post-callback.c

/***************************************************************************
 * _ _ ____ _
 * Project ___| | | | _ \| |
 * / __| | | | |_) | |
 * | (__| |_| | _ <| |___
 * \___|\___/|_| \_\_____|
 *
 * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 * SPDX-License-Identifier: curl
 *
 ***************************************************************************/
/* <DESC>
 * Issue an HTTP POST and provide the data through the read callback.
 * </DESC>
 */
#include <stdio.h>
#include <string.h>
#include <curl/curl.h>
 
/* silly test data to POST */
static const char data[]="Lorem ipsum dolor sit amet, consectetur adipiscing "
 "elit. Sed vel urna neque. Ut quis leo metus. Quisque eleifend, ex at "
 "laoreet rhoncus, odio ipsum semper metus, at tempus ante urna in mauris. "
 "Suspendisse ornare tempor venenatis. Ut dui neque, pellentesque a ______ "
 "eget, mattis vitae ligula. Fusce ut pharetra est. Ut ullamcorper mi ac "
 "sollicitudin semper. Praesent sit amet tellus ______, posuere nulla non, "
 "rhoncus ipsum.";
 
struct WriteThis {
 const char *readptr;
 size_t sizeleft;
};
 
static size_t read_callback(char *dest, size_t size, size_t nmemb, void *userp)
{
 struct WriteThis *wt = (struct WriteThis *)userp;
 size_t buffer_size = size*nmemb;
 
 if(wt->sizeleft) {
 /* copy as much as possible from the source to the destination */
 size_t copy_this_much = wt->sizeleft;
 if(copy_this_much > buffer_size)
 copy_this_much = buffer_size;
 memcpy(dest, wt->readptr, copy_this_much);
 
 wt->readptr += copy_this_much;
 wt->sizeleft -= copy_this_much;
 return copy_this_much; /* we copied this many bytes */
 }
 
 return 0; /* no more data left to deliver */
}
 
int main(void)
{
 CURL *curl;
 CURLcode res;
 
 struct WriteThis wt;
 
 wt.readptr = data;
 wt.sizeleft = strlen(data);
 
 /* In Windows, this inits the Winsock stuff */
 res = curl_global_init(CURL_GLOBAL_DEFAULT);
 /* Check for errors */
 if(res != CURLE_OK) {
 fprintf(stderr, "curl_global_init() failed: %s\n",
 curl_easy_strerror(res));
 return (int)res;
 }
 
 /* get a curl handle */
 curl = curl_easy_init();
 if(curl) {
 /* First set the URL that is about to receive our POST. */
 curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/index.cgi");
 
 /* Now specify we want to POST data */
 curl_easy_setopt(curl, CURLOPT_POST, 1L);
 
 /* we want to use our own read function */
 curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_callback);
 
 /* pointer to pass to our read function */
 curl_easy_setopt(curl, CURLOPT_READDATA, &wt);
 
 /* get verbose debug output please */
 curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
 
 /*
 If you use POST to an HTTP 1.1 server, you can send data without knowing
 the size before starting the POST if you use chunked encoding. You
 enable this by adding a header like "Transfer-Encoding: chunked" with
 CURLOPT_HTTPHEADER. With HTTP 1.0 or without chunked transfer, you must
 specify the size in the request.
 */
#ifdef USE_CHUNKED
 {
 struct curl_slist *chunk = NULL;
 
 chunk = curl_slist_append(chunk, "Transfer-Encoding: chunked");
 res = curl_easy_setopt(curl, CURLOPT_HTTPHEADER, chunk);
 /* use curl_slist_free_all() after the *perform() call to free this
 list again */
 }
#else
 /* Set the expected POST size. If you want to POST large amounts of data,
 consider CURLOPT_POSTFIELDSIZE_LARGE */
 curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, (long)wt.sizeleft);
#endif
 
#ifdef DISABLE_EXPECT
 /*
 Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue"
 header. You can disable this header with CURLOPT_HTTPHEADER as usual.
 NOTE: if you want chunked transfer too, you need to combine these two
 since you can only set one list of headers with CURLOPT_HTTPHEADER. */
 
 /* A less good option would be to enforce HTTP 1.0, but that might also
 have other implications. */
 {
 struct curl_slist *chunk = NULL;
 
 chunk = curl_slist_append(chunk, "Expect:");
 res = curl_easy_setopt(curl, CURLOPT_HTTPHEADER, chunk);
 /* use curl_slist_free_all() after the *perform() call to free this
 list again */
 }
#endif
 
 /* Perform the request, res gets the return code */
 res = curl_easy_perform(curl);
 /* Check for errors */
 if(res != CURLE_OK)
 fprintf(stderr, "curl_easy_perform() failed: %s\n",
 curl_easy_strerror(res));
 
 /* always cleanup */
 curl_easy_cleanup(curl);
 }
 curl_global_cleanup();
 return 0;
}

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