Fix consuming_buffers value_type (API Change):

This fixes a bug where instantiations of consuming_buffers with
buffer sequence types whose value_type is not const_buffer or
mutable_buffer can cause compilation errors.

The function consumed_buffers is removed.

include/beast/core/impl/consuming_buffers.ipp

@@ -18,10 +18,10 @@
 
 namespace beast {
 
-template<class BufferSequence, class ValueType>
-class consuming_buffers<BufferSequence, ValueType>::const_iterator
+template<class BufferSequence>
+class consuming_buffers<BufferSequence>::const_iterator
 {
-    friend class consuming_buffers<BufferSequence, ValueType>;
+    friend class consuming_buffers<BufferSequence>;
 
     using iter_type =
         typename BufferSequence::const_iterator;
@@ -30,8 +30,12 @@ class consuming_buffers<BufferSequence, ValueType>::const_iterator
     consuming_buffers const* b_ = nullptr;
 
 public:
-    using value_type =
-        typename std::iterator_traits<iter_type>::value_type;
+    using value_type = typename std::conditional<
+        std::is_convertible<typename
+            std::iterator_traits<iter_type>::value_type,
+                boost::asio::mutable_buffer>::value,
+                    boost::asio::mutable_buffer,
+                        boost::asio::const_buffer>::type;
     using pointer = value_type const*;
     using reference = value_type;
     using difference_type = std::ptrdiff_t;
@@ -59,8 +63,9 @@ public:
     reference
     operator*() const
     {
-        return it_ == b_->begin_ ?
-            *it_ + b_->skip_ : *it_;
+        return it_ == b_->begin_
+            ? value_type{*it_} + b_->skip_
+            : *it_;
     }
 
     pointer
@@ -105,8 +110,8 @@ private:
     }
 };
 
-template<class BufferSequence, class ValueType>
-consuming_buffers<BufferSequence, ValueType>::
+template<class BufferSequence>
+consuming_buffers<BufferSequence>::
 consuming_buffers(consuming_buffers&& other)
     : consuming_buffers(std::move(other),
         std::distance<iter_type>(
@@ -114,8 +119,8 @@ consuming_buffers(consuming_buffers&& other)
 {
 }
 
-template<class BufferSequence, class ValueType>
-consuming_buffers<BufferSequence, ValueType>::
+template<class BufferSequence>
+consuming_buffers<BufferSequence>::
 consuming_buffers(consuming_buffers const& other)
     : consuming_buffers(other,
         std::distance<iter_type>(
@@ -123,9 +128,9 @@ consuming_buffers(consuming_buffers const& other)
 {
 }
 
-template<class BufferSequence, class ValueType>
+template<class BufferSequence>
 auto
-consuming_buffers<BufferSequence, ValueType>::
+consuming_buffers<BufferSequence>::
 operator=(consuming_buffers&& other) ->
     consuming_buffers&
 {
@@ -137,9 +142,9 @@ operator=(consuming_buffers&& other) ->
     return *this;
 }
 
-template<class BufferSequence, class ValueType>
+template<class BufferSequence>
 auto
-consuming_buffers<BufferSequence, ValueType>::
+consuming_buffers<BufferSequence>::
 operator=(consuming_buffers const& other) ->
     consuming_buffers&
 {
@@ -151,35 +156,41 @@ operator=(consuming_buffers const& other) ->
     return *this;
 }
 
-template<class BufferSequence, class ValueType>
-consuming_buffers<BufferSequence, ValueType>::
+template<class BufferSequence>
+consuming_buffers<BufferSequence>::
 consuming_buffers(BufferSequence const& bs)
     : bs_(bs)
     , begin_(bs_.begin())
 {
-    static_assert(is_BufferSequence<BufferSequence, ValueType>::value,
-        "BufferSequence requirements not met");
+    static_assert(
+        is_BufferSequence<BufferSequence, value_type>::value,
+            "BufferSequence requirements not met");
 }
 
-template<class BufferSequence, class ValueType>
+template<class BufferSequence>
+inline
 auto
-consuming_buffers<BufferSequence, ValueType>::begin() const ->
+consuming_buffers<BufferSequence>::
+begin() const ->
     const_iterator
 {
     return const_iterator{*this, begin_};
 }
 
-template<class BufferSequence, class ValueType>
+template<class BufferSequence>
+inline
 auto
-consuming_buffers<BufferSequence, ValueType>::end() const ->
+consuming_buffers<BufferSequence>::
+end() const ->
     const_iterator
 {
     return const_iterator{*this, bs_.end()};
 }
 
-template<class BufferSequence, class ValueType>
+template<class BufferSequence>
 void
-consuming_buffers<BufferSequence, ValueType>::consume(std::size_t n)
+consuming_buffers<BufferSequence>::
+consume(std::size_t n)
 {
     using boost::asio::buffer_size;
     for(;n > 0 && begin_ != bs_.end(); ++begin_)
@@ -196,15 +207,6 @@ consuming_buffers<BufferSequence, ValueType>::consume(std::size_t n)
     }
 }
 
-template<class BufferSequence>
-consuming_buffers<BufferSequence, typename BufferSequence::value_type>
-consumed_buffers(BufferSequence const& bs, std::size_t n)
-{
-    consuming_buffers<BufferSequence> cb(bs);
-    cb.consume(n);
-    return cb;
-}
-
 } // beast
 
 #endif