diplodocus.org Git - nmh/blob - thirdparty/jsmn/example/simple.c

   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 }