Re: [Boost-users] Buffering and ASIO

Good day.I'm trying to read video data transferred by HTTP. I use the following function in order to read HTTP header:boost::asio::async_read_until(m_socket, m_headerBuffer, "\r\n\r\n", boost::bind(&CAXISParser::read_header, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred));, where m_headerBuffer is asio::streambuf object. During header parsing i can get video sample length. Now I want to read all video data in one function call, for example:boost::asio::async_read(m_socket, boost::asio::buffer(pSample->GetBody(), m_currentSampleLength), boost::bind(&CAXISParser::read_body, this, pSample, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred));, where pSample is object with buffer for video data. There is problem that async_read_until captures some data from video data, and that call's behavior is incorrect. How can i fight that problem? For example, how can i figure out number of bytes left in streambuf and copy them to my buffer, and then read rest with async_read? I'm will very appreciate for any advices.> It's not clear to me exactly what you're asking here. From what I can

tell, you have created a buffer of size m_currentSampleLength, and asked ASIO to call CAXISParser::read_body when it has received this many bytes. Is that what you intended to do? Is that what boost is doing? Or is the problem something else?

-----Scott.

Hello, Scott. Sorry for bad english, i'm will try explain. Yep, there is problem. When i'm read HTTP header with acync_read_until, it consume header and some bytes from video data (i think). After i'm calculate video data length from header and trying read data with async_read. But it works incorrect as previous call async_read_until captures some bytes from video data and video data readed with async_read have wrong offset. How can i understand, the problem that async_read_until and async_read used different buffers for reading (asio::streambuf and custom buffer), and some video data consumed by streambuf. Question: how to get video data captured with async_read_until and read rest from tcp buffer?There is is code sample:void read_header(PSample pSample, const boost::system::error_code& error, size_t bytes_transferred){ // Calculate data length with regex boost::asio::const_buffer data = m_headerBuffer.data(); const char* beg = boost::asio::buffer_cast(data); const char* end = beg + bytes_transferred; CalculateDataLength(beg, end); // Clear buffer std::vector<char> vec(bytes_transferred); m_headerBuffer.sgetn(&vec[0], bytes_transferred); ReadBody();}Before ReadBody call, i reject streambuf content with sgetn. But i think there ismore data in streambuf that is video data. How can i get it? Below non working sample, but it describe my wishes:// Add before read bodysize_t restBytes = m_headerBuffer.size() - bytes_transferred;if (0 != restBytes){ m_headerBuffer.sgetn(pSample->GetBody(), restBytes);}Then in ReadBody i can to read rest video data with single async_readcall. There is implementation sample:void ReadBody(NMMSS::PSample& pSample){1)//boost::asio::async_read(m_socket, m_headerBuffer.prepare(m_currentSampleLength),2)//boost::asio::async_read_until(m_socket, m_headerBuffer, "\r\n",3)//boost::asio::async_read(m_socket, boost::asio::buffer(pSample->GetBody(), m_currentSampleLength), boost::bind(&CAXISParser::read_body, this, pSample, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred));}I trying use 3 variants there:1) Trying read to buffer all video data (dont understand why it doesn't work)2) Very slow variant, as video data is big.3) Preferrable variant P.S. One question more: how can i correctly reject data consumed by streambuf? Now i used the following strategy: streambuf buf; ..... std::vector<char> vec(size); buf.sgetn(&vec[0], size); Is there another strategy for that? For example, commit and consume strategy? I dont need streambuf content in some cases. Best regards, Vadim