Question

I’m trying to get some data from a certain web-based api using the libcurl c api.
Curl calls the api fine. However, size_t nmemb is too small to hold the response. Somehow it is “cut off” at 1280. Does anyone know how to solve this? Also size_t size is 1..

These are the functions I use:

int http_call(char *url) {

    CURL *curl;
    FILE *curlfile;
    CURLcode res;

    char outfilename[FILENAME_MAX] = "/usr/local/var/log/ndcurl";
    curl = curl_easy_init();
    if (curl) {

        curlfile = fopen(outfilename,"w");
        curl_easy_setopt(curl, CURLOPT_URL, url);

        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_release_data);

        curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);

        res = curl_easy_perform(curl);

        curl_easy_cleanup(curl);
        fclose(curlfile);

    }

    return 0;

}

And the callback:

static size_t write_release_data(void *buffer, size_t size, size_t nmemb, void *userp) {

    char **response_ptr =  (char**)userp;
    *response_ptr = strndup(buffer, (size_t)(size *nmemb));
    printf("The Response: %s", *response_ptr);

    return 0;

}

Answer 1

You need to fix your callback to return the actual number of bytes written. From the documentation

Pass a pointer to a function that matches the following prototype:
size_t function( char *ptr, size_t size, size_t nmemb, void
*userdata); This function gets called by libcurl as soon as there is data received that needs to be saved. The size of the data pointed to
by ptr is size multiplied with nmemb, it will not be zero terminated.
Return the number of bytes actually taken care of. If that amount
differs from the amount passed to your function, it’ll signal an error
to the library. This will abort the transfer and return
CURLE_WRITE_ERROR.

If you return size * nmemb, libcurl should call your function again with the rest of the response.