README.md

JsonExtr

A very lightweight (300 lines) JSON parser for C

Usage

Add jsonextr.c to your build environment, and #include "jsonextr.h".

Alternatively, open JsonExtracter.sln with Visual Studio 2017 to try tests.

Extract value from objects (dicts)

Example: get json["key1"]["b"] from

{"key1":{"a":"a","b":"b"},"key2":"val2"}

Code:

const char *json = "{\"key1\":{\"a\":\"a\",\"b\":\"b\"},\"key2\":\"val2\"}";
const char *path = "key1\nb";
JsonExtrStru s = json_extract(json, 0, path);
if (json_isExtractError(s)) {
	printf("Error #%d\n", -s.type);
} else {
	printf("%s\n", json);
	for (size_t i = 0; i < s.start; i++) putchar(' ');
	for (size_t i = 0; i < s.len; i++) putchar('~');
	printf("\nType: %d\n", s.type);
}

Output:

{"key1":{"a":"a","b":"b"},"key2":"val2"}
                     ~~~
Type: 3

Extract value from lists

Example: get json[0][1] from

[[0,1,2],[3,4,5]]

Code:

const char *path = "\n0\n\n1";

Output:

[[0,1,2],[3,4,5]]
    ~
Type: 4

Notice the additional \n.

Hint: use numeric key on objects to retrieve object property name.

Iterate object properties (dict keys)

Code: See JsonExtr/test.c

Output:

[0,1,2,[3,4],{"key1":["zero",1,2],"key2":{"x":true,"y":false,"z":null}}]
#0: 0 (number)
#1: 1 (number)
#2: 2 (number)
#3: [3,4] (array)
    #0: 3 (number)
    #1: 4 (number)
#4: {"key1":["zero",1,2],"key2":{"x":true,"y":false,"z":null}} (object)
    "key1": ["zero",1,2] (array)
        #0: "zero" (string)
        #1: 1 (number)
        #2: 2 (number)
    "key2": {"x":true,"y":false,"z":null} (object)
        "x": true (true)
        "y": false (false)
        "z": null (null)