cj5

Very minimal single header JSON5 parser in C99, derived from jsmn

What is json 5

It is just a less strict standard JSON, which is easier to read and write as well ass some nice added features, for more info see JSON5. Some Json5 features maybe incomplete or not working properly, but currently the features are tested:

• Object keys may be an ECMAScript 5.1 IdentifierName.
• Objects may have a single trailing comma.
• Strings may be single quoted.
• Strings may span multiple lines by escaping new line characters.
• Strings may include character escapes.
• Numbers may be hexadecimal.
• Numbers may have a leading or trailing decimal point.
• Numbers may be IEEE 754 positive infinity, negative infinity, and NaN.
• Numbers may begin with an explicit plus sign.
• Single and multi-line comments are allowed.
• Additional white space characters are allowed.
• Multiline comments are allowed

Features

• No memory allocations. All allocatrions are managed on the user side
• Fast and Minimal.
• standard C library functions (memory,string functions) can be overriden
• Easy to use API (one function to parse)
• Portable C API
• Helper functions to use parsed data in DOM manner

Usage

The main function to parse json is cj5_parse. like jsmn, you provide all tokens to be filled as an array and provide the maximum count The result will be return in cj5_result struct, and num_tokens will represent the actual token count that is parsed.
In case of errors, cj_result.error will be set to an error code. Here's a quick example of the usage, first define CJ5_IMPLEMENT to include the implementation:

        #define CJ5_IMPLEMENT
        #include "cj5.h"

        cj5_token tokens[32];
        cj5_result r = cj5_parse(g_json, (int)strlen(g_json), tokens, 32);
        
        if (r.error != CJ5_ERROR_NONE) {
            if (r.error == CJ5_ERROR_OVERFLOW) {
                // you can use r.num_tokens to determine the actual token count and reparse
                printf("Error: line: %d, col: %d\n", r.error_line, r.error_code);    
            }
        } else {
            // use token helper functions (see below) to access the values 
            float my_num = cj5_seekget_float(&r, 0, "my_num", 0 /* default value if not found*/ );
        } 

NOTE: Unlike jsmn, if number of parsed tokens exceeds the provided ones, parser doesn't return immediately with an error. But parses the JSON to the end, counts all needed tokens and returns with an CJ5_ERROR_OVERFLOW, so the user can choose to reparse the json with new memory requirements.

Links

• jsmn: Jsmn is a world fastest JSON parser/tokenizer. This is the official repo replacing the old one at Bitbucket
• sjson: Fast and portable C single header json Encoder/Decoder

License (MIT)