1 #include <stdio.h> 2 #include <string.h> 3 #include "../jsmn.h" 4 5 /* 6 * A small example of jsmn parsing when JSON structure is known and number of 7 * tokens is predictable. 8 */ 9 10 const char *JSON_STRING = 11 "{\"user\": \"johndoe\", \"admin\": false, \"uid\": 1000,\n " 12 "\"groups\": [\"users\", \"wheel\", \"audio\", \"video\"]}"; 13 14 static int jsoneq(const char *json, jsmntok_t *tok, const char *s) { 15 if (tok->type == JSMN_STRING && (int) strlen(s) == tok->end - tok->start && 16 strncmp(json + tok->start, s, tok->end - tok->start) == 0) { 17 return 0; 18 } 19 return -1; 20 } 21 22 int main() { 23 int i; 24 int r; 25 jsmn_parser p; 26 jsmntok_t t[128]; /* We expect no more than 128 tokens */ 27 28 jsmn_init(&p); 29 r = jsmn_parse(&p, JSON_STRING, strlen(JSON_STRING), t, sizeof(t)/sizeof(t[0])); 30 if (r < 0) { 31 printf("Failed to parse JSON: %d\n", r); 32 return 1; 33 } 34 35 /* Assume the top-level element is an object */ 36 if (r < 1 || t[0].type != JSMN_OBJECT) { 37 printf("Object expected\n"); 38 return 1; 39 } 40 41 /* Loop over all keys of the root object */ 42 for (i = 1; i < r; i++) { 43 if (jsoneq(JSON_STRING, &t[i], "user") == 0) { 44 /* We may use strndup() to fetch string value */ 45 printf("- User: %.*s\n", t[i+1].end-t[i+1].start, 46 JSON_STRING + t[i+1].start); 47 i++; 48 } else if (jsoneq(JSON_STRING, &t[i], "admin") == 0) { 49 /* We may additionally check if the value is either "true" or "false" */ 50 printf("- Admin: %.*s\n", t[i+1].end-t[i+1].start, 51 JSON_STRING + t[i+1].start); 52 i++; 53 } else if (jsoneq(JSON_STRING, &t[i], "uid") == 0) { 54 /* We may want to do strtol() here to get numeric value */ 55 printf("- UID: %.*s\n", t[i+1].end-t[i+1].start, 56 JSON_STRING + t[i+1].start); 57 i++; 58 } else if (jsoneq(JSON_STRING, &t[i], "groups") == 0) { 59 int j; 60 printf("- Groups:\n"); 61 if (t[i+1].type != JSMN_ARRAY) { 62 continue; /* We expect groups to be an array of strings */ 63 } 64 for (j = 0; j < t[i+1].size; j++) { 65 jsmntok_t *g = &t[i+j+2]; 66 printf(" * %.*s\n", g->end - g->start, JSON_STRING + g->start); 67 } 68 i += t[i+1].size + 1; 69 } else { 70 printf("Unexpected key: %.*s\n", t[i].end-t[i].start, 71 JSON_STRING + t[i].start); 72 } 73 } 74 return 0; 75 } 76