[转]C++ 使用 curl 进行 http 请求（GET、POST、Download）的封装

原文连接：https://www.cnblogs.com/oftenlin/p/9478067.html

CommonTools.h

  /*

 * CommonTools.h
 *
 *  Created on: 2018年8月2日
 *      Author: didi
 */
#include <iostream>
#include <curl/curl.h>
#include "zlib.h"
#include <vector>
#include <string>
#include <unistd.h>
#include <memory.h>
#include <json/json.h>
#include <sstream>
using namespace std;

class CommonTools{
    public:
        CommonTools();
        ~CommonTools();
    public:
                static size_t receive_data(void *contents, size_t size, size_t nmemb, void *stream);
        // HTTP 下载文件的回掉函数
        static size_t writedata2file(void *ptr, size_t size, size_t nmemb, FILE *stream);
        // 文件下载接口
        static int download_file(const char* url, const char outfilename[FILENAME_MAX]);
        // http get 请求
        static CURLcode HttpGet(const std::string & strUrl, std::string & strResponse,int nTimeout);
        // htpp post 请求
        static CURLcode HttpPost(const std::string & strUrl, std::string szJson,std::string & strResponse,int nTimeout);
}

CommonTools.cpp

  #include "CommonTools.h"

using namespace std;

size_t CommonTools::receive_data(void *contents, size_t size, size_t nmemb, void *stream){
    string *str = (string*)stream;
    (*str).append((char*)contents, size*nmemb);
    return size * nmemb;
}

size_t CommonTools::writedata2file(void *ptr, size_t size, size_t nmemb, FILE *stream) {
    size_t written = fwrite(ptr, size, nmemb, stream);
    return written;
}

int CommonTools::download_file(const char* url, const char outfilename[FILENAME_MAX]){
    CURL *curl;
    FILE *fp;
    CURLcode res;
    /*   调用curl_global_init()初始化libcurl  */
    res = curl_global_init(CURL_GLOBAL_ALL);
    if (CURLE_OK != res)
    {
        printf("init libcurl failed.");
        curl_global_cleanup();
        return -1;
    }
    /*  调用curl_easy_init()函数得到 easy interface型指针  */
    curl = curl_easy_init();
    if (curl) {
        fp = fopen(outfilename,"wb");

        /*  调用curl_easy_setopt()设置传输选项 */
        res = curl_easy_setopt(curl, CURLOPT_URL, url);
        if (res != CURLE_OK)
        {
            fclose(fp);
            curl_easy_cleanup(curl);
            return -1;
        }
        /*  根据curl_easy_setopt()设置的传输选项，实现回调函数以完成用户特定任务  */
        res = curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, CommonTools::writedata2file);
        if (res != CURLE_OK){
            fclose(fp);
            curl_easy_cleanup(curl);
            return -1;
        }
        /*  根据curl_easy_setopt()设置的传输选项，实现回调函数以完成用户特定任务  */
        res = curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
        if (res != CURLE_OK)
        {
            fclose(fp);
            curl_easy_cleanup(curl);
            return -1;
        }

        res = curl_easy_perform(curl);
        // 调用curl_easy_perform()函数完成传输任务
        fclose(fp);
        /* Check for errors */
        if(res != CURLE_OK){
            fprintf(stderr, "curl_easy_perform() failed: %s\n",curl_easy_strerror(res));
            curl_easy_cleanup(curl);
            return -1;
        }

        /* always cleanup */
        curl_easy_cleanup(curl);
        // 调用curl_easy_cleanup()释放内存

    }
    curl_global_cleanup();
    return 0;
}

CURLcode CommonTools::HttpGet(const std::string & strUrl, std::string & strResponse,int nTimeout){
    CURLcode res;
    CURL* pCURL = curl_easy_init();

    if (pCURL == NULL) {
        return CURLE_FAILED_INIT;
    }

    curl_easy_setopt(pCURL, CURLOPT_URL, strUrl.c_str());
    //curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
    curl_easy_setopt(pCURL, CURLOPT_NOSIGNAL, 1L);
    curl_easy_setopt(pCURL, CURLOPT_TIMEOUT, nTimeout);
    curl_easy_setopt(pCURL, CURLOPT_NOPROGRESS, 1L);
    curl_easy_setopt(pCURL, CURLOPT_WRITEFUNCTION, CommonTools::receive_data);
    curl_easy_setopt(pCURL, CURLOPT_WRITEDATA, (void*)&strResponse);
    res = curl_easy_perform(pCURL);
    curl_easy_cleanup(pCURL);
    return res;
}

CURLcode CommonTools::HttpPost(const std::string & strUrl, std::string szJson,std::string & strResponse,int nTimeout){
    CURLcode res;
    char szJsonData[1024];
    memset(szJsonData, 0, sizeof(szJsonData));
    strcpy(szJsonData, szJson.c_str());
    CURL* pCURL = curl_easy_init();
    struct curl_slist* headers = NULL;
    if (pCURL == NULL) {
        return CURLE_FAILED_INIT;
    }

