[/
    Copyright (c) 2016-2019 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)

    Official repository: https://github.com/boostorg/beast
]

[section Release Notes]

[/-----------------------------------------------------------------------------]

[heading Boost 1.70]

[tip
  The namespace alias `net` is used throughout for `boost::asio`.
]

[/ includes up to version 209]



[*New Features]

* All composed operations use the new
  [@boost:/doc/html/boost_asio/reference/async_initiate.html `net::async_initiate`]
  internally.

* New `tcp_stream` and
  `basic_stream`
  support:
  * Timeouts,
    [link beast.ref.boost__beast__basic_stream.async_read_some `async_read_some`],
    [link beast.ref.boost__beast__basic_stream.async_write_some `async_write_some`]
    complete with
    [link beast.ref.boost__beast__error `error::timeout`]
    on expiration.
  * Traffic-shaping policies
    [link beast.ref.boost__beast__simple_rate_policy `simple`] and
    [link beast.ref.boost__beast__unlimited_rate_policy `unlimited`],
    or a user-defined
    [link beast.concepts.RatePolicy ['RatePolicy]].
  * Supports
    [@http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1322r0.html P1322R0].

* `websocket::stream`
   supports
   * Configurable handshake timeout
   * Configurable idle timeout
   * Automatic idle pings

* [link beast.ref.boost__beast__ssl_stream `ssl_stream`]
  is a public interface

* ([issue 1305]) Better
  `flat_buffer`,
  `flat_static_buffer`,
  `multi_buffer`, and
  `static_buffer`:
  * Revise all reference documentation
  * Move construction does not always invalidate buffers
  * non-const `data()` returns a mutable buffer sequence
  * Add `cdata()` to also return constant readable bytes
  * Eligible member functions are declared `noexcept`

* ([issue 1345]) Better
  `flat_buffer`,
  `multi_buffer`
  * Add `clear`, `reserve()`, `max_size()`, `shrink_to_fit()`
  * Respect Allocator `max_size()`
  * Specify exception safety

* ([issue 1384]) New functions
  `bind_front_handler`

* Better
  `static_buffer`,
  `flat_static_buffer`
  * Add `clear()`
  * More members are `noexcept`
  * Specify exception safety

* Faster
  `http::string_to_field`

* Dynamic buffer `clear` operations perserve capacity.

* New file <boost/beast/core/buffer_traits.hpp>
  * New variadic `is_const_buffer_sequence`
  * New variadic `is_mutable_buffer_sequence`
  * New trait `buffers_iterator_type`
  * New trait `buffers_type`

* New classes
  `async_base`,
  `stable_async_base`
  * Handle boilerplate for writing composed operations
  * New
    `allocate_stable`
    is preferred over `handler_ptr`

* New
  `buffer_bytes`
  replacement for `net::buffer_size`

* New:
  * `saved_handler`
  * `buffers_range_ref` 
  * `executor_type`
  * `get_lowest_layer`,
    `lowest_layer_type`
  * `close_socket`,
    `beast_close_socket`
  * `error`,
    `condition`

* These interfaces are now public (were experimental):
  [link beast.ref.boost__beast__flat_stream `flat_stream`],
  [link beast.ref.boost__beast__detect_ssl `detect_ssl`],
  [link beast.ref.boost__beast__async_detect_ssl `async_detect_ssl`].

* Websocket streams use PCG as the fast random number generator,
  for increased security.



[*Documentation]

* WebSocket reference documentation is revised

* Updated [link beast.using_io.asio_refresher Networking Refresher]

* Revised [link beast.using_io.writing_composed_operations.echo Asynchronous Echo]

* Rewritten [link beast.using_io.writing_composed_operations.detect_ssl [*Detect SSL Handshake]]



[*API Changes]

* The __Fields__ concept is deprecated and will be removed
  in a future version. ['Actions Required]: Do not rely on
  the ['Fields] concept.

* `handler_ptr` is deprecated. ['Actions Required]: Use
  `stable_async_base` and
  `allocate_stable`
  instead.

