis from the current ABI tags and version"
@echo "pretty - beautify code with Artistic Style"
@echo "pvs_studio - run the PVS-Studio static analyzer and open the report"
@echo "release - create the release files (include.zip, json.tar.xz, single headers, signatures, hashes)"
@@ -120,15 +120,13 @@ $(AMALGAMATED_VIEW_FILE): $(SRCS)
tools/amalgamate/amalgamate.py -c tools/amalgamate/config_json_view.json -s . --verbose=yes
NATVIS_VENV=tools/generate_natvis/venv
# extra options for generate_natvis.py, e.g. NATVIS_ARGS="--abi-tags _diag,_dp,_vns --output my.natvis"
NATVIS_ARGS=
# regenerate nlohmann_json.natvis from the ABI tags and version in include/nlohmann/detail/abi_macros.hpp
# (the dependencies are installed into a virtual environment first)
natvis:
@test -d $(NATVIS_VENV) || python3 -mvenv $(NATVIS_VENV)
@$(NATVIS_VENV)/bin/python3 -c 'import jinja2' 2>/dev/null || $(NATVIS_VENV)/bin/pip3 install --quiet -r tools/generate_natvis/requirements.txt
$(NATVIS_VENV)/bin/python3 tools/generate_natvis/generate_natvis.py $(NATVIS_ARGS) .
$(NATVIS_VENV)/bin/python3 tools/generate_natvis/generate_natvis.py .
# regenerate the two tools/macro_builder blocks of $(MACRO_SCOPE_HPP) (see its README.md) and diff against the
# checked-in header; phony, because it never writes $(MACRO_SCOPE_HPP) itself
+1 -1
View File
@@ -105,7 +105,7 @@ Thanks everyone!
:books: If you want to **learn more** about how to use the library, check out the rest of the [**README**](#examples), have a look at [**code examples**](https://github.com/nlohmann/json/tree/develop/docs/mkdocs/docs/examples), or browse through the [**help pages**](https://json.nlohmann.me).
:construction: If you want to understand the **API** better, check out the [**API Reference**](https://json.nlohmann.me/api/basic_json/) or have a look at the [quick reference](#quick-reference) below.
:construction: If you want to understand the **API** better, check out the [**API Reference**](https://json.nlohmann.me/api/basic_json/) or have a look at the [quick reference](#quick-reference) below. The public API surface is derived mechanically and checked for documentation coverage by the tooling in [`tools/api_checker/`](tools/api_checker/), whose [POLICY.md](tools/api_checker/POLICY.md) defines what counts as public API and what stability is guaranteed.
:bug: If you found a **bug**, please check the [**FAQ**](https://json.nlohmann.me/home/faq/) if it is a known issue or the result of a design decision. Please also have a look at the [**issue list**](https://github.com/nlohmann/json/issues) before you [**create a new issue**](https://github.com/nlohmann/json/issues/new/choose). Please provide as much information as possible to help us understand and reproduce your issue.
+1 -2
View File
@@ -341,14 +341,13 @@ def download(url, docs) -> str:
raise ValueError(f'not an http(s) URL: {url}')
req = urllib.request.Request(u.geturl(), headers={'User-Agent': USER_AGENT})
# (the scheme is checked above)
# nosemgrep: python.lang.security.audit.dynamic-urllib-use-detected.dynamic-urllib-use-detected
with urllib.request.urlopen(req, timeout=20) as r: # nosec B310
data = r.read()
ctype = r.headers.get_content_type()
path = urllib.parse.unquote(u.path).lstrip('/')
ext = os.path.splitext(path)[1]
if u.query or not ext or path.endswith('/'):
digest = hashlib.sha256(url.encode()).hexdigest()[:12]
digest = hashlib.sha1(url.encode(), usedforsecurity=False).hexdigest()[:12]
path = os.path.join(os.path.dirname(path), digest + CONTENT_TYPE_EXT.get(ctype, ext or '.bin'))
rel = os.path.normpath(os.path.join('assets', 'external', u.hostname, path))
out = os.path.join(docs, rel)
@@ -30,14 +30,6 @@ struct adl_serializer {
- [**from_json**](from_json.md) - convert a JSON value to any value type
- [**to_json**](to_json.md) - convert any value type to a JSON value
## See also
- [Arbitrary type conversions](../../features/arbitrary_types.md) - how to make your types convertible
- [**get**](../basic_json/get.md) / [**get_to**](../basic_json/get_to.md) - convert a JSON value to a C++ type
- [**basic_json**](../basic_json/basic_json.md) - construct a JSON value from a C++ value
- [**NLOHMANN_DEFINE_TYPE_INTRUSIVE**](../macros/nlohmann_define_type_intrusive.md) - generate the conversion functions for a type
- [Specializing enum conversion](../../features/enum_conversion.md)
## Version history
- Added in version 2.1.0.
+1 -25
View File
@@ -23,9 +23,6 @@ Checks whether the input is valid JSON.
respectively as UTF-8, UTF-16, and UTF-32. If `SentinelType` differs from `IteratorType`, it must be comparable to
the iterator type with `operator!=`.
Ill-formed UTF-16 and UTF-32 sequences are rejected: a lone surrogate, a high surrogate that is not followed by its
low surrogate, and a code point above `U+10FFFF` all make this function return `false`.
Unlike the [`parse()`](parse.md) function, this function neither throws an exception in case of invalid JSON input
(i.e., a parse error) nor creates diagnostic information.
@@ -38,12 +35,9 @@ Unlike the [`parse()`](parse.md) function, this function neither throws an excep
- a `#!c FILE` pointer (throws if null)
- a C-style array of characters
- a pointer to a null-terminated string of single byte characters (throws if null)
- a `std::string` or a `std::string_view` (C++17)
- a `std::string`
- a container `obj` for which `begin(obj)` and `end(obj)` produce a valid pair of iterators
(as found via ADL or member functions, with semantics compatible to `std::begin` and `std::end`)
- wide characters (`wchar_t`, `char16_t`, `char32_t`), which are converted to UTF-8: a wide string object
(`std::wstring`, `std::u16string`, `std::u32string`) or an array (e.g. a wide string literal); a pointer to a
null-terminated wide string (e.g. `std::u16string::c_str()`) is not supported
`IteratorType`
: a compatible iterator type, for instance.
@@ -131,21 +125,6 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
--8<-- "examples/accept__iterator_pair.output"
```
??? example "Example: (3) reading from UTF-16 strings"
The encoding is deduced from the character type of the input. String literals like `u"..."`, `U"..."`, and
`L"..."` work as well.
```cpp
--8<-- "examples/accept__wide_string.cpp"
```
Output:
```json
--8<-- "examples/accept__wide_string.output"
```
## See also
- [parse](parse.md) - deserialize from a compatible input
@@ -172,9 +151,6 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
([`JSON_DISABLE_STREAM_BULK_SCAN`](../macros/json_disable_stream_bulk_scan.md)).
- Parsing from a `FILE*` locks the file once instead of once per character in version 3.13.0
([`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md)).
- Ill-formed UTF-16 and UTF-32 input (a lone surrogate, a high surrogate that is not followed by its low surrogate, or
a code point above `U+10FFFF`) is rejected in version 3.13.0; before that, some such sequences were accepted or
ended the input silently.
!!! warning "Deprecation"
+3 -2
View File
@@ -239,8 +239,9 @@ Strong exception safety: if an exception occurs, the original value stays intact
1. Added in version 1.0.0.
2. Added in version 1.0.0.
3. Added in version 3.11.0. Support for keys convertible to `std::string_view` added in version 3.13.0, consistently
across the lookup functions.
3. Added in version 3.11.0. Fixed in version 3.13.0 to consistently accept `std::string_view`-convertible keys, as
already supported by [`operator[]`](operator[].md), [`value`](value.md), [`find`](find.md), and other lookup
functions.
4. Added in version 2.0.0. Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109) instead of
[`out_of_range.404`](../../home/exceptions.md#jsonexceptionout_of_range404) for a one-character array index that is not
a digit (e.g., `/x`) in version 3.13.0, as it already did for longer ones.
+1 -1
View File
@@ -63,4 +63,4 @@ Constant.
## Version history
- Added in version 1.0.0.
- Binary values are supported since version 3.8.0.
- Adjusted code to return reference to binary values in version 3.8.0.
+12 -10
View File
@@ -482,15 +482,17 @@ basic_json(basic_json&& other) noexcept;
## Version history
1. Added in version 1.0.0.
2. Added in version 1.0.0.
3. Added in version 2.1.0.
4. Added in version 3.1.2. Explicit for different string types if `JSON_USE_IMPLICIT_CONVERSIONS` is `0` since
version 3.13.0.
5. Added in version 1.0.0.
6. Added in version 1.0.0.
7. Added in version 1.0.0. Fixed in version 3.13.0 to also check the iterator range for binary values; before, a range
1. Since version 1.0.0.
2. Since version 1.0.0.
3. Since version 2.1.0.
4. Since version 3.2.0. Also initializes the position reported by
[`start_pos()`](start_pos.md)/[`end_pos()`](end_pos.md) from `val` when
[`JSON_DIAGNOSTIC_POSITIONS`](../macros/json_diagnostic_positions.md) is enabled, since version 3.12.0. Explicit
for different string types if `JSON_USE_IMPLICIT_CONVERSIONS` is `0` since version 3.13.0.
