boost::asio::streambuf 基本用法和注意事項

streamsize  sgetn(char_type *store,streamsize n)    返回緩沖區下n個字符并存儲到store中，并將緩沖區位置后移n個字節

代碼說明：本來是想不斷的通過sgetn函數獲取到streambuf的內容，由于沒有完全理解sgetn獲取流的方式，導致了問題的產生

int Teststreambuf()

{

boost::asio::streambuf request;

std::ostream request_stream(&request);

request_stream << "GET /cs/restfull/operationRestfullApi/testGet/ HTTP/1.1\r\n";

request_stream << "Accept: application/x-ms-application, p_w_picpath/jpeg, application/xaml+xml, p_w_picpath/gif, p_w_picpath/pjpeg, application/x-ms-xbap, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*\r\n";

request_stream << "Accept-Language: zh-CN\r\n";

request_stream << "User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; InfoPath.3)\r\n";

request_stream << "Host: " << "192.168.0.88:8080" << "\r\n";

request_stream << "Connection: Keep-Alive\r\n\r\n";

//當第一次使用sgetn函數的時候，已經將所有的數據讀完，指向流的結束位置

char buf[1024] = { 0 };

int len = request.size();

request.sgetn(buf, len);

//當第二次使用sgetn函數的時候，由于第一次函數調用指向了流的結束位置，

//所以第二次讀取到的buf1是空的

char buf1[1024] = { 0 };

int len1 = request.size();

request.sgetn(buf1, len1);

return 0;

}

實際的測試環境：希望組裝完成一次HTTP請求之后，循環發送構建的數據包，達到壓力測試的結果，但是在接收端只是接收到一次的數據，初步懷疑是服務器的代碼有問題，后面才發現是sgetn函數的使用方法有問題

#include <iostream>

#include <fstream>

#include <string>

#include <boost/asio.hpp>

using namespace std;

using namespace boost::asio;

int Teststreambuf()

{

io_service iosev;

ip::tcp::socket socket(iosev);

ip::tcp::endpoint ep(ip::address_v4::from_string("127.0.0.1"), 7002);

boost::system::error_code ec;

socket.connect(ep, ec);

if (ec) return -1;

boost::asio::streambuf request;

std::ostream request_stream(&request);

request_stream << "POST /cs/restfull/operationRestfullApi/testPost HTTP/1.1\r\n";

request_stream << "Accept: application/x-ms-application, p_w_picpath/jpeg, application/xaml+xml, p_w_picpath/gif, p_w_picpath/pjpeg, application/x-ms-xbap, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*\r\n";

request_stream << "Accept-Language: zh-CN\r\n";

request_stream << "User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; InfoPath.3)\r\n";

request_stream << "Host: " << "192.168.0.88:8080" << "\r\n";

request_stream << "Connection: Keep-Alive\r\n\r\n";

while (1)

{

//第一次調用write之后，request的數據已經發送完畢，作為一個流，已經指向數據的末尾，所以

//當再次循環的時候發送的數據len==0,本意是循環發送上面的HTTP數據，對服務器進行壓力測試

size_t len = boost::asio::write(socket, request);

std::cout << len << std::endl;

::Sleep(300);

}

return 0;

}

修改之后的代碼

#include <iostream>

#include <fstream>

#include <string>

#include <boost/asio.hpp>

using namespace std;

using namespace boost::asio;

int Teststreambuf()

{

io_service iosev;

ip::tcp::socket socket(iosev);

ip::tcp::endpoint ep(ip::address_v4::from_string("127.0.0.1"), 7002);

boost::system::error_code ec;

socket.connect(ep, ec);

if (ec) return -1;

boost::asio::streambuf request;

std::ostream request_stream(&request);

request_stream << "POST /cs/restfull/operationRestfullApi/testPost HTTP/1.1\r\n";

request_stream << "Accept: application/x-ms-application, p_w_picpath/jpeg, application/xaml+xml, p_w_picpath/gif, p_w_picpath/pjpeg, application/x-ms-xbap, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*\r\n";

request_stream << "Accept-Language: zh-CN\r\n";

request_stream << "User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; InfoPath.3)\r\n";

request_stream << "Host: " << "192.168.0.88:8080" << "\r\n";

request_stream << "Connection: Keep-Alive\r\n\r\n";

//跟上面的不一樣的做法，是將request的數據一次性讀取到buf數組中，然后循環發送buf的數據內容

  char buf[1024] = { 0 };

  request.sgetn(buf, request.size());

while (1)

{

size_t len = boost::asio::write(socket, boost::asio::buffer(buf));

std::cout << len << std::endl;

::Sleep(300);

}

return 0;

}