Expose recycling_allocator as part of public interface.

asio/include/Makefile.am

@@ -542,6 +542,7 @@ nobase_include_HEADERS = \
 	asio/read.hpp \
 	asio/read_until.hpp \
 	asio/readable_pipe.hpp \
+	asio/recycling_allocator.hpp \
 	asio/redirect_error.hpp \
 	asio/registered_buffer.hpp \
 	asio/require.hpp \

asio/include/asio.hpp

@@ -160,6 +160,7 @@
 #include "asio/read_at.hpp"
 #include "asio/read_until.hpp"
 #include "asio/readable_pipe.hpp"
+#include "asio/recycling_allocator.hpp"
 #include "asio/redirect_error.hpp"
 #include "asio/registered_buffer.hpp"
 #include "asio/require.hpp"

asio/include/asio/recycling_allocator.hpp

@@ -0,0 +1,138 @@
+//
+// recycling_allocator.hpp
+// ~~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2022 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)
+//
+
+#ifndef ASIO_RECYCLING_ALLOCATOR_HPP
+#define ASIO_RECYCLING_ALLOCATOR_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include "asio/detail/config.hpp"
+#include "asio/detail/recycling_allocator.hpp"
+
+#include "asio/detail/push_options.hpp"
+
+namespace asio {
+
+/// An allocator that caches memory blocks in thread-local storage for reuse.
+/**
+ * The @recycling_allocator uses a simple strategy where a limited number of
+ * small memory blocks are cached in thread-local storage, if the current
+ * thread is running an @c io_context or is part of a @c thread_pool.
+ */
+template <typename T>
+class recycling_allocator
+{
+public:
+  /// The type of object allocated by the recycling allocator.
+  typedef T value_type;
+
+  /// Rebind the allocator to another value_type.
+  template <typename U>
+  struct rebind
+  {
+    /// The rebound @c allocator type.
+    typedef recycling_allocator<U> other;
+  };
+
+  /// Default constructor.
+  ASIO_CONSTEXPR recycling_allocator() ASIO_NOEXCEPT
+  {
+  }
+
+  /// Converting constructor.
+  template <typename U>
+  ASIO_CONSTEXPR recycling_allocator(
+      const recycling_allocator<U>&) ASIO_NOEXCEPT
+  {
+  }
+
+  /// Equality operator. Always returns true.
+  ASIO_CONSTEXPR bool operator==(
+      const recycling_allocator&) const ASIO_NOEXCEPT
+  {
+    return true;
+  }
+
+  /// Inequality operator. Always returns false.
+  ASIO_CONSTEXPR bool operator!=(
+      const recycling_allocator&) const ASIO_NOEXCEPT
+  {
+    return false;
+  }
+
+  /// Allocate memory for the specified number of values.
+  T* allocate(std::size_t n)
+  {
+    return detail::recycling_allocator<T>().allocate(n);
+  }
+
+  /// Deallocate memory for the specified number of values.
+  void deallocate(T* p, std::size_t n)
+  {
+    detail::recycling_allocator<T>().deallocate(p, n);
+  }
+};
+
+/// A proto-allocator that caches memory blocks in thread-local storage for
+/// reuse.
+/**
+ * The @recycling_allocator uses a simple strategy where a limited number of
+ * small memory blocks are cached in thread-local storage, if the current
+ * thread is running an @c io_context or is part of a @c thread_pool.
+ */
+template <>
+class recycling_allocator<void>
+{
+public:
+  /// No values are allocated by a proto-allocator.
+  typedef void value_type;
+
+  /// Rebind the allocator to another value_type.
+  template <typename U>
+  struct rebind
+  {
+    /// The rebound @c allocator type.
+    typedef recycling_allocator<U> other;
+  };
+
+  /// Default constructor.
+  ASIO_CONSTEXPR recycling_allocator() ASIO_NOEXCEPT
+  {
+  }
+
+  /// Converting constructor.
+  template <typename U>
+  ASIO_CONSTEXPR recycling_allocator(
+      const recycling_allocator<U>&) ASIO_NOEXCEPT
+  {
+  }
+
+  /// Equality operator. Always returns true.
+  ASIO_CONSTEXPR bool operator==(
+      const recycling_allocator&) const ASIO_NOEXCEPT
+  {
+    return true;
+  }
+
+  /// Inequality operator. Always returns false.
+  ASIO_CONSTEXPR bool operator!=(
+      const recycling_allocator&) const ASIO_NOEXCEPT
+  {
+    return false;
+  }
+};
+
+} // namespace asio
+
+#include "asio/detail/pop_options.hpp"
+
+#endif // ASIO_RECYCLING_ALLOCATOR_HPP

asio/src/Makefile.msc

@@ -232,6 +232,7 @@ UNIT_TEST_EXES = \
 	tests\unit\read_at.exe \
 	tests\unit\read_until.exe \
 	tests\unit\readable_pipe.exe \
+	tests\unit\recycling_allocator.exe \
 	tests\unit\redirect_error.exe \
 	tests\unit\registered_buffer.exe \
 	tests\unit\serial_port.exe \

asio/src/doc/quickref.xml

@@ -286,6 +286,7 @@
             <member><link linkend="asio.reference.experimental__wait_for_one_error">experimental::wait_for_one_error</link></member>
             <member><link linkend="asio.reference.experimental__wait_for_one_success">experimental::wait_for_one_success</link></member>
             <member><link linkend="asio.reference.io_context__basic_executor_type">io_context::basic_executor_type</link></member>
+            <member><link linkend="asio.reference.recycling_allocator">recycling_allocator</link></member>
             <member><link linkend="asio.reference.redirect_error_t">redirect_error_t</link></member>
             <member><link linkend="asio.reference.strand">strand</link></member>
             <member><link linkend="asio.reference.thread_pool__basic_executor_type">thread_pool::basic_executor_type</link></member>