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yyjson 0.12.0
A high performance C JSON library.
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Introduction

BuildCodecovLicenseVersionPackaging status

A high performance JSON library written in ANSI C.

Features

  • Fast: can read or write gigabytes of JSON data per second on modern CPUs.
  • Portable: complies with ANSI C (C89) for cross-platform compatibility.
  • Strict: complies withRFC 8259 JSON standard, ensuring strict number formats and UTF-8 validation.
  • Extendable: offers options to enable individualJSON5 features and custom allocator.
  • Accuracy: can accurately read and writeint64,uint64, anddouble numbers.
  • Flexible: supports unlimited JSON nesting levels,\u0000 characters, and non-null-terminated strings.
  • Manipulation: supports querying and modifying withJSON Pointer,JSON Patch, andJSON Merge Patch.
  • Developer-Friendly: easy integration with just one.h and one.c file.

Limitations

  • An array or object is stored as adata structure such as linked list, which makes accessing elements by index or key slower than using an iterator.
  • Duplicate keys are allowed in an object, and the order of the keys is preserved.
  • JSON parsing result is immutable, requiring amutable copy for modification.

Performance

Benchmark project and dataset:yyjson_benchmark

The simdjson's newOn Demand API is faster if most JSON fields are known at compile-time. This benchmark project only checks the DOM API, a new benchmark will be added later.

AWS EC2 (AMD EPYC 7R32, gcc 9.3)

twitter.jsonparse (GB/s)stringify (GB/s)
yyjson(insitu)1.801.51
yyjson1.721.42
simdjson1.520.61
sajson1.16
rapidjson(insitu)0.77
rapidjson(utf8)0.260.39
cjson0.320.17
jansson0.050.11

iPhone (Apple A14, clang 12)

twitter.jsonparse (GB/s)stringify (GB/s)
yyjson(insitu)3.512.41
yyjson2.392.01
simdjson2.190.80
sajson1.74
rapidjson(insitu)0.75
rapidjson(utf8)0.300.58
cjson0.480.33
jansson0.090.24

More benchmark reports with interactive charts (update 2020-12-12)

PlatformCPUCompilerOSReport
Intel NUC 8i5Core i5-8259Umsvc 2019Windows 10 2004Charts
Intel NUC 8i5Core i5-8259Uclang 10.0Ubuntu 20.04Charts
Intel NUC 8i5Core i5-8259Ugcc 9.3Ubuntu 20.04Charts
AWS EC2 c5a.largeAMD EPYC 7R32gcc 9.3Ubuntu 20.04Charts
AWS EC2 t4g.mediumGraviton2 (ARM64)gcc 9.3Ubuntu 20.04Charts
Apple iPhone 12 ProA14 (ARM64)clang 12.0iOS 14Charts

For better performance, yyjson prefers:

  • A modern processor with:
    • high instruction level parallelism
    • excellent branch predictor
    • low penalty for misaligned memory access
  • A modern compiler with good optimizer (e.g. clang)

Sample Code

Read JSON string

constchar *json ="{\"name\":\"Mash\",\"star\":4,\"hits\":[2,2,1,3]}";
// Read JSON and get root
yyjson_doc *doc =yyjson_read(json, strlen(json), 0);
// Get root["name"]
yyjson_val *name =yyjson_obj_get(root,"name");
printf("name: %s\n",yyjson_get_str(name));
printf("name length:%d\n", (int)yyjson_get_len(name));
// Get root["star"]
yyjson_val *star =yyjson_obj_get(root,"star");
printf("star: %d\n", (int)yyjson_get_int(star));
// Get root["hits"], iterate over the array
yyjson_val *hits =yyjson_obj_get(root,"hits");
size_t idx, max;
yyjson_arr_foreach(hits, idx, max, hit) {
printf("hit%d: %d\n", (int)idx, (int)yyjson_get_int(hit));
}
// Free the doc
// All functions accept NULL input, and return NULL on error.
yyjson_api_inline yyjson_val * yyjson_obj_get(yyjson_val *obj, const char *key)
Definition yyjson.h:5483
yyjson_api_inline int yyjson_get_int(yyjson_val *val)
Definition yyjson.h:5252
#define yyjson_arr_foreach(arr, idx, max, val)
Definition yyjson.h:2046
yyjson_api_inline const char * yyjson_get_str(yyjson_val *val)
Definition yyjson.h:5264
yyjson_api_inline yyjson_val * yyjson_doc_get_root(yyjson_doc *doc)
Definition yyjson.h:5118
yyjson_api_inline void yyjson_doc_free(yyjson_doc *doc)
Definition yyjson.h:5130
yyjson_api_inline size_t yyjson_get_len(yyjson_val *val)
Definition yyjson.h:5268
yyjson_api_inline yyjson_doc * yyjson_read(const char *dat, size_t len, yyjson_read_flag flg)
Definition yyjson.h:983
Definition yyjson.h:4770
Definition yyjson.h:4765

