我从来没有真正在 C++ 中做过任何多线程或异步的事情，到目前为止我只使用 cURL 来做单个同步请求。
为了更好地可视化我正在尝试做的事情，我编写了一个简单的 Javascript，它可以用 C++ 中的 cURL 完成我想做的事情。
function AddRequest( method, url, data, id ) {
var httpObj = new ActiveXObject("Msxml2.XMLHTTP.6.0"); //new XMLHttpRequest();
httpObj.onreadystatechange = function() {
if (httpObj.readyState == 4)
ResponseCallback( httpObj, id );
};
httpObj.Open( method, url, true );
httpObj.Send( data );
}
function ResponseCallback( httpObj, id ) {
WScript.Echo( id ); //alert( id );
WScript.Echo( httpObj.ResponseText ); //alert( httpObj.ResponseText );
}
//It could now be used like this:
AddRequest("GET","http://example.com/","",1);
AddRequest("GET","https://www.facebook.com","",2);
WScript.Echo( "all requests sent" ); //alert( "all requests sent" );
//these requests are all done at the same time
//and every time a request has finished it calls the ResponseCallback() function,
//telling it which request has finished
CURL 似乎完全不同，而且比 XmlHttpRequest 更复杂，即使两者都只是发送 http 请求...
这是我的第一种方法(基于 hogren 的回答):
#include "stdafx.hpp"
#include <iostream> //#include <stdio.h>
#include <curl.h>
#include <pthread.h>
#include <map>
#include <string>
using namespace std;
bool printing = false; //will allow us to prevent prints overlapping each other
struct requestStruct { //will allow us to pass more than one argument to the threaded functions
int id;
const char* url;
const char* method;
const char* body;
map<const char*, const char*> headers;
const char* proxy;
int timeout;
};
struct responseStruct { //will allow us to return more than one value from the Request function
long statusCode;
//map<const char*, const char*> headers;
const char* body;
};
size_t writeToString(void *ptr, size_t size, size_t count, void *stream) {
((string*)stream)->append((char*)ptr, 0, size* count);
return size* count;
}
static void *ResponseCallback(int id, struct responseStruct *response) {
long statusCode = response -> statusCode;
//map<const char*, const char*> headers = response -> headers;
const char* body = response -> body;
//while (printing) {} //wait for other threads to stop printing
printing = true; //tell other threads to not print anything
cout << id << " response received! Code: " << statusCode << endl << body << endl;
printing = false; //tell other threads printing is okay again
return NULL;
}
struct responseStruct HttpRequest(const char* url, const char* method, const char* body, map<const char*, const char*> &headers, const char* proxy, long timeout) {
CURL *curl;
curl = curl_easy_init();
long statusCode = 0;
map<const char*, const char*> respHeaders;
string respBody;
string _url(url);
string _method(method);
string _proxy(proxy);
struct curl_slist *headerList = NULL;
string headerString;
curl_easy_setopt(curl, CURLOPT_URL, url); //set url
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, method); //set method
for (auto header=headers.begin(); header!=headers.end(); ++header) { //make header list
headerString = header->first;
headerString.append(": ").append(header->second);
headerList = curl_slist_append(headerList, headerString.c_str());
//cout << headerString << '\n';
}
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerList); //set headers
if (_method == "POST" || _method == "PUT" || _method == "DELETE") //set body if the request method would allow it
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, body);
if (_url.find(string("https://")) != string::npos) //set ssl verifypeer if it's an https url
curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
if (_proxy != "") //set proxy
curl_easy_setopt(curl, CURLOPT_PROXY, proxy);
if (timeout != 0) //set timeout
curl_easy_setopt(curl, CURLOPT_TIMEOUT, timeout);
curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L); //follow redirects
//curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, writeToString);
//curl_easy_setopt(curl, CURLOPT_WRITEHEADER, &respHeaders); //to receive response headers
//??
