JSON C Parsing Example

main.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "jsmn.h"

char* types[] = {"UNDEFINED", "OBJECT", "ARRAY", "STRING", "PRIMITIVE"};

int main() {
    char* json = NULL;
    size_t len = 0;
    getline(&json, &len, stdin);

    jsmn_parser parser;
    jsmntok_t   tokens[32];

    jsmn_init(&parser);
    int count = jsmn_parse(&parser, json, strlen(json), tokens, 32);

    if (count > 0) {
        for (int i = 0; i < count; i++) {
            printf("token %d:\n", i);
            printf("  type: %s\n", types[tokens[i].type]);
            printf("  size: %d\n", tokens[i].size);
            printf("  value: ");
            fwrite(json + tokens[i].start,
                    tokens[i].end - tokens[i].start,
                    1, stdout);
            printf("\n\n");
        }
    }
    else if (count < 0) {
        fprintf(stderr, "error: parser failed");
        if (count == JSMN_ERROR_INVAL) {
            fprintf(stderr, " by bad token.");
        } else if (count == JSMN_ERROR_NOMEM) {
            fprintf(stderr, " by not enought tokens.");
        } else if (count == JSMN_ERROR_PART) {
            fprintf(stderr, " by json too short.");
        }
        fprintf(stderr, "\n");
    }
   
    free(json);
    return 0;
}