forked from boostorg/beast
120 lines
4.1 KiB
Plaintext
120 lines
4.1 KiB
Plaintext
[/
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Copyright (c) 2013-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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]
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[section:BodyWriter BodyWriter]
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A [*BodyWriter] provides an online algorithm to transfer a series of zero
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or more buffers containing parsed body octets into a message container. The
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__parser__ creates an instance of this type when needed, and calls into
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it zero or more times to transfer buffers. The interface of [*BodyWriter]
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is intended to allow the conversion of buffers into these scenarios for
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representation:
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* Storing a body in a dynamic buffer
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* Storing a body in a user defined container with a custom allocator
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* Transformation of incoming body data before storage, for example
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to compress it first.
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* Saving body data to a file
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In this table:
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* `X` denotes a type meeting the requirements of [*BodyWriter].
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* `B` denotes a __Body__ where
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`std::is_same<X, B::writer>::value == true`.
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* `a` denotes a value of type `X`.
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* `b` is an object whose type meets the requirements of __ConstBufferSequence__
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* `m` denotes a value of type `message&` where
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`std::is_same<decltype(m.body), Body::value_type>::value == true`.
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* `n` is a value of type `boost::optional<std::uint64_t>`.
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* `ec` is a value of type [link beast.ref.beast__error_code `error_code&`].
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[heading Associated Types]
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* __Body__
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* [link beast.ref.beast__http__is_body_writer `is_body_writer`]
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[table Writer requirements
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[[expression] [type] [semantics, pre/post-conditions]]
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[
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[`X(m);`]
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[]
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[
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Constructible from `m`. The lifetime of `m` is guaranteed to
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end no earlier than after the `X` is destroyed. The constructor
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will be called after a complete header is stored in `m`, and
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before parsing body octets for messages indicating that a body
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is present The writer shall not access the contents of `m` before
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the first call to `init`, permitting lazy construction of the
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message.
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The function will ensure that `!ec` is `true` if there was
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no error or set to the appropriate error code if there was one.
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]
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][
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[`a.init(n, ec)`]
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[]
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[
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Called once to fully initialize the object before any calls to
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`put`. The message body is valid before entering this function,
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and remains valid until the writer is destroyed.
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The value of `n` will be set to the content length of the
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body if known, otherwise `n` will be equal to `boost::none`.
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Implementations of [*BodyWriter] may use this information to
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optimize allocation.
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The function will ensure that `!ec` is `true` if there was
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no error or set to the appropriate error code if there was one.
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]
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][
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[`a.put(b,ec)`]
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[`std::size_t`]
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[
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This function is called to append some or all of the buffers
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specified by `b` into the body representation. The number of
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bytes inserted from `b` is returned. If the number of bytes
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inserted is less than the total input, the remainder of the
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input will be presented in the next call to `put`.
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The function will ensure that `!ec` is `true` if there was
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no error or set to the appropriate error code if there was one.
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]
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][
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[`a.finish(ec)`]
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[]
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[
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This function is called when no more body octets are remaining.
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The function will ensure that `!ec` is `true` if there was
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no error or set to the appropriate error code if there was one.
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]
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][
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[`is_body_writer<B>`]
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[`std::true_type`]
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[
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An alias for `std::true_type` for `B`, otherwise an alias
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for `std::false_type`.
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]
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]
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]
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[heading Exemplar]
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[concept_BodyWriter]
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[heading Models]
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* [link beast.ref.beast__http__basic_dynamic_body.writer `basic_dynamic_body::writer`]
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* [link beast.ref.beast__http__basic_file_body__reader `basic_file_body::writer`]
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* [link beast.ref.beast__http__basic_string_body.writer `basic_string_body::writer`]
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* [link beast.ref.beast__http__empty_body.writer `empty_body::writer`]
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[endsect]
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