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writeToString);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &respBody); //to receive response body
curl_easy_perform(curl); //send the request
curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &statusCode); //get status code
struct responseStruct response;
response.statusCode = statusCode;
//response.headers;
response.body = respBody.c_str();
curl_easy_cleanup(curl);
return response;
}
static void *AddRequest( void *arguments ) {
// get arguments:
struct requestStruct *args = (struct requestStruct*)arguments;
int id = args->id;
const char* url = args->url;
const char* method = args->method;
const char* body = args->body;
map<const char*, const char*> headers = args->headers;
const char* proxy = args->proxy;
int timeout = args->timeout;
// print arguments:
//while (printing) {} //wait for other threads to stop printing
//printing = true; //tell other threads to not print anything
// cout << id << endl << url << endl << method << endl;
//printing = false; //tell the other threads it's okay to print again now
struct responseStruct response = HttpRequest(url, method, body, headers, proxy, timeout);
ResponseCallback(id,&response);
pthread_exit(0);
return NULL;
}
int main() {
//map<const char*, const char*> headers;
//headers["User-Agent"] = "Mozilla/5.0 (Windows NT 6.2; WOW64; rv:32.0) Gecko/20100101 Firefox/32.0";
//struct responseStruct response = HttpRequest("https://facebook.com", "GET", "", headers, "localhost:8888", 6000);
//cout << response.body << endl;
pthread_t threads[3];
struct requestStruct reqArguments[3];
map<const char*, const char*> headers;
headers["User-Agent"] = "Mozilla/5.0 (Windows NT 6.2; WOW64; rv:32.0) Gecko/20100101 Firefox/32.0";
const char* proxy = "";
reqArguments[0].id = 0;
reqArguments[0].url = "https://www.facebook.com/";
reqArguments[0].method = "GET";
reqArguments[0].headers = headers;
reqArguments[0].body = "";
reqArguments[0].proxy = proxy;
reqArguments[0].timeout = 6000;
pthread_create(&threads[0], NULL, &AddRequest, (void *)&reqArguments[0]); //create a thread on AddRequest() passing a full struct of arguments
reqArguments[1].id = 1;
reqArguments[1].url = "https://www.facebook.com/";
reqArguments[1].method = "GET";
reqArguments[1].headers = headers;
reqArguments[1].body = "";
reqArguments[1].proxy = proxy;
reqArguments[1].timeout = 6000;
pthread_create(&threads[1], NULL, &AddRequest, (void *)&reqArguments[1]); //create a thread on AddRequest() passing a full struct of arguments
reqArguments[2].id = 2;
reqArguments[2].url = "https://www.facebook.com/";
reqArguments[2].method = "GET";
reqArguments[2].headers = headers;
reqArguments[2].body = "";
reqArguments[2].proxy = proxy;
reqArguments[2].timeout = 6000;
pthread_create(&threads[2], NULL, &AddRequest, (void *)&reqArguments[2]); //create a thread on AddRequest() passing a full struct of arguments
getchar(); //prevent console from closing instantly
return 0;
}
我不太确定我是否正确地完成了整个 pthread 的事情..
有一些问题:
1. 由于某些原因，只有第一个请求成功，其他请求甚至都没有发送。
除非我取消注释 main 函数的前 4 行，这将在没有新线程的情况下直接请求，但我显然不想使用该代码。
2. HttpRequest() 函数没有正确返回响应 html 代码，I only receive garbage .
我认为问题 2 可能是与 HttpRequest() 的返回结构相关的指针问题，但我无法修复它。 :(
3. 我最后一个不是那么重要的问题是我不知道如何接收响应 header 并将它们放在 map 中。
顺便说一句:我正在使用 Visual C++ 2010 进行编译，并且正在使用 Fiddler 调试 http 流量。
最佳答案
编辑:这是我更正过的代码。
并没有真正的错误。但经过多次测试，我发现同时启动多个 curl_perform 会导致问题。所以我加了一个延迟(5000ms 很大，你可以减少它)。
并且 pthread_exit() 导致响应错误的问题。
#include "stdafx.hpp"
#include <iostream> //#include <stdio.h>
#include <curl/curl.h>
#include <pthread.h>
#include <map>
#include <string>
using namespace std;
bool printing = false; //will allow us to prevent prints overlapping each other
#if defined(__WIN32__) || defined(_WIN32) || defined(WIN32) || defined(__WINDOWS__) || defined(__TOS_WIN__)
#include <windows.h>
inline void delay( unsigned long ms )
{
Sleep( ms );
}
#else /* presume POSIX */
#include <unistd.h>
inline void delay( unsigned long ms )
{
usleep( ms * 1000 );
}
#endif
struct requestStruct { //will allow us to pass more than one argument to the threaded functions
int id;
const char* url;
const char* method;
const char* body;
map<const char*, const char*> headers;
const char* proxy;
int timeout;
};
struct responseStruct { //will allow us to return more than one value from the Request function
long statusCode;
//map<const char*, const char*> headers;
const char* body;
};
size_t writeToString(void *ptr, size_t size, size_t count, void *stream) {
((string*)stream)->append((char*)ptr, 0, size* count);
return size* count;
}
static void *ResponseCallback(int id, struct responseStruct *response) {
long statusCode = response -> statusCode;
//map<const char*, const char*> headers = response -> headers;
const char* body = response -> body;
//while (printing) {} //wait for other threads to stop printing
printing = true; //tell other threads to not print anything
cout << id << " response received! Code: " << statusCode << endl << body << endl;
printing = false; //tell other threads printing is okay again
return NULL;
}
struct responseStruct HttpRequest(const char* url, const char* method, const char* body, map<const char*, const char*> &headers, const char* proxy, long timeout) {
CURL *curl;
curl = curl_easy_init();
long statusCode = 0;
map<const char*, const char*> respHeaders;
string respBody;
string _url(url);
string _method(method);
string _proxy(proxy);
struct curl_slist *headerList = NULL;
string headerString;
curl_easy_setopt(curl, CURLOPT_URL, url); //set url
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, method); //set method
for (std::map<const char*, const char*>::iterator header=headers.begin(); header!=headers.end(); ++header) { //make header list
headerString = header->first;
headerString.append(": ").append(header->second);
headerList = curl_slist_append(headerList, headerString.c_str());
//cout << headerString << '\n';
}
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerList); //set headers
if (_method == "POST" || _method == "PUT" || _method == "DELETE") //set body if the request method would allow it
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, body);
if (_url.find(string("https://")) != string::npos) //set ssl verifypeer if it's an https url
curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
if (_proxy != "") //set proxy
curl_easy_setopt(curl, CURLOPT_PROXY, proxy);
if (timeout != 0) //set timeout
curl_easy_setopt(curl, CURLOPT_TIMEOUT, timeout);
curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L); //follow redirects
//curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, writeToString);
//curl_easy_setopt(curl, CURLOPT_WRITEHEADER, &respHeaders); //to receive response headers
//??
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writeToString);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &respBody); //to receive response body
static int i=0;
delay(5000*(i++));
std::cout << "url: " << _url << ";" << std::endl;
curl_easy_perform(curl); //send the request
curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &statusCode); //get status code
struct responseStruct response;
response.statusCode = statusCode;
//response.headers;
response.body = respBody.c_str();
curl_easy_cleanup(curl);
return response;
}
static void *AddRequest( void *arguments ) {
// get arguments:
struct requestStruct *args = (struct requestStruct*)arguments;
int id = args->id;
const char* url = args->url;
const char* method = args->method;
const char* body = args->body;
map<const char*, const char*> headers = args->headers;
const char* proxy = args->proxy;
int timeout = args->timeout;
