Re: [Boost-users] [asio] async_read and 100% CPU

On Tue, Jun 30, 2009 at 2:24 PM, Etienne Philip Pretorius wrote:

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Zachary Turner wrote: What is contained inside your buffer object?  If your buffer has a size of 0, then this seems like it would cause the problem.

yip, it has a size of 0. I hoped that the async receive would just increase the size of the vector as it puts the contents into it, but that is not happening.

I'm 99% sure this is your problem. I haven't used asio with sockets, but I have used it with other types of input sources. It doesn't know how much data to read unless you tell it. The way you tell it is by giving it a buffer whose size is how much data you want to read. That means that allocation / deletion of the buffer is also your responsibility. boost::asio::const_buffer and boost::asio::mutable_buffer have no ownership over the memory contained in these buffers. It seems like this makes the library a little less intuitive at first, I struggled for quite a while with buffer management in my own project, but in the end it is this way to help you. Otherwise there would be excessive copying and allocation. mutable_buffer and const_buffer are just very thin wrappers over a chunk of memory. So you have to allocate a buffer up front that contains enough memory for whatever it is you're trying to read. Then you pass that to async_receive and it should work. const size_t expected = 4096; unsigned char* buf = new unsigned char[expected]; boost::asio::mutable_buffer(buf, expected); socket.async_receive( boost::asio::buffer(buffer), boost::bind( &client::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred Now in your handler you will either need to free this buffer, release it to some cache, or whatever else you want to do with it.