text: /*
   * 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
   * copyright notice, this list of conditions and the following disclaimer
   * in the documentation and/or other materials provided with the
   * distribution.
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   * contributors may be used to endorse or promote products derived from
   * this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #ifndef SKY_ENGINE_WTF_PARTITIONALLOC_H_
  #define SKY_ENGINE_WTF_PARTITIONALLOC_H_
  
  // DESCRIPTION
  // partitionAlloc() / partitionAllocGeneric() and partitionFree() /
  // partitionFreeGeneric() are approximately analagous to malloc() and free().
  //
  // The main difference is that a PartitionRoot / PartitionRootGeneric object
  // must be supplied to these functions, representing a specific "heap partition"
  // that will be used to satisfy the allocation. Different partitions are
  // guaranteed to exist in separate address spaces, including being separate from
  // the main system heap. If the contained objects are all freed, physical memory
  // is returned to the system but the address space remains reserved.
  //
  // THE ONLY LEGITIMATE WAY TO OBTAIN A PartitionRoot IS THROUGH THE
  // SizeSpecificPartitionAllocator / PartitionAllocatorGeneric classes. To
  // minimize the instruction count to the fullest extent possible, the
  // PartitonRoot is really just a header adjacent to other data areas provided
  // by the allocator class.
  //
  // The partitionAlloc() variant of the API has the following caveats:
  // - Allocations and frees against a single partition must be single threaded.
  // - Allocations must not exceed a max size, chosen at compile-time via a
  // templated parameter to PartitionAllocator.
  // - Allocation sizes must be aligned to the system pointer size.
  // - Allocations are bucketed exactly according to size.
  //
  // And for partitionAllocGeneric():
  // - Multi-threaded use against a single partition is ok; locking is handled.
  // - Allocations of any arbitrary size can be handled (subject to a limit of
  // INT_MAX bytes for security reasons).
  // - Bucketing is by approximate size, for example an allocation of 4000 bytes
  // might be placed into a 4096-byte bucket. Bucket sizes are chosen to try and
  // keep worst-case waste to ~10%.
  //
  // The allocators are designed to be extremely fast, thanks to the following
  // properties and design:
  // - Just a single (reasonably predicatable) branch in the hot / fast path for
  // both allocating and (significantly) freeing.
  // - A minimal number of operations in the hot / fast path, with the slow paths
  // in separate functions, leading to the possibility of inlining.
  // - Each partition page (which is usually multiple physical pages) has a
  // metadata structure which allows fast mapping of free() address to an
  // underlying bucket.
  // - Supports a lock-free API for fast performance in single-threaded cases.
  // - The freelist for a given bucket is split across a number of partition
  // pages, enabling various simple tricks to try and minimize fragmentation.
  // - Fine-grained bucket sizes leading to less waste and better packing.
  //
  // The following security properties are provided at this time:
  // - Linear overflows cannot corrupt into the partition.
  // - Linear overflows cannot corrupt out of the partition.
  // - Freed pages will only be re-used within the partition.
  //   (exception: large allocations > ~1MB)
  // - Freed pages will only hold same-sized objects when re-used.
  // - Dereference of freelist pointer should fault.
  // - Out-of-line main metadata: linear over or underflow cannot corrupt it.
  // - Partial pointer overwrite of freelist pointer should fault.
  // - Rudimentary double-free detection.
  // - Large allocations (> ~1MB) are guard-paged at the beginning and end.
  //
  // The following security properties could be investigated in the future:
  // - Per-object bucketing (instead of per-size) is mostly available at the API,
  // but not used yet.
  // - No randomness of freelist entries or bucket position.
  // - Better checking for wild pointers in free().
  // - Better freelist masking function to guarantee fault on 32-bit.
  
  #include "sky/engine/wtf/Assertions.h"
  #include "sky/engine/wtf/BitwiseOperations.h"
  #include "sky/engine/wtf/ByteSwap.h"
  #include "sky/engine/wtf/CPU.h"
  #include "sky/engine/wtf/PageAllocator.h"
  #include "sky/engine/wtf/SpinLock.h"
  
  #include <limits.h>
  
  #if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
  #include <stdlib.h>
  #endif
  
  #if ENABLE(ASSERT)
  #include <string.h>
  #endif
  
  namespace WTF {
  
  // Maximum size of a partition's mappings. 2046MB. Note that the total amount of
  // bytes allocatable at the API will be smaller. This is because things like
  // guard pages, metadata, page headers and wasted space come out of the total.
  // The 2GB is not necessarily contiguous in virtual address space.
  static const size_t kMaxPartitionSize = 2046u * 1024u * 1024u;
  
