Add buffer_sequence_begin/end overloads for types that are convertibl…

…e to buffers.
chriskohlhoff · Oct 22, 2024 · ab3ae0e · ab3ae0e
1 parent a03e4d6
commit ab3ae0e
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Showing 2 changed files with 101 additions and 4 deletions.
diff --git a/asio/include/asio/buffer.hpp b/asio/include/asio/buffer.hpp
@@ -331,12 +331,38 @@ inline const const_buffer* buffer_sequence_begin(const ConstBuffer& b,
   return static_cast<const const_buffer*>(detail::addressof(b));
 }
 
+/// Get an iterator to the first element in a buffer sequence.
+template <typename ConvertibleToBuffer>
+inline const ConvertibleToBuffer* buffer_sequence_begin(
+    const ConvertibleToBuffer& b,
+    constraint_t<
+      !is_convertible<const ConvertibleToBuffer*, const mutable_buffer*>::value
+    > = 0,
+    constraint_t<
+      !is_convertible<const ConvertibleToBuffer*, const const_buffer*>::value
+    > = 0,
+    constraint_t<
+      is_convertible<ConvertibleToBuffer, mutable_buffer>::value
+        || is_convertible<ConvertibleToBuffer, const_buffer>::value
+    > = 0) noexcept
+{
+  return detail::addressof(b);
+}
+
 /// Get an iterator to the first element in a buffer sequence.
 template <typename C>
 inline auto buffer_sequence_begin(C& c,
     constraint_t<
       !is_convertible<const C*, const mutable_buffer*>::value
-        && !is_convertible<const C*, const const_buffer*>::value
+    > = 0,
+    constraint_t<
+      !is_convertible<const C*, const const_buffer*>::value
+    > = 0,
+    constraint_t<
+      !is_convertible<C, mutable_buffer>::value
+    > = 0,
+    constraint_t<
+      !is_convertible<C, const_buffer>::value
     > = 0) noexcept -> decltype(c.begin())
 {
   return c.begin();
@@ -347,7 +373,15 @@ template <typename C>
 inline auto buffer_sequence_begin(const C& c,
     constraint_t<
       !is_convertible<const C*, const mutable_buffer*>::value
-        && !is_convertible<const C*, const const_buffer*>::value
+    > = 0,
+    constraint_t<
+      !is_convertible<const C*, const const_buffer*>::value
+    > = 0,
+    constraint_t<
+      !is_convertible<C, mutable_buffer>::value
+    > = 0,
+    constraint_t<
+      !is_convertible<C, const_buffer>::value
     > = 0) noexcept -> decltype(c.begin())
 {
   return c.begin();
@@ -382,12 +416,38 @@ inline const const_buffer* buffer_sequence_end(const ConstBuffer& b,
   return static_cast<const const_buffer*>(detail::addressof(b)) + 1;
 }
 
+/// Get an iterator to one past the end element in a buffer sequence.
+template <typename ConvertibleToBuffer>
+inline const ConvertibleToBuffer* buffer_sequence_end(
+    const ConvertibleToBuffer& b,
+    constraint_t<
+      !is_convertible<const ConvertibleToBuffer*, const mutable_buffer*>::value
+    > = 0,
+    constraint_t<
+      !is_convertible<const ConvertibleToBuffer*, const const_buffer*>::value
+    > = 0,
+    constraint_t<
+      is_convertible<ConvertibleToBuffer, mutable_buffer>::value
+        || is_convertible<ConvertibleToBuffer, const_buffer>::value
+    > = 0) noexcept
+{
+  return detail::addressof(b) + 1;
+}
+
 /// Get an iterator to one past the end element in a buffer sequence.
 template <typename C>
 inline auto buffer_sequence_end(C& c,
     constraint_t<
       !is_convertible<const C*, const mutable_buffer*>::value
-        && !is_convertible<const C*, const const_buffer*>::value
+    > = 0,
+    constraint_t<
+      !is_convertible<const C*, const const_buffer*>::value
+    > = 0,
+    constraint_t<
+      !is_convertible<C, mutable_buffer>::value
+    > = 0,
+    constraint_t<
+      !is_convertible<C, const_buffer>::value
     > = 0) noexcept -> decltype(c.end())
 {
   return c.end();
@@ -398,7 +458,15 @@ template <typename C>
 inline auto buffer_sequence_end(const C& c,
     constraint_t<
       !is_convertible<const C*, const mutable_buffer*>::value
-        && !is_convertible<const C*, const const_buffer*>::value
+    > = 0,
+    constraint_t<
+      !is_convertible<const C*, const const_buffer*>::value
+    > = 0,
+    constraint_t<
+      !is_convertible<C, mutable_buffer>::value
+    > = 0,
+    constraint_t<
+      !is_convertible<C, const_buffer>::value
     > = 0) noexcept -> decltype(c.end())
 {
   return c.end();

diff --git a/asio/src/tests/unit/buffer.cpp b/asio/src/tests/unit/buffer.cpp
@@ -496,6 +496,17 @@ struct valid_mutable_b
   mutable_buffer* end() const { return 0; }
 };
 
+struct custom_const_buffer_sequence
+{
+  operator const_buffer() const { return const_buffer(0, 0); }
+};
+
+struct custom_mutable_buffer_sequence
+{
+  operator mutable_buffer() const { return mutable_buffer(0, 0); }
+  operator const_buffer() const { return mutable_buffer(0, 0); }
+};
+
 struct invalid_const_a
 {
   typedef int value_type;
@@ -624,6 +635,24 @@ void test()
   ASIO_CHECK(buffer_sequence_begin(b8) == b8.begin());
   ASIO_CHECK(buffer_sequence_end(b8) == b8.end());
 
+  ASIO_CHECK(is_const_buffer_sequence<
+      custom_const_buffer_sequence>::value);
+  ASIO_CHECK(!is_mutable_buffer_sequence<
+      custom_const_buffer_sequence>::value);
+
+  custom_const_buffer_sequence b11;
+  ASIO_CHECK(buffer_sequence_begin(b11) == &b11);
+  ASIO_CHECK(buffer_sequence_end(b11) == &b11 + 1);
+
+  ASIO_CHECK(is_const_buffer_sequence<
+      custom_mutable_buffer_sequence>::value);
+  ASIO_CHECK(is_mutable_buffer_sequence<
+      custom_mutable_buffer_sequence>::value);
+
+  custom_mutable_buffer_sequence b12;
+  ASIO_CHECK(buffer_sequence_begin(b12) == &b12);
+  ASIO_CHECK(buffer_sequence_end(b12) == &b12 + 1);
+
   ASIO_CHECK(!is_const_buffer_sequence<invalid_const_a>::value);
   ASIO_CHECK(!is_mutable_buffer_sequence<invalid_const_a>::value);