5. Since version 1.0.0.
6. Since version 1.0.0.
7. Since version 1.0.0. Fixed in version 3.13.0 to also check the iterator range for binary values; before, a range
that did not cover the whole value (such as `(end(), end())`) was accepted and the whole binary value was copied,
unlike the other primitive types.
8. Added in version 1.0.0.
9. Added in version 1.0.0.
8. Since version 1.0.0.
9. Since version 1.0.0.
@@ -0,0 +1,38 @@
# <small>nlohmann::basic_json::</small>bjdata_version_t
```cpp
enum class bjdata_version_t
{
draft2,
draft3,
};
```
This enumeration is used in the [`to_bjdata`](to_bjdata.md) function to choose which draft version of
the BJData specification to encode ND-array extensions for:
draft2
: encode using the BJData Draft 2 ND-array format
draft3
: encode using the BJData Draft 3 ND-array format
## Examples
??? example
The example shows how `bjdata_version_t` selects the BJData draft used by `to_bjdata`.
```cpp
--8<-- "examples/bjdata_version_t.cpp"
```
Output:
```
--8<-- "examples/bjdata_version_t.output"
```
## Version history
- Added in version 3.12.0.
+3 -2
View File
@@ -141,8 +141,9 @@ Logarithmic in the size of the JSON object.
## Version history
1. Added in version 3.11.0.
2. Added in version 3.6.0. Extended template `KeyType` to support comparable types in version 3.11.0. Support for keys
convertible to `std::string_view` added in version 3.13.0, consistently across the lookup functions.
2. Added in version 3.6.0. Extended template `KeyType` to support comparable types in version 3.11.0. Fixed in
version 3.13.0 to consistently accept `std::string_view`-convertible keys, as already supported by
[`operator[]`](operator[].md), [`at`](at.md), [`value`](value.md), and other lookup functions.
3. Added in version 3.7.0.
4. Deleted overloads for integral key types added in version 3.13.0 to reject such calls at compile time instead of
causing undefined behavior at runtime.
+3 -2
View File
@@ -92,7 +92,8 @@ Logarithmic in the size of the JSON object.
## Version history
1. Added in version 3.11.0.
2. Added in version 1.0.0. Changed to support comparable key types in version 3.11.0. Support for keys convertible to
`std::string_view` added in version 3.13.0, consistently across the lookup functions.
2. Added in version 1.0.0. Changed parameter `key` type to `KeyType&&` in version 3.11.0. Fixed in version 3.13.0 to
consistently accept `std::string_view`-convertible keys, as already supported by [`operator[]`](operator[].md),
[`at`](at.md), [`value`](value.md), and other lookup functions.
3. Deleted overload for integral key types added in version 3.13.0 to reject such calls at compile time instead of
causing undefined behavior at runtime.
+1 -1
View File
@@ -69,6 +69,6 @@ Logarithmic in the size of the container, O(log(`size()`)).
## Version history
- Added in version 2.0.8.
- Since version 2.0.8.
- Fixed in version 3.13.0: for [`ordered_json`](../ordered_json.md), the value could previously only be passed as an
rvalue; it can now also be passed as an lvalue or a `#!cpp const` lvalue, matching the behavior of `json`.
@@ -67,5 +67,5 @@ Amortized constant.
## Version history
- Added in version 2.0.8.
- Since version 2.0.8.
- Returns reference since 3.7.0.
+3 -2
View File
@@ -213,6 +213,7 @@ Strong exception safety: if an exception occurs, the original value stays intact
1. Added in version 1.0.0. Added support for binary types in version 3.8.0.
2. Added in version 1.0.0. Added support for binary types in version 3.8.0.
3. Added in version 1.0.0.
4. Added in version 3.11.0. Support for keys convertible to `std::string_view` added in version 3.13.0, consistently
across the lookup functions.
4. Added in version 3.11.0. Fixed in version 3.13.0 to consistently accept `std::string_view`-convertible keys, as
already supported by [`operator[]`](operator[].md), [`at`](at.md), [`value`](value.md), and other lookup
functions.
5. Added in version 1.0.0.
+1 -1
View File
@@ -84,4 +84,4 @@ constructor.
## Version history
- Added in version 3.0.0.
- Since version 3.0.0.
+3 -2
View File
@@ -99,7 +99,8 @@ Logarithmic in the size of the JSON object.
## Version history
1. Added in version 3.11.0.
2. Added in version 1.0.0. Changed to support comparable types in version 3.11.0. Support for keys convertible to
`std::string_view` added in version 3.13.0, consistently across the lookup functions.
2. Added in version 1.0.0. Changed to support comparable types in version 3.11.0. Fixed in version 3.13.0 to
consistently accept `std::string_view`-convertible keys, as already supported by [`operator[]`](operator[].md),
[`at`](at.md), [`value`](value.md), and other lookup functions.
3. Deleted overloads for integral key types added in version 3.13.0 to reject such calls at compile time instead of
causing undefined behavior at runtime.
+1 -1
View File
@@ -57,4 +57,4 @@ Constant.
## Version history
- Added in version 1.0.0.
- Binary values are supported since version 3.8.0.
- Adjusted code to return reference to binary values in version 3.8.0.
+3 -3
View File
@@ -188,6 +188,6 @@ overload (3).
## Version history
1. Added in version 2.1.0.
2. Added in version 2.1.0. Extended to work with other specializations of `basic_json` in version 3.1.2.
3. Added in version 1.0.0.
1. Since version 2.1.0.
2. Since version 2.1.0. Extended to work with other specializations of `basic_json` in version 3.2.0.
3. Since version 1.0.0.
+1 -1
View File
@@ -76,5 +76,5 @@ Depends on the `json_serializer<ValueType>::from_json()` implementation.
## Version history
- Added in version 3.3.0.
- Since version 3.3.0.
- Added a `static_assert` with a clear message for `const` arguments in version 3.13.0.
-19
View File
@@ -44,22 +44,6 @@ are collected in [Template Parameter Requirements](../../features/types/template
- [**json**](../json.md) - default specialization
- [**ordered_json**](../ordered_json.md) - a specialization that maintains the insertion order of object keys
## Documents and views
Besides `basic_json`, the library offers a second way to hold a parsed JSON text: a
[`basic_json_document`](../basic_json_document/index.md), which owns or borrows the text and holds a flat index of the
values in it, and a [`basic_json_view`](../basic_json_view/index.md), a read-only handle to one value of such a document.
Both are defined in the header `<nlohmann/json_view.hpp>`; see
[Zero-copy JSON views](../../features/json_view.md) for the concept and the trade-offs.
- [**json_document**](../json_document.md) / [**ordered_json_document**](../ordered_json_document.md) - read-only
documents of the `basic_json` specialization they belong to
- [**json_editable_document**](../json_editable_document.md) /
[**ordered_json_editable_document**](../ordered_json_editable_document.md) - documents that can be modified in place
- [**json_view**](../json_view.md) / [**ordered_json_view**](../ordered_json_view.md) - views of a document
- [**json_editable_view**](../json_editable_view.md) /
[**ordered_json_editable_view**](../ordered_json_editable_view.md) - views of an editable document
## Iterator invalidation
All operations that add values to an **array** ([`push_back`](push_back.md) , [`operator+=`](operator+=.md),
@@ -359,9 +343,6 @@ Access to the JSON value
## See also
- [RFC 8259: The JavaScript Object Notation (JSON) Data Interchange Format](https://tools.ietf.org/html/rfc8259)
- [basic_json_document](../basic_json_document/index.md) / [basic_json_view](../basic_json_view/index.md) - parse a JSON
text into a flat index and read it through a view
- [Zero-copy JSON views](../../features/json_view.md) - when to use a document and a view instead of a `basic_json`
## Version history
@@ -0,0 +1,32 @@
# <small>nlohmann::basic_json::</small>initializer_list_t
```cpp
using initializer_list_t = std::initializer_list<detail::json_ref<basic_json>>;
```
The type used for the initializer-list [constructor](basic_json.md) (overload 5) and for functions
such as [`operator=`](operator=.md) that accept a braced-init-list of JSON values. Each element wraps a
`basic_json` value or something convertible to one, deferring the decision of whether the list should be
parsed as a JSON array or a JSON object to the constructor itself.
See the [constructor](basic_json.md) documentation for how `initializer_list_t` values are interpreted.
## Examples
??? example
The example shows how an `initializer_list_t` is used to construct a JSON value.
```cpp
--8<-- "examples/initializer_list_t.cpp"
```
Output:
```
--8<-- "examples/initializer_list_t.output"
```
## Version history
- Since version 1.0.0.
@@ -75,4 +75,4 @@ classDiagram
## Version history
- Added in version 3.0.0.