  // Allocation granularity of sizeof(void*) bytes.
  static const size_t kAllocationGranularity = sizeof(void*);
  static const size_t kAllocationGranularityMask = kAllocationGranularity - 1;
  static const size_t kBucketShift = (kAllocationGranularity == 8) ? 3 : 2;
  
  // Underlying partition storage pages are a power-of-two size. It is typical
  // for a partition page to be based on multiple system pages. Most references to
  // "page" refer to partition pages.
  // We also have the concept of "super pages" -- these are the underlying system
  // allocations we make. Super pages contain multiple partition pages inside them
  // and include space for a small amount of metadata per partition page.
  // Inside super pages, we store "slot spans". A slot span is a continguous range
  // of one or more partition pages that stores allocations of the same size.
  // Slot span sizes are adjusted depending on the allocation size, to make sure
  // the packing does not lead to unused (wasted) space at the end of the last
  // system page of the span. For our current max slot span size of 64k and other
  // constant values, we pack _all_ partitionAllocGeneric() sizes perfectly up
  // against the end of a system page.
  static const size_t kPartitionPageShift = 14; // 16KB
  static const size_t kPartitionPageSize = 1 << kPartitionPageShift;
  static const size_t kPartitionPageOffsetMask = kPartitionPageSize - 1;
  static const size_t kPartitionPageBaseMask = ~kPartitionPageOffsetMask;
  static const size_t kMaxPartitionPagesPerSlotSpan = 4;
  
  // To avoid fragmentation via never-used freelist entries, we hand out partition
  // freelist sections gradually, in units of the dominant system page size.
  // What we're actually doing is avoiding filling the full partition page
  // (typically 16KB) will freelist pointers right away. Writing freelist
  // pointers will fault and dirty a private page, which is very wasteful if we
  // never actually store objects there.
  static const size_t kNumSystemPagesPerPartitionPage = kPartitionPageSize / kSystemPageSize;
  static const size_t kMaxSystemPagesPerSlotSpan = kNumSystemPagesPerPartitionPage * kMaxPartitionPagesPerSlotSpan;
  
  // We reserve virtual address space in 2MB chunks (aligned to 2MB as well).
  // These chunks are called "super pages". We do this so that we can store
  // metadata in the first few pages of each 2MB aligned section. This leads to
  // a very fast free(). We specifically choose 2MB because this virtual address
  // block represents a full but single PTE allocation on ARM, ia32 and x64.
  static const size_t kSuperPageShift = 21; // 2MB
  static const size_t kSuperPageSize = 1 << kSuperPageShift;
  static const size_t kSuperPageOffsetMask = kSuperPageSize - 1;
  static const size_t kSuperPageBaseMask = ~kSuperPageOffsetMask;
  static const size_t kNumPartitionPagesPerSuperPage = kSuperPageSize / kPartitionPageSize;
  
  static const size_t kPageMetadataShift = 5; // 32 bytes per partition page.
  static const size_t kPageMetadataSize = 1 << kPageMetadataShift;
  
  // The following kGeneric* constants apply to the generic variants of the API.
  // The "order" of an allocation is closely related to the power-of-two size of
  // the allocation. More precisely, the order is the bit index of the
  // most-significant-bit in the allocation size, where the bit numbers starts
  // at index 1 for the least-significant-bit.
  // In terms of allocation sizes, order 0 covers 0, order 1 covers 1, order 2
  // covers 2->3, order 3 covers 4->7, order 4 covers 8->15.
  static const size_t kGenericMinBucketedOrder = 4; // 8 bytes.
  static const size_t kGenericMaxBucketedOrder = 20; // Largest bucketed order is 1<<(20-1) (storing 512KB -> almost 1MB)
  static const size_t kGenericNumBucketedOrders = (kGenericMaxBucketedOrder - kGenericMinBucketedOrder) + 1;
  static const size_t kGenericNumBucketsPerOrderBits = 3; // Eight buckets per order (for the higher orders), e.g. order 8 is 128, 144, 160, ..., 240
  static const size_t kGenericNumBucketsPerOrder = 1 << kGenericNumBucketsPerOrderBits;
  static const size_t kGenericSmallestBucket = 1 << (kGenericMinBucketedOrder - 1);
  static const size_t kGenericMaxBucketSpacing = 1 << ((kGenericMaxBucketedOrder - 1) - kGenericNumBucketsPerOrderBits);
  static const size_t kGenericMaxBucketed = (1 << (kGenericMaxBucketedOrder - 1)) + ((kGenericNumBucketsPerOrder - 1) * kGenericMaxBucketSpacing);
  static const size_t kGenericMinDirectMappedDownsize = kGenericMaxBucketed + 1; // Limit when downsizing a direct mapping using realloc().
  static const size_t kGenericMaxDirectMapped = INT_MAX - kSystemPageSize;
  static const size_t kBitsPerSizet = sizeof(void*) * CHAR_BIT;
  
