如何在boost :: asio中读取数据包

Question

how do i read a packet in boost::asio for example 0x01, current code i have only reads texts:

   m_socket.async_read_some(boost::asio::buffer(buffer),
       strand.wrap(boost::bind(&Client::handleRead, shared_from_this(),
       boost::asio::placeholders::error,
       boost::asio::placeholders::bytes_transferred)));

thanks

Answer 1

Hi you can assign buffer with your int variable and than use value you read from socket

int m_hdr_size = 0; // this var must be not local

boost::asio::async_read_some(
boost::asio::buffer(reinterpret_cast<char*>(&m_hdr_size), size_t(4))...

if i understand your question. Just set variable and it size to buffer

http://think-async.com/Asio/boost_asio_1_3_1/doc/html/boost_asio/reference/buffer.html

Answer 2

Doubt you need this answer a year later, but for the general public:

In your code, buffer is being passed by reference. This is so that when asio asynchronously calls your read handler ( Client::handleRead ), it will have updated the contents of that buffer to whatever it received.

A buffer is simply an array with a specified size. Asio will not fill the buffer past the size you specify in boost::asio::buffer(ptr, size) , so if you need a 32 bit integer, then pass it a pointer to the beginning of an array with size = 4 bytes, and then cast it to a 32-bit int type (probably uint32_t from stdint.h ) when it calls the read handler.

You can usually save a good chunk of memory by passing 16 bits or 8 bits when you don't need an entire 32 bit integer. uint8_t and uint16_t will let you do this without having to worry about whether your architecture's int is not 32 bits.