- Since version 3.0.0.
+2 -2
View File
@@ -104,8 +104,8 @@ When iterating over an array, `key()` will return the index of the element as st
## Version history
- Added in version 3.1.0 as the replacement of the static function `iterator_wrapper`, which was available since
version 1.0.0 and is deprecated since version 3.1.0.
- Added `iterator_wrapper` in version 3.0.0.
- Added `items` and deprecated `iterator_wrapper` in version 3.1.0.
- Added structured binding support in version 3.5.0.
!!! warning "Deprecation"
@@ -0,0 +1,31 @@
# <small>nlohmann::basic_json::</small>json_sax_t
```cpp
using json_sax_t = json_sax<basic_json>;
```
The [`json_sax`](../json_sax/index.md) interface bound to this `basic_json` specialization, i.e. with
`BasicJsonType` fixed to `basic_json`. Used as the SAX interface type by [`sax_parse`](sax_parse.md) and
other SAX-based parsing functions.
See [`nlohmann::json_sax`](../json_sax/index.md) for more information.
## Examples
??? example
The example shows the type `json_sax_t`.
```cpp
--8<-- "examples/json_sax_t.cpp"
```
Output:
```
--8<-- "examples/json_sax_t.output"
```
## Version history
- Added in version 3.2.0.
@@ -51,4 +51,4 @@ deserializes. See [Template Parameter Requirements](../../features/types/templat
## Version history
- Added in version 2.1.0.
- Since version 2.0.0.
@@ -38,7 +38,7 @@ Strong guarantee: `source` and `target` are never modified.
Linear in the total number of values (including nested ones) in `source` and `target`, times the cost of a key-based
object operation (looking up a key, or adding one to the patch): logarithmic for [`json`](../json.md), and linear for
[`ordered_json`](../ordered_json.md) (see [`ordered_map` complexity](../ordered_map.md#complexity)). For
[`ordered_json`](../ordered_json.md) (see [`ordered_map` complexity](../ordered_map/index.md#complexity)). For
`ordered_json`, diffing two objects with `n` and `m` members therefore takes O((n+m)²).
## Notes
@@ -71,6 +71,6 @@ returned by `#!cpp (*this)[key]`); it is read as it was when `merge_patch()` was
## Version history
- Added in version 3.1.0.
- Added in version 3.0.0.
- Fixed use of freed or relocated memory when `apply_patch` is `#!cpp *this` or refers to a value contained in
`#!cpp *this`, in version 3.13.0.
@@ -128,6 +128,6 @@ interpreted as `object_t::value_type` or `std::initializer_list<basic_json>`, se
## Version history
1. Added in version 1.0.0.
2. Added in version 1.0.0.
3. Added in version 2.0.0.
1. Since version 1.0.0.
2. Since version 1.0.0.
3. Since version 2.0.0.
@@ -51,3 +51,5 @@ Linear.
## Version history
- Added in version 1.0.0.
- The `noexcept` specification was extended to also depend on
[`json_base_class_t`](json_base_class_t.md)'s move-assignment in version 3.11.3.
@@ -284,10 +284,10 @@ Strong exception safety: if an exception occurs, the original value stays intact
1. Added in version 1.0.0. Fixed in version 3.13.0 to throw `#!cpp std::length_error` instead of emptying the array and
accessing it out of bounds when `idx` equals the maximum value of `size_type`. A missing index in the const version
is guarded by a runtime assertion since version 3.13.0.
2. Added in version 1.0.0. Added overloads for `T* key` in version 1.1.0. The `T* key` overloads forward to
overload 3 since version 3.11.0.
3. Added in version 3.11.0. Support for keys convertible to `std::string_view` added in version 3.13.0, consistently
across the lookup functions.
2. Added in version 1.0.0. Added overloads for `T* key` in version 1.1.0. Removed overloads for `T* key` (replaced by 3)
in version 3.11.0.
3. Added in version 3.11.0. Fixed in version 3.13.0 to consistently accept `std::string_view`-convertible keys, as
already supported by [`at`](at.md), [`value`](value.md), [`find`](find.md), and other lookup functions.
4. Added in version 2.0.0. A missing array index in the const version is guarded by a runtime assertion since
version 3.13.0. Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109) instead of
[`out_of_range.404`](../../home/exceptions.md#jsonexceptionout_of_range404) for a one-character array index that is not
@@ -89,6 +89,11 @@ Linear in the size of the JSON value.
## Version history
- Added in version 1.0.0.
- Since version 1.0.0.
- Macros `JSON_EXPLICIT`/[`JSON_USE_IMPLICIT_CONVERSIONS`](../macros/json_use_implicit_conversions.md) added
in version 3.9.0.
- The exclusion of `std::any` from this conversion became conditional on
[`JSON_HAS_STATIC_RTTI`](../macros/json_has_static_rtti.md) in version 3.11.3.
- `std::optional<T>` excluded from this conversion in version 3.13.0; use
[`get<std::optional<T>>()`](get.md)/[`get_to()`](get_to.md) instead (see
[Converting values](../../features/conversions.md)).
@@ -75,4 +75,4 @@ classDiagram
## Version history
- Added in version 3.0.0.
- Since version 3.0.0.
@@ -76,4 +76,4 @@ classDiagram
## Version history
- Added in version 3.0.0.
- Since version 3.0.0.
+1 -34
View File
@@ -25,10 +25,6 @@ static basic_json parse(IteratorType first, SentinelType last,
respectively as UTF-8, UTF-16, and UTF-32. If `SentinelType` differs from `IteratorType`, it must be comparable to
the iterator type with `operator!=`.
Ill-formed UTF-16 and UTF-32 sequences are rejected: a lone surrogate, a high surrogate that is not followed by its
low surrogate, and a code point above `U+10FFFF` all yield a
[`parse_error.101`](../../home/exceptions.md#jsonexceptionparse_error101).
## Template parameters
`InputType`
@@ -38,12 +34,9 @@ static basic_json parse(IteratorType first, SentinelType last,
- a `FILE` pointer (throws if null)
- a C-style array of characters
- a pointer to a null-terminated string of single byte characters (throws if null)
- a `std::string` or a `std::string_view` (C++17)
- a `std::string`
- a container `obj` for which `begin(obj)` and `end(obj)` produce a valid pair of iterators
(as found via ADL or member functions, with semantics compatible to `std::begin` and `std::end`)
- wide characters (`wchar_t`, `char16_t`, `char32_t`), which are converted to UTF-8: a wide string object
(`std::wstring`, `std::u16string`, `std::u32string`) or an array (e.g. a wide string literal); a pointer to a
null-terminated wide string (e.g. `std::u16string::c_str()`) is not supported
`IteratorType`
: a compatible iterator type, for instance.
@@ -119,13 +112,6 @@ By default, a `'\0'` (NUL) byte anywhere in the input is treated as end of input
outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-bytes-in-the-input) for details and the
[`JSON_STRICT_NUL_HANDLING`](../macros/json_strict_nul_handling.md) macro to opt into rejecting it instead.
!!! tip "Parsing into a document instead of a value"
[`basic_json_document::parse`](../basic_json_document/parse.md) accepts the same inputs and the same options, but
keeps the result as a flat index of the parsed values instead of a tree of `basic_json` values. It is faster and uses
less memory when only parts of the document are read, and it also accepts a pointer to a null-terminated wide string,
which `parse()` does not. See [Zero-copy JSON views](../../features/json_view.md).
!!! tip "Performance"
Contiguous inputs (strings, string views, vectors, arrays, pointer ranges) are the fastest to parse. A
@@ -264,22 +250,6 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
--8<-- "examples/trailing_commas.output"
```
??? example "Example: parse from UTF-16, UTF-32, and wide strings"
The encoding is deduced from the character type of the input; `std::u16string` and `std::u32string` are interpreted
as UTF-16 and UTF-32, and `std::wstring` uses the platform's `wchar_t` width. String literals like `u"..."`,
`U"..."`, and `L"..."` work as well, as do iterators over wide characters.
```cpp
--8<-- "examples/parse__wide_string.cpp"
```
Output:
```json
--8<-- "examples/parse__wide_string.output"
```
## See also
- [accept](accept.md) - check if the input is valid JSON
@@ -310,9 +280,6 @@ outside of a string, invalid) byte; see the [FAQ entry](../../home/faq.md#nul-by
time).
- Parsing from a `FILE*` locks the file once instead of once per character in version 3.13.0
([`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md) restores `std::fgetc`).
- Ill-formed UTF-16 and UTF-32 input (a lone surrogate, a high surrogate that is not followed by its low surrogate, or
a code point above `U+10FFFF`) is rejected with `parse_error.101` in version 3.13.0; before that, some such
sequences were accepted or ended the input silently.
!!! warning "Deprecation"
@@ -84,4 +84,4 @@ or the end of file. This also holds true when reading a byte vector for binary f
## Version history
- Added in version 3.0.0.
- Since version 3.0.0.
+3 -3
View File
@@ -125,6 +125,6 @@ throws.
