Modify allocator_shim to support _aligned_alloc(), _aligned_free().

base/allocator/win_allocator.cc

 // Copyright (c) 2009 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.
 
 // This is a simple allocator based on the windows heap.
 
 extern "C" {
 
 HANDLE win_heap;
 
@@ skipping 29 matching lines @@
     win_heap_free(ptr);
     return NULL;
   }
   return HeapReAlloc(win_heap, 0, ptr, size);
 }
 
 size_t win_heap_msize(void* ptr) {
   return HeapSize(win_heap, 0, ptr);
 }
 
+void* win_heap_memalign(size_t alignment, size_t size) {
+  // Reserve enough space to ensure we can align and set aligned_ptr[-1] to the
+  // original allocation for use with win_heap_memalign_free() later.
+  size_t allocation_size = size + (alignment - 1) + sizeof(void*);
+
+  // Check for overflow.  Alignment and size are checked in allocator_shim.
+  DCHECK_LT(size, allocation_size);
+  DCHECK_LT(alignment, allocation_size);
+
+  void* ptr = win_heap_malloc(allocation_size);
+  char* aligned_ptr = static_cast<char*>(ptr) + sizeof(void*);
+  aligned_ptr +=
+      alignment - reinterpret_cast<uintptr_t>(aligned_ptr) & (alignment - 1);
+
+  reinterpret_cast<void**>(aligned_ptr)[-1] = ptr;
+  return aligned_ptr;
+}
+
+void win_heap_memalign_free(void* ptr) {
+  win_heap_free(static_cast<void**>(ptr)[-1]);
+}
+
 }  // extern "C"