Beast.Asio:

New classes:

  class async_completion:
    Helper class for implementing asynchronous initiation functions.
    See n3964:
        Library Foundations for Asynchronous Operations, Revision 1
        http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3964.pdf

  class basic_streambuf:
    Meets the requirements of Streambuf.

  class buffered_readstream:
    Buffers a ReadStream with a ConstBufferSequence.

  class consuming_buffers:
    Adapts a BufferSequence which wraps the underlying buffer
    sequence and presents fewer bytes, with the retained bytes
    occurring at the end of the sequence.

  class handler_alloc:
    A C++ Allocator the uses asio handler allocation hooks.

  class static_streambuf:
    An implementation of the Streambuf concept that uses a
    fixed size buffer with size determined at compile-time.

  class streambuf_readstream:
    Buffers a ReadStream with a Streambuf.

New functions:

  append_buffers()
    Returns a new BufferSequence which efficiently concatenates
    two or more buffer sequences together.

  prepare_buffers()
    Shortens a buffer sequence. The bytes excluded are at the
    end of the underlying buffer sequence.

  boost::asio::read_until()
    A copy of boost::asio::read_until overloads, modified to work
    with a beast::asio::basic_streambuf.

Debugging:

  buffers_to_string()

    Convert a ConstBufferSequence to a human readable string
    suitable for diagnostics.

type_check.h:

  Metafunctions for checking asio concepts:
    AsyncReadStream, AsyncWriteStream
    SyncReadStream, SyncWriteStream
    ConstBufferSequence, MutableBufferSequence
    Streambuf
    Handler

Changes:

* All symbols moved up a namespace level.
* streambuf provides all move and copy special members,
  behavior of moved from objects is well-defined.

Fixes:

* Fix basic_streambuf iterator category.

test/asio/prepare_buffers.cpp

@@ -0,0 +1,103 @@
+//
+// Copyright (c) 2013-2016 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)
+//
+
+// Test that header file is self-contained.
+#include <beast/asio/prepare_buffers.h>
+
+#include <beast/asio/consuming_buffers.h>
+#include <beast/unit_test/suite.h>
+#include <boost/asio/buffer.hpp>
+#include <string>
+
+namespace beast {
+namespace asio {
+namespace test {
+
+class prepare_buffers_test : public unit_test::suite
+{
+public:
+    template<class ConstBufferSequence>
+    static
+    std::string
+    to_string(ConstBufferSequence const& bs)
+    {
+        using boost::asio::buffer_cast;
+        using boost::asio::buffer_size;
+        std::string s;
+        s.reserve(buffer_size(bs));
+        for(auto const& b : bs)
+            s.append(buffer_cast<char const*>(b),
+                buffer_size(b));
+        return s;
+    }
+
+    void testBuffers()
+    {
+        using boost::asio::buffer_size;
+        using boost::asio::const_buffer;
+        std::string const s = "Hello, world";
+        expect(s.size() == 12);
+        for(std::size_t x = 1; x < 4; ++x) {
+        for(std::size_t y = 1; y < 4; ++y) {
+        std::size_t z = s.size() - (x + y);
+        {
+            std::array<const_buffer, 3> bs{{
+                const_buffer{&s[0], x},
+                const_buffer{&s[x], y},
+                const_buffer{&s[x+y], z}}};
+            for(std::size_t i = 0; i <= s.size() + 1; ++i)
+            {
+                auto pb = prepare_buffers(i, bs);
+                expect(to_string(pb) == s.substr(0, i));
+                auto pb2 = pb;
+                expect(to_string(pb2) == to_string(pb));
+                pb = prepare_buffers(0, bs);
+                pb2 = pb;
+                expect(buffer_size(pb2) == 0);
+                pb2 = prepare_buffers(i, bs);
+                expect(to_string(pb2) == s.substr(0, i));
+            }
+        }
+        }}
+    }
+
+    void testNullBuffers()
+    {
+        using boost::asio::buffer_copy;
+        using boost::asio::buffer_size;
+        using boost::asio::null_buffers;
+        auto pb0 = prepare_buffers(0, null_buffers{});
+        expect(buffer_size(pb0) == 0);
+        auto pb1 = prepare_buffers(1, null_buffers{});
+        expect(buffer_size(pb1) == 0);
+        expect(buffer_copy(pb0, pb1) == 0);
+
+        using pb_type = decltype(pb0);
+        consuming_buffers<pb_type> cb(pb0);
+        expect(buffer_size(cb) == 0);
+        expect(buffer_copy(cb, pb1) == 0);
+        cb.consume(1);
+        expect(buffer_size(cb) == 0);
+        expect(buffer_copy(cb, pb1) == 0);
+        
+        auto pbc = prepare_buffers(2, cb);
+        expect(buffer_size(pbc) == 0);
+        expect(buffer_copy(pbc, cb) == 0);
+    }
+
+    void run() override
+    {
+        testBuffers();
+        testNullBuffers();
+    }
+};
+
+BEAST_DEFINE_TESTSUITE(prepare_buffers,asio,beast);
+
+} // test
+} // asio
+} // beast