## Version history
1. Added in version 1.0.0.
2. Added in version 1.0.0.
3. Added in version 2.0.0.
1. Since version 1.0.0.
2. Since version 1.0.0.
3. Since version 2.0.0.
@@ -31,10 +31,6 @@ Read from input and generate SAX events
respectively as UTF-8, UTF-16, and UTF-32. If `SentinelType` differs from `IteratorType`, it must be comparable to
the iterator type with `operator!=`.
Ill-formed UTF-16 and UTF-32 sequences are rejected: a lone surrogate, a high surrogate that is not followed by its
low surrogate, and a code point above `U+10FFFF` all yield a
[`parse_error.101`](../../home/exceptions.md#jsonexceptionparse_error101).
The SAX event lister must follow the interface of [`json_sax`](../json_sax/index.md).
## Template parameters
@@ -46,12 +42,8 @@ The SAX event lister must follow the interface of [`json_sax`](../json_sax/index
- a `FILE` pointer
- a C-style array of characters
- a pointer to a null-terminated string of single byte characters
- a `std::string` or a `std::string_view` (C++17)
- a container `obj` for which `begin(obj)` and `end(obj)` produce a valid pair of iterators
(as found via ADL or member functions, with semantics compatible to `std::begin` and `std::end`)
- wide characters (`wchar_t`, `char16_t`, `char32_t`), which are converted to UTF-8: a wide string object
(`std::wstring`, `std::u16string`, `std::u32string`) or an array (e.g. a wide string literal); a pointer to a
null-terminated wide string (e.g. `std::u16string::c_str()`) is not supported
`IteratorType`
: a compatible iterator type for overload (2); a pair of character iterators whose `value_type` is an integral type
@@ -168,9 +160,6 @@ use the same file with stdio functions, but it must not wait for another thread
([`JSON_DISABLE_STREAM_BULK_SCAN`](../macros/json_disable_stream_bulk_scan.md)).
- Parsing from a `FILE*` locks the file once instead of once per character in version 3.13.0
([`JSON_DISABLE_UNLOCKED_FILE_IO`](../macros/json_disable_unlocked_file_io.md)).
- Ill-formed UTF-16 and UTF-32 input (a lone surrogate, a high surrogate that is not followed by its low surrogate, or
a code point above `U+10FFFF`) is rejected with `parse_error.101` in version 3.13.0; before that, some such
sequences were accepted or ended the input silently.
!!! warning "Deprecation"
+7 -7
View File
@@ -182,10 +182,10 @@ Constant.
## Version history
1. Added in version 1.0.0. Exchanges the `json_base_class_t` subobject along with the value since version 3.13.0.
2. Added in version 1.0.0. Exchanges the `json_base_class_t` subobject along with the value since version 3.13.0.
3. Added in version 1.0.0.
4. Added in version 1.0.0.
5. Added in version 1.0.0.
6. Added in version 3.8.0.
7. Added in version 3.8.0.
1. Since version 1.0.0. Exchanges the `json_base_class_t` subobject along with the value since version 3.13.0.
2. Since version 1.0.0. Exchanges the `json_base_class_t` subobject along with the value since version 3.13.0.
3. Since version 1.0.0.
4. Since version 1.0.0.
5. Since version 1.0.0.
6. Since version 3.8.0.
7. Since version 3.8.0.
@@ -124,3 +124,5 @@ Linear in the size of the JSON value `j`.
[`JSON_STRICT_BINARY_UTF8`](../macros/json_strict_binary_utf8.md) is enabled) throws `type_error.316`.
- Throws `type_error.321` for a discarded value since version 3.13.0; previously, a discarded value nested in an
array or object was silently skipped, producing invalid BJData.
- Writes unsigned integers wider than 64 bits as high-precision numbers since version 3.13.0; previously, they were
silently truncated to 64 bits.
@@ -76,4 +76,4 @@ classDiagram
## Version history
- Added in version 3.0.0.
- Since version 3.0.0.
+6 -3
View File
@@ -231,8 +231,11 @@ changes to any JSON value.
1. Added in version 1.0.0. Changed parameter `default_value` type from `const ValueType&` to `ValueType&&` in version
3.11.0. Deleted overload for integral key types added in version 3.13.0 to reject such calls at compile time
instead of causing undefined behavior at runtime.
2. Added in version 3.11.0. Made `ValueType` the first template parameter in version 3.11.2. Support for keys
convertible to `std::string_view` added in version 3.13.0, consistently across the lookup functions.
3. Added in version 2.0.2. Extended to work with arrays in version 3.13.0. Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109)
2. Added in version 3.11.0. Made `ValueType` the first template parameter in version 3.11.2. Fixed in version 3.13.0
to consistently accept `std::string_view`-convertible keys, as already supported by
[`operator[]`](operator[].md), [`at`](at.md), [`find`](find.md), and other lookup functions.
3. Added in version 2.0.2. Extended to work with arrays in version 3.13.0, including fixing an issue where resolving
`ptr` through an array unexpectedly threw `out_of_range` instead of returning the resolved element (or
`default_value`, as documented). Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109)
instead of returning `default_value` for a one-character array index that is not a digit (e.g., `/x`) in version
3.13.0, as it already did for longer ones.
@@ -12,7 +12,7 @@ void erase(view_type array, I idx);
std::size_t erase(const json_pointer& ptr);
```
Only an **editable** document (`#!cpp view_mode::editable`, e.g. [`json_editable_document`](../json_editable_document.md))
Only an **editable** document (`#!cpp Editable == true`, e.g. [`json_editable_document`](../json_editable_document.md))
has `erase`; calling it on a read-only `basic_json_document` fails to compile (`#!cpp static_assert`).
1. Removes every member of `object` whose key is `key` (see [Notes](#notes) on duplicate keys) and returns how many
@@ -3,14 +3,14 @@
<small>Defined in header `<nlohmann/json_view.hpp>`</small>
```cpp
template<typename BasicJsonType, view_mode Mode = view_mode::read_only>
template<typename BasicJsonType, bool Editable = false>
class basic_json_document;
```
A parsed JSON text, held as a flat index of its values
([16 bytes per value](../../home/architecture.md#node-index-of-json-views)) instead of a tree of `BasicJsonType` values.
Strings and floating-point numbers stay in the source text; integers are converted while parsing, and strings that
contain escapes are decoded into one buffer owned by the document. [`basic_json_view`](../basic_json_view/index.md) is a read-only handle to one value of a
Strings and numbers stay in the source text; only strings that contain escapes are decoded, into one buffer owned by
the document. [`basic_json_view`](../basic_json_view/index.md) is a read-only handle to one value of a
`basic_json_document`; [`materialize()`](../basic_json_view/materialize.md) turns a subtree into the
`BasicJsonType` value that [`BasicJsonType::parse()`](../basic_json/parse.md) would have produced for it.
@@ -20,9 +20,9 @@ is move-only: a copy would duplicate the whole index, the decoded-string buffer,
enough in every use we know of. The index, the decoded strings, and the owned text live in one heap block that the
document holds through a `#!cpp std::unique_ptr`; this is also why views survive a move of the document.
With `#!cpp Mode == view_mode::editable`, the document also offers [`set`](set.md), [`push_back`](push_back.md),
With `#!cpp Editable == true`, the document also offers [`set`](set.md), [`push_back`](push_back.md),
[`insert`](insert.md), and [`erase`](erase.md) to change values in place, see [Edits](#edits) below. The source text
itself is never written; a read-only document (`#!cpp view_mode::read_only`, the default) does not carry any of the
itself is never written; a read-only document (`#!cpp Editable == false`, the default) does not carry any of the
bookkeeping edits need, and calling any of them on one fails to compile (`#!cpp static_assert`).
## Template parameters
@@ -32,10 +32,9 @@ bookkeeping edits need, and calling any of them on one fails to compile (`#!cpp
[`ordered_json`](../ordered_json.md). Only 64-bit `number_integer_t`/`number_unsigned_t` types are supported; this
is checked with a `static_assert`.
`Mode`
: a [`view_mode`](../view_mode.md): `#!cpp view_mode::editable` if the document supports [`set`](set.md),
[`push_back`](push_back.md), [`insert`](insert.md), and [`erase`](erase.md) (optional, `#!cpp view_mode::read_only`
by default). See [Edits](#edits) below.
`Editable`
: whether the document supports [`set`](set.md), [`push_back`](push_back.md), [`insert`](insert.md), and
[`erase`](erase.md) (optional, `#!cpp false` by default). See [Edits](#edits) below.