* On Windows, Visual Studio 2017 or later is required

* OpenSSL is required to build the examples and tests

* HTTP stream algorithms return the number of bytes transferred
  from the stream. Previously, they returned the number of bytes
  consumed by the parser.
  ['Actions Required]:
  * Callers depending on the return value of
    `http::read` or
    `http::async_read`
    overloads should adjust the usage of
    the returned value as needed.

* Metafunctions
  `has_get_executor`,
  `is_sync_stream`,
  `is_sync_read_stream`,
  `is_sync_write_stream`,
  `is_async_stream`,
  `is_async_read_stream`, and
  `is_async_write_stream`
  are in stream_traits.hpp.
  ['Actions Required]: Include stream_traits.hpp as needed.

* `basic_parser`
  is abstract.
  ['Actions Required]
  * Change uses of the `basic_parser` type to omit the `Derived`
    template parameter
  * Classes derived from `basic_parser` no longer need to friend
    the base.
  * Virtual functions in the derived class may be marked `override`.

* Metafunction
  `is_file`
  is in file_base.hpp.
  ['Actions Required]: Include file_base.hpp as needed.

* `flat_static_buffer::reset()`
  is deprecated.
  ['Actions Required]:
  * call
    `clear()` instead.

* `buffers_adapter` is spelled
  `buffers_adaptor`.
  ['Actions Required]:
  * Replace `buffers_adapter` with
    `buffers_adaptor`,
    or define `BOOST_BEAST_ALLOW_DEPRECATED`.

* `buffers` is spelled
  `make_printable`.
  ['Actions Required]:
  * Replace `buffers` with
    `make_printable`,
    and include "make_printable.hpp" instead of "ostream.hpp".

* `file_mode::append_new` is removed, as it makes no sense.
  ['Actions Required]:
  - Replace `file_mode::append_new` with either
    `file_mode::append` or
    `file_mode::append_existing`
    as needed.

* `role_type` is moved from `websocket` to `beast`

* `buffers_range_ref`
  is preferred to `std::reference_wrapper`.
  ['Actions Required]:
  - Call
    `buffers_range_ref`
    with the buffer, instead of calling
    `buffers_range`
    with a reference wrapper constructed from the buffer.

* Nested `lowest_layer` and `lowest_layer_type` are removed.
  ['Actions Required]: Use the free function
  `get_lowest_layer` and the
  type trait
  `lowest_layer_type` instead.

* WebSocket decorator is a socket option:
  * Overloads of the following functions which accept a Decorator
    are deprecated:
    - `accept`, `accept_ex`
    - `handshake`, `handshake_ex`
    - `async_accept`, `async_accept_ex`
    - `async_handshake`, `async_handshake_ex`

* ([issue 1375]) The value returned from `basic_parser::content_length`
  no longer changes as the body of the message is received.
  ['Actions Required]: Call `basic_parser::content_length_remaining` instead
  of `basic_parser::content_length` in order to determine the remaining
  number of bytes in the body.


[*Examples]

* All example programs are updated:
  * Use
    `tcp_stream`
    with timeouts (HTTP)
  * Use
    `ssl_stream`
  * Set timeouts for WebSocket streams.
  * Use
    `bind_front_handler`

* ([issue 1100]) http-crawl clears the response before each read

* ([issue 1347]) echo-op is rewritten

* ([issue 1401]) Examples use
  `flat_buffer`

* Advanced servers use HTTP parser interfaces for reading

* detect-ssl is rewritten

* New example [path_link example/websocket/server/chat-multi example/websocket/server/chat-multi]

* `async_echo` works with move-only handlers

* cppcon2018 example is removed



[*Fixes]

