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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "../jsmn.h"
/*
* A small example of jsmn parsing when JSON structure is known and number of
* tokens is predictable.
*/
static const char *JSON_STRING =
"{\"user\": \"johndoe\", \"admin\": false, \"uid\": 1000,\n "
"\"groups\": [\"users\", \"wheel\", \"audio\", \"video\"]}";
static int jsoneq(const char *json, jsmntok_t *tok, const char *s) {
if (tok->type == JSMN_STRING && (int) strlen(s) == tok->end - tok->start &&
strncmp(json + tok->start, s, tok->end - tok->start) == 0) {
return 0;
}
return -1;
}
int main() {
int i;
int r;
jsmn_parser p;
jsmntok_t t[128]; /* We expect no more than 128 tokens */
jsmn_init(&p);
r = jsmn_parse(&p, JSON_STRING, strlen(JSON_STRING), t, sizeof(t)/sizeof(t[0]));
if (r < 0) {
printf("Failed to parse JSON: %d\n", r);
return 1;
}
/* Assume the top-level element is an object */
if (r < 1 || t[0].type != JSMN_OBJECT) {
printf("Object expected\n");
return 1;
}
/* Loop over all keys of the root object */
for (i = 1; i < r; i++) {
if (jsoneq(JSON_STRING, &t[i], "user") == 0) {
/* We may use strndup() to fetch string value */
printf("- User: %.*s\n", t[i+1].end-t[i+1].start,
JSON_STRING + t[i+1].start);
i++;
} else if (jsoneq(JSON_STRING, &t[i], "admin") == 0) {
/* We may additionally check if the value is either "true" or "false" */
printf("- Admin: %.*s\n", t[i+1].end-t[i+1].start,
JSON_STRING + t[i+1].start);
i++;
} else if (jsoneq(JSON_STRING, &t[i], "uid") == 0) {
/* We may want to do strtol() here to get numeric value */
printf("- UID: %.*s\n", t[i+1].end-t[i+1].start,
JSON_STRING + t[i+1].start);
i++;
} else if (jsoneq(JSON_STRING, &t[i], "groups") == 0) {
int j;
printf("- Groups:\n");
if (t[i+1].type != JSMN_ARRAY) {
continue; /* We expect groups to be an array of strings */
}
for (j = 0; j < t[i+1].size; j++) {
jsmntok_t *g = &t[i+j+2];
printf(" * %.*s\n", g->end - g->start, JSON_STRING + g->start);
}
i += t[i+1].size + 1;
} else {
printf("Unexpected key: %.*s\n", t[i].end-t[i].start,
JSON_STRING + t[i].start);
}
}
return EXIT_SUCCESS;
}
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