## Specializations
@@ -48,7 +47,7 @@ bookkeeping edits need, and calling any of them on one fails to compile (`#!cpp
## Member types
- **view_type** - the type of view returned by [`root()`](root.md) (`#!cpp basic_json_view<BasicJsonType, Mode>`)
- **view_type** - the type of view returned by [`root()`](root.md) (`#!cpp basic_json_view<BasicJsonType, Editable>`)
- **value_t** - the JSON type enumeration, see [`basic_json::value_t`](../basic_json/value_t.md)
- **image_check** - how [`load()`](load.md) validates an image (`full`, `bounds`, `none`), see [`image_check`](load.md#image_check)
@@ -81,15 +80,15 @@ bookkeeping edits need, and calling any of them on one fails to compile (`#!cpp
### Edits
- [**set**](set.md) - replace a value, or set an object member, an array element, or the value a JSON pointer refers
to (editable documents only)
- [**push_back**](push_back.md) - append to an array (editable documents only)
- [**insert**](insert.md) - insert an element into an array before a given position (editable documents only)
to (`#!cpp Editable` documents only)
- [**push_back**](push_back.md) - append to an array (`#!cpp Editable` documents only)
- [**insert**](insert.md) - insert an element into an array before a given position (`#!cpp Editable` documents only)
- [**erase**](erase.md) - remove an object member, an array element, or the value a JSON pointer refers to
(editable documents only)
(`#!cpp Editable` documents only)
## Edits
An editable document (`#!cpp view_mode::editable`) can be changed after parsing, with [`set`](set.md),
An editable document (`#!cpp Editable == true`) can be changed after parsing, with [`set`](set.md),
[`push_back`](push_back.md), [`insert`](insert.md), and [`erase`](erase.md);
[`json_editable_document`](../json_editable_document.md) and
[`ordered_json_editable_document`](../ordered_json_editable_document.md) are the corresponding specializations. A few
@@ -116,13 +115,6 @@ points apply to every edit:
[`source_offset()`](../basic_json_view/source_offset.md) of a value introduced by an edit is
`#!cpp static_cast<std::size_t>(-1)`, the same value it reports for a decoded string.
## See also
- [Zero-copy JSON views](../../features/json_view.md) - guide to documents and views
- [**basic_json_view**](../basic_json_view/index.md) - the non-owning handle to a value in a document
- [**json_document**](../json_document.md) and [**json_editable_document**](../json_editable_document.md) - the default specializations
- [**materialize**](../basic_json_view/materialize.md) - build a `basic_json` value from a view
## Version history
- Added in version 3.13.0.
@@ -5,7 +5,7 @@ template<typename I, typename V>
view_type insert(view_type array, I idx, V&& value);
```
Only an **editable** document (`#!cpp view_mode::editable`, e.g. [`json_editable_document`](../json_editable_document.md))
Only an **editable** document (`#!cpp Editable == true`, e.g. [`json_editable_document`](../json_editable_document.md))
has `insert`; calling it on a read-only `basic_json_document` fails to compile (`#!cpp static_assert`).
Inserts `value` into `array` as a new element before position `idx`, which must not be past the end
@@ -55,7 +55,10 @@ validate with overload 2 first, if the original vector must survive a failed loa
## Exceptions
Throws [`parse_error.116`](../../home/exceptions.md#jsonexceptionparse_error116) if `image` is not one
On a big-endian target, throws [`type_error.320`](../../home/exceptions.md#jsonexceptiontype_error320) -- the same
exception [`save()`](save.md#exceptions) throws there, since the image format is little-endian only.
Otherwise throws [`parse_error.116`](../../home/exceptions.md#jsonexceptionparse_error116) if `image` is not one
`save()` could have written, or fails the requested `check`:
| message | when |
@@ -92,9 +95,6 @@ are checked once, however many nodes refer to it.
## Notes
**Little-endian targets only.** On a big-endian target, `load()` does not exist, just like
[`save()`](save.md#notes): the image format is little-endian, so a call fails to compile.
### `image_check` { #image_check }
```cpp
@@ -21,19 +21,17 @@ static basic_json_document parse(IteratorType first, IteratorType last,
Both overloads accept the same JSON text as [`BasicJsonType::parse()`](../basic_json/parse.md), with the same
`ignore_comments`/`ignore_trailing_commas` options, but build a [`basic_json_document`](index.md) (a flat index into
the input) instead of a tree of `BasicJsonType` values. They accept every input `BasicJsonType::parse()` takes, and in
addition a pointer to a null-terminated wide string (which `BasicJsonType::parse()` rejects). Contiguous inputs of
single-byte characters that stay alive can be borrowed; all others (streams, `#!cpp FILE*`, wide characters, which
must be converted to UTF-8, and non-contiguous iterators) are read into a copy that the document owns -- see the
Notes. Use [`parse_copy()`](parse_copy.md) to get an owned copy of a borrowable input
as well.
the input) instead of a tree of `BasicJsonType` values. They take the same inputs as `BasicJsonType::parse()`. Byte
inputs that stay alive can be borrowed; all others (streams, `#!cpp FILE*`, wide characters, non-contiguous
iterators) are read into a copy that the document owns -- see the Notes. Use [`parse_copy()`](parse_copy.md) to get an
owned copy of a borrowable input as well.
## Template parameters
`InputType`
: A compatible input, for instance:
- a `#!cpp std::string`, a `#!cpp std::string_view` (C++17), or a C-style array of single-byte characters
- a `#!cpp std::string`, `#!cpp std::string_view`, or a C-style array of single-byte characters
- a pointer to a null-terminated string of single-byte characters (`#!cpp char`, `#!cpp signed char`,
`#!cpp unsigned char`, `#!cpp std::uint8_t`)
- a container for which `#!cpp obj.data()` and `#!cpp obj.size()` give contiguous single-byte access, e.g.
@@ -49,10 +47,6 @@ as well.
`#!cpp std::string::iterator`; the iterators of single-byte characters are borrowed or read like the byte inputs
above, those of wide characters are converted to UTF-8
Ill-formed UTF-16 and UTF-32 sequences are rejected: a lone surrogate, a high surrogate that is not followed by its low
surrogate, and a code point above `U+10FFFF` all yield a
[`parse_error.101`](../../home/exceptions.md#jsonexceptionparse_error101).
## Parameters
`input` (in)
@@ -161,5 +155,3 @@ buffer of a given length, pass a pair of pointers: `#!cpp parse(ptr, ptr + len)`
## Version history
- Added in version 3.13.0.
- Ill-formed UTF-16 and UTF-32 input (a lone surrogate, a high surrogate that is not followed by its low surrogate, or
a code point above `U+10FFFF`) is rejected with `parse_error.101`.
@@ -13,7 +13,7 @@ editable, and it does not have to be `array`'s own document -- which is copied s
source document afterward; a `BasicJsonType` value; or anything `BasicJsonType` can be constructed from (numbers,
strings, `#!cpp bool`, `#!cpp nullptr`, containers, ...).
Only an **editable** document (`#!cpp view_mode::editable`, e.g. [`json_editable_document`](../json_editable_document.md))
Only an **editable** document (`#!cpp Editable == true`, e.g. [`json_editable_document`](../json_editable_document.md))
has `push_back`; calling it on a read-only `basic_json_document` fails to compile (`#!cpp static_assert`).
## Template parameters
@@ -12,7 +12,7 @@ An edited document is written in its *current* state, with its values in documen
parser would have produced them for that JSON text: a member [`set`](set.md) added goes at the end, an
[`erase`](erase.md)d member leaves no trace, and a float that is not finite (NaN or positive/negative infinity)
becomes null, the same substitution [`dump()`](../basic_json_view/dump.md) makes. The same document always saves to
the same bytes -- also across `BasicJsonType` and the [`view_mode`](../view_mode.md), since the image reflects document order and
the same bytes -- also across `BasicJsonType` and `#!cpp Editable`, since the image reflects document order and
values only, not which specialization produced them.
## Return value
@@ -31,6 +31,9 @@ Throws [`type_error.320`](../../home/exceptions.md#jsonexceptiontype_error320) i
[discarded](is_discarded.md) -- a default-constructed document, or one a failed [`parse()`](parse.md)/
[`read()`](read.md) with `allow_exceptions == false` left discarded.
On a big-endian target, throws `type_error.320` with a different message instead: the image format is little-endian
only (see [Notes](#notes)).
Throws [`out_of_range.416`](../../home/exceptions.md#jsonexceptionout_of_range416) if the node count, the text, or
the decoded strings of the image would individually reach 4 GiB -- the same 32-bit offsets
[`parse()`](parse.md#exceptions) and, for edits, [`set`](set.md)/[`push_back`](push_back.md) are already limited to.
@@ -41,6 +44,9 @@ the decoded strings of the image would individually reach 4 GiB -- the same 32-b
[json.exception.type_error.320] cannot save a discarded json_document
```
```
[json.exception.type_error.320] json_document images need a little-endian target
```
```
[json.exception.out_of_range.416] images of 4 GiB or more are not supported by json_document
```
@@ -64,9 +70,9 @@ else -- see [`load`'s Exceptions](load.md#exceptions).
the *same* build on the *same* (little-endian) machine -- not as a long-term storage format. Keep the original
JSON text if you need to read a saved document back with a future library version.
**Little-endian targets only.** The image is written as raw little-endian bytes, with no byte-swapping. On a
big-endian target, `save()` and [`load`](load.md) do not exist: a call fails to compile rather than produce bytes a
big-endian reader could not interpret correctly.