* ([issue 38]) Better treatment of SSL short reads

* ([issue 1223]) HTTP read counts bytes correctly when an error occurs

* ([issue 1247]) Update `ssl_stream`
  for Asio changes

* ([issue 1279]) Enable explicit instantiations of
  `websocket::stream`

* ([issue 1290]) Don't use deprecated Asio interfaces

* ([issue 1306]) `http::message`
  is not-a `boost::empty_value`

* ([issue 1306]) `test::stream`
  has fewer dependencies

* ([issue 1358]) Destroy abandoned websocket ops on shutdown

* ([issue 1365]) Handler wrappers decay parameters sooner

* ([issue 1408]) `session_alloc`
  is thread-safe

* ([issue 1414]) Boost.System is header-only

* ([issue 1418]) `test::stream`
  maintains a handler work guard

* ([issue 1445]) Fix posix_file::close handling of EINTR

* ([issue 1460]) Large WebSocket Upgrade response no longer overflows

* Reusing an HTTP parser returns an error

* Handler bind wrappers use the associated allocator

* `buffers_cat`
  correctly skips empty buffers when iterated

* `ostream`
  does not overflow or exceed the dynamic buffer's maximum size

* Fixes to
  `test::stream::async_read`

* `file_mode::append_existing`
  works correctly

* A handler work guard is maintained on paused websocket operations

* All behavior of default-constructed iterators is conforming

[/-----------------------------------------------------------------------------]

[heading Boost 1.69]

[*New Videos]

[block'''
<mediaobject>
  <videoobject>
    <videodata fileref="https://www.youtube.com/embed/7FQwAjELMek"
        align="center" contentwidth="448" contentdepth="252"/>
  </videoobject>
</mediaobject>
''']

[*New Features]

* ([issue 1133]) Add `BOOST_BEAST_USE_STD_STRING_VIEW`

[*Examples]

* New WebSocket server and browser-based client: example/cppcon2018

[*Fixes]

* ([issue 1245]) Fix a rare case of incorrect UTF8 validation

* ([issue 1237]) Verify certificates in client examples

* ([issue 1233]) Use [@boost:/doc/html/core/empty_value.html `boost::empty_value`]

* ([issue 1091]) Fix timer on websocket upgrade in examples

* ([issue 1270]) [link beast.ref.boost__beast__http__basic_fields `basic_fields`] uses intrusive base hooks

* ([issue 1267]) Fix parsing of out-of-bounds hex values

* ([issue 1263]) Fix uninitialized comparison in buffers iterator

* ([issue 1288]) Remove extraneous strand from example

* Workaround for http-server-fast and libstdc++

* Partial support for `BOOST_NO_EXCEPTIONS`

[*Experimental]

* Add `timeout_socket`




[heading Boost 1.68]

This version fixes a missing executor work guard in all composed operations
used in the implementation. Users who are experiencing crashes related to
asynchronous completion handlers are encouraged to upgrade. Also included
is an improved mechanism for generating random numbers used to mask outgoing
websocket frames when operating in the client mode. This resolves a
vulnerability described in the Beast Hybrid Assessment Report from Bishop Fox.

[*New Features]

The include directory `<beast/experimental>` contains features which are not
part of the stable public interface but are available anyway. They may change
in future versions.

* ([issue 1108]) New [link beast.ref.boost__beast__flat_stream `flat_stream`] for working around an SSL stream performance limitation

* ([issue 1151], [issue 595]) New [link beast.ref.boost__beast__http__icy_stream `http::icy_stream`] stream filter allows parsing ICY HTTP response handshakes

* New [link beast.ref.boost__beast__ssl_stream `ssl_stream`] for better SSL performance and move constructability

* New
  [link beast.ref.boost__beast__test__error `test::connect`],
  [link beast.ref.boost__beast__test__error `test::error`],
  [link beast.ref.boost__beast__test__error `test::fail_count`], and
  [link beast.ref.boost__beast__test__error `test::stream`] utilities for writing unit tests.

