asio之buffer篇

使用read_until() 和 async_read_until() 读取line-based

（使用”rn”或者其它自定义字符序列作为分隔符）

数据时需要boost::asio::streambuf来缓存读取到的数据。

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示例：

boost::asio::streambuf sb;
...
std::size_t n = boost::asio::read_until(sock, sb, 'n');
boost::asio::streambuf::const_buffers_type bufs = sb.data();
std::string line(
    boost::asio::buffers_begin(bufs),
    boost::asio::buffers_begin(bufs) + n);

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按行读取:

    boost::system::error_code error;
    boost::asio::streambuf content;
    istream content_stream(&content);
    char _buffer[8192];
    while(true)
    {
        bzero(_buffer, 8192);
        size_t n = read_until(*_sock, content, "n", error);
        content_stream.getline(_buffer, n);
        if(error)
        {
    ...
    }
    ...
}

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例子:

//
// sync_client.cpp
// ~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2011 Christopher M. Kohlhoff (chris at kohlhoff dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//

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

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

int main(int argc, char* argv[])
{
  try
  {
    if (argc != 3)
    {
      std::cout << "Usage: sync_client <server> <path>n";
      std::cout << "Example:n";
      std::cout << "  sync_client www.boost.org /LICENSE_1_0.txtn";
      return 1;
    }

    boost::asio::io_service io_service;

    // Get a list of endpoints corresponding to the server name.
    tcp::resolver resolver(io_service);
    tcp::resolver::query query(argv[1], "http");
    tcp::resolver::iterator endpoint_iterator = resolver.resolve(query);

    // Try each endpoint until we successfully establish a connection.
    tcp::socket socket(io_service);
    boost::asio::connect(socket, endpoint_iterator);

    // Form the request. We specify the "Connection: close" header so that the
    // server will close the socket after transmitting the response. This will
    // allow us to treat all data up until the EOF as the content.
    boost::asio::streambuf request;
    std::ostream request_stream(&request);
    request_stream << "GET " << argv[2] << " HTTP/1.0rn";
    request_stream << "Host: " << argv[1] << "rn";
    request_stream << "Accept: */*rn";
    request_stream << "Connection: closernrn";

    // Send the request.
    boost::asio::write(socket, request);

    // Read the response status line. The response streambuf will automatically
    // grow to accommodate the entire line. The growth may be limited by passing
    // a maximum size to the streambuf constructor.
    boost::asio::streambuf response;
    boost::asio::read_until(socket, response, "rn");

    // Check that response is OK.
    std::istream response_stream(&response);
    std::string http_version;
    response_stream >> http_version;
    unsigned int status_code;
    response_stream >> status_code;
    std::string status_message;
    std::getline(response_stream, status_message);
    if (!response_stream || http_version.substr(0, 5) != "HTTP/")
    {
      std::cout << "Invalid responsen";
      return 1;
    }
    if (status_code != 200)
    {
      std::cout << "Response returned with status code " << status_code << "n";
      return 1;
    }

    // Read the response headers, which are terminated by a blank line.
    boost::asio::read_until(socket, response, "rnrn");

    // Process the response headers.
    std::string header;
    while (std::getline(response_stream, header) && header != "r")
      std::cout << header << "n";
    std::cout << "n";

    // Write whatever content we already have to output.
    if (response.size() > 0)
      std::cout << &response;

    // Read until EOF, writing data to output as we go.
    boost::system::error_code error;
    while (boost::asio::read(socket, response,
      boost::asio::transfer_at_least(1), error))
      std::cout << &response;
    if (error != boost::asio::error::eof)
      throw boost::system::system_error(error);
  }
  catch (std::exception& e)
  {
    std::cout << "Exception: " << e.what() << "n";
  }

  return 0;
}

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