jsmn_parse in loop results: Object expected Error #181
Description
Dear All,
I am playing with JSMN for the first time. It is working for my purposes but I would like to run it in a loop, continouly updating information.
When I run the function for the first time everything works, after that in each loop I receive: Object expected error message.
here is the code: (you have to get your own api key )
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>
#include <conio.h>
#include <jsmn.h>
struct memory{
char* memory;
size_t size;
};
static size_t writecallback(char* contents, size_t size, size_t nmemb, void *userp){
size_t realsize = size * nmemb;
struct memory* mem = (struct memory*)userp;
char *ptr = (char*) realloc(mem->memory, mem->size + realsize + 1); //VC++ miatt kell a (char*) a realloc elé.
if (ptr == NULL)
return(0);
mem->memory = ptr;
memcpy(&mem->memory[mem->size], contents, realsize);
mem->size += realsize;
mem->memory[mem->size] = 0;
return realsize;
//fprintf(stderr, "\r%s", contents);
//fflush(stdout);
//return size * nmemb;
}
//jsmn
static const char *JSON_STRING = "";
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;
}
//JSMN vége
int get_coordinates(double *lat, double *lon, double *alt, double *azi, double *ele, double *_ra, double *_dec, long long *_times) {
CURL* curl;
CURLcode res;
struct memory chunk;
chunk.memory = NULL;
chunk.size = 0;
curl_global_init(CURL_GLOBAL_ALL);
//jsmn rész
int i = 0;
int r = -1;
jsmn_parser p;
jsmntok_t t[500]; /* We expect no more than 128 tokens */
//jsmn rész vége
curl = curl_easy_init();
if (curl) {
curl_easy_setopt(curl, CURLOPT_URL, "https://www.n2yo.com/rest/v1/satellite/positions/25544/46.3185/17.7515/0/1/&apiKey=*HERE IS MY KEY*");
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writecallback);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &chunk);
res = curl_easy_perform(curl);
if (res != CURLE_OK) {
fprintf(stderr, "curl_easy_perform() returned %s\n",
curl_easy_strerror(res));
}
else {
//Itt töltöttük le az adatokat:
//printf("We got %d bytes to our callback. We received the following text:\n\n", (int)chunk.size);
printf("%s\n\n", chunk.memory);
//
// JSMN próba
//
static const char* JSON_STRING = chunk.memory;
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");
//printf("%d\n", r);
//printf("%d\n", t[0]);
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("%.*s, i: %d\n", t[i].end - t[i].start, JSON_STRING + t[i].start, i);
//strncpy_s(tomb, t[i].end - t[i].start, JSON_STRING + t[i].start, t[i].end - t[i].start);
}
}
//printf("% .*s: % .*s\n", t[1].end - t[1].start, JSON_STRING + t[1].start, t[2].end - t[2].start, JSON_STRING + t[2].start);
//printf("% .*s: % .*s\n", t[5].end - t[5].start, JSON_STRING + t[5].start, t[6].end - t[6].start, JSON_STRING + t[6].start );
//printf("% .*s: % .*s\n", t[7].end - t[7].start, JSON_STRING + t[7].start, t[8].end - t[8].start, JSON_STRING + t[8].start);
sscanf_s((JSON_STRING + t[13].start), "%lf", lat);
sscanf_s((JSON_STRING + t[15].start), "%lf", lon);
sscanf_s((JSON_STRING + t[17].start), "%lf", alt);
sscanf_s((JSON_STRING + t[19].start), "%lf", azi);
sscanf_s((JSON_STRING + t[21].start), "%lf", ele);
sscanf_s((JSON_STRING + t[23].start), "%lf", _ra);
sscanf_s((JSON_STRING + t[25].start), "%lf", _dec);
sscanf_s((JSON_STRING + t[27].start), "%d", _times);
//
//JSMN vége
//
}
free(chunk.memory);
curl_easy_cleanup(curl);
}
curl_global_cleanup();
return(0);
};
int main(void) {
double latitude, longitude, altitude, azimuth, elevation, ra, dec;
long long timestamp;
int c = 1;
//-------------------------------------------------------------------
while (c != 'n') // until correct key is pressed
{
do { // forever
//do
//
get_coordinates(&latitude, &longitude, &altitude, &azimuth, &elevation, &ra, &dec, ×tamp);
printf("\nLatitude:\t%lf", latitude);
printf("\nLongitude:\t%lf", longitude);
printf("\nAltitude:\t%lf", altitude);
printf("\nAzimuth:\t%lf", azimuth);
printf("\nElevation:\t%lf", elevation);
printf("\nRa:\t\t%lf", ra);
printf("\nDec:\t\t%lf", dec);
printf("\nTimestamp:\t%ld", timestamp);
printf("\n");
//-------------------------------------------------------------------
//do
} while (!_kbhit()); // until a key press detected
c = _getch(); // fetch that key press
}
//
return(0);
}
(Visual Studio 2019, windows 10)
The received text looks like this:
{"info":{"satname":"SPACE STATION","satid":25544,"transactionscount":91},"positions":[{"satlatitude":-51.79721854,"satlongitude":-12.7783,"sataltitude":439.3,"azimuth":198.83,"elevation":-49.23,"ra":316.23335672,"dec":-77.09388627,"timestamp":1577393729}]}
I learned to program in C about 15 years ago in Linux - I was quite good at it and never used it since. I am sure the code is not elegant. First I want it to work.
I appreciate any help you can provide.
Robert