  // Constants for the memory reclaim logic.
  static const size_t kMaxFreeableSpans = 16;
  
  #if ENABLE(ASSERT)
  // These two byte values match tcmalloc.
  static const unsigned char kUninitializedByte = 0xAB;
  static const unsigned char kFreedByte = 0xCD;
  static const uint32_t kCookieValue = 0xDEADBEEFu;
  static const size_t kCookieSize = 16; // Handles alignment up to XMM instructions on Intel.
  #endif
  
  struct PartitionBucket;
  struct PartitionRootBase;
  
  struct PartitionFreelistEntry {
      PartitionFreelistEntry* next;
  };
  
  // Some notes on page states. A page can be in one of three major states:
  // 1) Active.
  // 2) Full.
  // 3) Free.
  // An active page has available free slots. A full page has no free slots. A
  // free page has had its backing memory released back to the system.
  // There are two linked lists tracking the pages. The "active page" list is an
  // approximation of a list of active pages. It is an approximation because both
  // free and full pages may briefly be present in the list until we next do a
  // scan over it. The "free page" list is an accurate list of pages which have
  // been returned back to the system.
  // The significant page transitions are:
  // - free() will detect when a full page has a slot free()'d and immediately
  // return the page to the head of the active list.
  // - free() will detect when a page is fully emptied. It _may_ add it to the
  // free list and it _may_ leave it on the active list until a future list scan.
  // - malloc() _may_ scan the active page list in order to fulfil the request.
  // If it does this, full and free pages encountered will be booted out of the
  // active list. If there are no suitable active pages found, a free page (if one
  // exists) will be pulled from the free list on to the active list.
  struct PartitionPage {
      PartitionFreelistEntry* freelistHead;
      PartitionPage* nextPage;
      PartitionBucket* bucket;
      int16_t numAllocatedSlots; // Deliberately signed, -1 for free page, -n for full pages.
      uint16_t numUnprovisionedSlots;
      uint16_t pageOffset;
      int16_t freeCacheIndex; // -1 if not in the free cache.
  };
  
  struct PartitionBucket {
      PartitionPage* activePagesHead; // Accessed most in hot path => goes first.
      PartitionPage* freePagesHead;
      uint32_t slotSize;
      uint16_t numSystemPagesPerSlotSpan;
      uint16_t numFullPages;
  };
  
  // An "extent" is a span of consecutive superpages. We link to the partition's
  // next extent (if there is one) at the very start of a superpage's metadata
  // area.
  struct PartitionSuperPageExtentEntry {
      PartitionRootBase* root;
      char* superPageBase;
      char* superPagesEnd;
      PartitionSuperPageExtentEntry* next;
  };
  
  struct WTF_EXPORT PartitionRootBase {
      size_t totalSizeOfCommittedPages;
      size_t totalSizeOfSuperPages;
      unsigned numBuckets;
      unsigned maxAllocation;
      bool initialized;
      char* nextSuperPage;
      char* nextPartitionPage;
      char* nextPartitionPageEnd;
      PartitionSuperPageExtentEntry* currentExtent;
      PartitionSuperPageExtentEntry* firstExtent;
      PartitionPage* globalEmptyPageRing[kMaxFreeableSpans];
      size_t globalEmptyPageRingIndex;
      uintptr_t invertedSelf;
  
      static int gInitializedLock;
      static bool gInitialized;
      static PartitionPage gSeedPage;
      static PartitionBucket gPagedBucket;
  };
  
  // Never instantiate a PartitionRoot directly, instead use PartitionAlloc.
  struct PartitionRoot : public PartitionRootBase {
      // The PartitionAlloc templated class ensures the following is correct.
      ALWAYS_INLINE PartitionBucket* buckets() { return reinterpret_cast<PartitionBucket*>(this + 1); }
      ALWAYS_INLINE const PartitionBucket* buckets() const { return reinterpret_cast<const PartitionBucket*>(this + 1); }
  };
  
