amorfo77/json
1
0 Fork 0
mirror of https://github.com/nlohmann/json.git synced 2026-10-23 06:18:56 +00:00
Code Issues Packages Projects Releases Wiki Activity

deploy: 52fecc1fab

Browse Source
This commit is contained in:
nlohmann committed 2026-10-21 19:07:29 +00:00
1 parent 73e6e76732
commit b3d9aca8da
375 files changed
+582 -388
Download Patch File Download Diff File Expand all files Collapse all files

No files matched your search

api/macros/json_no_simd/index.html
+14
View File
@@ -0,0 +1,14 @@
<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/api/macros/json_no_simd/" rel="canonical"><link href=../json_no_io/ rel=prev><link href=../json_no_thread_local/ rel=next><link rel=icon href=../../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.7"><title>JSON_NO_SIMD - JSON for Modern C++</title><link rel=stylesheet href=../../../assets/stylesheets/main.ec1eaa64.min.css><link rel=stylesheet href=../../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../../css/custom.css><script>__md_scope=new URL("../../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#json_no_simd class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> JSON_NO_SIMD </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio name=__palette id=__palette_0> <label class="md-header__button md-icon" title="Switch to dark mode" for=__palette_1 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class=md-option data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme=slate data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to light mode" type=radio name=__palette id=__palette_1> <label class="md-header__button md-icon" title="Switch to light mode" for=__palette_0 hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for=__search> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5Line truncated
</code></pre></div> <p>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.</p> <p>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.</p> <h2 id=default-definition>Default definition<a class=headerlink href=#default-definition title="Permanent link">&para;</a></h2> <p>By default, <code class=highlight><span class=n>JSON_NO_SIMD</span></code> is not defined, and vector instructions are used where the target has them.</p> <div class=highlight><pre><span></span><code><span class=cp>#undef JSON_NO_SIMD</span>
</code></pre></div> <h2 id=notes>Notes<a class=headerlink href=#notes title="Permanent link">&para;</a></h2> <div class="admonition note"> <p class=admonition-title>Which instructions are used</p> <ul> <li><strong>x86-64:</strong> 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 <abbr title="Unicode Transformation Format">UTF</abbr>-8 check of non-<abbr title="American Standard Code for Information Interchange">ASCII</abbr> 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 <code>-mssse3</code> or <code>-march=native</code>) skips this check of the CPU. 32-bit x86 uses SSE2 for strings when the compiler targets it.</li> <li><strong>AArch64:</strong> NEON, which every 64-bit Arm CPU has, checks <abbr title="Unicode Transformation Format">UTF</abbr>-8 text and long runs of plain string characters 16 bytes at a time, and writes the digits of floating-point numbers. With <abbr title="Microsoft Visual C++">MSVC</abbr>, only the floating-point digits use NEON.</li> <li><strong>Other targets:</strong> portable code only.</li> </ul> <p>Strings are only scanned this way for contiguous input and for the characters a <code class=highlight><span class=n>std</span><span class=o>::</span><span class=n>istream</span></code> holds in its stream buffer (see <a href=../json_disable_stream_bulk_scan/ ><code>JSON_DISABLE_STREAM_BULK_SCAN</code></a>); other inputs are read one character at a time.</p> </div> <div class="admonition note"> <p class=admonition-title>Interaction with <code>JSON_USE_SIMDUTF</code></p> <p>With <a href=../json_use_simdutf/ ><code>JSON_USE_SIMDUTF</code></a>, 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. <code>JSON_NO_SIMD</code> does not affect simdutf.</p> </div> <div class="admonition note"> <p class=admonition-title>ABI compatibility</p> <p>The macro selects between two definitions of the library's internal scanning and formatting functions. Whether it is defined is encoded in the <a href=../../../features/namespace/ >namespace</a> (tag <code>_ns</code>), 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.</p> </div> <h2 id=examples>Examples<a class=headerlink href=#examples title="Permanent link">&para;</a></h2> <details class=example> <summary>Example: switching off vector instructions</summary> <p>The program parses and serializes the same values with and without the macro:</p> <div class=highlight><pre><span></span><code><span class=cp>#define JSON_NO_SIMD</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;iostream&gt;</span>
