json_lib

Simple and dirty JSON processing library written in C. Made as hobby project, is not intended for use in production.

Usage

Header

To use library you need to include header json.h

#include "/root-of-library/include/json.h"

Parsing

There two versions of parsers: json_parser for null-terminated string and json_parserNoNul for general string buffers. Both return status code and put their output in passed pointer. Input string should be in UTF-8.

json_Status json_parser(const char* input, json_Value* output);

• Return value - status code
• input - null-terminated input string
• output - pointer to struct of type json_Value in which parser will put root value node (e.g. array or object) of json document

json_Status json_parserNoNul(const char* input, size_t len, json_Value* output);

• Return value - status code
• input - input string
• len - length of input string
• output - pointer to struct of type json_Value in which parser will put root node (e.g. array or object) of value tree of json document

Example

char* jsonStringNulTerm = "{\"json\": []}"; // null-terminated string

json_Value root;
json_Status status = json_parser(jsonStringNulTerm, &root);

char jsonStringNoNulTerm[2] = {'{', '}'}; // not null-terminated

json_Value root;
json_Status status = json_parserNoNul(jsonStringNoNulTerm, 2, &root);

Stringifiying

Converting JSON value tree into string is done by json_stringifier. It returns status code and puts its output into dynamically allocated char buffer. Its address and size are being put into argument pointers. Output string is in UTF-8. String is null-terminated. If some JSON strings in tree contain NUL characters, they will be added to output as any other character.

json_Status json_stringify(json_Value* value, char** output, size_t* len);

• Return value - status code
• value - input JSON value
• output - pointer to char pointer in which function will put address of output string buffer
• len - pointer to variable in which function will put length of output string

Example

char* output = NULL;
size_t outputLen = 0;

json_Status status = json_stringifier(&root, &output, &outputLen);

Status codes

Represented by enum of type json_Status

• json_status_OK - returned if function executed normally
• json_status_InvalidInput - returned if function found that input is invalid (NOTE: validation is not guaranteed, parser may accept some invalid input strings)
• json_status_AllocError - returned if there is error from memory allocator (e.g. out of memory situation)
• json_status_ElemNotExist - returned if asked element does not exist (NOTE: currently no function uses it)

Value type

Represented by struct of type json_Value It has two fields:

• type - type of JSON value. Represented by enum json_ValueType, its values are json_Object, json_Array, json_String, json_Number, json_Boolean, json_Null, they associate with built-in JSON types*
• value - value of given type. Represented by union json_Data, its fields are:
  • number - floating point number of type double, valid if type is json_Number
  • boolean - boolean value of type bool (from standard library), valid if type is json_Boolean
  • string - pointer to null-terminated string (char array), valid if type is json_String
  • arr - pointer to struct of type ds_Vector_value which is dynamic vector (from data_structures library) containing other JSON values, valid if type is json_Array
  • obj - pointer to struct of type ds_um_Map_value which is hash map (from data_structures library) containing other JSON values, valid if type is json_Object