  // Never instantiate a PartitionRootGeneric directly, instead use PartitionAllocatorGeneric.
  struct PartitionRootGeneric : public PartitionRootBase {
      int lock;
      // Some pre-computed constants.
      size_t orderIndexShifts[kBitsPerSizet + 1];
      size_t orderSubIndexMasks[kBitsPerSizet + 1];
      // The bucket lookup table lets us map a size_t to a bucket quickly.
      // The trailing +1 caters for the overflow case for very large allocation sizes.
      // It is one flat array instead of a 2D array because in the 2D world, we'd
      // need to index array[blah][max+1] which risks undefined behavior.
      PartitionBucket* bucketLookups[((kBitsPerSizet + 1) * kGenericNumBucketsPerOrder) + 1];
      PartitionBucket buckets[kGenericNumBucketedOrders * kGenericNumBucketsPerOrder];
  };
  
  // Flags for partitionAllocGenericFlags.
  enum PartitionAllocFlags {
      PartitionAllocReturnNull = 1 << 0,
  };
  
  WTF_EXPORT void partitionAllocInit(PartitionRoot*, size_t numBuckets, size_t maxAllocation);
  WTF_EXPORT bool partitionAllocShutdown(PartitionRoot*);
  WTF_EXPORT void partitionAllocGenericInit(PartitionRootGeneric*);
  WTF_EXPORT bool partitionAllocGenericShutdown(PartitionRootGeneric*);
  
  WTF_EXPORT NEVER_INLINE void* partitionAllocSlowPath(PartitionRootBase*, int, size_t, PartitionBucket*);
  WTF_EXPORT NEVER_INLINE void partitionFreeSlowPath(PartitionPage*);
  WTF_EXPORT NEVER_INLINE void* partitionReallocGeneric(PartitionRootGeneric*, void*, size_t);
  
  #ifndef NDEBUG
  WTF_EXPORT void partitionDumpStats(const PartitionRoot&);
  #endif
  
  ALWAYS_INLINE PartitionFreelistEntry* partitionFreelistMask(PartitionFreelistEntry* ptr)
  {
      // We use bswap on little endian as a fast mask for two reasons:
      // 1) If an object is freed and its vtable used where the attacker doesn't
      // get the chance to run allocations between the free and use, the vtable
      // dereference is likely to fault.
      // 2) If the attacker has a linear buffer overflow and elects to try and
      // corrupt a freelist pointer, partial pointer overwrite attacks are
      // thwarted.
      // For big endian, similar guarantees are arrived at with a negation.
  #if CPU(BIG_ENDIAN)
      uintptr_t masked = ~reinterpret_cast<uintptr_t>(ptr);
  #else
      uintptr_t masked = bswapuintptrt(reinterpret_cast<uintptr_t>(ptr));
  #endif
      return reinterpret_cast<PartitionFreelistEntry*>(masked);
  }
  
  ALWAYS_INLINE size_t partitionCookieSizeAdjustAdd(size_t size)
  {
  #if ENABLE(ASSERT)
      // Add space for cookies, checking for integer overflow.
      ASSERT(size + (2 * kCookieSize) > size);
      size += 2 * kCookieSize;
  #endif
      return size;
  }
  
  ALWAYS_INLINE size_t partitionCookieSizeAdjustSubtract(size_t size)
  {
  #if ENABLE(ASSERT)
      // Remove space for cookies.
      ASSERT(size >= 2 * kCookieSize);
      size -= 2 * kCookieSize;
  #endif
      return size;
  }
  
  ALWAYS_INLINE void* partitionCookieFreePointerAdjust(void* ptr)
  {
  #if ENABLE(ASSERT)
      // The value given to the application is actually just after the cookie.
      ptr = static_cast<char*>(ptr) - kCookieSize;
  #endif
      return ptr;
  }
  
  ALWAYS_INLINE void partitionCookieWriteValue(void* ptr)
  {
  #if ENABLE(ASSERT)
      uint32_t* cookiePtr = reinterpret_cast<uint32_t*>(ptr);
      for (size_t i = 0; i < kCookieSize / sizeof(kCookieValue); ++i, ++cookiePtr)
          *cookiePtr = kCookieValue;
  #endif
  }
  
