PartitionAlloc: support in-place resize of directly mapped allocation

Source/wtf/PartitionAlloc.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 553 matching lines @@
     partitionFreeWithPage(ptr, page);
     spinLockUnlock(&root->lock);
 #endif
 }
 
 ALWAYS_INLINE bool partitionBucketIsDirectMapped(PartitionBucket* bucket)
 {
     return !bucket->numSystemPagesPerSlotSpan;
 }
 
+ALWAYS_INLINE bool partitionSizeIsDirectMapped(size_t size)

[Chris Evans, 2014/03/05 07:57:04]

I think we can make this private by moving to the .cpp (see comment in test
file).

+{
+    size = partitionCookieSizeAdjustAdd(size);
+    return size > kGenericMaxBucketed && size <= kGenericMaxDirectMapped;

[Chris Evans, 2014/03/05 07:57:04]

I think the second condition is a bit subtle here. I think I prefer a direct
RELEASE_ASSERT() check against newSize in realloc itself?

+}
+
 ALWAYS_INLINE size_t partitionDirectMapSize(size_t size)
 {
     // Caller must check that the size is not above the kGenericMaxDirectMapped
     // limit before calling. This also guards against integer overflow in the
     // calculation here.
     ASSERT(size <= kGenericMaxDirectMapped);
     return (size + kSystemPageOffsetMask) & kSystemPageBaseMask;
 }
 
 ALWAYS_INLINE size_t partitionAllocActualSize(PartitionRootGeneric* root, size_t size)
@@ skipping 72 matching lines @@
 using WTF::partitionAlloc;
 using WTF::partitionFree;
 using WTF::partitionAllocGeneric;
 using WTF::partitionFreeGeneric;
 using WTF::partitionReallocGeneric;
 using WTF::partitionAllocActualSize;
 using WTF::partitionAllocSupportsGetSize;
 using WTF::partitionAllocGetSize;
 
 #endif // WTF_PartitionAlloc_h