**Little-endian only.** The image is written as raw little-endian bytes, with no byte-swapping. `save()` (and
[`load`](load.md)) throw `type_error.320` on a big-endian target rather than silently produce bytes a big-endian
reader could not interpret correctly.
## Examples
@@ -18,7 +18,7 @@ template<typename V>
view_type set(const json_pointer& ptr, V&& value);
```
Only an **editable** document (`#!cpp view_mode::editable`, e.g. [`json_editable_document`](../json_editable_document.md))
Only an **editable** document (`#!cpp Editable == true`, e.g. [`json_editable_document`](../json_editable_document.md))
has `set`; calling it on a read-only `basic_json_document` fails to compile (`#!cpp static_assert`).
1. Replaces the value `target` refers to with `value`.
+1 -2
View File
@@ -80,8 +80,7 @@ None of these exceptions carry a [`JSON_DIAGNOSTICS`](../macros/json_diagnostics
Objects with 128 or more members get a hash index of their keys while parsing, so that a lookup in them takes
constant time on average.
2. Linear in `idx`: elements are skipped one at a time from the first one, since they are not a fixed size in the
index (unlike `BasicJsonType`'s array, which is random-access). Constant if no element of the array is an array
or object, since the elements are then adjacent in the index.
index (unlike `BasicJsonType`'s array, which is random-access).
3. Linear in the number of reference tokens of `ptr` and, for each token, in the number of members of the object at
that level (as 1.) or the index into the array (as 2.).
+1 -2
View File
@@ -28,8 +28,7 @@ This exception does not carry a [`JSON_DIAGNOSTICS`](../macros/json_diagnostics.
Linear in the size of the array or object: unlike [`front()`](front.md), which only ever looks at the first
element, `back()` has to walk every element to find where they end, since elements are not a fixed size in the
index. Constant if no element of the array is an array or object, since the elements are then adjacent
in the index.
index.
## Notes
+5 -13
View File
@@ -3,7 +3,7 @@
<small>Defined in header `<nlohmann/json_view.hpp>`</small>
```cpp
template<typename BasicJsonType, view_mode Mode = view_mode::read_only>
template<typename BasicJsonType, bool Editable = false>
class basic_json_view;
```
@@ -37,7 +37,7 @@ Moving the document itself does not invalidate its views: the index is heap-allo
`#!cpp operator ValueType()`), and no `#!cpp get_ptr()` or `#!cpp get_ref()`; see [`get`](get.md).
`basic_json_view` itself is always read-only -- it never has a `set` or `push_back` of its own. A view of an
**editable** document (`#!cpp view_mode::editable`) sees every edit made through
**editable** document (`#!cpp Editable == true`) sees every edit made through
[`basic_json_document::set`](../basic_json_document/set.md) and
[`basic_json_document::push_back`](../basic_json_document/push_back.md): once a value is changed, every view that
still refers to it -- including ones taken before the change -- reads the new value. See
@@ -49,10 +49,9 @@ still refers to it -- including ones taken before the change -- reads the new va
: a specialization of [`basic_json`](../basic_json/index.md), matching the
[`basic_json_document`](../basic_json_document/index.md) the view was taken from.
`Mode`
: a [`view_mode`](../view_mode.md): whether the view is of an editable document, matching the
[`basic_json_document`](../basic_json_document/index.md) it was taken from (optional, `#!cpp view_mode::read_only` by
default). See [Edits](../basic_json_document/index.md#edits).
`Editable`
: whether the view is of an editable document, matching the [`basic_json_document`](../basic_json_document/index.md)
it was taken from (optional, `#!cpp false` by default). See [Edits](../basic_json_document/index.md#edits).
## Specializations
@@ -144,13 +143,6 @@ still refers to it -- including ones taken before the change -- reads the new va
- [**source_offset**](source_offset.md) - byte offset of this value in the document's source text
## See also
- [Zero-copy JSON views](../../features/json_view.md) - guide to documents and views
- [**basic_json_document**](../basic_json_document/index.md) - the document that owns the parsed data
- [**json_view**](../json_view.md) and [**json_editable_view**](../json_editable_view.md) - the default specializations
- [**materialize**](materialize.md) - build a `basic_json` value from a view
## Version history
- Added in version 3.13.0.
@@ -86,8 +86,7 @@ None of these exceptions carry a [`JSON_DIAGNOSTICS`](../macros/json_diagnostics
Objects with 128 or more members get a hash index of their keys while parsing, so that a lookup in them takes
constant time on average.
2. Linear in `idx`: elements are skipped one at a time from the first one, since they are not a fixed size in the
index (unlike `BasicJsonType`'s array, which is random-access). Constant if no element of the array is an array
or object, since the elements are then adjacent in the index.
index (unlike `BasicJsonType`'s array, which is random-access).
3. Linear in the number of reference tokens of `ptr` and, for each token, in the number of members of the object at
that level (as 1.) or the index into the array (as 2.).
@@ -51,4 +51,4 @@ byte_container_with_subtype(container_type&& container, subtype_type subtype);
## Version history
Added in version 3.8.0.
Since version 3.8.0.
@@ -39,4 +39,4 @@ Constant.
## Version history
Added in version 3.8.0.
Since version 3.8.0.
@@ -0,0 +1,32 @@
# <small>nlohmann::byte_container_with_subtype::</small>container_type
```cpp
using container_type = BinaryType;
```
The type of the underlying binary container, forwarded from the `BinaryType` template parameter that
`byte_container_with_subtype` is instantiated with. `byte_container_with_subtype` publicly inherits from
`container_type`.
See [`basic_json::binary_t`](../basic_json/binary_t.md) for the type typically used to instantiate
`BinaryType`.
## Examples
??? example
The example shows the type `container_type`.
```cpp
--8<-- "examples/byte_container_with_subtype__container_type.cpp"
```
Output:
```
--8<-- "examples/byte_container_with_subtype__container_type.output"
```
## Version history
- Since version 3.8.0.
@@ -42,4 +42,4 @@ Constant.
## Version history
Added in version 3.8.0.
Since version 3.8.0.
@@ -29,14 +29,6 @@ specific naming scheme in order to override the binary type.
- [**has_subtype**](has_subtype.md) - return whether the value has a subtype
- [**clear_subtype**](clear_subtype.md) - clears the binary subtype
## See also
- [Binary values](../../features/binary_values.md) - how binary values and subtypes are handled
- [**binary**](../basic_json/binary.md) - create a binary array value
- [**get_binary**](../basic_json/get_binary.md) - get a reference to the stored binary value
- [**binary_t**](../basic_json/binary_t.md) - type for binary arrays
- [Binary formats](../../features/binary_formats/index.md) - formats that can store binary values
## Version history
- Added in version 3.8.0.
@@ -44,4 +44,4 @@ Constant.
## Version history
Added in version 3.8.0.
Since version 3.8.0.
@@ -0,0 +1,28 @@
# <small>nlohmann::byte_container_with_subtype::</small>subtype_type
```cpp
using subtype_type = std::uint64_t;
```
The type used to store the optional binary subtype tag. See [`subtype`](subtype.md) and
[`set_subtype`](set_subtype.md).
## Examples
??? example
The example shows the type `subtype_type`.
```cpp
--8<-- "examples/byte_container_with_subtype__subtype_type.cpp"
```
Output:
```
--8<-- "examples/byte_container_with_subtype__subtype_type.output"
```
## Version history
- Since version 3.8.0.
+1 -1
View File
@@ -30,4 +30,4 @@ types.
## Version history
Added in version 1.0.0.
Since version 1.0.0.
+1 -1
View File
@@ -32,4 +32,4 @@ specialization.
## Version history
Added in version 3.13.0.
Since version 3.13.0.
@@ -3,7 +3,7 @@
<small>Defined in header `<nlohmann/json_view.hpp>`</small>
```cpp
using json_editable_document = basic_json_document<json, view_mode::editable>;
using json_editable_document = basic_json_document<json, true>;
```
This type is an **editable** [`basic_json_document`](basic_json_document/index.md) of the default
@@ -40,4 +40,4 @@ parsing, without ever rewriting the source text -- see [Edits](basic_json_docume
## Version history
Added in version 3.13.0.
Since version 3.13.0.
+2 -2
View File
@@ -3,7 +3,7 @@
<small>Defined in header `<nlohmann/json_view.hpp>`</small>
```cpp
using json_editable_view = basic_json_view<json, view_mode::editable>;
using json_editable_view = basic_json_view<json, true>;
```
This type is a [`basic_json_view`](basic_json_view/index.md) of a value of a
@@ -38,4 +38,4 @@ still referring to it seeing the change, see [Edits](basic_json_document/index.m
## Version history
Added in version 3.13.0.
Since version 3.13.0.
@@ -51,5 +51,5 @@ operator string_t() const
## Version history
- Added in version 2.0.0.
- Since version 2.0.0.
- Changed type to `string_t` and deprecated in version 3.11.0.
@@ -49,5 +49,5 @@ ptr == json_pointer(ptr.to_string());
## Version history
- Added in version 2.0.0.