  ALWAYS_INLINE void partitionCookieCheckValue(void* ptr)
  {
  #if ENABLE(ASSERT)
      uint32_t* cookiePtr = reinterpret_cast<uint32_t*>(ptr);
      for (size_t i = 0; i < kCookieSize / sizeof(kCookieValue); ++i, ++cookiePtr)
          ASSERT(*cookiePtr == kCookieValue);
  #endif
  }
  
  ALWAYS_INLINE char* partitionSuperPageToMetadataArea(char* ptr)
  {
      uintptr_t pointerAsUint = reinterpret_cast<uintptr_t>(ptr);
      ASSERT(!(pointerAsUint & kSuperPageOffsetMask));
      // The metadata area is exactly one system page (the guard page) into the
      // super page.
      return reinterpret_cast<char*>(pointerAsUint + kSystemPageSize);
  }
  
  ALWAYS_INLINE PartitionPage* partitionPointerToPageNoAlignmentCheck(void* ptr)
  {
      uintptr_t pointerAsUint = reinterpret_cast<uintptr_t>(ptr);
      char* superPagePtr = reinterpret_cast<char*>(pointerAsUint & kSuperPageBaseMask);
      uintptr_t partitionPageIndex = (pointerAsUint & kSuperPageOffsetMask) >> kPartitionPageShift;
      // Index 0 is invalid because it is the metadata area and the last index is invalid because it is a guard page.
      ASSERT(partitionPageIndex);
      ASSERT(partitionPageIndex < kNumPartitionPagesPerSuperPage - 1);
      PartitionPage* page = reinterpret_cast<PartitionPage*>(partitionSuperPageToMetadataArea(superPagePtr) + (partitionPageIndex << kPageMetadataShift));
      // Many partition pages can share the same page object. Adjust for that.
      size_t delta = page->pageOffset << kPageMetadataShift;
      page = reinterpret_cast<PartitionPage*>(reinterpret_cast<char*>(page) - delta);
      return page;
  }
  
  ALWAYS_INLINE void* partitionPageToPointer(PartitionPage* page)
  {
      uintptr_t pointerAsUint = reinterpret_cast<uintptr_t>(page);
      uintptr_t superPageOffset = (pointerAsUint & kSuperPageOffsetMask);
      ASSERT(superPageOffset > kSystemPageSize);
      ASSERT(superPageOffset < kSystemPageSize + (kNumPartitionPagesPerSuperPage * kPageMetadataSize));
      uintptr_t partitionPageIndex = (superPageOffset - kSystemPageSize) >> kPageMetadataShift;
      // Index 0 is invalid because it is the metadata area and the last index is invalid because it is a guard page.
      ASSERT(partitionPageIndex);
      ASSERT(partitionPageIndex < kNumPartitionPagesPerSuperPage - 1);
      uintptr_t superPageBase = (pointerAsUint & kSuperPageBaseMask);
      void* ret = reinterpret_cast<void*>(superPageBase + (partitionPageIndex << kPartitionPageShift));
      return ret;
  }
  
  ALWAYS_INLINE PartitionPage* partitionPointerToPage(void* ptr)
  {
      PartitionPage* page = partitionPointerToPageNoAlignmentCheck(ptr);
      // Checks that the pointer is a multiple of bucket size.
      ASSERT(!((reinterpret_cast<uintptr_t>(ptr) - reinterpret_cast<uintptr_t>(partitionPageToPointer(page))) % page->bucket->slotSize));
      return page;
  }
  
  ALWAYS_INLINE PartitionRootBase* partitionPageToRoot(PartitionPage* page)
  {
      PartitionSuperPageExtentEntry* extentEntry = reinterpret_cast<PartitionSuperPageExtentEntry*>(reinterpret_cast<uintptr_t>(page) & kSystemPageBaseMask);
      return extentEntry->root;
  }
  
  ALWAYS_INLINE bool partitionPointerIsValid(void* ptr)
  {
      PartitionPage* page = partitionPointerToPage(ptr);
      PartitionRootBase* root = partitionPageToRoot(page);
      return root->invertedSelf == ~reinterpret_cast<uintptr_t>(root);
  }
  
