libcurl使用示例

远程下载文件，并将http 头信息存放内存中以及文件大小等相关信息：

 #include <stdio.h>
 #include <curl/curl.h>
 #include <stdlib.h>
 #include <string.h>

 struct MemoryStruct {
     char* memory;
     size_t allsize;
 };

 static size_t WriteMemoryCallback(void* contents, size_t _size, size_t nmemb, void* userp)
 {
     size_t realsize = _size * nmemb;
     struct MemoryStruct *mem = (struct MemoryStruct*)userp;

     mem->memory = (char*)realloc(mem->memory, mem->allsize + realsize + );
     if(mem->memory == NULL){
         printf("realloc error...\n");
         return ;
     }

     memcpy(&(mem->memory[mem->allsize]), contents, realsize);
     mem->allsize += realsize;
     mem->memory[mem->allsize] = ;

     return realsize;
 }

 size_t write_data(char* buffer, size_t size, size_t items, void* outstream)
 {
     int written = fwrite(buffer, size, items, (FILE*)(outstream));
     return written;
 }

 double get_download_size(char* url){
     CURL* curl;
     CURLcode res;
     double size = 0.0;
     int httpcode=;
     FILE* fd = fopen("./aaa.txt", "wb+");
     char *type = (char*)malloc();
     struct MemoryStruct chunk;
     chunk.memory = (char*)malloc();
     chunk.allsize = ;

     curl = curl_easy_init();
     curl_easy_setopt(curl, CURLOPT_URL, url);
     //curl_easy_setopt(curl, CURLOPT_NOBODY, 1L);
     curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, );    //不跳转
     curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT_MS, );
     curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void*)fd);
     curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);

     curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, WriteMemoryCallback);
     curl_easy_setopt(curl, CURLOPT_HEADERDATA, (void*)&chunk);

     res = curl_easy_perform(curl);
     if(res != CURLE_OK){
         fprintf(stderr, "curl_easy_getinfo() failed: %s\n", curl_easy_strerror(res));
     }
     res = curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &httpcode);
     if(res != CURLE_OK || httpcode !=  ){
         fprintf(stdout, "httpcode error!\n");
     }
     res = curl_easy_getinfo(curl, CURLINFO_CONTENT_LENGTH_DOWNLOAD, &size);
     if(res != CURLE_OK ){
         fprintf(stdout, "httpcode xxxerror!\n");
     }

     res = curl_easy_getinfo(curl, CURLINFO_CONTENT_TYPE, &type);
     if(res != CURLE_OK ){
         fprintf(stdout, "TYPE xxxerror!\n");
     }
     printf("type:\n%s\n", type);
     printf("header:\n%s\n", chunk.memory);
     fclose(fd);
     free(chunk.memory);
     curl_easy_cleanup(curl);

     return size;
 }

 int main(int argc, char* argv[])
 {
     char url[] = "http://www.fastcgi.com/dist/fcgi.tar.gz";

     double filesize = get_download_size(url);
     printf("[%0.0lf] %s\n", filesize, url);
     return ;
 }