forked from boostorg/beast
Vinnie Falco
121 lines
3.5 KiB
Plaintext
121 lines
3.5 KiB
Plaintext
[/
|
|
Copyright (c) 2013-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
|
|
|
|
Distributed under the Boost Software License, Version 1.0. (See accompanying
|
|
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
|
|
]
|
|
|
|
[section Stream Types]
|
|
|
|
A __Stream__ is a communication channel where data is transferred as
|
|
an ordered sequence of octet buffers. Streams are either synchronous
|
|
or asynchronous, and may allow reading, writing, or both. Note that
|
|
a particular type may model more than one concept. For example, the
|
|
Asio types __socket__ and __ssl_stream__ and support everything.
|
|
All stream algorithms in Beast are declared as template functions
|
|
with specific concept requirements chosen from this list:
|
|
|
|
[table Stream Concepts
|
|
[[Concept][Description]]
|
|
[
|
|
[__SyncReadStream__]
|
|
[
|
|
Supports buffer-oriented blocking reads.
|
|
]
|
|
][
|
|
[__SyncWriteStream__]
|
|
[
|
|
Supports buffer-oriented blocking writes.
|
|
]
|
|
][
|
|
[__SyncStream__]
|
|
[
|
|
A stream supporting buffer-oriented blocking reads and writes.
|
|
]
|
|
][
|
|
[__AsyncReadStream__]
|
|
[
|
|
Supports buffer-oriented asynchronous reads.
|
|
]
|
|
][
|
|
[__AsyncWriteStream__]
|
|
[
|
|
Supports buffer-oriented asynchronous writes.
|
|
]
|
|
][
|
|
[__AsyncStream__]
|
|
[
|
|
A stream supporting buffer-oriented asynchronous reads and writes.
|
|
]
|
|
]
|
|
]
|
|
|
|
These template metafunctions check whether a given type meets the
|
|
requirements for the various stream concepts, and some additional
|
|
useful utilities. The library uses these type checks internally
|
|
and also provides them as public interfaces so users may use the
|
|
same techniques to augment their own code. The use of these type
|
|
checks helps provide more concise errors during compilation:
|
|
|
|
[table Stream Type Checks
|
|
[[Name][Description]]
|
|
[[
|
|
[link beast.ref.beast__get_lowest_layer `get_lowest_layer`]
|
|
][
|
|
Returns `T::lowest_layer_type` if it exists, else returns `T`.
|
|
]]
|
|
[[
|
|
[link beast.ref.beast__has_get_io_service `has_get_io_service`]
|
|
][
|
|
Determine if the `get_io_service` member function is present,
|
|
and returns an __io_service__.
|
|
]]
|
|
[[
|
|
[link beast.ref.beast__is_async_read_stream `is_async_read_stream`]
|
|
][
|
|
Determine if a type meets the requirements of __AsyncReadStream__.
|
|
]]
|
|
[[
|
|
[link beast.ref.beast__is_async_stream `is_async_stream`]
|
|
][
|
|
Determine if a type meets the requirements of both __AsyncReadStream__
|
|
and __AsyncWriteStream__.
|
|
]]
|
|
[[
|
|
[link beast.ref.beast__is_async_write_stream `is_async_write_stream`]
|
|
][
|
|
Determine if a type meets the requirements of __AsyncWriteStream__.
|
|
]]
|
|
[[
|
|
[link beast.ref.beast__is_completion_handler `is_completion_handler`]
|
|
][
|
|
Determine if a type meets the requirements of __CompletionHandler__,
|
|
and is callable with a specified signature.
|
|
]]
|
|
[[
|
|
[link beast.ref.beast__is_sync_read_stream `is_sync_read_stream`]
|
|
][
|
|
Determine if a type meets the requirements of __SyncReadStream__.
|
|
]]
|
|
[[
|
|
[link beast.ref.beast__is_sync_stream `is_sync_stream`]
|
|
][
|
|
Determine if a type meets the requirements of both __SyncReadStream__
|
|
and __SyncWriteStream__.
|
|
]]
|
|
[[
|
|
[link beast.ref.beast__is_sync_write_stream `is_sync_write_stream`]
|
|
][
|
|
Determine if a type meets the requirements of __SyncWriteStream__.
|
|
]]
|
|
]
|
|
|
|
Using the type checks with `static_assert` on function or class template
|
|
types will provide users with helpful error messages and prevent undefined
|
|
behaviors. This example shows how a template function which writes to a
|
|
synchronous stream may check its argument:
|
|
|
|
[snippet_core_3]
|
|
|
|
[endsect]
|