  ALWAYS_INLINE void* partitionBucketAlloc(PartitionRootBase* root, int flags, size_t size, PartitionBucket* bucket)
  {
      PartitionPage* page = bucket->activePagesHead;
      ASSERT(page->numAllocatedSlots >= 0);
      void* ret = page->freelistHead;
      if (LIKELY(ret != 0)) {
          // If these asserts fire, you probably corrupted memory.
          ASSERT(partitionPointerIsValid(ret));
          PartitionFreelistEntry* newHead = partitionFreelistMask(static_cast<PartitionFreelistEntry*>(ret)->next);
          page->freelistHead = newHead;
          ASSERT(!ret || partitionPointerIsValid(ret));
          page->numAllocatedSlots++;
      } else {
          ret = partitionAllocSlowPath(root, flags, size, bucket);
      }
  #if ENABLE(ASSERT)
      if (!ret)
          return 0;
      // Fill the uninitialized pattern. and write the cookies.
      page = partitionPointerToPage(ret);
      size_t bucketSize = page->bucket->slotSize;
      memset(ret, kUninitializedByte, bucketSize);
      partitionCookieWriteValue(ret);
      partitionCookieWriteValue(reinterpret_cast<char*>(ret) + bucketSize - kCookieSize);
      // The value given to the application is actually just after the cookie.
      ret = static_cast<char*>(ret) + kCookieSize;
  #endif
      return ret;
  }
  
  ALWAYS_INLINE void* partitionAlloc(PartitionRoot* root, size_t size)
  {
  #if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
      void* result = malloc(size);
      RELEASE_ASSERT(result);
      return result;
  #else
      size = partitionCookieSizeAdjustAdd(size);
      ASSERT(root->initialized);
      size_t index = size >> kBucketShift;
      ASSERT(index < root->numBuckets);
      ASSERT(size == index << kBucketShift);
      PartitionBucket* bucket = &root->buckets()[index];
      return partitionBucketAlloc(root, 0, size, bucket);
  #endif // defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
  }
  
  ALWAYS_INLINE void partitionFreeWithPage(void* ptr, PartitionPage* page)
  {
      // If these asserts fire, you probably corrupted memory.
  #if ENABLE(ASSERT)
      size_t bucketSize = page->bucket->slotSize;
      partitionCookieCheckValue(ptr);
      partitionCookieCheckValue(reinterpret_cast<char*>(ptr) + bucketSize - kCookieSize);
      memset(ptr, kFreedByte, bucketSize);
  #endif
      ASSERT(page->numAllocatedSlots);
      PartitionFreelistEntry* freelistHead = page->freelistHead;
      ASSERT(!freelistHead || partitionPointerIsValid(freelistHead));
      RELEASE_ASSERT(ptr != freelistHead); // Catches an immediate double free.
      ASSERT(!freelistHead || ptr != partitionFreelistMask(freelistHead->next)); // Look for double free one level deeper in debug.
      PartitionFreelistEntry* entry = static_cast<PartitionFreelistEntry*>(ptr);
      entry->next = partitionFreelistMask(freelistHead);
      page->freelistHead = entry;
      --page->numAllocatedSlots;
      if (UNLIKELY(page->numAllocatedSlots <= 0))
          partitionFreeSlowPath(page);
  }
  
  ALWAYS_INLINE void partitionFree(void* ptr)
  {
  #if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
      free(ptr);
  #else
      ptr = partitionCookieFreePointerAdjust(ptr);
      ASSERT(partitionPointerIsValid(ptr));
      PartitionPage* page = partitionPointerToPage(ptr);
      partitionFreeWithPage(ptr, page);
  #endif
  }
  
  ALWAYS_INLINE PartitionBucket* partitionGenericSizeToBucket(PartitionRootGeneric* root, size_t size)
  {
      size_t order = kBitsPerSizet - countLeadingZerosSizet(size);
      // The order index is simply the next few bits after the most significant bit.
      size_t orderIndex = (size >> root->orderIndexShifts[order]) & (kGenericNumBucketsPerOrder - 1);
      // And if the remaining bits are non-zero we must bump the bucket up.
      size_t subOrderIndex = size & root->orderSubIndexMasks[order];
      PartitionBucket* bucket = root->bucketLookups[(order << kGenericNumBucketsPerOrderBits) + orderIndex + !!subOrderIndex];
      ASSERT(!bucket->slotSize || bucket->slotSize >= size);
      ASSERT(!(bucket->slotSize % kGenericSmallestBucket));
      return bucket;
  }
  
