libcurl的简单实例使用

https://curl.haxx.se/
https://curl.haxx.se/libcurl/c/example.html官网的例子
#include <curl/curl.h>
#include <iostream>
#include <string.h>

using namespace std;


struct WriteThis{
	const char* readptr;
	long sizeleft;
};

size_t readData(void* buffer,size_t size, size_t nmemb, void* userdata)
{
    struct WriteThis* data = (struct WriteThis*)userdata;
    if(data == NULL)
    {
    	return -1;

    }
    if(size*nmemb < 1)
    {
    	return 0;
    }
                
    if(data->sizeleft)
    {
        *(char*)buffer = data->readptr[0];
        data->readptr++;
        data->sizeleft--;
        return 1;
    }
    return 0;
}

//buffer为接收到的数据，size＊nmemb为接收的数据大小，userdata返回的数据指定的输出流
static size_t OnWriteData(void* buffer, size_t size, size_t nmemb, void* userdata)
{
    string* str = dynamic_cast<string*>((string *)userdata);
    if( NULL == str || NULL == buffer )
    {
        return -1;
    }
    
    char* pData = (char*)buffer;
    str->append(pData, size * nmemb);
    return nmemb;
}

bool get()
{
	string body;
	string head;
	CURL* curl;
	CURLcode res;
	FILE* file = fopen("./resp.html","wb");

	struct curl_slist* headers = NULL;
	headers = curl_slist_append(headers,"Accept:Agent-000");
	curl = curl_easy_init();
	if(curl)
	{
		curl_easy_setopt(curl,CURLOPT_HTTPHEADER,headers);
		curl_easy_setopt(curl,CURLOPT_URL,"www.baidu.com");

		//test
		curl_easy_setopt(curl,CURLOPT_READFUNCTION,readData);

//如果没有注册CURLOPT_WRITEDATA和CURLOPT_WRITEFUNCTION测执行默认的回调函数（打印到控制台）
//		curl_easy_setopt(curl,CURLOPT_HEADERDATA,file);//存入本地文件      对接收的数据处理方式  *****方式1*＊＊＊＊＊
 //		curl_easy_setopt(curl,CURLOPT_WRITEDATA,file);

		curl_easy_setopt(curl,CURLOPT_WRITEFUNCTION,OnWriteData);	 	///                 ******方式2*********
		curl_easy_setopt(curl,CURLOPT_WRITEDATA,(void*)&body);//读入string

		curl_easy_setopt(curl,CURLOPT_ACCEPT_ENCODING,"gzip");
		res = curl_easy_perform(curl);
		if(res != 0)
		{
			curl_slist_free_all(headers);
		}
	}else{

	}
	if(!body.empty())
	{
		cout << body << endl;
	}else{
		cout << "resp empty" << endl;
	}
	fclose(file);
	curl_easy_cleanup(curl);
	return true;

}

bool post()
{
	string resp_data;
	char data[] = "{\"content\":\"hello world\"}";
	struct WriteThis pooh;
	pooh.readptr = data;
	pooh.sizeleft = (long)strlen(data);
	CURL* curl;
	CURLcode res;
	curl = curl_easy_init();
	if(curl)
	{
		curl_easy_setopt(curl,CURLOPT_URL,"www.baidu.com");
		curl_easy_setopt(curl,CURLOPT_POST,1);
		curl_easy_setopt(curl,CURLOPT_WRITEFUNCTION,OnWriteData);
		curl_easy_setopt(curl,CURLOPT_WRITEDATA,(void*)&resp_data);	
		curl_easy_setopt(curl,CURLOPT_READFUNCTION,readData);	//使用定制的read function
		curl_easy_setopt(curl,CURLOPT_READDATA,&pooh);
		curl_easy_setopt(curl,CURLOPT_POSTFIELDSIZE,pooh.sizeleft);//不设定size，注册的read function不会被执行
		
                //curl_easy_setopt(curl,CURLOPT_POSTFIELDS,data);//使用默认的read function的方式
		//curl_easy_setopt(curl,CURLOPT_POSTFIELDSIZE,strlen(data));
		//curl_easy_setopt(curl,CURLOPT_TIMEOUT,1);
		res = curl_easy_perform(curl);
	}
	if(res != 0){}
	curl_easy_cleanup(curl);
	return true;
}
int main()
{
	//get();
	post();
	return 0;
}