Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is the documentation for an old version of Boost. Click here to view this page for the latest version.
PrevUpHomeNext

streambuf

Typedef for the typical usage of basic_streambuf.

typedef basic_streambuf streambuf;
Types

Name

Description

const_buffers_type

The type used to represent the input sequence as a list of buffers.

mutable_buffers_type

The type used to represent the output sequence as a list of buffers.

Member Functions

Name

Description

basic_streambuf

Construct a basic_streambuf object.

capacity

Get the current capacity of the basic_streambuf.

commit

Move characters from the output sequence to the input sequence.

consume

Remove characters from the input sequence.

data

Get a list of buffers that represents the input sequence.

max_size

Get the maximum size of the basic_streambuf.

prepare

Get a list of buffers that represents the output sequence, with the given size.

size

Get the size of the input sequence.

Protected Member Functions

Name

Description

overflow

Override std::streambuf behaviour.

reserve

underflow

Override std::streambuf behaviour.

The basic_streambuf class is derived from std::streambuf to associate the streambuf's input and output sequences with one or more character arrays. These character arrays are internal to the basic_streambuf object, but direct access to the array elements is provided to permit them to be used efficiently with I/O operations. Characters written to the output sequence of a basic_streambuf object are appended to the input sequence of the same object.

The basic_streambuf class's public interface is intended to permit the following implementation strategies:

The constructor for basic_streambuf accepts a size_t argument specifying the maximum of the sum of the sizes of the input sequence and output sequence. During the lifetime of the basic_streambuf object, the following invariant holds:

size() <= max_size()

Any member function that would, if successful, cause the invariant to be violated shall throw an exception of class std::length_error.

The constructor for basic_streambuf takes an Allocator argument. A copy of this argument is used for any memory allocation performed, by the constructor and by all member functions, during the lifetime of each basic_streambuf object.

Examples

Writing directly from an streambuf to a socket:

boost::asio::streambuf b;
std::ostream os(&b);
os << "Hello, World!\n";

// try sending some data in input sequence
size_t n = sock.send(b.data());

b.consume(n); // sent data is removed from input sequence

Reading from a socket directly into a streambuf:

boost::asio::streambuf b;

// reserve 512 bytes in output sequence
boost::asio::streambuf::mutable_buffers_type bufs = b.prepare(512);

size_t n = sock.receive(bufs);

// received data is "committed" from output sequence to input sequence
b.commit(n);

std::istream is(&b);
std::string s;
is >> s;
Requirements

Header: boost/asio/streambuf.hpp

Convenience header: boost/asio.hpp


PrevUpHomeNext