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cojson v2.0

C++ pull-type JSON parser/generator for constrained platforms with automated code generation.

Please visit changelog.v2.0.md and changelog.v2.1.md to read about changes introduced in v2

COJSON Introduction

cojson is a C++ pull-type JSON parser/serializer for constrained platforms, such as bare metal applications on low-end MCUs. It does not use memory allocation and has almost no external dependencies. It is not intrusive - it neither forces nor implies any particular design of the application. Instead it adapts to fit any existing application code. It is tolerant to data type mismatching. When such occurs, parser just skips mismatching data and makes best efforts to continue parsing.

The parser is recursive, e.g. nested JSON elements are handled with the recursion. However, this recursion is driven by the structure definition, not by the input data, which prevents stack faults on malformed input data.

cojson is character type neutral - it can work with signed or unsigned character, as well as with standard wide character types: wchar_t, char16_t and char32_t.

It is also transparent for UTF8 and properly handles BOM sequence.

cojson works against a user-defined structure which specifies data model - hierarchy, data types, and data storage access methods. Thus, when parsing is complete, the data already delivered to the application and no further processing needed.

The same structure definition is also used for writing JSON. The JSON structure is defined with a set of templetized functions.

Please visit project's home page, tutorial for more details and tutorial for C++17 for more details

Code generation

Starting from v2.0 cojson facilitates generation of C++ code from a JSON sample.

Online version is available at this link For more details please visit codegen directory in this repository.

Requirements

  • Compiler: cojson sources need a C++11 enabled compiler, such as g++-4.9 and up.
  • Library: libstdc++ v3 highly desirable. But if not available a workaround exists
  • Code space: Depending on the platform and JSON structure complexity varies from 4kB to 20kB.
  • RAM space: 20-80 bytes per entry in the defined JSON structure

Tested On

  • Debian i686, g++-4.9.2
  • Debian i686, g++-7.1.0
  • Debian x64, g++-6.3.0
  • Arduino Mega ATmega2560, avr-g++-4.9.2
  • Arduino Mega ATmega2560, avr-g++-5.4.0
  • Teensy 3.1 ARM Cortex-M4 arm-none-eabi-g++-4.9.3
  • Teensy 3.1 ARM Cortex-M4 arm-none-eabi-g++-5.4.1
  • Carambola2 Atheros AR9331 mips-openwrt-linux-g++-4.8.3
  • MSP430FR6989 MSP430FR6989 msp430-elf-g++-4.9.1
  • NodeMCU V3 ESP8266 xtensa-lx106-elf-g++-4.8.5