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.

CHANGELOG.md

@@ -4,6 +4,7 @@
 * Improvements to code coverage
 * Use boost::lexical_cast instead of std::to_string
 * Fix prepare_buffers value_type
+* Fix consuming_buffers value_type
 
 HTTP
 
@@ -21,6 +22,7 @@ API Changes:
 
 * Refactor message and message_headers declarations
 * prepared_buffers is private
+* consume_buffers is removed
 
 --------------------------------------------------------------------------------
 

doc/quickref.xml

@@ -177,7 +177,6 @@
           <simplelist type="vert" columns="1">
             <member><link linkend="beast.ref.bind_handler">bind_handler</link></member>
             <member><link linkend="beast.ref.buffer_cat">buffer_cat</link></member>
-            <member><link linkend="beast.ref.consumed_buffers">consumed_buffers</link></member>
             <member><link linkend="beast.ref.prepare_buffer">prepare_buffer</link></member>
             <member><link linkend="beast.ref.prepare_buffers">prepare_buffers</link></member>
             <member><link linkend="beast.ref.to_string">to_string</link></member>

include/beast/core/consuming_buffers.hpp

@@ -37,20 +37,12 @@ namespace beast {
     consumable `ConstBufferSequence`. Violations of buffer const safety
     are not permitted, and will result in a compile error.
 */
-template<class BufferSequence,
-    class ValueType = typename BufferSequence::value_type>
+template<class BufferSequence>
 class consuming_buffers
 {
     using iter_type =
         typename BufferSequence::const_iterator;
 
-    static_assert(is_BufferSequence<BufferSequence, ValueType>::value,
-        "BufferSequence requirements not met");
-
-    static_assert(std::is_constructible<ValueType,
-        typename std::iterator_traits<iter_type>::value_type>::value,
-            "ValueType requirements not met");
-
     BufferSequence bs_;
     iter_type begin_;
     std::size_t skip_ = 0;
@@ -65,7 +57,12 @@ class consuming_buffers
 
 public:
     /// The type for each element in the list of buffers.
-    using value_type = ValueType;
+    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;
 
 #if GENERATING_DOCS
     /// A bidirectional iterator type that may be used to read elements.
@@ -100,7 +97,7 @@ public:
     const_iterator
     begin() const;
 
-    /// Get a bidirectional iterator for one past the last element.
+    /// Get a bidirectional iterator to one past the last element.
     const_iterator
     end() const;
 
@@ -114,25 +111,6 @@ public:
     consume(std::size_t n);
 };
 
-/** Returns a new, consumed buffer sequence.
-
-    This function returns a new buffer sequence which when iterated,
-    efficiently represents the portion of the original buffer sequence
-    with `n` bytes removed from the beginning.
-
-    Copies will be made of the buffer sequence passed, but ownership
-    of the underlying memory is not transferred.
-
-    @param buffers The buffer sequence to consume.
-
-    @param n The number of bytes to remove from the front. If this is
-    larger than the size of the buffer sequence, an empty buffer sequence
-    is returned.
-*/
-template<class BufferSequence>
-consuming_buffers<BufferSequence, typename BufferSequence::value_type>
-consumed_buffers(BufferSequence const& buffers, std::size_t n);
-
 } // beast
 
 #include <beast/core/impl/consuming_buffers.ipp>

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

test/core/consuming_buffers.cpp

@@ -19,6 +19,16 @@ namespace beast {
 class consuming_buffers_test : public beast::unit_test::suite
 {
 public:
+    template<class BufferSequence>
+    static
+    consuming_buffers<BufferSequence>
+    consumed_buffers(BufferSequence const& bs, std::size_t n)
+    {
+        consuming_buffers<BufferSequence> cb(bs);
+        cb.consume(n);
+        return cb;
+    }
+
     template<class Buffers1, class Buffers2>
     static
     bool

test/websocket/utf8_checker.cpp

@@ -283,10 +283,10 @@ public:
             {
                 static std::size_t constexpr size = 3;
                 std::size_t n = s.size();
-                auto cb = consumed_buffers(
-                    boost::asio::const_buffers_1(
-                        s.data(), n), 0);
-                streambuf sb(size);
+                consuming_buffers<
+                    boost::asio::const_buffers_1> cb{
+                        boost::asio::const_buffers_1(s.data(), n)};
+                streambuf sb{size};
                 while(n)
                 {
                     auto const amount = (std::min)(n, size);