# Introduction
[](https://github.com/ibireme/yyjson/actions/workflows/cmake.yml)
[](https://codecov.io/gh/ibireme/yyjson)
[](https://github.com/ibireme/yyjson/blob/master/LICENSE)
[](https://github.com/ibireme/yyjson/releases)
[](https://repology.org/project/yyjson/versions)
A high performance JSON library written in ANSI C.
# Features
- **Fast**: can read or write gigabytes per second JSON data on modern CPUs.
- **Portable**: complies with ANSI C (C89) for cross-platform compatibility.
- **Strict**: complies with [RFC 8259](https://datatracker.ietf.org/doc/html/rfc8259) JSON standard, ensuring strict number format and UTF-8 validation.
- **Extendable**: offers options to allow comments, trailing commas, NaN/Inf, and custom memory allocator.
- **Accuracy**: can accurately read and write `int64`, `uint64`, and `double` numbers.
- **Flexible**: supports unlimited JSON nesting levels, `\u0000` characters, and non null-terminated strings.
- **Manipulation**: supports querying and modifying using [JSON Pointer](https://datatracker.ietf.org/doc/html/rfc6901), [JSON Patch](https://datatracker.ietf.org/doc/html/rfc6902) and [JSON Merge Patch](https://datatracker.ietf.org/doc/html/rfc7386).
- **Developer-Friendly**: easy integration with only one `h` and one `c` file.
# Limitations
- An array or object is stored as a [data structure](https://ibireme.github.io/yyjson/doc/doxygen/html/md_doc__data_structure.html) 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 a `mutable copy` for modification.
# Performance
Benchmark project and dataset: [yyjson_benchmark](https://github.com/ibireme/yyjson_benchmark)
The simdjson's new `On 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)
|yyjson(insitu)|1.80|1.51|
|yyjson|1.72|1.42|
|simdjson|1.52|0.61|
|sajson|1.16| |
|rapidjson(insitu)|0.77| |
|rapidjson(utf8)|0.26|0.39|
|cjson|0.32|0.17|
|jansson|0.05|0.11|
#### iPhone (Apple A14, clang 12)
|yyjson(insitu)|3.51|2.41|
|yyjson|2.39|2.01|
|simdjson|2.19|0.80|
|sajson|1.74||
|rapidjson(insitu)|0.75| |
|rapidjson(utf8)|0.30|0.58|
|cjson|0.48|0.33|
|jansson|0.09|0.24|
More benchmark reports with interactive charts (update 2020-12-12)
|Intel NUC 8i5|Core i5-8259U|msvc 2019|Windows 10 2004|[Charts](https://ibireme.github.io/yyjson_benchmark/reports/Intel_NUC_8i5_msvc_2019.html)|
|Intel NUC 8i5|Core i5-8259U|clang 10.0|Ubuntu 20.04|[Charts](https://ibireme.github.io/yyjson_benchmark/reports/Intel_NUC_8i5_clang_10.html)|
|Intel NUC 8i5|Core i5-8259U|gcc 9.3|Ubuntu 20.04|[Charts](https://ibireme.github.io/yyjson_benchmark/reports/Intel_NUC_8i5_gcc_9.html)|
|AWS EC2 c5a.large|AMD EPYC 7R32|gcc 9.3|Ubuntu 20.04|[Charts](https://ibireme.github.io/yyjson_benchmark/reports/EC2_c5a.large_gcc_9.html)|
|AWS EC2 t4g.medium|Graviton2 (ARM64)|gcc 9.3|Ubuntu 20.04|[Charts](https://ibireme.github.io/yyjson_benchmark/reports/EC2_t4g.medium_gcc_9.html)|
|Apple iPhone 12 Pro|A14 (ARM64)|clang 12.0|iOS 14|[Charts](https://ibireme.github.io/yyjson_benchmark/reports/Apple_A14_clang_12.html)|
### 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
```c
const char *json = "{\"name\":\"Mash\",\"star\":4,\"hits\":[2,2,1,3]}";
// Read JSON and get root
yyjson_doc *doc = yyjson_read(json, strlen(json), 0);
yyjson_val *root = yyjson_doc_get_root(doc);
// 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_val *hit;
yyjson_arr_foreach(hits, idx, max, hit) {
printf("hit%d: %d\n", (int)idx, (int)yyjson_get_int(hit));
}
// Free the doc
yyjson_doc_free(doc);
// All functions accept NULL input, and return NULL on error.
