Support handshake with re-use of data already read from the wire.

Add new overloads of the SSL stream's handshake() and async_handshake()
functions, that accepts a ConstBufferSequence to be used as initial
input to the ssl engine for the handshake procedure.

Thanks go to Nick Jones <nick dot fa dot jones at gmail dot com>, on
whose work this commit is partially based.

asio/include/Makefile.am

@@ -320,6 +320,7 @@ nobase_include_HEADERS = \
 	asio/ssl/context_base.hpp \
 	asio/ssl/context.hpp \
 	asio/ssl/context_service.hpp \
+	asio/ssl/detail/buffered_handshake_op.hpp \
 	asio/ssl/detail/engine.hpp \
 	asio/ssl/detail/handshake_op.hpp \
 	asio/ssl/detail/impl/engine.ipp \

asio/include/asio/detail/handler_type_requirements.hpp

@@ -368,6 +368,33 @@ struct handler_type_requirements
             asio::detail::lvref<const asio::error_code>()), \
         char(0))>
 
+#define ASIO_BUFFERED_HANDSHAKE_HANDLER_CHECK( \
+    handler_type, handler) \
+  \
+  typedef ASIO_HANDLER_TYPE(handler_type, \
+      void(asio::error_code, std::size_t)) \
+    asio_true_handler_type; \
+  \
+  ASIO_HANDLER_TYPE_REQUIREMENTS_ASSERT( \
+      sizeof(asio::detail::two_arg_handler_test( \
+          asio::detail::clvref< \
+            asio_true_handler_type>(), \
+          static_cast<const asio::error_code*>(0), \
+          static_cast<const std::size_t*>(0))) == 1, \
+      "BufferedHandshakeHandler type requirements not met") \
+  \
+  typedef asio::detail::handler_type_requirements< \
+      sizeof( \
+        asio::detail::argbyv( \
+          asio::detail::clvref< \
+            asio_true_handler_type>())) + \
+      sizeof( \
+        asio::detail::lvref< \
+          asio_true_handler_type>()( \
+          asio::detail::lvref<const asio::error_code>(), \
+          asio::detail::lvref<const std::size_t>()), \
+        char(0))>
+
 #define ASIO_SHUTDOWN_HANDLER_CHECK( \
     handler_type, handler) \
   \
@@ -435,6 +462,10 @@ struct handler_type_requirements
     handler_type, handler) \
   typedef int
 
+#define ASIO_BUFFERED_HANDSHAKE_HANDLER_CHECK( \
+    handler_type, handler) \
+  typedef int
+
 #define ASIO_SHUTDOWN_HANDLER_CHECK( \
     handler_type, handler) \
   typedef int

