原文連接：http://m.shnenglu.com/jinq0123/archive/2007/12/24/CompletionPortExamples.html
試運行asio的async_client例程時，發現CPU占用很高，
所以又寫了一個相同功能但直接調用完成端口API的代碼，
進行比較，發現同樣占用CPU。
與flashget比較，下載速度差不多，但flashget不占CPU。
將直接API調用代碼和利用asio的代碼都列在下面。
進行測試時，要將其中的參數定義改改，如SERVER參數。
并且要找個大文件下載才有明顯結果。
#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;
}