* New [link beast.ref.boost__beast__http__is_mutable_body_writer `http::is_mutable_body_writer`] metafunction

* New [link beast.ref.boost__beast__websocket__seed_prng `websocket::seed_prng`] for manually providing entropy to the PRNG

* New [link beast.ref.boost__beast__websocket__stream.secure_prng `websocket::stream::secure_prng`] to control whether the connection uses a secure PRNG

[*Improvements]

* Generated WebSocket masks use a secure PRNG by default

* Improvements to [link beast.ref.boost__beast__buffers_adaptor `buffers_adaptor`]

* ([issue 1188]) Set "/permissive-" for MSVC builds

* ([issue 1109]) Use a shared string for example HTTP server doc roots 

* ([issue 1079]) Add `handler_ptr::has_value`

[*Fixes]

* ([issue 1073]) Fix race in advanced server examples

* ([issue 1076]) Use executor_work_guard in composed operations

* ([issue 1079]) Remove spurious assert

* ([issue 1113]) Add `const` and non-`const` overloads for message based HTTP writes

* ([issue 1119]) Fix unused variable warning

* ([issue 1121]) Examples use the root certificate which matches the fingerprint

* ([issue 1141]) Tidy up composed operation doc

* ([issue 1186]) Check error in example set_option

* ([issue 1210]) Fix http_server_stackless_ssl.cpp example

* ([issue 1211]) Fix parse_dec algorithm

* ([issue 1214]) Silence ubsan false positive

* Tidy up websocket stream javadocs

* Fix move-only arguments in [link beast.ref.boost__beast__bind_handler `bind_handler`]

* Fix [link beast.ref.boost__beast__http__parser `http::parser`] constructor javadoc

* Fix [link beast.ref.boost__beast__buffers_adaptor `buffers_adaptor`] iterator value type

* Fix [link beast.ref.boost__beast__buffers_adaptor.max_size `buffers_adaptor::max_size`]

* Fix [link beast.ref.boost__beast__buffers_prefix `buffers_prefix`] iterator decrement

* Fix __Fields__, __FieldsWriter__ concept docs

* Fix __BodyReader__ constructor requirements doc

[*Breaking Changes]

* Remove deprecated `serializer::reader_impl`

* Remove deprecated __Body__ `reader` and `writer` ctor signatures





[heading Boost 1.67]

This version fixes significant defects in
[link beast.ref.boost__beast__websocket__stream `websocket::stream`]
which can lead to asserts or undefined behavior. Users are encouraged
to update to the latest Boost release.

[*New Features]

* Move-only completion handlers are supported throughout the library

* ([issue 899]) Advanced server examples support idle websocket pings and timeouts

* ([issue 849]) WebSocket permessage-deflate support is now a compile-time
  feature.  This adds an additional `bool` template parameter to
  [link beast.ref.boost__beast__websocket__stream `websocket::stream`]
  When `deflateSupported` is `true`, the stream will be capable of
  negotiating the permessage-deflate websocket extension per the
  configured run-time settings.
  When `deflateSupported` is `false`, the stream will never negotiate
  the permessage-deflate websocket extension. Furthermore, all of the
  code necessary for implementing the permessage-deflate extension
  will be excluded from function instantiations. Programs which set
  `deflateSupported` to `false` when instantiating streams will be smaller.

* ([issue 949]) WebSocket error codes are revised. New
  [link beast.ref.boost__beast__websocket__error error codes]
  are added for more fine-grained failure outcomes. Messages for error
  codes are more verbose to help pinpoint the problem. Error codes are
  now also mapped to newly added
  [link beast.ref.boost__beast__websocket__condition error conditions]
  to simplify comparisons. The error codes `websocket::error::failed`
  and `websocket::error::handshake_failed` are removed.
  Actions required:
  Code which explicitly compares `error_code` values against
  the constant `websocket::error::handshake_failed` should compare
  against
  [link beast.ref.boost__beast__websocket__condition `websocket::condition::handshake_failed`]
  instead.
  Code which explicitly compares error_code values against the
  constant `websocket::error::failed` should compare
  against
  [link beast.ref.boost__beast__websocket__condition `websocket::condition::protocol_violation`]
  instead.

