Upgrade AlignedMemory to support dynamic allocations.

base/memory/aligned_memory.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // AlignedMemory is a POD type that gives you a portable way to specify static
 // or local stack data of a given alignment and size. For example, if you need
 // static storage for a class, but you want manual control over when the object
 // is constructed and destructed (you don't want static initialization and
 // destruction), use AlignedMemory:
 //
 //   static AlignedMemory<sizeof(MyClass), ALIGNOF(MyClass)> my_class;
 //
 //   // ... at runtime:
 //   new(my_class.void_data()) MyClass();
 //
 //   // ... use it:
 //   MyClass* mc = my_class.data_as<MyClass>();
 //
 //   // ... later, to destruct my_class:
 //   my_class.data_as<MyClass>()->MyClass::~MyClass();
+//
+// Alternatively, a runtime sized aligned allocation can be created:
+//
+//   float* my_array = reinterpret_cast<float*>(AlignedAlloc(size, alignment));
+//
+//   // ... later, to release the memory:
+//   AlignedFree(my_array);
+//
+// Or using scoped_ptr_malloc:
+//
+//   scoped_ptr_malloc<float, ScopedAlignedFree> my_array(
+//       reinterpret_cast<float*>(AlignedAlloc(size, alignment)));
 
 #ifndef BASE_MEMORY_ALIGNED_MEMORY_H_
 #define BASE_MEMORY_ALIGNED_MEMORY_H_
 
+#if defined(COMPILER_MSVC) || defined(OS_ANDROID)
+#include <malloc.h>
+#endif
+#include <stdlib.h>
+
+#include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
-#include "base/logging.h"
 
 namespace base {
 
 // AlignedMemory is specialized for all supported alignments.
 // Make sure we get a compiler error if someone uses an unsupported alignment.
 template <size_t Size, size_t ByteAlignment>

[Jeffrey Yasskin, 2012/07/21 20:38:49]

Could you revert the argument order flip, now that it's no longer necessary?

[DaleCurtis, 2012/07/21 22:18:41]

I already did; this is the original order.

[Jeffrey Yasskin, 2012/07/21 22:42:07]

Oops, sorry, I compared the wrong versions of the file.

 struct AlignedMemory {};
 
 #define BASE_DECL_ALIGNED_MEMORY(byte_alignment) \
     template <size_t Size> \
     class AlignedMemory<Size, byte_alignment> { \
      public: \
-      ALIGNAS(byte_alignment) uint8 data_[Size]; \
       void* void_data() { return reinterpret_cast<void*>(data_); } \
       const void* void_data() const { \
         return reinterpret_cast<const void*>(data_); \
       } \
       template<typename Type> \
       Type* data_as() { return reinterpret_cast<Type*>(void_data()); } \
       template<typename Type> \
       const Type* data_as() const { \
         return reinterpret_cast<const Type*>(void_data()); \
       } \
      private: \
+      ALIGNAS(byte_alignment) uint8 data_[Size]; \
       void* operator new(size_t); \
       void operator delete(void*); \
     }
 
 // Specialization for all alignments is required because MSVC (as of VS 2008)
 // does not understand ALIGNAS(ALIGNOF(Type)) or ALIGNAS(template_param).
 // Greater than 4096 alignment is not supported by some compilers, so 4096 is
 // the maximum specified here.
 BASE_DECL_ALIGNED_MEMORY(1);
 BASE_DECL_ALIGNED_MEMORY(2);
 BASE_DECL_ALIGNED_MEMORY(4);
 BASE_DECL_ALIGNED_MEMORY(8);
 BASE_DECL_ALIGNED_MEMORY(16);
 BASE_DECL_ALIGNED_MEMORY(32);
 BASE_DECL_ALIGNED_MEMORY(64);
 BASE_DECL_ALIGNED_MEMORY(128);
 BASE_DECL_ALIGNED_MEMORY(256);
 BASE_DECL_ALIGNED_MEMORY(512);
 BASE_DECL_ALIGNED_MEMORY(1024);
 BASE_DECL_ALIGNED_MEMORY(2048);
 BASE_DECL_ALIGNED_MEMORY(4096);
 
-}  // base
+#undef BASE_DECL_ALIGNED_MEMORY
+
+BASE_EXPORT void* AlignedAlloc(size_t size, size_t alignment);

[Jeffrey Yasskin, 2012/07/21 20:38:49]

Please make this signature match C11's aligned_alloc(), which is declared as
"void *aligned_alloc(size_t alignment, size_t size);"

[DaleCurtis, 2012/07/21 22:18:41]

I used this since it matches the original AlignedMemory order above, it seems
reasonable to keep them the same. Do you want to flip them both?

[Jeffrey Yasskin, 2012/07/21 22:42:07]

It does seem reasonable to keep them the same. Unfortunately, C++11's
aligned_storage<> and C11's aligned_alloc() picked opposite orders. Let's get a
third opinion from someone with more Chrome experience.

+
+inline void AlignedFree(void* ptr) {
+#if defined(COMPILER_MSVC)
+  _aligned_free(ptr);
+#else
+  free(ptr);
+#endif
+}
+
+// Helper class for use with scoped_ptr_malloc.
+class BASE_EXPORT ScopedAlignedFree {

[Jeffrey Yasskin, 2012/07/21 20:38:49]

This name seems awkward, but I don't have a concrete suggestion for a better
one.

[DaleCurtis, 2012/07/21 22:18:41]

AlignedFreeHelper, AlignedFreeScoper? The default one in scoped_ptr is called
ScopedPtrMallocFree, so this could be ScopedPtrAlignedFree.

[Jeffrey Yasskin, 2012/07/21 22:42:07]

ScopedPtrAlignedFree seems the least bad of those, but it is annoyingly long. No
strong opinions from me.

[DaleCurtis, 2012/07/22 00:45:40]

Changed to ScopedPtrAlignedFree for consistency with scoped_ptr.

+ public:
+  inline void operator()(void* x) const {
+    AlignedFree(x);
+  }
+};
+
+}  // namespace base
 
 #endif  // BASE_MEMORY_ALIGNED_MEMORY_H_