Change Body::size signature (API Change):

fix #497

This changes the function signature to accept the `value_type`
instead of the entire message.

Actions Required:

* For any user-defined models of Body, change the function signature
  to accept `value_type const&` and modify the function definition
  accordingly.

include/beast/http/detail/type_traits.hpp

@@ -62,17 +62,17 @@ struct has_value_type<T, beast::detail::void_t<
 /** Determine if a @b Body type has a size
 
     This metafunction is equivalent to `std::true_type` if
-    Body contains a static member function called `content_lengeth`.
+    Body contains a static member function called `size`.
 */
-template<class T, class M, class = void>
+template<class T, class = void>
 struct is_body_sized : std::false_type {};
 
-template<class T, class M>
-struct is_body_sized<T, M, beast::detail::void_t<
+template<class T>
+struct is_body_sized<T, beast::detail::void_t<
     typename T::value_type,
         decltype(
     std::declval<std::uint64_t&>() =
-        T::size(std::declval<M const&>()),
+        T::size(std::declval<typename T::value_type const&>()),
     (void)0)>> : std::true_type {};
 
 } // detail

include/beast/http/dynamic_body.hpp

@@ -29,13 +29,11 @@ struct basic_dynamic_body
     using value_type = DynamicBuffer;
 
     /// Returns the content length of this body in a message.
-    template<bool isRequest, class Fields>
     static
     std::uint64_t
-    size(message<isRequest,
-        basic_dynamic_body, Fields> const& m)
+    size(value_type const& v)
     {
-        return m.body.size();
+        return v.size();
     }
 
 #if BEAST_DOXYGEN

include/beast/http/empty_body.hpp

@@ -36,10 +36,9 @@ struct empty_body
     };
 
     /// Returns the content length of the body in a message.
-    template<bool isRequest, class Fields>
     static
     std::uint64_t
-    size(message<isRequest, empty_body, Fields> const& m)
+    size(empty_body)
     {
         return 0;
     }

include/beast/http/impl/message.ipp

@@ -285,8 +285,7 @@ size() const
     static_assert(is_body_reader<Body>::value,
         "BodyReader requirements not met");
 
-    return size(detail::is_body_sized<
-        Body, decltype(*this)>{});
+    return size(detail::is_body_sized<Body>{});
 }
 
 template<bool isRequest, class Body, class Fields>

include/beast/http/message.hpp

@@ -558,7 +558,7 @@ private:
     boost::optional<std::uint64_t>
     size(std::true_type) const
     {
-        return Body::size(*this);
+        return Body::size(body);
     }
 
     boost::optional<std::uint64_t>

include/beast/http/string_body.hpp

@@ -31,13 +31,11 @@ struct string_body
     using value_type = std::string;
 
     /// Returns the content length of the body in a message.
-    template<bool isRequest, class Fields>
     static
     std::uint64_t
-    size(
-        message<isRequest, string_body, Fields> const& m)
+    size(value_type const& v)
     {
-        return m.body.size();
+        return v.size();
     }
 
 #if BEAST_DOXYGEN

include/beast/http/string_view_body.hpp

@@ -32,13 +32,11 @@ struct string_view_body
     using value_type = string_view;
 
     /// Returns the content length of this body in a message.
-    template<bool isRequest, class Fields>
     static
     std::uint64_t
-    size(message<isRequest,
-        string_view_body, Fields> const& m)
+    size(value_type const& v)
     {
-        return m.body.size();
+        return v.size();
     }
 
 #if BEAST_DOXYGEN