1 files changed, 136 insertions, 0 deletions
diff --git a/memory/volatile/VolatileBufferWindows.cpp b/memory/volatile/VolatileBufferWindows.cpp
new file mode 100644
index 0000000000..6615f89299
--- /dev/null
+++ b/memory/volatile/VolatileBufferWindows.cpp
@@ -0,0 +1,136 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "VolatileBuffer.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/mozalloc.h"
+#include "mozilla/WindowsVersion.h"
+
+#include <windows.h>
+
+#ifdef MOZ_MEMORY
+extern "C" int posix_memalign(void** memptr, size_t alignment, size_t size);
+#endif
+
+#ifndef MEM_RESET_UNDO
+#  define MEM_RESET_UNDO 0x1000000
+#endif
+
+#define MIN_VOLATILE_ALLOC_SIZE 8192
+
+namespace mozilla {
+
+VolatileBuffer::VolatileBuffer()
+    : mMutex("VolatileBuffer"),
+      mBuf(nullptr),
+      mSize(0),
+      mLockCount(0),
+      mHeap(false),
+      mFirstLock(true) {}
+
+bool VolatileBuffer::Init(size_t aSize, size_t aAlignment) {
+  MOZ_ASSERT(!mSize && !mBuf, "Init called twice");
+  MOZ_ASSERT(!(aAlignment % sizeof(void*)),
+             "Alignment must be multiple of pointer size");
+
+  mSize = aSize;
+  if (aSize < MIN_VOLATILE_ALLOC_SIZE) {
+    goto heap_alloc;
+  }
+
+  static bool sUndoSupported = IsWin8OrLater();
+  if (!sUndoSupported) {
+    goto heap_alloc;
+  }
+
+  mBuf = VirtualAllocEx(GetCurrentProcess(), nullptr, mSize,
+                        MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
+  if (mBuf) {
+    return true;
+  }
+
+heap_alloc:
+#ifdef MOZ_MEMORY
+  posix_memalign(&mBuf, aAlignment, aSize);
+#else
+  mBuf = _aligned_malloc(aSize, aAlignment);
+#endif
+  mHeap = true;
+  return !!mBuf;
+}
+
+VolatileBuffer::~VolatileBuffer() {
+  MOZ_ASSERT(mLockCount == 0, "Being destroyed with non-zero lock count?");
+
+  if (OnHeap()) {
+#ifdef MOZ_MEMORY
+    free(mBuf);
+#else
+    _aligned_free(mBuf);
+#endif
+  } else {
+    VirtualFreeEx(GetCurrentProcess(), mBuf, 0, MEM_RELEASE);
+  }
+}
+
+bool VolatileBuffer::Lock(void** aBuf) {
+  MutexAutoLock lock(mMutex);
+
+  MOZ_ASSERT(mBuf, "Attempting to lock an uninitialized VolatileBuffer");
+
+  *aBuf = mBuf;
+  if (++mLockCount > 1 || OnHeap()) {
+    return true;
+  }
+
+  // MEM_RESET_UNDO's behavior is undefined when called on memory that
+  // hasn't been MEM_RESET.
+  if (mFirstLock) {
+    mFirstLock = false;
+    return true;
+  }
+
+  void* addr = VirtualAllocEx(GetCurrentProcess(), mBuf, mSize, MEM_RESET_UNDO,
+                              PAGE_READWRITE);
+  return !!addr;
+}
+
+void VolatileBuffer::Unlock() {
+  MutexAutoLock lock(mMutex);
+
+  MOZ_ASSERT(mLockCount > 0, "VolatileBuffer unlocked too many times!");
+  if (--mLockCount || OnHeap()) {
+    return;
+  }
+
+  DebugOnly<void*> addr = VirtualAllocEx(GetCurrentProcess(), mBuf, mSize,
+                                         MEM_RESET, PAGE_READWRITE);
+  MOZ_ASSERT(addr, "Failed to MEM_RESET");
+}
+
+bool VolatileBuffer::OnHeap() const { return mHeap; }
+
+size_t VolatileBuffer::HeapSizeOfExcludingThis(
+    MallocSizeOf aMallocSizeOf) const {
+  if (OnHeap()) {
+#ifdef MOZ_MEMORY
+    return aMallocSizeOf(mBuf);
+#else
+    return mSize;
+#endif
+  }
+
+  return 0;
+}
+
+size_t VolatileBuffer::NonHeapSizeOfExcludingThis() const {
+  if (OnHeap()) {
+    return 0;
+  }
+
+  return (mSize + 4095) & ~4095;
+}
+
+}  // namespace mozilla