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README.md

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UJSON

UJSON is:

  • Complete and simple JSON reader and writer written in C
  • Produces nice and human readable error messages
  • Passes JSONTestSuite

See generated documentation at: https://metan-ucw.github.io/ujson/files.html

The key point of this parser is that:

  • works on a buffer in a memory that is not modified during the parsing
  • parser does not allocate memory
  • nearly stateless, the only state the parser maintains is an offset to the string buffer, recursion depth and error flag
  • if error flag is raised all parser functions return immediatelly with error

The parser is started by a call to ujson_start() function in order to determine if first element in the buffer is object or an array.

	switch (ujson_reader_start(reader)) {
	case UJSON_ARR:
		//parse array
	break;
	case UJSON_OBJ:
		//parse object
	break;
	default:
	break;
	}

	if (ujson_reader_err(reader))
		ujson_err_print(reader);

Then you can loop recursively over arrays and objects with:

	char sbuf[128];
	struct ujson_val json = {.buf = sbuf, .buf_size = sizeof(sbuf)};

	UJSON_OBJ_FOREACH(reader, &json) {
		switch (json.type) {
		case UJSON_OBJ:
			//parse object
		break;
		case UJSON_ARR:
			//parse array
		break;
		case UJSON_STR:
		...

		}
	}

The supported types are:

  • UJSON_ARR - an array, needs to be parsed recursivelly
  • UJSON_OBJ - an object, needs to be parsed recursivelly
  • UJSON_INT - an integer number stored as val_int (also sets val_float for convinience)
  • UJSON_FLOAT - a floating point number stored as val_float
  • UJSON_BOOL - a boolean stored as val_bool
  • UJSON_NULL - a null has no value
  • UJSON_STR - a string, stored in user supplied buffer