// print arguments:
//while (printing) {} //wait for other threads to stop printing
//printing = true; //tell other threads to not print anything
// cout << id << endl << url << endl << method << endl;
//printing = false; //tell the other threads it's okay to print again now
struct responseStruct response = HttpRequest(url, method, body, headers, proxy, timeout);
ResponseCallback(id,&response);
/* this code cause trouble (no response code) */
//pthread_exit(0);
return NULL;
}
int main() {
//map<const char*, const char*> headers;
//headers["User-Agent"] = "Mozilla/5.0 (Windows NT 6.2; WOW64; rv:32.0) Gecko/20100101 Firefox/32.0";
//struct responseStruct response = HttpRequest("https://facebook.com", "GET", "", headers, "localhost:8888", 6000);
//cout << response.body << endl;
pthread_t threads[3];
struct requestStruct reqArguments[3];
map<const char*, const char*> headers;
headers["User-Agent"] = "Mozilla/5.0 (Windows NT 6.2; WOW64; rv:32.0) Gecko/20100101 Firefox/32.0";
const char* proxy = "";
reqArguments[0].id = 0;
reqArguments[0].url = "https://www.duckduckgo.com/";
reqArguments[0].method = "GET";
reqArguments[0].headers = headers;
reqArguments[0].body = "";
reqArguments[0].proxy = proxy;
reqArguments[0].timeout = 6000;
pthread_create(&threads[0], NULL, &AddRequest, (void *)&reqArguments[0]); //create a thread on AddRequest() passing a full struct of arguments
reqArguments[1].id = 1;
reqArguments[1].url = "https://www.google.com/";
reqArguments[1].method = "GET";
reqArguments[1].headers = headers;
reqArguments[1].body = "";
reqArguments[1].proxy = proxy;
reqArguments[1].timeout = 6000;
pthread_create(&threads[1], NULL, &AddRequest, (void *)&reqArguments[1]); //create a thread on AddRequest() passing a full struct of arguments
reqArguments[2].id = 2;
reqArguments[2].url = "https://www.facebook.com/";
reqArguments[2].method = "GET";
reqArguments[2].headers = headers;
reqArguments[2].body = "";
reqArguments[2].proxy = proxy;
reqArguments[2].timeout = 6000;
pthread_create(&threads[2], NULL, &AddRequest, (void *)&reqArguments[2]); //create a thread on AddRequest() passing a full struct of arguments
// getchar();
// that is cleaner
for (int i=0; i<3; ++i) {
int rc = pthread_join(threads[i], NULL);
printf("In main: thread %d is complete\n", i);
}
return 0;
}
关于标题的最后一个问题，请在stackoverflow 上发布另一个问题。因为(我认为)还有很多主题。
还有一点建议，使用对象更容易编写和阅读代码源。
结束编辑
这是使用 libcurl 制作多线程的官方示例的拷贝: http://curl.haxx.se/libcurl/c/multithread.html
/***************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) 1998 - 2011, Daniel Stenberg, <daniel@haxx.se>, et al.
*
* This software is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at http://curl.haxx.se/docs/copyright.html.
*
* You may opt to use, copy, modify, merge, publish, distribute and/or sell
* copies of the Software, and permit persons to whom the Software is
* furnished to do so, under the terms of the COPYING file.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
***************************************************************************/
/* A multi-threaded example that uses pthreads extensively to fetch
* X remote files at once */
#include <stdio.h>
#include <pthread.h>
#include <curl/curl.h>
#define NUMT 4
/*
List of URLs to fetch.
If you intend to use a SSL-based protocol here you MUST setup the OpenSSL
callback functions as described here:
http://www.openssl.org/docs/crypto/threads.html#DESCRIPTION
*/
const char * const urls[NUMT]= {
"http://curl.haxx.se/",
"ftp://cool.haxx.se/",
"http://www.contactor.se/",
"www.haxx.se"
};
static void *pull_one_url(void *url)
{
CURL *curl;
curl = curl_easy_init();
curl_easy_setopt(curl, CURLOPT_URL, url);
curl_easy_perform(curl); /* ignores error */
curl_easy_cleanup(curl);
return NULL;
}
/*
int pthread_create(pthread_t *new_thread_ID,
const pthread_attr_t *attr,
void * (*start_func)(void *), void *arg);
*/
int main(int argc, char **argv)
{
pthread_t tid[NUMT];
int i;
int error;
/* Must initialize libcurl before any threads are started */
curl_global_init(CURL_GLOBAL_ALL);
for(i=0; i< NUMT; i++) {
error = pthread_create(&tid[i],
NULL, /* default attributes please */
pull_one_url,
(void *)urls[i]);
if(0 != error)
fprintf(stderr, "Couldn't run thread number %d, errno %d\n", i, error);
else
fprintf(stderr, "Thread %d, gets %s\n", i, urls[i]);
}
/* now wait for all threads to terminate */
for(i=0; i< NUMT; i++) {
error = pthread_join(tid[i], NULL);
fprintf(stderr, "Thread %d terminated\n", i);
}
return 0;
}
为了交互使用，您可以将 urls 数组转换为 vector 。
希望对您有所帮助!
关于c++ - cURL:处理多个异步请求，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/25686185/