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