Boost C++ Libraries

Create a new modifiable buffer from an existing buffer.

mutable_buffers_1 buffer(
    const mutable_buffer & b);

mutable_buffers_1 buffer(
    const mutable_buffer & b,
    std::size_t max_size_in_bytes);

const_buffers_1 buffer(
    const const_buffer & b);

const_buffers_1 buffer(
    const const_buffer & b,
    std::size_t max_size_in_bytes);

mutable_buffers_1 buffer(
    void * data,
    std::size_t size_in_bytes);

const_buffers_1 buffer(
    const void * data,
    std::size_t size_in_bytes);

template<
    typename PodType,
    std::size_t N>
mutable_buffers_1 buffer(
    PodType & data);

template<
    typename PodType,
    std::size_t N>
mutable_buffers_1 buffer(
    PodType & data,
    std::size_t max_size_in_bytes);

template<
    typename PodType,
    std::size_t N>
const_buffers_1 buffer(
    const PodType & data);

template<
    typename PodType,
    std::size_t N>
const_buffers_1 buffer(
    const PodType & data,
    std::size_t max_size_in_bytes);

template<
    typename PodType,
    std::size_t N>
mutable_buffers_1 buffer(
    boost::array< PodType, N > & data);

template<
    typename PodType,
    std::size_t N>
mutable_buffers_1 buffer(
    boost::array< PodType, N > & data,
    std::size_t max_size_in_bytes);

template<
    typename PodType,
    std::size_t N>
const_buffers_1 buffer(
    boost::array< const PodType, N > & data);

template<
    typename PodType,
    std::size_t N>
const_buffers_1 buffer(
    boost::array< const PodType, N > & data,
    std::size_t max_size_in_bytes);

template<
    typename PodType,
    std::size_t N>
const_buffers_1 buffer(
    const boost::array< PodType, N > & data);

template<
    typename PodType,
    std::size_t N>
const_buffers_1 buffer(
    const boost::array< PodType, N > & data,
    std::size_t max_size_in_bytes);

template<
    typename PodType,
    typename Allocator>
mutable_buffers_1 buffer(
    std::vector< PodType, Allocator > & data);

template<
    typename PodType,
    typename Allocator>
mutable_buffers_1 buffer(
    std::vector< PodType, Allocator > & data,
    std::size_t max_size_in_bytes);

template<
    typename PodType,
    typename Allocator>
const_buffers_1 buffer(
    const std::vector< PodType, Allocator > & data);

template<
    typename PodType,
    typename Allocator>
const_buffers_1 buffer(
    const std::vector< PodType, Allocator > & data,
    std::size_t max_size_in_bytes);

const_buffers_1 buffer(
    const std::string & data);

const_buffers_1 buffer(
    const std::string & data,
    std::size_t max_size_in_bytes);

The simplest use case involves reading or writing a single buffer of a specified size:

sock.write(boost::asio::buffer(data, size)); 

In the above example, the return value of boost::asio::buffer meets the requirements of the ConstBufferSequence concept so that it may be directly passed to the socket's write function. A buffer created for modifiable memory also meets the requirements of the MutableBufferSequence concept.

An individual buffer may be created from a builtin array, std::vector or boost::array of POD elements. This helps prevent buffer overruns by automatically determining the size of the buffer:

char d1[128];
size_t bytes_transferred = sock.read(boost::asio::buffer(d1));

std::vector<char> d2(128);
bytes_transferred = sock.read(boost::asio::buffer(d2));

boost::array<char, 128> d3;
bytes_transferred = sock.read(boost::asio::buffer(d3)); 

To read or write using multiple buffers (i.e. scatter-gather I/O), multiple buffer objects may be assigned into a container that supports the MutableBufferSequence (for read) or ConstBufferSequence (for write) concepts:

char d1[128];
std::vector<char> d2(128);
boost::array<char, 128> d3;

boost::array<mutable_buffer, 3> bufs1 = {
  boost::asio::buffer(d1),
  boost::asio::buffer(d2),
  boost::asio::buffer(d3) };
bytes_transferred = sock.read(bufs1);

std::vector<const_buffer> bufs2;
bufs2.push_back(boost::asio::buffer(d1));
bufs2.push_back(boost::asio::buffer(d2));
bufs2.push_back(boost::asio::buffer(d3));
bytes_transferred = sock.write(bufs2);