- Since version 2.0.0.
- Changed return type to `string_t` in version 3.11.0.
+30
View File
@@ -0,0 +1,30 @@
# <small>nlohmann::json_sax::</small>binary_t
```cpp
using binary_t = typename BasicJsonType::binary_t;
```
The type used by the [`binary`](binary.md) callback for JSON binary values, forwarded from the
`BasicJsonType` template parameter.
See [`basic_json::binary_t`](../basic_json/binary_t.md) for more information.
## Examples
??? example
The example shows the type `binary_t` and its relation to `basic_json::binary_t`.
```cpp
--8<-- "examples/json_sax__binary_t.cpp"
```
Output:
```
--8<-- "examples/json_sax__binary_t.output"
```
## Version history
- Added in version 3.8.0.
-7
View File
@@ -59,13 +59,6 @@ leading `-` sign.
- [**start_object**](start_object.md) (_virtual_) - the beginning of an object was read
- [**string**](string.md) (_virtual_) - a string value was read
## See also
- [SAX interface](../../features/parsing/sax_interface.md) - guide to event-based parsing
- [**sax_parse**](../basic_json/sax_parse.md) - generate SAX events from an input
- [**parse**](../basic_json/parse.md) - DOM parsing, with optional [parser callbacks](../../features/parsing/parser_callbacks.md)
- [Parse exceptions](../../features/parsing/parse_exceptions.md)
## Version history
- Added in version 3.2.0.
+33
View File
@@ -0,0 +1,33 @@
# <small>nlohmann::json_sax::</small>json_sax
```cpp
// (1)
json_sax() = default;
// (2)
json_sax(const json_sax&) = default;
// (3)
json_sax(json_sax&&) noexcept = default;
```
1. Default constructor.
2. Copy constructor.
3. Move constructor.
`json_sax` is a pure abstract base class with no data members of its own, so all three constructors are
defaulted and only exist to make derived SAX consumers explicitly copyable/movable.
## Exception safety
No-throw guarantee: none of these constructors throw exceptions.
## Complexity
Constant.
<!-- NOLINT Examples -->
## Version history
- Added in version 3.2.0.
@@ -0,0 +1,30 @@
# <small>nlohmann::json_sax::</small>number_float_t
```cpp
using number_float_t = typename BasicJsonType::number_float_t;
```
The type used by the [`number_float`](number_float.md) callback for JSON floating-point numbers,
forwarded from the `BasicJsonType` template parameter.
See [`basic_json::number_float_t`](../basic_json/number_float_t.md) for more information.
## Examples
??? example
The example shows the type `number_float_t` and its relation to `basic_json::number_float_t`.
```cpp
--8<-- "examples/json_sax__number_float_t.cpp"
```
Output:
```
--8<-- "examples/json_sax__number_float_t.output"
```
## Version history
- Added in version 3.2.0.
@@ -0,0 +1,30 @@
# <small>nlohmann::json_sax::</small>number_integer_t
```cpp
using number_integer_t = typename BasicJsonType::number_integer_t;
```
The type used by the [`number_integer`](number_integer.md) callback for JSON integer numbers, forwarded
from the `BasicJsonType` template parameter.
See [`basic_json::number_integer_t`](../basic_json/number_integer_t.md) for more information.
## Examples
??? example
The example shows the type `number_integer_t` and its relation to `basic_json::number_integer_t`.
```cpp
--8<-- "examples/json_sax__number_integer_t.cpp"
```
Output:
```
--8<-- "examples/json_sax__number_integer_t.output"
```
## Version history
- Added in version 3.2.0.
@@ -0,0 +1,30 @@
# <small>nlohmann::json_sax::</small>number_unsigned_t
```cpp
using number_unsigned_t = typename BasicJsonType::number_unsigned_t;
```
The type used by the [`number_unsigned`](number_unsigned.md) callback for JSON unsigned integer numbers,
forwarded from the `BasicJsonType` template parameter.
See [`basic_json::number_unsigned_t`](../basic_json/number_unsigned_t.md) for more information.
## Examples
??? example
The example shows the type `number_unsigned_t` and its relation to `basic_json::number_unsigned_t`.
```cpp
--8<-- "examples/json_sax__number_unsigned_t.cpp"
```
Output:
```
--8<-- "examples/json_sax__number_unsigned_t.output"
```
## Version history
- Added in version 3.2.0.
@@ -0,0 +1,29 @@
# <small>nlohmann::json_sax::</small>operator=
```cpp
// (1)
json_sax& operator=(const json_sax&) = default;
// (2)
json_sax& operator=(json_sax&&) noexcept = default;
```
1. Copy assignment operator.
2. Move assignment operator.
`json_sax` is a pure abstract base class with no data members of its own, so both assignment operators
are defaulted and only exist to make derived SAX consumers explicitly copy-/move-assignable.
## Exception safety
No-throw guarantee: neither operator throws exceptions.
## Complexity
Constant.
<!-- NOLINT Examples -->
## Version history
- Added in version 3.2.0.
+30
View File
@@ -0,0 +1,30 @@
# <small>nlohmann::json_sax::</small>string_t
```cpp
using string_t = typename BasicJsonType::string_t;
```
The type used by the [`string`](string.md) and [`key`](key.md) callbacks for JSON strings and object
keys, forwarded from the `BasicJsonType` template parameter.
See [`basic_json::string_t`](../basic_json/string_t.md) for more information.
## Examples
??? example
The example shows the type `string_t` and its relation to `basic_json::string_t`.
```cpp
--8<-- "examples/json_sax__string_t.cpp"
```
Output:
```
--8<-- "examples/json_sax__string_t.output"
```
## Version history
- Added in version 3.2.0.
@@ -0,0 +1,22 @@
# <small>nlohmann::json_sax::</small>~json_sax
```cpp
virtual ~json_sax() = default;
```
Destructor. Virtual to allow proper destruction of derived SAX consumer classes through a
pointer/reference to `json_sax`.
## Exception safety
No-throw guarantee: this destructor never throws exceptions.
## Complexity
Constant.
<!-- NOLINT Examples -->
## Version history
- Added in version 3.2.0.
+1 -1
View File
@@ -31,4 +31,4 @@ This type is a [`basic_json_view`](basic_json_view/index.md) of a value of a [`j
## Version history
Added in version 3.13.0.
Since version 3.13.0.
+1 -11
View File
@@ -38,7 +38,6 @@ header. See also the [macro overview page](../../features/macros.md).
- [**JSON_HAS_THREE_WAY_COMPARISON**](json_has_three_way_comparison.md) - control 3-way comparison support
- [**JSON_NO_AUTOMATIC_UDLS**](json_no_automatic_udls.md) - do not include the user-defined string literals (UDLs) automatically
- [**JSON_NO_IO**](json_no_io.md) - switch off functions relying on certain C++ I/O headers
- [**JSON_NO_SIMD**](json_no_simd.md) - use only portable code instead of vector instructions (SSE2, SSSE3, NEON)
- [**JSON_NO_THREAD_LOCAL**](json_no_thread_local.md) - switch off the use of `thread_local` storage
- [**JSON_SKIP_UNSUPPORTED_COMPILER_CHECK**](json_skip_unsupported_compiler_check.md) - do not warn about unsupported compilers
- [**JSON_USE_GLOBAL_UDLS**](json_use_global_udls.md) - place user-defined string literals (UDLs) into the global namespace
@@ -137,13 +136,4 @@ header. See also the [macro overview page](../../features/macros.md).
- [**NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES**](nlohmann_define_type_with_names.md) - serialize/deserialize
a derived class; uses default values; uses custom names
- [**NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES**](nlohmann_define_type_with_names.md) - serialize a derived
class; uses custom names
## See also
- [Macros](../../features/macros.md) - guide to the supported macros
- [Runtime assertions](../../features/assertions.md)
- [Arbitrary type conversions](../../features/arbitrary_types.md) - using the `NLOHMANN_DEFINE_TYPE_*` macros
- [Enum conversion](../../features/enum_conversion.md) - using `NLOHMANN_JSON_SERIALIZE_ENUM`
- [The `nlohmann` namespace](../../features/namespace.md)
- [CMake integration](../../integration/cmake.md) - setting macros from the build system
class; uses custom names
@@ -1,83 +0,0 @@
# JSON_NO_SIMD
```cpp
#define JSON_NO_SIMD
```
When defined, the library uses only portable C++ code where it would otherwise use vector instructions: when scanning
strings during parsing, and when writing floating-point numbers during serialization.
The macro is an escape hatch, for example for toolchains that cannot compile the vector code, for sanitizers or
analyzers that do not understand it, or to compare the speed of both variants. It does not change any result: values,
exceptions, and error positions are the same either way. Only the speed differs.
## Default definition
By default, `#!cpp JSON_NO_SIMD` is not defined, and vector instructions are used where the target has them.
