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Boost Users : |
Subject: Re: [Boost-users] Buffering and ASIO
From: Emil Mieilica (Emil.Mieilica_at_[hidden])
Date: 2008-12-17 10:25:36
Hello Vadim,
This is a piece of code from an application that inadvertently does what your application appears to be doing: receives a stream of images over a HTTP connection.
We had the same problems and you have in bold the solution we found: we call in_avail() on the read-buffer of the stream that tells us the amount of data already read but left in the buffer and then we readsome to get the actual data.
void onConnect(boost::system::error_code ErrorCode,unsigned int fps)
{
boost::asio::streambuf response;
boost::asio::read_until(*Socket, response, "\r\n");
std::istream response_stream(&response);
response_stream >> http_version;
response_stream >> status_code;
std::getline(response_stream, status_message);
if (!response_stream || http_version.substr(0, 5) != "HTTP/")
{
THROW_EXCEPTION(logic_error("Invalid HTTP response"));
}
// Read the response headers, which are terminated by a blank line.
boost::asio::read_until(*Socket, response, "\r\n\r\n");
while (std::getline(response_stream, header) && header != "\r")
{
LOG_DEBUG(log,"Got http header: "<<header);
}
//Get the number of bytes we have received after the HTTP header
size_t avail = response_stream.rdbuf()->in_avail();
//Read that data into the buffer
response_stream.readsome(Buffer.data(), avail );
LOG_DEBUG(log,"Connection succeded. Already received "<<avail);
//Call the asynchronous receive handler as if an read operation was completed with avail bytes of data
onReadComplete(ErrorCode,avail ,fps);
}
void onReadComplete(const boost::system::error_code& ErrorCode,size_t bytesTransfered,unsigned int fps)
{
if (!ErrorCode) {
boost::asio::async_read(
*Socket,
boost::asio::buffer(Buffer),
boost::asio::transfer_all(),
boost::bind(
& onReadComplete,
this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred,
fps
)
);
}
}
Best regards,