1 /***************************************************************************
2 * _ _ ____ _
3 * Project ___| | | | _ \| |
4 * / __| | | | |_) | |
5 * | (__| |_| | _ <| |___
6 * \___|\___/|_| \_\_____|
7 *
8 * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
9 *
10 * This software is licensed as described in the file COPYING, which
11 * you should have received as part of this distribution. The terms
12 * are also available at https://curl.se/docs/copyright.html.
13 *
14 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
15 * copies of the Software, and permit persons to whom the Software is
16 * furnished to do so, under the terms of the COPYING file.
17 *
18 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
19 * KIND, either express or implied.
20 *
21 * SPDX-License-Identifier: curl
22 *
23 ***************************************************************************/
24 /* <DESC>
25 * Shows how the write callback function can be used to download data into a
26 * chunk of memory instead of storing it in a file.
27 * </DESC>
28 */
29
30 #include <stdio.h>
31 #include <stdlib.h>
32 #include <string.h>
33
34 #include <curl/curl.h>
35
36 struct MemoryStruct {
37 char *memory;
38 size_t size;
39 };
40
41 static size_t
WriteMemoryCallback(void * contents,size_t size,size_t nmemb,void * userp)42 WriteMemoryCallback(void *contents, size_t size, size_t nmemb, void *userp)
43 {
44 size_t realsize = size * nmemb;
45 struct MemoryStruct *mem = (struct MemoryStruct *)userp;
46
47 char *ptr = realloc(mem->memory, mem->size + realsize + 1);
48 if(!ptr) {
49 /* out of memory! */
50 printf("not enough memory (realloc returned NULL)\n");
51 return 0;
52 }
53
54 mem->memory = ptr;
55 memcpy(&(mem->memory[mem->size]), contents, realsize);
56 mem->size += realsize;
57 mem->memory[mem->size] = 0;
58
59 return realsize;
60 }
61
main(void)62 int main(void)
63 {
64 CURL *curl_handle;
65 CURLcode res;
66
67 struct MemoryStruct chunk;
68
69 chunk.memory = malloc(1); /* grown as needed by the realloc above */
70 chunk.size = 0; /* no data at this point */
71
72 curl_global_init(CURL_GLOBAL_ALL);
73
74 /* init the curl session */
75 curl_handle = curl_easy_init();
76
77 /* specify URL to get */
78 curl_easy_setopt(curl_handle, CURLOPT_URL, "https://www.example.com/");
79
80 /* send all data to this function */
81 curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
82
83 /* we pass our 'chunk' struct to the callback function */
84 curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, (void *)&chunk);
85
86 /* some servers do not like requests that are made without a user-agent
87 field, so we provide one */
88 curl_easy_setopt(curl_handle, CURLOPT_USERAGENT, "libcurl-agent/1.0");
89
90 /* get it! */
91 res = curl_easy_perform(curl_handle);
92
93 /* check for errors */
94 if(res != CURLE_OK) {
95 fprintf(stderr, "curl_easy_perform() failed: %s\n",
96 curl_easy_strerror(res));
97 }
98 else {
99 /*
100 * Now, our chunk.memory points to a memory block that is chunk.size
101 * bytes big and contains the remote file.
102 *
103 * Do something nice with it!
104 */
105
106 printf("%lu bytes retrieved\n", (unsigned long)chunk.size);
107 }
108
109 /* cleanup curl stuff */
110 curl_easy_cleanup(curl_handle);
111
112 free(chunk.memory);
113
114 /* we are done with libcurl, so clean it up */
115 curl_global_cleanup();
116
117 return 0;
118 }
119