<span class=cp>#include</span><span class=w> </span><span class=cpf>&lt;nlohmann/json.hpp&gt;</span>
<span class=k>using</span><span class=w> </span><span class=n>json</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=p>;</span>
<span class=kt>int</span><span class=w> </span><span class=nf>main</span><span class=p>()</span>
<span class=p>{</span>
<span class=w> </span><span class=k>const</span><span class=w> </span><span class=n>json</span><span class=w> </span><span class=n>j</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>json</span><span class=o>::</span><span class=n>parse</span><span class=p>(</span><span class=sa>R</span><span class=s>"</span><span class=dl>(</span><span class=s>{"name": "日本語 text", "pi": 3.141592653589793}</span><span class=dl>)</span><span class=s>"</span><span class=p>);</span>
<span class=w> </span><span class=n>std</span><span class=o>::</span><span class=n>cout</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=n>j</span><span class=p>.</span><span class=n>dump</span><span class=p>()</span><span class=w> </span><span class=o>&lt;&lt;</span><span class=w> </span><span class=sc>'\n'</span><span class=p>;</span><span class=w> </span><span class=c1>// {"name":"日本語 text","pi":3.141592653589793}</span>
<span class=p>}</span>
</code></pre></div> </details> <h2 id=see-also>See also<a class=headerlink href=#see-also title="Permanent link">&para;</a></h2> <ul> <li><a href=../../basic_json/parse/ ><strong>parse</strong></a> - deserialize from a compatible input</li> <li><a href=../../basic_json/dump/ ><strong>dump</strong></a> - serialization</li> <li><a href=../json_use_simdutf/ ><strong>JSON_USE_SIMDUTF</strong></a> - use the simdutf library to accelerate <abbr title="Unicode Transformation Format">UTF</abbr>-8 validation</li> <li><a href=../json_disable_stream_bulk_scan/ ><strong>JSON_DISABLE_STREAM_BULK_SCAN</strong></a> - read a <code>std::istream</code> one character at a time</li> <li><a href=../../../features/parsing/#input-sources-and-performance>Parsing: input sources and performance</a></li> </ul> <h2 id=version-history>Version history<a class=headerlink href=#version-history title="Permanent link">&para;</a></h2> <ul> <li>Added in version 3.13.0 <span class=unreleased-version title="Not part of a release yet; the latest release is 3.12.0.">unreleased</span>.</li> </ul> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="October 21, 2026 18:00:50 UTC">October 21, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4Line truncated
api/macros/json_no_simd/index.md
+67
View File
@@ -0,0 +1,67 @@
# JSON_NO_SIMD
```
#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, `JSON_NO_SIMD` is not defined, and vector instructions are used where the target has them.
```
#undef JSON_NO_SIMD
```
## Notes
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 `std::istream` holds in its stream buffer (see [`JSON_DISABLE_STREAM_BULK_SCAN`](https://json.nlohmann.me/api/macros/json_disable_stream_bulk_scan/index.md)); other inputs are read one character at a time.
Interaction with `JSON_USE_SIMDUTF`
With [`JSON_USE_SIMDUTF`](https://json.nlohmann.me/api/macros/json_use_simdutf/index.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.
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](https://json.nlohmann.me/features/namespace/index.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: switching off vector instructions
The program parses and serializes the same values with and without the macro:
```
#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**](https://json.nlohmann.me/api/basic_json/parse/index.md) - deserialize from a compatible input
- [**dump**](https://json.nlohmann.me/api/basic_json/dump/index.md) - serialization
- [**JSON_USE_SIMDUTF**](https://json.nlohmann.me/api/macros/json_use_simdutf/index.md) - use the simdutf library to accelerate UTF-8 validation
- [**JSON_DISABLE_STREAM_BULK_SCAN**](https://json.nlohmann.me/api/macros/json_disable_stream_bulk_scan/index.md) - read a `std::istream` one character at a time
- [Parsing: input sources and performance](https://json.nlohmann.me/features/parsing/#input-sources-and-performance)
## Version history
- Added in version 3.13.0 unreleased.