```
### Write JSON string
```c
// Create a mutable doc
yyjson_mut_doc *doc = yyjson_mut_doc_new(NULL);
yyjson_mut_val *root = yyjson_mut_obj(doc);
yyjson_mut_doc_set_root(doc, root);
// 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
const char *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_mut_doc_free(doc);
```
### Read JSON file with options
```c
// Read JSON file, allowing comments and trailing commas
yyjson_read_flag flg = YYJSON_READ_ALLOW_COMMENTS | YYJSON_READ_ALLOW_TRAILING_COMMAS;
yyjson_read_err err;
yyjson_doc *doc = yyjson_read_file("/tmp/config.json", flg, NULL, &err);
// Iterate over the root object
if (doc) {
yyjson_val *obj = yyjson_doc_get_root(doc);
yyjson_obj_iter iter;
yyjson_obj_iter_init(obj, &iter);
yyjson_val *key, *val;
while ((key = yyjson_obj_iter_next(&iter))) {
val = yyjson_obj_iter_get_val(key);
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
yyjson_doc_free(doc);
```
### Write JSON file with options
```c
// Read the JSON file as a mutable doc
yyjson_doc *idoc = yyjson_read_file("/tmp/config.json", 0, NULL, NULL);
yyjson_mut_doc *doc = yyjson_doc_mut_copy(idoc, NULL);
yyjson_mut_val *obj = yyjson_mut_doc_get_root(doc);
// Remove null values in root object
yyjson_mut_obj_iter iter;
yyjson_mut_obj_iter_init(obj, &iter);
yyjson_mut_val *key, *val;
while ((key = yyjson_mut_obj_iter_next(&iter))) {
val = yyjson_mut_obj_iter_get_val(key);
if (yyjson_mut_is_null(val)) {
yyjson_mut_obj_iter_remove(&iter);
}
}
// 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_doc_free(idoc);
yyjson_mut_doc_free(doc);
```
# Documentation
The latest (unreleased) documentation can be accessed in the [doc](https://github.com/ibireme/yyjson/tree/master/doc) directory.
The pre-generated Doxygen HTML for the release version can be viewed here:
* [Home Page](https://ibireme.github.io/yyjson/doc/doxygen/html/)
* [Build and test](https://ibireme.github.io/yyjson/doc/doxygen/html/md_doc__build_and_test.html)
* [API and sample code](https://ibireme.github.io/yyjson/doc/doxygen/html/md_doc__a_p_i.html)
* [Data structure](https://ibireme.github.io/yyjson/doc/doxygen/html/md_doc__data_structure.html)
* [Changelog](https://ibireme.github.io/yyjson/doc/doxygen/html/md__c_h_a_n_g_e_l_o_g.html)
# Packaging status
[](https://repology.org/project/yyjson/versions)
# 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.
| [py_yyjson][] | Python | Python bindings for yyjson |
| [orjson][] | Python | JSON library for Python with an optional yyjson backend |
| [cpp-yyjson][] | C++ | C++ JSON library with a yyjson backend |
| [reflect-cpp][] | C++ | C++ library for serialization through automated field name retrieval from structs |
| [yyjsonr][] | R | R binding for yyjson |
| [Ananda][] | Swift | JSON model decoding based on yyjson |
| [duckdb][] | C++ | DuckDB is an in-process SQL OLAP Database Management System |
| [fastfetch][] | C | A neofetch-like tool for fetching system information and displaying them in a pretty way |
| [Zrythm][] | C | Digital Audio Workstation that uses yyjson to serialize JSON project files |
| [bemorehuman][] | C | Recommendation engine with a focus on uniqueness of the person receiving the rec |
# 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] Add `RAW` type for JSON reader and writer.
* [ ] Add option to limit real number output precision.
* [ ] Add option to support JSON5 (if feasible).
* [ ] Add functions to diff two JSON documents.
* [ ] Add documentation on performance optimizations.
* [ ] Ensure ABI stability.
# License
This project is released under the MIT license.
[py_yyjson]: https://github.com/tktech/py_yyjson
[orjson]: https://github.com/ijl/orjson
[cpp-yyjson]: https://github.com/yosh-matsuda/cpp-yyjson
[reflect-cpp]: https://github.com/getml/reflect-cpp
[yyjsonr]: https://github.com/coolbutuseless/yyjsonr
[Ananda]: https://github.com/nixzhu/Ananda
[duckdb]: https://github.com/duckdb/duckdb
[fastfetch]: https://github.com/fastfetch-cli/fastfetch
[Zrythm]: https://github.com/zrythm/zrythm
[bemorehuman]: https://github.com/BeMoreHumanOrg/bemorehuman