JIM

Immediate Mode JSON Serialization Library in C. Similar to imgui but for generating JSON.

Example

example.c:

#include <stdio.h>

#define JIM_IMPLEMENTATION
#include "./jim.h"

int main()
{
    Jim jim = {.pp = 4};

    jim_object_begin(&jim);
        jim_member_key(&jim, "null");
        jim_null(&jim);

        jim_member_key(&jim, "bool");
        jim_array_begin(&jim);
            jim_bool(&jim, 0);
            jim_bool(&jim, 1);
        jim_array_end(&jim);

        jim_member_key(&jim, "integers");
        jim_array_begin(&jim);
            for (int i = -3; i <= 3; ++i) {
                jim_integer(&jim, i);
            }
        jim_array_end(&jim);

        jim_member_key(&jim, "floats");
        jim_array_begin(&jim);
            jim_float(&jim, 0.0, 4);
            jim_float(&jim, -0.0, 4);
            jim_float(&jim, 3.1415, 4);
            jim_float(&jim, 2.71828, 5);
            jim_float(&jim, 1.6180, 4);
            jim_float(&jim, 0.0 / 0.0, 4);
            jim_float(&jim, 1.0 / 0.0, 4);
            jim_float(&jim, -1.0 / 0.0, 4);
        jim_array_end(&jim);

        jim_member_key(&jim, "string");
        jim_array_begin(&jim);
            jim_string(&jim, "Hello\tWorld\n");
            jim_string_sized(&jim, "\0\0\0\0", 4);
        jim_array_end(&jim);

        jim_member_key(&jim, "nested_object");
        jim_object_begin(&jim);
            jim_member_key(&jim, "foo");
            jim_integer(&jim, 69);
            jim_member_key(&jim, "bar");
            jim_integer(&jim, 420);
            jim_member_key(&jim, "baz");
            jim_integer(&jim, 1337);
        jim_object_end(&jim);

        jim_member_key(&jim, "empty_array"),
        jim_array_begin(&jim);
        jim_array_end(&jim);

        jim_member_key(&jim, "empty_object"),
        jim_object_begin(&jim);
        jim_object_end(&jim);
    jim_object_end(&jim);

    fwrite(jim.sink, jim.sink_count, 1, stdout);

    return 0;
}

Output

$ cc -o example example.c
$ ./example
{
    "null": null,
    "bool": [
        false,
        true
    ],
    "integers": [
        -3,
        -2,
        -1,
        0,
        1,
        2,
        3
    ],
    "floats": [
        0.0,
        0.0,
        3.1415,
        2.71828,
        1.6180,
        null,
        null,
        null
    ],
    "string": [
        "Hello\tWorld\n",
        "\u0000\u0000\u0000\u0000"
    ],
    "nested_object": {
        "foo": 69,
        "bar": 420,
        "baz": 1337
    },
    "empty_array": [],
    "empty_object": {}
}

Testing

$ make
$ ./test

The expected outputs of the test cases are stored in ./test_expected.h. To regenerate it just run:

$ ./test record

Notes

1. Does not depends on libc. Could be theoretically used in embedded, but I know nothing about embedded, so maybe not.
2. jim_float() is quite likely very stupid and imprecise