Algorithms
Algorithms which operate on buffer sequences are written as function templates,
using one or more template parameters to reflect the sequence types. The
metafunctions is_const_buffer_sequence and is_mutable_buffer_sequence
determine whether or not a specified type meets the syntactic requirements for
buffer sequences. They can be used for generating precise error messages at
compile time when parameters are misused, or they can be used to constrain a
function’s overload set as shown:
template< class ConstBufferSequence >
requires is_const_buffer_sequence< ConstBufferSequence >
void print( ConstBufferSequence const& bs );To iterate over a sequence the functions :begin and
end are used to obtain the starting and ending iterators. This
example writes each individual buffer in the sequence to standard output,
separated by a newline:
template< class ConstBufferSequence >
requires is_const_buffer_sequenc<ConstBufferSequence>
void print( ConstBufferSequence const& bs )
{
auto const end_ = buffers::end( bs );
for( auto it = buffers::begin( bs ); it != end_; ++it )
{
buffers::const_buffer cb( *it );
std::cout << std::string_view( static_cast<char const*>cb.data(), cb.size() ) << "\n";
}
}
Care must be exercised when a raw pointer is cast to other data
types such as char or to aggregate types. It is the caller’s responsibility
to ensure that such casts do not violate the type safety features of the
language.
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Calculating Size
The function size returns the total number of bytes represented in
a sequence of buffers, with this equivalent signature:
template< class ConstBufferSequence >
std::size_t
size(
ConstBufferSequence const& bs);The default implementation performs a straightforward summation of individual elements visited through iteration. The size customization point, discussed later, permits optimizations of the algorithm for types which can do better.
Copying Bytes
To facilitate copying data between arbitrary buffer sequences, the function
copy is provided, with this equivalent signature:
template<
class MutableBufferSequence,
class ConstBufferSequence >
std::size_t
copy(
MutableBufferSequence const& dest,
ConstBufferSequence const& src,
std::size_t at_most = std::numeric_limits<std::size_t>::max );This function copies up to at_most bytes from the source buffer sequence to
the destination sequence, or less depending on the size of the smaller of the
two sequences. The return value indicates the actual number of bytes copied.