```cpp
#undef JSON_NO_SIMD
```
## Notes
!!! note "Which instructions are used"
- **x86-64:** SSE2, which every x86-64 CPU has, finds the end of runs of plain string characters 16 bytes at a time
and writes the digits of floating-point numbers. The UTF-8 check of non-ASCII text needs SSSE3, which is not part
of x86-64: it is compiled for SSSE3 with a function attribute and used when the CPU has SSSE3 (every x86-64 CPU
since about 2011), else the portable check. Code compiled for SSSE3 anyway (e.g., with `-mssse3` or `-march=native`)
skips this check of the CPU. 32-bit x86 uses SSE2 for strings when the compiler targets it.
- **AArch64:** NEON, which every 64-bit Arm CPU has, checks UTF-8 text and long runs of plain string characters 16
bytes at a time, and writes the digits of floating-point numbers. With MSVC, only the floating-point digits use
NEON.
- **Other targets:** portable code only.
Strings are only scanned this way for contiguous input and for the characters a `#!cpp std::istream` holds in its
stream buffer (see [`JSON_DISABLE_STREAM_BULK_SCAN`](json_disable_stream_bulk_scan.md)); other inputs are read one
character at a time.
!!! note "Interaction with `JSON_USE_SIMDUTF`"
With [`JSON_USE_SIMDUTF`](json_use_simdutf.md), runs of string characters are first validated by simdutf; the code
described here is used for what simdutf does not accept, so that errors are reported at the same position.
`JSON_NO_SIMD` does not affect simdutf.
!!! note "ABI compatibility"
The macro selects between two definitions of the library's internal scanning and formatting functions. Whether it
is defined is encoded in the [namespace](../../features/namespace.md) (tag `_ns`), resulting in distinct symbol
names. Translation units compiled with and without it can therefore be linked into the same program without One
Definition Rule (ODR) violations, but they cannot exchange instances of library types.
## Examples
??? example "Example: switching off vector instructions"
The program parses and serializes the same values with and without the macro:
```cpp
#define JSON_NO_SIMD
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
const json j = json::parse(R"({"name": "日本語 text", "pi": 3.141592653589793})");
std::cout << j.dump() << '\n'; // {"name":"日本語 text","pi":3.141592653589793}
}
```
## See also
- [**parse**](../basic_json/parse.md) - deserialize from a compatible input
- [**dump**](../basic_json/dump.md) - serialization
- [**JSON_USE_SIMDUTF**](json_use_simdutf.md) - use the simdutf library to accelerate UTF-8 validation
- [**JSON_DISABLE_STREAM_BULK_SCAN**](json_disable_stream_bulk_scan.md) - read a `std::istream` one character at a time
- [Parsing: input sources and performance](../../features/parsing/index.md#input-sources-and-performance)
## Version history
- Added in version 3.13.0.
@@ -6,9 +6,8 @@
When defined, the parser validates the UTF-8 content of JSON strings that come from a **contiguous byte input**
(`std::string`, `std::vector<char>`/`<std::uint8_t>`, string literals, `const char*` ranges, …) using the
[simdutf](https://github.com/simdutf/simdutf) library instead of the built-in validator (which uses SSSE3 or NEON where
available, see [`JSON_NO_SIMD`](json_no_simd.md)). On text with many non-ASCII characters (e.g. CJK or emoji) this can
validate faster, depending on the CPU.
[simdutf](https://github.com/simdutf/simdutf) library instead of the built-in scalar validator. On text with many
non-ASCII characters (e.g. CJK or emoji) this can validate several times faster.
This is an **opt-in external dependency**. The library itself remains header-only and its behavior is unchanged: the
same input is accepted or rejected either way, and every parse error is reported at the same position with the same
@@ -39,6 +39,6 @@ the library.
## Version history
- Added in version 3.11.0. Changed inline namespace name in version 3.11.2. Added the ABI tag `_dp` in
version 3.12.0, and the ABI tags `_bics`, `_psp`, `_snul`, `_sbu8`, `_ekmo`, `_dsbs`, `_dufio`, `_ns`, `_vns`,
and `_vssse3` in version 3.13.0; see
version 3.12.0, and the ABI tags `_bics`, `_psp`, `_snul`, `_sbu8`, `_ekmo`, `_dsbs`, `_dufio`, `_vns`, and
`_vssse3` in version 3.13.0; see
[`nlohmann` Namespace](../../features/namespace.md#structure).
+5 -5
View File
@@ -8,16 +8,16 @@ This type preserves the insertion order of object keys.
## Iterator invalidation
The type is based on [`ordered_map`](ordered_map.md) which in turn uses a `std::vector` to store object elements.
The type is based on [`ordered_map`](ordered_map/index.md) which in turn uses a `std::vector` to store object elements.
Therefore, adding object elements can yield a reallocation in which case all iterators (including the
[`end()`](basic_json/end.md) iterator) and all references to the elements are invalidated. Also, any iterator or
reference after the insertion point will point to the same index, which is now a different value.
## Complexity
[`ordered_map`](ordered_map.md) has no lookup index: every key-based object operation is a linear scan, so building or
[`ordered_map`](ordered_map/index.md) has no lookup index: every key-based object operation is a linear scan, so building or
parsing an object of `n` keys costs O(n²) rather than O(n log n). See
[`ordered_map` complexity](ordered_map.md#complexity) for the per-operation table and for measured numbers.
[`ordered_map` complexity](ordered_map/index.md#complexity) for the per-operation table and for measured numbers.
## Examples
@@ -37,9 +37,9 @@ parsing an object of `n` keys costs O(n²) rather than O(n log n). See
## See also
- [ordered_map](ordered_map.md)
- [ordered_map](ordered_map/index.md)
- [Object Order](../features/object_order.md)
## Version history
Added in version 3.9.0.
Since version 3.9.0.
@@ -35,4 +35,4 @@ of object keys, instead of sorting them like [`json_document`](json_document.md)
## Version history
Added in version 3.13.0.
Since version 3.13.0.
@@ -3,7 +3,7 @@
<small>Defined in header `<nlohmann/json_view.hpp>`</small>
```cpp
using ordered_json_editable_document = basic_json_document<ordered_json, view_mode::editable>;
using ordered_json_editable_document = basic_json_document<ordered_json, true>;
```
This type is an **editable** [`basic_json_document`](basic_json_document/index.md) of the
@@ -44,4 +44,4 @@ members [`set`](basic_json_document/set.md) added -- instead of sorting them lik
## Version history
Added in version 3.13.0.
Since version 3.13.0.
@@ -3,7 +3,7 @@
<small>Defined in header `<nlohmann/json_view.hpp>`</small>
```cpp
using ordered_json_editable_view = basic_json_view<ordered_json, view_mode::editable>;
using ordered_json_editable_view = basic_json_view<ordered_json, true>;
```
This type is a [`basic_json_view`](basic_json_view/index.md) of a value of an
@@ -37,4 +37,4 @@ This type is a [`basic_json_view`](basic_json_view/index.md) of a value of an
## Version history
Added in version 3.13.0.
Since version 3.13.0.
+1 -1
View File
@@ -32,4 +32,4 @@ This type is a [`basic_json_view`](basic_json_view/index.md) of a value of an
## Version history
Added in version 3.13.0.
Since version 3.13.0.
@@ -0,0 +1,28 @@
# <small>nlohmann::ordered_map::</small>Container
```cpp
using Container = std::vector<std::pair<const Key, T>, Allocator>;
```
The base container type that `ordered_map` publicly inherits from. Elements are stored in insertion
order as `#!cpp std::pair<const Key, T>` entries in a `std::vector`.
## Examples
??? example
The example shows the type `Container`.
```cpp
--8<-- "examples/ordered_map__Container.cpp"
```
Output:
```
--8<-- "examples/ordered_map__Container.output"
```
## Version history
- Added in version 3.9.0 to implement [`nlohmann::ordered_json`](../ordered_json.md).
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# <small>nlohmann::ordered_map::</small>at
```cpp
// (1)
T& at(const key_type& key);
const T& at(const key_type& key) const;
// (2)
template<class KeyType>
T& at(KeyType&& key);
template<class KeyType>
const T& at(KeyType&& key) const;
```
1. Returns a reference to the value mapped to `key`.
2. Same as (1), but for any `KeyType` comparable to `key_type` via [`key_compare`](key_compare.md)
(heterogeneous lookup, e.g. looking up by a `#!cpp const char*` without constructing a temporary
`key_type`). Only participates in overload resolution if `KeyType` is usable as a key type.
## Template parameters
`KeyType`
: a type comparable to `key_type` via [`key_compare`](key_compare.md)
## Parameters
`key` (in)
: key of the element to find
## Return value
reference to the mapped value of the element with key equal to `key`
## Exceptions
Throws `std::out_of_range` if no element with key `key` exists.
## Complexity
Linear in the number of elements.
## Examples
??? example
The example shows how `at` is used.
```cpp
--8<-- "examples/ordered_map__at.cpp"
```
Output:
```
--8<-- "examples/ordered_map__at.output"
```
## Version history
- Added in version 3.9.1 to implement [`nlohmann::ordered_json`](../ordered_json.md).
- Overload (2) added in version 3.11.0.
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