How to get data out of Boost mutable_buffers_1? - c++11

Question

I’m developing a system for our application to get data from an external device. As soon as I send it a specific message, it sends back short messages to us 10x/second (so about 1 message per 100 milliseconds). I’m using Boost for this communication.
The process is rather simple: I create the socket, send the message, giving it a handler for the message receive:
// Header file:
...
std::unique_ptr<boost::asio::io_service> _theIOService;
std::unique_ptr<boost::asio::ip::tcp::socket> _theSocket;
int size_of_the_data = 100;
std::vector<char> _raw_buffer = std::vector<char>(size_of_the_data);
boost::asio::mutable_buffers_1 _data_buffer = boost::asio::buffer(_raw_buffer, size_of_the_data);
...
// Implementation file:
...
void DeviceDataListener::initiateTransfer() {
// create and connect the socket up here
...
// send the message
boost::system::error_code error;
boost::asio::write(*_theSocket,
boost::asio::buffer(beginMessage),
boost::asio::transfer_all(), error);
// start the receive
auto handler = boost::bind(&SCUDataListener::dataHandler, this, _1, _2);
_theSocket->async_receive( _data_buffer, handler );
std::thread run_thread([&]{ _theIOService->run(); });
...
}
void DeviceDataListener::dataHandler (
const boost::system::error_code& error, // Result of operation.
std::size_t bytes_transferred // Number of bytes received.
) {
int foo = bytes_transferred;
// this line crashes application
char* pData = static_cast<char*>(_data_buffer.data());
}
It works, my handler gets called immediately, as it should. The problem is, I can’t get the data out of _data_buffer. This:
auto it = _data_buffer.begin();
causes a crash, even though _data_buffer is valid. This:
const char* pData = static_cast<char*>(_data_buffer.data());
won’t compile. The error is “Method 'data' could not be resolved”. The mutable_buffer_1 API says data() is a completely valid method that returns the beginning of the memory range.
Inspecting via a debugger, I can see that there is no error and I can see data as a member of _data_buffer and the memory address it contains does contain the data we’re expecting. The thing is, I can’t get to it via code. Does anyone know how to get to the data in a Boost mutable_buffers_1?
We’re using Eclipse CDT, C++11 and gcc running on Linux.

Answer 1

“Method 'data' could not be resolved”.
this error may be true, but it depends on what version of Boost you use. data() is member of mutable_buffer since >= 1.66 version. Because mutable_buffer is the base class for mutable_buffers_1 your code should compile if you use at least 1.66 version of Boost.
If your version is < 1.66 you should use
char* p1 = boost::asio::buffer_cast<char*>(_data_buffer);
to get the pointer to data in the buffer.
_data_buffer.begin();
you should not use begin() method, it returns pointer to mutable_buffer_1 itself. This method is used by internal functions of asio-boost library, for instance to copy sequence of buffers, then begin() points the particular buffer to be copied.