Write JSON string

// Create a mutable doc
// Set root["name"] and root["star"]
yyjson_mut_obj_add_str(doc, root,"name","Mash");
yyjson_mut_obj_add_int(doc, root,"star", 4);
// Set root["hits"] with an array
int hits_arr[] = {2, 2, 1, 3};
yyjson_mut_val *hits =yyjson_mut_arr_with_sint32(doc, hits_arr, 4);
yyjson_mut_obj_add_val(doc, root,"hits", hits);
// To string, minified
constchar *json =yyjson_mut_write(doc, 0, NULL);
if (json) {
printf("json: %s\n", json);// {"name":"Mash","star":4,"hits":[2,2,1,3]}
free((void *)json);
}
// Free the doc
yyjson_api_inline bool yyjson_mut_obj_add_val(yyjson_mut_doc *doc, yyjson_mut_val *obj, const char *key, yyjson_mut_val *val)
Definition yyjson.h:7297
yyjson_api_inline yyjson_mut_val * yyjson_mut_arr_with_sint32(yyjson_mut_doc *doc, const int32_t *vals, size_t count)
Definition yyjson.h:6264
yyjson_api_inline bool yyjson_mut_obj_add_int(yyjson_mut_doc *doc, yyjson_mut_val *obj, const char *key, int64_t val)
Definition yyjson.h:7201
yyjson_api_inline yyjson_mut_val * yyjson_mut_obj(yyjson_mut_doc *doc)
Definition yyjson.h:6870
yyjson_api void yyjson_mut_doc_free(yyjson_mut_doc *doc)
yyjson_api_inline char * yyjson_mut_write(const yyjson_mut_doc *doc, yyjson_write_flag flg, size_t *len)
Definition yyjson.h:1461
yyjson_api_inline void yyjson_mut_doc_set_root(yyjson_mut_doc *doc, yyjson_mut_val *root)
Definition yyjson.h:5705
yyjson_api_inline bool yyjson_mut_obj_add_str(yyjson_mut_doc *doc, yyjson_mut_val *obj, const char *key, const char *val)
Definition yyjson.h:7229
yyjson_api yyjson_mut_doc * yyjson_mut_doc_new(const yyjson_alc *alc)
Definition yyjson.h:5638
Definition yyjson.h:5590

Read JSON file with options

// Read JSON file, allowing comments and trailing commas
yyjson_doc *doc =yyjson_read_file("/tmp/config.json", flg, NULL, &err);
// Iterate over the root object
if (doc) {
yyjson_val *key, *val;
while ((key =yyjson_obj_iter_next(&iter))) {
printf("%s: %s\n",yyjson_get_str(key),yyjson_get_type_desc(val));
}
}else {
printf("read error (%u): %s at position: %ld\n", err.code, err.msg, err.pos);
}
// Free the doc
static const yyjson_read_flag YYJSON_READ_ALLOW_TRAILING_COMMAS
Definition yyjson.h:750
yyjson_api_inline bool yyjson_obj_iter_init(yyjson_val *obj, yyjson_obj_iter *iter)
Definition yyjson.h:5508
yyjson_api_inline yyjson_val * yyjson_obj_iter_get_val(yyjson_val *key)
Definition yyjson.h:5541
uint32_t yyjson_read_flag
Definition yyjson.h:723
yyjson_api_inline const char * yyjson_get_type_desc(yyjson_val *val)
Definition yyjson.h:5219
yyjson_read_code code
Definition yyjson.h:881
yyjson_api_inline yyjson_val * yyjson_obj_iter_next(yyjson_obj_iter *iter)
Definition yyjson.h:5531
yyjson_api yyjson_doc * yyjson_read_file(const char *path, yyjson_read_flag flg, const yyjson_alc *alc, yyjson_read_err *err)
size_t pos
Definition yyjson.h:885
const char * msg
Definition yyjson.h:883
static const yyjson_read_flag YYJSON_READ_ALLOW_COMMENTS
Definition yyjson.h:753
Definition yyjson.h:2114
Definition yyjson.h:879