  ALWAYS_INLINE void* partitionAllocGenericFlags(PartitionRootGeneric* root, int flags, size_t size)
  {
  #if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
      void* result = malloc(size);
      RELEASE_ASSERT(result);
      return result;
  #else
      ASSERT(root->initialized);
      size = partitionCookieSizeAdjustAdd(size);
      PartitionBucket* bucket = partitionGenericSizeToBucket(root, size);
      spinLockLock(&root->lock);
      void* ret = partitionBucketAlloc(root, flags, size, bucket);
      spinLockUnlock(&root->lock);
      return ret;
  #endif
  }
  
  ALWAYS_INLINE void* partitionAllocGeneric(PartitionRootGeneric* root, size_t size)
  {
      return partitionAllocGenericFlags(root, 0, size);
  }
  
  ALWAYS_INLINE void partitionFreeGeneric(PartitionRootGeneric* root, void* ptr)
  {
  #if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
      free(ptr);
  #else
      ASSERT(root->initialized);
  
      if (UNLIKELY(!ptr))
          return;
  
      ptr = partitionCookieFreePointerAdjust(ptr);
      ASSERT(partitionPointerIsValid(ptr));
      PartitionPage* page = partitionPointerToPage(ptr);
      spinLockLock(&root->lock);
      partitionFreeWithPage(ptr, page);
      spinLockUnlock(&root->lock);
  #endif
  }
  
  ALWAYS_INLINE bool partitionBucketIsDirectMapped(PartitionBucket* bucket)
  {
      return !bucket->numSystemPagesPerSlotSpan;
  }
  
  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)
  {
  #if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
      return size;
  #else
      ASSERT(root->initialized);
      size = partitionCookieSizeAdjustAdd(size);
      PartitionBucket* bucket = partitionGenericSizeToBucket(root, size);
      if (LIKELY(!partitionBucketIsDirectMapped(bucket))) {
          size = bucket->slotSize;
      } else if (size > kGenericMaxDirectMapped) {
          // Too large to allocate => return the size unchanged.
      } else {
          ASSERT(bucket == &PartitionRootBase::gPagedBucket);
          size = partitionDirectMapSize(size);
      }
      return partitionCookieSizeAdjustSubtract(size);
  #endif
  }
  
  ALWAYS_INLINE bool partitionAllocSupportsGetSize()
  {
  #if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
      return false;
  #else
      return true;
  #endif
  }
  
  ALWAYS_INLINE size_t partitionAllocGetSize(void* ptr)
  {
      // No need to lock here. Only 'ptr' being freed by another thread could
      // cause trouble, and the caller is responsible for that not happening.
      ASSERT(partitionAllocSupportsGetSize());
      ptr = partitionCookieFreePointerAdjust(ptr);
      ASSERT(partitionPointerIsValid(ptr));
      PartitionPage* page = partitionPointerToPage(ptr);
      size_t size = page->bucket->slotSize;
      return partitionCookieSizeAdjustSubtract(size);
  }
  
  // N (or more accurately, N - sizeof(void*)) represents the largest size in
  // bytes that will be handled by a SizeSpecificPartitionAllocator.
  // Attempts to partitionAlloc() more than this amount will fail.
  template <size_t N>
  class SizeSpecificPartitionAllocator {
  public:
      static const size_t kMaxAllocation = N - kAllocationGranularity;
      static const size_t kNumBuckets = N / kAllocationGranularity;
      void init() { partitionAllocInit(&m_partitionRoot, kNumBuckets, kMaxAllocation); }
      bool shutdown() { return partitionAllocShutdown(&m_partitionRoot); }
      ALWAYS_INLINE PartitionRoot* root() { return &m_partitionRoot; }
  private:
      PartitionRoot m_partitionRoot;
      PartitionBucket m_actualBuckets[kNumBuckets];
  };
  
  class PartitionAllocatorGeneric {
  public:
      void init() { partitionAllocGenericInit(&m_partitionRoot); }
      bool shutdown() { return partitionAllocGenericShutdown(&m_partitionRoot); }
      ALWAYS_INLINE PartitionRootGeneric* root() { return &m_partitionRoot; }
  private:
      PartitionRootGeneric m_partitionRoot;
  };
  
  } // namespace WTF
  
  using WTF::SizeSpecificPartitionAllocator;
  using WTF::PartitionAllocatorGeneric;
  using WTF::PartitionRoot;
  using WTF::partitionAllocInit;
  using WTF::partitionAllocShutdown;
  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  // SKY_ENGINE_WTF_PARTITIONALLOC_H_
  