asio/include/asio/ssl/detail/buffered_handshake_op.hpp

@@ -0,0 +1,110 @@
+//
+// ssl/detail/buffered_handshake_op.hpp
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2012 Christopher M. Kohlhoff (chris at kohlhoff 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)
+//
+
+#ifndef ASIO_SSL_DETAIL_BUFFERED_HANDSHAKE_OP_HPP
+#define ASIO_SSL_DETAIL_BUFFERED_HANDSHAKE_OP_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include "asio/detail/config.hpp"
+
+#if !defined(ASIO_ENABLE_OLD_SSL)
+# include "asio/ssl/detail/engine.hpp"
+#endif // !defined(ASIO_ENABLE_OLD_SSL)
+
+#include "asio/detail/push_options.hpp"
+
+namespace asio {
+namespace ssl {
+namespace detail {
+
+#if !defined(ASIO_ENABLE_OLD_SSL)
+
+template <typename ConstBufferSequence>
+class buffered_handshake_op
+{
+public:
+  buffered_handshake_op(stream_base::handshake_type type,
+      const ConstBufferSequence& buffers)
+    : type_(type),
+      buffers_(buffers),
+      total_buffer_size_(asio::buffer_size(buffers_))
+  {
+  }
+
+  engine::want operator()(engine& eng,
+      asio::error_code& ec,
+      std::size_t& bytes_transferred) const
+  {
+    typename ConstBufferSequence::const_iterator iter = buffers_.begin();
+    typename ConstBufferSequence::const_iterator end = buffers_.end();
+    std::size_t accumulated_size = 0;
+
+    for (;;)
+    {
+      engine::want want = eng.handshake(type_, ec);
+      if (want != engine::want_input_and_retry
+          || bytes_transferred == total_buffer_size_)
+        return want;
+
+      // Find the next buffer piece to be fed to the engine.
+      while (iter != end)
+      {
+        const_buffer buffer(*iter);
+
+        // Skip over any buffers which have already been consumed by the engine.
+        if (bytes_transferred >= accumulated_size + buffer_size(buffer))
+        {
+          accumulated_size += buffer_size(buffer);
+          ++iter;
+          continue;
+        }
+
+        // The current buffer may have been partially consumed by the engine on
+        // a previous iteration. If so, adjust the buffer to point to the
+        // unused portion.
+        if (bytes_transferred > accumulated_size)
+          buffer = buffer + (bytes_transferred - accumulated_size);
+
+        // Pass the buffer to the engine, and update the bytes transferred to
+        // reflect the total number of bytes consumed so far.
+        bytes_transferred += buffer_size(buffer);
+        buffer = eng.put_input(buffer);
+        bytes_transferred -= buffer_size(buffer);
+        break;
+      }
+    }
+  }
+
+  template <typename Handler>
+  void call_handler(Handler& handler,
+      const asio::error_code& ec,
+      const std::size_t& bytes_transferred) const
+  {
+    handler(ec, bytes_transferred);
+  }
+
+private:
+  stream_base::handshake_type type_;
+  ConstBufferSequence buffers_;
+  std::size_t total_buffer_size_;
+};
+
+#endif // !defined(ASIO_ENABLE_OLD_SSL)
+
+} // namespace detail
+} // namespace ssl
+} // namespace asio
+
+#include "asio/detail/pop_options.hpp"
+
+#endif // ASIO_SSL_DETAIL_BUFFERED_HANDSHAKE_OP_HPP

asio/include/asio/ssl/stream.hpp

@@ -26,6 +26,7 @@
 # include "asio/detail/noncopyable.hpp"
 # include "asio/detail/type_traits.hpp"
 # include "asio/ssl/context.hpp"
+# include "asio/ssl/detail/buffered_handshake_op.hpp"
 # include "asio/ssl/detail/handshake_op.hpp"
 # include "asio/ssl/detail/io.hpp"
 # include "asio/ssl/detail/read_op.hpp"
@@ -343,6 +344,47 @@ public:
     return ec;
   }
 
+  /// Perform SSL handshaking.
+  /**
+   * This function is used to perform SSL handshaking on the stream. The
+   * function call will block until handshaking is complete or an error occurs.
+   *
+   * @param type The type of handshaking to be performed, i.e. as a client or as
+   * a server.
+   *
+   * @param buffers The buffered data to be reused for the handshake.
+   *
+   * @throws asio::system_error Thrown on failure.
+   */
+  template <typename ConstBufferSequence>
+  void handshake(handshake_type type, const ConstBufferSequence& buffers)
+  {
+    asio::error_code ec;
+    handshake(type, buffers, ec);
+    asio::detail::throw_error(ec, "handshake");
+  }
+
+  /// Perform SSL handshaking.
+  /**
+   * This function is used to perform SSL handshaking on the stream. The
+   * function call will block until handshaking is complete or an error occurs.
+   *
+   * @param type The type of handshaking to be performed, i.e. as a client or as
+   * a server.
+   *
+   * @param buffers The buffered data to be reused for the handshake.
+   *
+   * @param ec Set to indicate what error occurred, if any.
+   */
+  template <typename ConstBufferSequence>
+  asio::error_code handshake(handshake_type type,
+      const ConstBufferSequence& buffers, asio::error_code& ec)
+  {
+    detail::io(next_layer_, core_,
+        detail::buffered_handshake_op<ConstBufferSequence>(type, buffers), ec);
+    return ec;
+  }
+
   /// Start an asynchronous SSL handshake.
   /**
    * This function is used to asynchronously perform an SSL handshake on the
@@ -378,6 +420,49 @@ public:
     return init.result.get();
   }
 