Write JSON file with options

// Read the JSON file as a mutable doc
yyjson_doc *idoc =yyjson_read_file("/tmp/config.json", 0, NULL, NULL);
// Remove null values in root object
yyjson_mut_val *key, *val;
while ((key =yyjson_mut_obj_iter_next(&iter))) {
if (yyjson_mut_is_null(val)) {
}
}
// Write the json pretty, escape unicode
yyjson_mut_write_file("/tmp/config.json", doc, flg, NULL, &err);
if (err.code) {
printf("write error (%u): %s\n", err.code, err.msg);
}
// Free the doc
yyjson_api yyjson_mut_doc * yyjson_doc_mut_copy(yyjson_doc *doc, const yyjson_alc *alc)
yyjson_api_inline bool yyjson_mut_is_null(yyjson_mut_val *val)
Definition yyjson.h:5720
const char * msg
Definition yyjson.h:1251
yyjson_api_inline yyjson_mut_val * yyjson_mut_obj_iter_next(yyjson_mut_obj_iter *iter)
Definition yyjson.h:6804
yyjson_api_inline yyjson_mut_val * yyjson_mut_obj_iter_remove(yyjson_mut_obj_iter *iter)
Definition yyjson.h:6821
yyjson_api_inline yyjson_mut_val * yyjson_mut_doc_get_root(yyjson_mut_doc *doc)
Definition yyjson.h:5701
yyjson_api_inline yyjson_mut_val * yyjson_mut_obj_iter_get_val(yyjson_mut_val *key)
Definition yyjson.h:6816
static const yyjson_write_flag YYJSON_WRITE_ESCAPE_UNICODE
Definition yyjson.h:1168
yyjson_api bool yyjson_mut_write_file(const char *path, const yyjson_mut_doc *doc, yyjson_write_flag flg, const yyjson_alc *alc, yyjson_write_err *err)
yyjson_api_inline bool yyjson_mut_obj_iter_init(yyjson_mut_val *obj, yyjson_mut_obj_iter *iter)
Definition yyjson.h:6779
yyjson_write_code code
Definition yyjson.h:1249
static const yyjson_write_flag YYJSON_WRITE_PRETTY
Definition yyjson.h:1165
uint32_t yyjson_write_flag
Definition yyjson.h:1155
Definition yyjson.h:3537
Definition yyjson.h:1247

Documentation

The latest (unreleased) documentation can be accessed in thedoc directory. The pre-generated Doxygen HTML for the release version can be viewed here:

Packaging status

Packaging status

Built With yyjson

A non-exhaustive list of projects that expose yyjson to other languages or use yyjson internally for a major feature. If you have a project that uses yyjson, feel free to open a PR to add it to this list.

ProjectLanguageDescription
py_yyjsonPythonPython bindings for yyjson
orjsonPythonJSON library for Python with an optional yyjson backend
cpp-yyjsonC++C++ JSON library with a yyjson backend
reflect-cppC++C++ library for serialization through automated field name retrieval from structs
yyjsonrRR binding for yyjson
AnandaSwiftJSON model decoding based on yyjson
duckdbC++DuckDB is an in-process SQL OLAP Database Management System
fastfetchCA neofetch-like tool for fetching system information and displaying them in a pretty way
ZrythmCDigital Audio Workstation that uses yyjson to serialize JSON project files
bemorehumanCRecommendation engine with a focus on uniqueness of the person receiving the rec
mruby-yyjsonmrubyEfficient JSON parsing and serialization library for mruby using yyjson
YYJSON.jlJuliaJulia bindings for yyjson

TODO for v1.0

  • [x] Add documentation page.
  • [x] Add GitHub workflow for CI and codecov.
  • [x] Add more tests: valgrind, sanitizer, fuzzing.
  • [x] Support JSON Pointer to query and modify JSON.
  • [x] AddRAW type for JSON reader and writer.
  • [x] Add option to limit real number output precision.
  • [x] Add option to support JSON5.
  • [ ] Add functions to diff two JSON documents.
  • [ ] Add documentation on performance optimizations.
  • [ ] Ensure ABI stability.

License

This project is released under the MIT license.

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