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 + 1);
    if(mem->memory == NULL){
        printf("realloc error...
");
        return 0;
    }

    memcpy(&(mem->memory[mem->allsize]), contents, realsize);
    mem->allsize += realsize;
    mem->memory[mem->allsize] = 0;

    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=0;
    FILE* fd = fopen("./aaa.txt", "wb+");
    char *type = (char*)malloc(32);
    struct MemoryStruct chunk;
    chunk.memory = (char*)malloc(1);
    chunk.allsize = 0;
        


    curl = curl_easy_init();
    curl_easy_setopt(curl, CURLOPT_URL, url);
    //curl_easy_setopt(curl, CURLOPT_NOBODY, 1L);
    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 0);    //不跳转
    curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT_MS, 3000);
    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
", curl_easy_strerror(res));
    }
    res = curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &httpcode);
    if(res != CURLE_OK || httpcode != 200 ){
        fprintf(stdout, "httpcode error!
");        
    }
    res = curl_easy_getinfo(curl, CURLINFO_CONTENT_LENGTH_DOWNLOAD, &size);
    if(res != CURLE_OK ){
        fprintf(stdout, "httpcode xxxerror!
");        
    }
    
    res = curl_easy_getinfo(curl, CURLINFO_CONTENT_TYPE, &type);
    if(res != CURLE_OK ){
        fprintf(stdout, "TYPE xxxerror!
");        
    }
    printf("type:
%s
", type);
    printf("header:
%s
", 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
", filesize, url);
    return 0;
}