[*Improvements]

* ([issue 857])
  [link beast.ref.boost__beast__http__basic_fields `http::basic_fields`]
  uses less storage

* ([issue 894])
  [link beast.ref.boost__beast__http__basic_fields `http::basic_fields`]
  exception specifiers are provided

* Implementation no longer uses deprecated `asio::null_buffers`

* Add [include_file boost/beast/websocket/stream_fwd.hpp]

* ([issue 955]) The asynchronous SSL detector example uses a stackless coroutine

* [link beast.ref.boost__beast__bind_handler `bind_handler`]
  works with boost placeholders

* Examples set `reuse_address(true)`

* ([issue 1026]) Advanced servers support clean shutdown via SIGINT or SIGTERM

* Some basic_fields operations now give the strong exception guarantee

[*Fixes]

* Fix "warning: ‘const’ type qualifier on return type has no effect"

* ([issue 916]) Tidy up `ssl_stream` special members

* ([issue 918]) Calls to `<algorithm>` are protected from macros

* ([issue 954]) The control callback is invoked on the proper executor

* ([issue 994]) Fix iterator version of
  [link beast.ref.boost__beast__http__basic_fields.erase.overload1 `http::basic_fields::erase`]

* ([issue 992]) Fix use-after-move in example request handlers

* ([issue 988]) Type check completion handlers

* ([issue 985]) Tidy up
  [link beast.ref.boost__beast__bind_handler `bind_handler`]
  doc

* Fix memory leak in advanced server examples

* ([issue 1000]) Fix soft-mutex assert in websocket stream.
  This resolves the assert `"ws_.wr_block_ == tok_"`.

* ([issue 1019]) Fix fallthrough warnings

* ([issue 1024]) Fix teardown for TIME_WAIT

* ([issue 1030]) Fix big-endian websocket masking

* Safe treatment of zero-length string arguments in basic_fields

* ([issue 1043]) Examples clear the HTTP message before reading

* ([issue 1012]) Add asio_handler_invoke overloads for stream algorithms

* Add Access-Control-Expose-Headers field constant

[*API Changes]

* Remove unintended public members of
  `handler_ptr`.
  Actions required: don't call non-public members.

* `handler_ptr`
  is a move-only type, with `unique_ptr` semantics.
  Actions required: user-defined composed operations using `handler_ptr`
  to manage state can only be moved, not copied.

* `handler_ptr`
  gives the strong exception guarantee. The constructor signature
  for managed objects constructed by `handler_ptr` now receives a
  `const` reference to the handler. Actions required: Change the
  constructor signature for state objects used with `handler_ptr`
  to receive a `const` reference to the handler.

* ([issue 896])
  [link beast.ref.boost__beast__http__basic_fields `http::basic_fields`]
  does not support fancy pointers

* [link beast.ref.boost__beast__http__parser `http::parser`]
  is no longer [*MoveConstructible]

* ([issue 930]) `http::serializer::reader_impl` is deprecated and will
  be removed in the next release. Actions required: Call
  [link beast.ref.boost__beast__http__serializer.writer_impl `http::serializer::writer_impl`]
  instead of `serializer::reader_impl`.

* ([issue 884]) The __BodyReader__ and __BodyWriter__ concept constructor
  requirements have changed. They now require the header and body
  elements to be passed as distinct
  [link beast.ref.boost__beast__http__header `http::header`]
  and `value_type` objects. This enables the composition of body types.
  The previous single-argument constructors are deprecated and will be
  removed in the next version.
  Actions required: Change user-defined instances of __BodyReader__ or
  __BodyWriter__ constructor signatures to the two-argument form.
  Alternatively. define the macro `BOOST_BEAST_ALLOW_DEPRECATED` in
  the project (which will cause both the new and the deprecated
  signatures to be accepted).

* [link beast.ref.boost__beast__websocket__stream.control_callback `websocket::stream::control_callback`]
  now copies or moves the function object.

* ([issue 1014]) DynamicBuffer input areas are not mutable.
  Actions required: do not attempt to write to input areas of dynamic
  buffers.

* ([issue 941]) `get_lowest_layer` is now a type alias.
  Actions required: Replace instances of `typename get_lowest_layer<T>::type`
  with `get_lowest_layer<T>`.

[heading Boost 1.66]

* Initial release

[endsect]
