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使用完成端口HTTP下載的代碼

使用完成端口HTTP下載的代碼

（轉(zhuǎn)載請注明來源于金慶的專欄）

試運行asio的async_client例程時，發(fā)現(xiàn)CPU占用很高，
所以又寫了一個相同功能但直接調(diào)用完成端口API的代碼，
進(jìn)行比較，發(fā)現(xiàn)同樣占用CPU。

與flashget比較，下載速度差不多，但flashget不占CPU。

將直接API調(diào)用代碼和利用asio的代碼都列在下面。
進(jìn)行測試時，要將其中的參數(shù)定義改改，如SERVER參數(shù)。
并且要找個大文件下載才有明顯結(jié)果。

#include <iostream>
#include <winsock2.h>

// Modify these:
// "http://server.test.com/jinq/test.zip"
#define SERVER "server.test.com"
#define REQ_PATH "/jinq/test.zip"
const char * SVR_IP = "127.0.0.1";

int main(int argc, char* argv[])
{
    // Init.
    WSADATA wsd;
    WSAStartup(MAKEWORD(2, 2), &wsd);
    HANDLE hCp = CreateIoCompletionPort(
        INVALID_HANDLE_VALUE, NULL, 0, 0);
    SOCKET skt = WSASocket(AF_INET,
        SOCK_STREAM, 0, NULL, 0, WSA_FLAG_OVERLAPPED);
    assert(INVALID_SOCKET != skt);

    // connect skt and request
    SOCKADDR_IN addr;
    addr.sin_family = PF_INET;
    addr.sin_port = htons(80);
    addr.sin_addr.s_addr = inet_addr(SVR_IP);
    connect(skt, (SOCKADDR*)&addr, sizeof(addr));
    const char * REQ =
        "GET " REQ_PATH " HTTP/1.0\r\n"
        "Host: " SERVER "\r\n"
        "Accept: */*\r\n"
        "Connection: close\r\n\r\n";
    send(skt, REQ, strlen(REQ), 0);

    // Associate skt to completion port.
    const DWORD COMPLETION_KEY = 12345;
    CreateIoCompletionPort((HANDLE)skt,
        hCp, COMPLETION_KEY, 0);

    WSABUF wsaBuf;
    wsaBuf.len = 64 * 1024 - 1;
    wsaBuf.buf = new char[64 * 1024];
    DWORD dwReceived;
    DWORD dwFlags = 0;
    WSAOVERLAPPED overlapped;

    // Start recv.
    ZeroMemory(&overlapped, sizeof(overlapped));
    WSARecv(skt, &wsaBuf, 1,
            &dwReceived,
            &dwFlags,
            &overlapped,
            NULL);

    // Check the completion port in loop.
    while (true)
    {
        DWORD dwTransferred;
        LPOVERLAPPED lpOverlapped;
        DWORD dwKey;
        BOOL bRet = GetQueuedCompletionStatus(
            hCp, &dwTransferred, &dwKey, &lpOverlapped, 1000);
        if (!bRet) continue;
        assert(COMPLETION_KEY == dwKey);
        std::cout << "Transferred: " << dwTransferred << std::endl;
        assert(dwTransferred <= wsaBuf.len);
        wsaBuf.buf[50] = '\0';
        std::cout << "Content: " << wsaBuf.buf << std::endl;

        // next recv
        ZeroMemory(&overlapped, sizeof(overlapped));
        WSARecv(skt, &wsaBuf, 1,
                &dwReceived,
                &dwFlags,
                &overlapped,
                NULL);
    }

    return 0;
}

#include <iostream>
#include <istream>
#include <ostream>
#include <string>
#include <boost/asio.hpp>
#include <boost/bind.hpp>

const std::string SERVER("MyServer");
const std::string PATH("/jinq/test.zip");

using boost::asio::ip::tcp;

class client
{
public:
    client(boost::asio::io_service& io_service,
           const std::string& server, const std::string& path)
            : socket_(io_service)
    {
        // Query server and try to connect.
        tcp::resolver resolver(io_service);
        tcp::resolver::query query(server, "http");
        tcp::resolver::iterator endpoint_iterator = resolver.resolve(query);
        tcp::resolver::iterator end;

        // Try each endpoint until we successfully establish a connection.
        boost::system::error_code error = boost::asio::error::host_not_found;
        while (error && endpoint_iterator != end)
        {
            socket_.close();
            socket_.connect(*endpoint_iterator++, error);
        }
        if (error)
            throw boost::system::system_error(error);

        // Send the request.
        boost::asio::streambuf request;
        std::ostream request_stream(&request);
        request_stream << "GET " << path << " HTTP/1.0\r\n";
        request_stream << "Host: " << server << "\r\n";
        request_stream << "Accept: */*\r\n";
        request_stream << "Connection: close\r\n\r\n";
        boost::asio::write(socket_, request);

        // start reading...
        boost::asio::async_read(socket_, response_,
            boost::asio::transfer_at_least(1),
            boost::bind(&client::handle_read_content, this,
                boost::asio::placeholders::error));
    }

private:
    void handle_read_content(const boost::system::error_code& err)
    {
        if (!err)
        {
            // Write all of the data that has been read so far.
            // std::cout << &response_ << "\n";
            std::cout << "Received: " << response_.size() << std::endl;
            response_.consume(response_.size());

            // Continue reading remaining data until EOF.
            boost::asio::async_read(socket_, response_,
                boost::asio::transfer_at_least(1),
                boost::bind(&client::handle_read_content, this,
                    boost::asio::placeholders::error));
        }
        else if (err != boost::asio::error::eof)
        {
            std::cout << "Error: " << err << "\n";
        }
    }

    tcp::socket socket_;
    boost::asio::streambuf response_;
};

int main(int argc, char* argv[])
{
    try
    {
        boost::asio::io_service io_service;
        client c(io_service, SERVER, PATH);
        io_service.run();
    }
    catch (std::exception& e)
    {
        std::cout << "Exception: " << e.what() << "\n";
    }
    return 0;
}

posted on 2007-12-24 16:25 金慶閱讀(2331) 評論(4) 編輯收藏引用所屬分類: 1. C/C++

只要有一個包到達(dá)，完成端口就執(zhí)行一次從緩沖里讀操作檢測執(zhí)行，而通常應(yīng)用，一個數(shù)據(jù)段會由很多包組成，這樣，內(nèi)核線程需要調(diào)度很多次，而如果使用非阻塞 SOCKET讀，通過定時檢查機(jī)制，可以避免這種內(nèi)部的頻繁調(diào)度. 參見: 網(wǎng)絡(luò)編程--走出完成端口的誤區(qū) ( http://blog.csdn.net/danscort2000/article/details/4703391 ) 回復(fù) 更多評論

# re: 使用完成端口HTTP下載的代碼 2013-04-17 00:30 cmi

通過運行博主的iocp寫的下載代碼，下載一個300m的文件，速度150～300k/s
cpu的占用率為0～1，沒有出現(xiàn)樓主所說cpu占用率很高的情況。

博主還記得你的問題到底是什么原因引起的嗎？

我在考慮是否要用iocp寫，看了博主提供的這篇文章
http://blog.csdn.net/danscort2000/article/details/4703391 ，很是糾結(jié)。
我感覺這篇文章說的并不正確。回復(fù) 更多評論

# re: 使用完成端口HTTP下載的代碼 2013-12-16 16:39 金慶

@cmi
需要內(nèi)網(wǎng)測試，速度接近網(wǎng)絡(luò)帶寬。回復(fù) 更多評論

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