+  /// Start an asynchronous SSL handshake.
+  /**
+   * This function is used to asynchronously perform an SSL handshake on the
+   * stream. This function call always returns immediately.
+   *
+   * @param type The type of handshaking to be performed, i.e. as a client or as
+   * a server.
+   *
+   * @param buffers The buffered data to be reused for the handshake. Although
+   * the buffers object may be copied as necessary, ownership of the underlying
+   * buffers is retained by the caller, which must guarantee that they remain
+   * valid until the handler is called.
+   *
+   * @param handler The handler to be called when the handshake operation
+   * completes. Copies will be made of the handler as required. The equivalent
+   * function signature of the handler must be:
+   * @code void handler(
+   *   const asio::error_code& error, // Result of operation.
+   *   std::size_t bytes_transferred // Amount of buffers used in handshake.
+   * ); @endcode
+   */
+  template <typename ConstBufferSequence, typename BufferedHandshakeHandler>
+  ASIO_INITFN_RESULT_TYPE(BufferedHandshakeHandler,
+      void (asio::error_code, std::size_t))
+  async_handshake(handshake_type type, const ConstBufferSequence& buffers,
+      ASIO_MOVE_ARG(BufferedHandshakeHandler) handler)
+  {
+    // If you get an error on the following line it means that your handler does
+    // not meet the documented type requirements for a BufferedHandshakeHandler.
+    ASIO_BUFFERED_HANDSHAKE_HANDLER_CHECK(
+        BufferedHandshakeHandler, handler) type_check;
+
+    asio::detail::async_result_init<BufferedHandshakeHandler,
+      void (asio::error_code, std::size_t)> init(
+        ASIO_MOVE_CAST(BufferedHandshakeHandler)(handler));
+
+    detail::async_io(next_layer_, core_,
+        detail::buffered_handshake_op<ConstBufferSequence>(type, buffers),
+        init.handler);
+
+    return init.result.get();
+  }
+
   /// Shut down SSL on the stream.
   /**
    * This function is used to shut down SSL on the stream. The function call

asio/src/doc/quickref.xml

@@ -317,6 +317,7 @@
           </simplelist>
           <bridgehead renderas="sect3">Type Requirements</bridgehead>
           <simplelist type="vert" columns="1">
+            <member><link linkend="asio.reference.BufferedHandshakeHandler">BufferedHandshakeHandler</link></member>
             <member><link linkend="asio.reference.HandshakeHandler">HandshakeHandler</link></member>
             <member><link linkend="asio.reference.ShutdownHandler">ShutdownHandler</link></member>
           </simplelist>

asio/src/doc/reference.xsl

@@ -42,6 +42,7 @@
 [include requirements/AsyncRandomAccessWriteDevice.qbk]
 [include requirements/AsyncReadStream.qbk]
 [include requirements/AsyncWriteStream.qbk]
+[include requirements/BufferedHandshakeHandler.qbk]
 [include requirements/CompletionHandler.qbk]
 [include requirements/ComposedConnectHandler.qbk]
 [include requirements/ConnectHandler.qbk]

asio/src/doc/requirements/BufferedHandshakeHandler.qbk

@@ -0,0 +1,54 @@
+[/
+ / Copyright (c) 2003-2012 Christopher M. Kohlhoff (chris at kohlhoff 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:BufferedHandshakeHandler Buffered handshake handler requirements]
+
+A buffered handshake handler must meet the requirements for a [link
+asio.reference.Handler handler]. A value `h` of a buffered handshake handler
+class should work correctly in the expression `h(ec, s)`, where `ec` is an
+lvalue of type `const error_code` and `s` is an lvalue of type `const size_t`.
+
+[heading Examples]
+
+A free function as a buffered handshake handler:
+
+  void handshake_handler(
+      const asio::error_code& ec,
+      std::size_t bytes_transferred)
+  {
+    ...
+  }
+
+A buffered handshake handler function object:
+
+  struct handshake_handler
+  {
+    ...
+    void operator()(
+        const asio::error_code& ec,
+        std::size_t bytes_transferred)
+    {
+      ...
+    }
+    ...
+  };
+
+A non-static class member function adapted to a buffered handshake handler using `bind()`:
+
+  void my_class::handshake_handler(
+      const asio::error_code& ec,
+      std::size_t bytes_transferred)
+  {
+    ...
+  }
+  ...
+  socket.async_handshake(...,
+      boost::bind(&my_class::handshake_handler,
+        this, asio::placeholders::error,
+        asio::placeholders::bytes_transferred));
+
+[endsect]

asio/src/tests/unit/ssl/stream.cpp

@@ -41,6 +41,10 @@ void handshake_handler(const asio::error_code&)
 {
 }
 
+void buffered_handshake_handler(const asio::error_code&, std::size_t)
+{
+}
+
 void shutdown_handler(const asio::error_code&)
 {
 }
@@ -110,6 +114,21 @@ void test()
     stream1.handshake(ssl::stream_base::client, ec);
     stream1.handshake(ssl::stream_base::server, ec);
 
