How do I parse a JSON string in C with json-c?

Use json_tokener_parse_ex() from json_tokener.h, which returns a json_object tree. Manage memory with json_object_put() on the root object when done to avoid leaks.

json-c vs jansson: which is better for embedded systems?

json-c uses reference counting for easier memory management, while jansson might have different performance profiles. For embedded C, json-c's simplicity is a plus, but evaluate based on threading and memory needs.

Does json-c support JSON Schema validation?

No, json-c focuses on core JSON handling per RFC 8259 and does not include JSON Schema validation. You'll need to implement it separately or use another library.

How to build json-c for Android?

Use CMake with the Android NDK toolchain, as detailed in the README. Set flags like -DANDROID_ABI and -DANDROID_PLATFORM, and enable threading if needed with -DENABLE_THREADING=ON.

Is json-c thread-safe?

It has partial threading support: atomic operations for json_object_get() and json_object_put() aid threaded use, but full thread safety for object trees is not guaranteed, so caution is required.

What's the best way to iterate over JSON objects in json-c?

Use the json_object_object_foreach() macro from json_object.h or json_object_iterator from json_object_iterator.h for safe and efficient iteration over object properties.

Open-Awesome

json-c

NOASSERTIONC

A JSON implementation in C with reference counting object model for constructing, parsing, and serializing JSON objects.

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What is json-c?

JSON-C is a JSON implementation in C that provides a reference counting object model for constructing, parsing, and serializing JSON objects. It enables C applications to handle JSON data easily by offering functions to create JSON objects, convert them to strings, and parse JSON strings back into C structures. The library conforms to RFC 8259 and is designed for reliability and interoperability in JSON processing.

Target Audience

C developers working on applications that require JSON data interchange, such as embedded systems, network services, or cross-platform tools. It is also suitable for projects needing a lightweight, standard-compliant JSON library without external dependencies.

Value Proposition

Developers choose JSON-C for its straightforward reference counting model, which simplifies memory management, and its adherence to JSON standards. Its partial threading support and flexible build options make it adaptable to various performance and deployment requirements.

Overview

https://github.com/json-c/json-c is the official code repository for json-c. See the wiki for release tarballs for download. API docs at http://json-c.github.io/json-c/

Use Cases

Best For

Embedded systems requiring JSON data parsing in C
Network services that need to serialize/deserialize JSON payloads
Cross-platform C applications with JSON configuration files
Tools and utilities that process JSON data in resource-constrained environments
Educational projects demonstrating JSON handling in C
Legacy C codebases integrating modern JSON interchange

Not Ideal For

Projects requiring full multi-threaded safety without performance penalties
High-performance applications where JSON parsing speed is critical
Modern C++ projects where libraries like RapidJSON offer more features
Systems with minimal memory footprint, as reference counting adds overhead

Pros & Cons

Pros

Reference Counting Simplicity

Automates memory management through json_object_get() and json_object_put(), reducing manual allocation errors and simplifying object lifecycle.

Standards Compliance

Conforms to RFC 8259, ensuring JSON interoperability and correctness in data interchange.

Flexible Build Configuration

Offers CMake options for static/shared libraries and supports niche platforms like Android and Amiga, as shown in the build instructions.

JSON Pointer Support

Implements RFC 6901 for precise object retrieval from JSON trees, enhancing data manipulation capabilities.

Cons

Performance Overhead

Partial threading support uses atomic operations that can make json_object_get() and json_object_put() 3x slower, impacting performance in threaded programs.

Limited Thread Safety

Only provides atomic operations for basic functions, not full multi-threaded access to object trees, which can lead to concurrency issues.

Build Complexity

Setting up for platforms like Android or Amiga requires specific toolchains and Docker containers, adding development overhead.

Frequently Asked Questions

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