Squashed 'OpenVPN Adapter/Vendors/asio/' content from commit 524288c

git-subtree-dir: OpenVPN Adapter/Vendors/asio
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asio/src/doc/requirements/ReadHandler.qbk

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+[/
+ / Copyright (c) 2003-2016 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:ReadHandler Read handler requirements]
+
+A read handler must meet the requirements for a [link
+asio.reference.Handler handler]. A value `h` of a read 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 read handler:
+
+  void read_handler(
+      const asio::error_code& ec,
+      std::size_t bytes_transferred)
+  {
+    ...
+  }
+
+A read handler function object:
+
+  struct read_handler
+  {
+    ...
+    void operator()(
+        const asio::error_code& ec,
+        std::size_t bytes_transferred)
+    {
+      ...
+    }
+    ...
+  };
+
+A lambda as a read handler:
+
+  socket.async_read(...
+      [](const asio::error_code& ec,
+        std::size_t bytes_transferred)
+      {
+        ...
+      });
+
+A non-static class member function adapted to a read handler using
+`std::bind()`:
+
+  void my_class::read_handler(
+      const asio::error_code& ec,
+      std::size_t bytes_transferred)
+  {
+    ...
+  }
+  ...
+  socket.async_read(...,
+      std::bind(&my_class::read_handler,
+        this, std::placeholders::_1,
+        std::placeholders::_2));
+
+A non-static class member function adapted to a read handler using
+`boost::bind()`:
+
+  void my_class::read_handler(
+      const asio::error_code& ec,
+      std::size_t bytes_transferred)
+  {
+    ...
+  }
+  ...
+  socket.async_read(...,
+      boost::bind(&my_class::read_handler,
+        this, asio::placeholders::error,
+        asio::placeholders::bytes_transferred));
+
+[endsect]