    CURLcode ret;
    ret = curl_easy_setopt(pCURL, CURLOPT_URL, strUrl.c_str());
//    std::cout << ret << std::endl;

    ret = curl_easy_setopt(pCURL, CURLOPT_POST, 1L);
    headers = curl_slist_append(headers,"content-type:application/json");

    ret = curl_easy_setopt(pCURL, CURLOPT_HTTPHEADER, headers);

    ret = curl_easy_setopt(pCURL, CURLOPT_POSTFIELDS, szJsonData);
    //curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
    ret = curl_easy_setopt(pCURL, CURLOPT_TIMEOUT, nTimeout);

    ret = curl_easy_setopt(pCURL, CURLOPT_WRITEFUNCTION, CommonTools::receive_data);

    ret = curl_easy_setopt(pCURL, CURLOPT_WRITEDATA, (void*)&strResponse);

    res = curl_easy_perform(pCURL);
    curl_easy_cleanup(pCURL);
    return res;
}

使用方法

Main.cpp

  // get 请求

string strURL = "http://www.baidu.com";
string strResponse;
CURLcode nRes = CommonTools::HttpGet(strURL, strResponse,300);
size_t nSrcLength = strResponse.length();

//下载文件
string strURL = "http://www.baidu.com/aaa.dat";
char local_file[50] = {0};
sprintf(local_file,"./pb_%d_%s.dat",1,"aaaa");
int iDownlaod_Success = CommonTools::download_file(url.c_str(),local_file);
if(iDownlaod_Success<0){
    char download_failure_info[100] ={0};
    sprintf(download_failure_info,"download file :%s ,failure,url:",local_file,url);
    FATAL(download_failure_info);
}

C++用libcurl通过HTTP以表单的方式Post数据到服务器

一、Post 字符串

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

int main(void)
{
    CURL* curl = NULL;
    CURLcode res;

    curl = curl_easy_init();
    if(curl == NULL)
    {
        return CURLE_FAILED_INIT;
    }

    struct curl_slist* headerlist = NULL; 

    // 设置表头，表头内容可能不同
    headerlist = curl_slist_append(headerlist, "Content-Type:application/x-www-form-urlencoded");
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerlist);  

    // 设置URL
    curl_easy_setopt(curl, CURLOPT_URL, "http://postit.example.com/moo.cgi");

    // 设置参数，比如"ParamName1=ParamName1Content&ParamName2=ParamName2Content&..."
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, "name=daniel&project=curl");

    // 设置为Post
    curl_easy_setopt(curl, CURLOPT_POST, );

    // 发送
    res = curl_easy_perform(curl);

    if(res != CURLE_OK)
    {
        // 获取详细错误信息
        char* szErr = curl_easy_strerror(res);
        fprintf(stderr, "curl_easy_perform() failed: %s\n", szErr);
    }

    // 清空
    curl_easy_cleanup(curl);

    // 释放表头
    curl_slist_free_all (headerlist);  

    return ;
}

二、Post 文件

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

size_t OnWriteData(void* buffer, size_t size, size_t nmemb, void* lpVoid);

int main(void)
{
    CURL* curl = NULL;
    CURLcode res;

    curl = curl_easy_init();
    if(curl == NULL)
    {
        return CURLE_FAILED_INIT;
    }

    struct curl_slist*        headerlist    = NULL;
    struct curl_httppost*    formpost    = NULL;
    struct curl_httppost*    lastptr        = NULL;
    std::string strResponse;    // 回复

    curl_formadd(&formpost, &lastptr,
        CURLFORM_COPYNAME, "ParamName1",
        CURLFORM_COPYCONTENTS, "ParamName1Content", CURLFORM_END);

    curl_formadd(&formpost, &lastptr,
        CURLFORM_COPYNAME, "ParamName2",
        CURLFORM_COPYCONTENTS, "ParamName2Content", CURLFORM_END);

    curl_formadd(&formpost, &lastptr,
        CURLFORM_COPYNAME, "ParamName3",
        CURLFORM_COPYCONTENTS, "ParamName3Content", CURLFORM_END);

    curl_formadd(&formpost, &lastptr,
        CURLFORM_COPYNAME, "registerImgs",
        CURLFORM_FILE, "C:/Image.png", CURLFORM_END);    // 设置要上传的文件

    // 设置表单参数
    curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost);

    // 设置表头，表头内容可能不同
    headerlist = curl_slist_append(headerlist, "Content-Type:application/x-www-form-urlencoded");
    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerlist);  

    // 设置URL
    curl_easy_setopt(curl, CURLOPT_URL, "http://postit.example.com/moo.cgi");

    // 设置参数，比如"ParamName1=ParamName1Content&ParamName2=ParamName2Content&..."
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, "name=daniel&project=curl");

    // 设置为Post
    curl_easy_setopt(curl, CURLOPT_POST, );

    curl_easy_setopt(curl, CURLOPT_READFUNCTION, NULL);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, OnWriteData);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void*)&strResponse);
    curl_easy_setopt(curl, CURLOPT_NOSIGNAL, );
    curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, );
    curl_easy_setopt(curl, CURLOPT_TIMEOUT, );

    // 发送
    res = curl_easy_perform(curl);

    if(res != CURLE_OK)
    {
        // 获取详细错误信息
        char* szErr = curl_easy_strerror(res);
        fprintf(stderr, "curl_easy_perform() failed: %s\n", szErr);
    }

    // 清空
    curl_easy_cleanup(curl);

    // 释放表单
    curl_formfree(formpost);

    // 释放表头
    curl_slist_free_all (headerlist);  

    return ;
}

size_t OnWriteData(void* buffer, size_t size, size_t nmemb, void* lpVoid)
{
    std::string* str = dynamic_cast<std::string*>((std::string *)lpVoid);
    if( NULL == str || NULL == buffer )
    {
        return -;
    }

    char* pData = (char*)buffer;
    str->append(pData, size * nmemb);
    return nmemb;
}