memory/volatile/VolatileBufferWindows.cpp

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #include "VolatileBuffer.h"
   6 #include "mozilla/Assertions.h"
   7 #include "mozilla/DebugOnly.h"
   8 #include "mozilla/mozalloc.h"
   9
  10 #include <windows.h>
  11
  12 #ifdef MOZ_MEMORY
  13 extern "C" int posix_memalign(void** memptr, size_t alignment, size_t size);
  14 #endif
  15
  16 #ifndef MEM_RESET_UNDO
  17 #  define MEM_RESET_UNDO 0x1000000
  18 #endif
  19
  20 #define MIN_VOLATILE_ALLOC_SIZE 8192
  21
  22 namespace mozilla {
  23
  24 VolatileBuffer::VolatileBuffer()
  25     : mMutex("VolatileBuffer"),
  26       mBuf(nullptr),
  27       mSize(0),
  28       mLockCount(0),
  29       mHeap(false),
  30       mFirstLock(true) {}
  31
  32 bool VolatileBuffer::Init(size_t aSize, size_t aAlignment) {
  33   MOZ_ASSERT(!mSize && !mBuf, "Init called twice");
  34   MOZ_ASSERT(!(aAlignment % sizeof(void*)),
  35              "Alignment must be multiple of pointer size");
  36
  37   mSize = aSize;
  38   if (aSize < MIN_VOLATILE_ALLOC_SIZE) {
  39     goto heap_alloc;
  40   }
  41
  42   mBuf = VirtualAllocEx(GetCurrentProcess(), nullptr, mSize,
  43                         MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
  44   if (mBuf) {
  45     return true;
  46   }
  47
  48 heap_alloc:
  49 #ifdef MOZ_MEMORY
  50   posix_memalign(&mBuf, aAlignment, aSize);
  51 #else
  52   mBuf = _aligned_malloc(aSize, aAlignment);
  53 #endif
  54   mHeap = true;
  55   return !!mBuf;
  56 }
  57
  58 VolatileBuffer::~VolatileBuffer() {
  59   MOZ_ASSERT(mLockCount == 0, "Being destroyed with non-zero lock count?");
  60
  61   if (OnHeap()) {
  62 #ifdef MOZ_MEMORY
  63     free(mBuf);
  64 #else
  65     _aligned_free(mBuf);
  66 #endif
  67   } else {
  68     VirtualFreeEx(GetCurrentProcess(), mBuf, 0, MEM_RELEASE);
  69   }
  70 }
  71
  72 bool VolatileBuffer::Lock(void** aBuf) {
  73   MutexAutoLock lock(mMutex);
  74
  75   MOZ_ASSERT(mBuf, "Attempting to lock an uninitialized VolatileBuffer");
  76
  77   *aBuf = mBuf;
  78   if (++mLockCount > 1 || OnHeap()) {
  79     return true;
  80   }
  81
  82   // MEM_RESET_UNDO's behavior is undefined when called on memory that
  83   // hasn't been MEM_RESET.
  84   if (mFirstLock) {
  85     mFirstLock = false;
  86     return true;
  87   }
  88
  89   void* addr = VirtualAllocEx(GetCurrentProcess(), mBuf, mSize, MEM_RESET_UNDO,
  90                               PAGE_READWRITE);
  91   return !!addr;
  92 }
  93
  94 void VolatileBuffer::Unlock() {
  95   MutexAutoLock lock(mMutex);
  96
  97   MOZ_ASSERT(mLockCount > 0, "VolatileBuffer unlocked too many times!");
  98   if (--mLockCount || OnHeap()) {
  99     return;
 100   }
 101
 102   DebugOnly<void*> addr = VirtualAllocEx(GetCurrentProcess(), mBuf, mSize,
 103                                          MEM_RESET, PAGE_READWRITE);
 104   MOZ_ASSERT(addr, "Failed to MEM_RESET");
 105 }
 106
 107 bool VolatileBuffer::OnHeap() const { return mHeap; }
 108
 109 size_t VolatileBuffer::HeapSizeOfExcludingThis(
 110     MallocSizeOf aMallocSizeOf) const {
 111   if (OnHeap()) {
 112 #ifdef MOZ_MEMORY
 113     return aMallocSizeOf(mBuf);
 114 #else
 115     return mSize;
 116 #endif
 117   }
 118
 119   return 0;
 120 }
 121
 122 size_t VolatileBuffer::NonHeapSizeOfExcludingThis() const {
 123   if (OnHeap()) {
 124     return 0;
 125   }
 126
 127   return (mSize + 4095) & ~4095;
 128 }
 129
 130 }  // namespace mozilla