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

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Buffer Types

To facilitate working with instances of the ConstBufferSequence and MutableBufferSequence concepts introduced in Boost.Asio, Beast treats those sequences as a special type of range. The following algorithms and wrappers are provided which transform these ranges efficiently using lazy evaluation. No memory allocations are used in the transformations; instead, they create lightweight iterators over the existing, unmodified memory buffers. Control of buffers is retained by the caller; ownership is not transferred.

Table 1.4. Buffer Algorithms and Types

Name

Description

buffers_cat

This functions returns a new buffer sequence which, when iterated, traverses the sequence which would be formed if all of the input buffer sequences were concatenated. With this routine, multiple calls to a stream's write_some function may be combined into one, eliminating expensive system calls.

buffers_cat_view

This class represents the buffer sequence formed by concatenating two or more buffer sequences. This is type of object returned by buffers_cat.

buffers_front

This function returns the first buffer in a buffer sequence, or a buffer of size zero if the buffer sequence has no elements.

buffers_prefix

This function returns a new buffer or buffer sequence which represents a prefix of the original buffers.

buffers_prefix_view

This class represents the buffer sequence formed from a prefix of an existing buffer sequence. This is the type of buffer returned by buffers_prefix.

buffers_suffix

This class wraps the underlying memory of an existing buffer sequence and presents a suffix of the original sequence. The length of the suffix may be progressively shortened. This lets callers work with sequential increments of a buffer sequence.

buffers_to_string

This function converts a buffer sequence to a std::string. It can be used for diagnostic purposes and tests.


The DynamicBuffer concept introduced in Boost.Asio models a buffer sequence which supports an owning, resizable range. Beast provides this set of additional implementations of the dynamic buffer concept:

Table 1.5. Dynamic Buffer Implementations

Name

Description

buffers_adapter

This wrapper adapts any MutableBufferSequence into a DynamicBuffer with an upper limit on the total size of the input and output areas equal to the size of the underlying mutable buffer sequence. The implementation does not perform heap allocations.

flat_buffer basic_flat_buffer

Guarantees that input and output areas are buffer sequences with length one. Upon construction an optional upper limit to the total size of the input and output areas may be set. The basic container is an AllocatorAwareContainer.

multi_buffer basic_multi_buffer

Uses a sequence of one or more character arrays of varying sizes. Additional character array objects are appended to the sequence to accommodate changes in the size of the character sequence. The basic container is an AllocatorAwareContainer.

flat_static_buffer flat_static_buffer_base

Guarantees that input and output areas are buffer sequences with length one. Provides the facilities of a dynamic buffer, subject to an upper limit placed on the total size of the input and output areas defined by a constexpr template parameter. The storage for the sequences are kept in the class; the implementation does not perform heap allocations.

static_buffer static_buffer_base

Provides the facilities of a circular dynamic buffer. subject to an upper limit placed on the total size of the input and output areas defined by a constexpr template parameter. The implementation never moves memory during buffer operations. The storage for the sequences are kept in the class; the implementation does not perform heap allocations.


These two functions facilitate buffer interoperability with standard output streams.

Table 1.6. Buffer Output Streams

Name

Description

buffers

This function wraps a ConstBufferSequence so it may be used with operator<< and std::ostream.

ostream

This function returns a std::ostream which wraps a dynamic buffer. Characters sent to the stream using operator<< are stored in the dynamic buffer.



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