+#if !defined(ASIO_ENABLE_OLD_SSL)
+    stream1.handshake(ssl::stream_base::client, buffer(mutable_char_buffer));
+    stream1.handshake(ssl::stream_base::server, buffer(mutable_char_buffer));
+    stream1.handshake(ssl::stream_base::client, buffer(const_char_buffer));
+    stream1.handshake(ssl::stream_base::server, buffer(const_char_buffer));
+    stream1.handshake(ssl::stream_base::client,
+        buffer(mutable_char_buffer), ec);
+    stream1.handshake(ssl::stream_base::server,
+        buffer(mutable_char_buffer), ec);
+    stream1.handshake(ssl::stream_base::client,
+        buffer(const_char_buffer), ec);
+    stream1.handshake(ssl::stream_base::server,
+        buffer(const_char_buffer), ec);
+#endif // !defined(ASIO_ENABLE_OLD_SSL)
+
     stream1.async_handshake(ssl::stream_base::client, handshake_handler);
     stream1.async_handshake(ssl::stream_base::server, handshake_handler);
     int i1 = stream1.async_handshake(ssl::stream_base::client, lazy);
@@ -117,12 +136,35 @@ void test()
     int i2 = stream1.async_handshake(ssl::stream_base::server, lazy);
     (void)i2;
 
+#if !defined(ASIO_ENABLE_OLD_SSL)
+    stream1.async_handshake(ssl::stream_base::client,
+        buffer(mutable_char_buffer), buffered_handshake_handler);
+    stream1.async_handshake(ssl::stream_base::server,
+        buffer(mutable_char_buffer), buffered_handshake_handler);
+    stream1.async_handshake(ssl::stream_base::client,
+        buffer(const_char_buffer), buffered_handshake_handler);
+    stream1.async_handshake(ssl::stream_base::server,
+        buffer(const_char_buffer), buffered_handshake_handler);
+    int i3 = stream1.async_handshake(ssl::stream_base::client,
+        buffer(mutable_char_buffer), lazy);
+    (void)i3;
+    int i4 = stream1.async_handshake(ssl::stream_base::server,
+        buffer(mutable_char_buffer), lazy);
+    (void)i4;
+    int i5 = stream1.async_handshake(ssl::stream_base::client,
+        buffer(const_char_buffer), lazy);
+    (void)i5;
+    int i6 = stream1.async_handshake(ssl::stream_base::server,
+        buffer(const_char_buffer), lazy);
+    (void)i6;
+#endif // !defined(ASIO_ENABLE_OLD_SSL)
+
     stream1.shutdown();
     stream1.shutdown(ec);
 
     stream1.async_shutdown(shutdown_handler);
-    int i3 = stream1.async_shutdown(lazy);
-    (void)i3;
+    int i7 = stream1.async_shutdown(lazy);
+    (void)i7;
 
     stream1.write_some(buffer(mutable_char_buffer));
     stream1.write_some(buffer(const_char_buffer));
@@ -131,17 +173,17 @@ void test()
 
     stream1.async_write_some(buffer(mutable_char_buffer), write_some_handler);
     stream1.async_write_some(buffer(const_char_buffer), write_some_handler);
-    int i4 = stream1.async_write_some(buffer(mutable_char_buffer), lazy);
-    (void)i4;
-    int i5 = stream1.async_write_some(buffer(const_char_buffer), lazy);
-    (void)i5;
+    int i8 = stream1.async_write_some(buffer(mutable_char_buffer), lazy);
+    (void)i8;
+    int i9 = stream1.async_write_some(buffer(const_char_buffer), lazy);
+    (void)i9;
 
     stream1.read_some(buffer(mutable_char_buffer));
     stream1.read_some(buffer(mutable_char_buffer), ec);
 
     stream1.async_read_some(buffer(mutable_char_buffer), read_some_handler);
-    int i6 = stream1.async_read_some(buffer(mutable_char_buffer), lazy);
-    (void)i6;
+    int i10 = stream1.async_read_some(buffer(mutable_char_buffer), lazy);
+    (void)i10;
 
 #if defined(ASIO_ENABLE_OLD_SSL)
     stream1.peek(buffer(mutable_char_buffer));