开发windows客户端接收RTP视频流，当h264视频达到1080P 60fps的时候，按包来调用recvfrom的函数压力比较大，存在丢包的问题，windows的完成端口的性能效果当然可以解决这个问题，而boost的asio在windows上是基于完成端口来开发的，所以采用boost的asio和环形缓冲区的方法，可以解决接收单路大数据量udp包中丢包的问题。
需要引入的头文件为：
- #include "CircledBuffer.h"
- #include <iostream>
- #include <boost/asio.hpp>
- #include <boost/bind.hpp>
其中CircledBuffer.h是自定义的缓冲区的类，之后会有介绍，boost的两个文件是asio必需的两个文件。
需要定义的全局变量为：
- using boost::asio::ip::udp;
- boost::asio::io_service service;
- boost::asio::ip::udp::socket sock(service);
- boost::asio::ip::udp::endpoint sender_ep;
- CircledBuffer readBuffer;
- PacketBuffer* packet;
其中io_service是用来标示启动的，后面会调用run。sock和endpoint类似于描述符和sockaddr_in的关系。CircledBuffer和PacketBuffer*，是自定义缓冲区。
主函数为：
- int main(int argc, char* argv[]) {
- boost::asio::ip::udp::endpoint ep( boost::asio::ip::address::from_string("192.168.1.206"),
- 9002);
- sock.open(ep.protocol());
- sock.set_option(boost::asio::ip::udp::socket::reuse_address(true));
- boost::asio::socket_base::receive_buffer_size recv_option(8*65534);
- sock.set_option(recv_option);
- sock.bind(ep);
- packet = readBuffer.GetLast();
- sock.async_receive_from(boost::asio::buffer(packet->data, packet->bufferSize), sender_ep, &on_read);
- service.run();
- }
初始化ep和sock，其中udp接收的数量比较大的话，需要设定receive_buffer_size，然后bind，设置接受buffer为packet。
介绍一下async_receive_from函数，它有三个参数，分别为接收的buffer，远端的ep，注意与本端的ep不同，远端的ep不用初始化设置，再就是buffer收满后的回调函数。
回调函数的内容是：
- void on_read(const boost::system::error_code & err, std::size_t
- read_bytes) {
- std::cout << "read: " << read_bytes << std::endl;
- readBuffer.MoveNext();
- packet= readBuffer.GetLast();
- sock.async_receive_from(boost::asio::buffer(packet->data, packet->bufferSize), sender_ep, &on_read);
- }
与main函数的接收部分一致，这里用了不断的自身回调，来实现while recvfrom的功能。
补充说一句，用申请好的CircledBuffer，便于后期的多线程或者异步strand的处理，而不阻塞接收。
缓冲区类的代码：
头文件：
- #ifndef CIRCLED_BUFFER_H
- #define CIRCLED_BUFFER_H
-
- #include <memory.h>
- #include <boost/atomic.hpp>
- #define CIRCLED_BUFFER_SIZE 300
- #define BUFFER_SIZE 2000
-
- struct PacketBuffer
- {
- PacketBuffer(){bufferSize=BUFFER_SIZE;dataSize=0;}
- unsigned int bufferSize;
- unsigned int dataSize;
- char data[BUFFER_SIZE];
-
- PacketBuffer& operator=(PacketBuffer& other)
- {
- memcpy(data,other.data,other.dataSize);
- dataSize = other.dataSize;
- bufferSize = other.bufferSize;
- return *this;
- }
- };
-
- class CircledBuffer
- {
- public:
- CircledBuffer(unsigned int bufSize=CIRCLED_BUFFER_SIZE);
- public:
- ~CircledBuffer(void);
- PacketBuffer* GetAt(unsigned int idx){return &packets[idx];}
- PacketBuffer* GetLast()
- {
- return GetAt(writeIndex.load(boost::memory_order_consume));
- };
- void MoveNext()
- {
- unsigned int idx = writeIndex.load(boost::memory_order_relaxed);
- writeIndex.store((idx+1)%bufferSize,boost::memory_order_release);
- };
- unsigned int GetLastIndex(){return writeIndex.load(boost::memory_order_consume);};
- unsigned int GetSize(){return bufferSize;};
- protected:
- boost::atomic<unsigned int> writeIndex;
- unsigned int bufferSize;
- PacketBuffer* packets;
- };
- #endif
缓冲区类的构造函数与析构函数
- #include "CircledBuffer.h"
-
- CircledBuffer::CircledBuffer(unsigned int bufSize)
- :bufferSize(bufSize),
- writeIndex(0)
- {
- packets = new PacketBuffer[bufSize];
- }
-
- CircledBuffer::~CircledBuffer(void)
- {
- delete []packets;
- }
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