1 files changed, 105 insertions, 0 deletions
diff --git a/memory/volatile/VolatileBufferOSX.cpp b/memory/volatile/VolatileBufferOSX.cpp
new file mode 100644
index 0000000000..c6299d1db0
--- /dev/null
+++ b/memory/volatile/VolatileBufferOSX.cpp
@@ -0,0 +1,105 @@
+/* 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 <mach/mach.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#define MIN_VOLATILE_ALLOC_SIZE 8192
+
+namespace mozilla {
+
+VolatileBuffer::VolatileBuffer()
+    : mMutex("VolatileBuffer"),
+      mBuf(nullptr),
+      mSize(0),
+      mLockCount(0),
+      mHeap(false) {}
+
+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;
+
+  kern_return_t ret = 0;
+  if (aSize < MIN_VOLATILE_ALLOC_SIZE) {
+    goto heap_alloc;
+  }
+
+  ret = vm_allocate(mach_task_self(), (vm_address_t*)&mBuf, mSize,
+                    VM_FLAGS_PURGABLE | VM_FLAGS_ANYWHERE);
+  if (ret == KERN_SUCCESS) {
+    return true;
+  }
+
+heap_alloc:
+  (void)posix_memalign(&mBuf, aAlignment, aSize);
+  mHeap = true;
+  return !!mBuf;
+}
+
+VolatileBuffer::~VolatileBuffer() {
+  MOZ_ASSERT(mLockCount == 0, "Being destroyed with non-zero lock count?");
+
+  if (OnHeap()) {
+    free(mBuf);
+  } else {
+    vm_deallocate(mach_task_self(), (vm_address_t)mBuf, mSize);
+  }
+}
+
+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;
+  }
+
+  int state = VM_PURGABLE_NONVOLATILE;
+  kern_return_t ret = vm_purgable_control(mach_task_self(), (vm_address_t)mBuf,
+                                          VM_PURGABLE_SET_STATE, &state);
+  return ret == KERN_SUCCESS && !(state & VM_PURGABLE_EMPTY);
+}
+
+void VolatileBuffer::Unlock() {
+  MutexAutoLock lock(mMutex);
+
+  MOZ_ASSERT(mLockCount > 0, "VolatileBuffer unlocked too many times!");
+  if (--mLockCount || OnHeap()) {
+    return;
+  }
+
+  int state = VM_PURGABLE_VOLATILE | VM_VOLATILE_GROUP_DEFAULT;
+  DebugOnly<kern_return_t> ret = vm_purgable_control(
+      mach_task_self(), (vm_address_t)mBuf, VM_PURGABLE_SET_STATE, &state);
+  MOZ_ASSERT(ret == KERN_SUCCESS, "Failed to set buffer as purgable");
+}
+
+bool VolatileBuffer::OnHeap() const { return mHeap; }
+
+size_t VolatileBuffer::HeapSizeOfExcludingThis(
+    MallocSizeOf aMallocSizeOf) const {
+  return OnHeap() ? aMallocSizeOf(mBuf) : 0;
+}
+
+size_t VolatileBuffer::NonHeapSizeOfExcludingThis() const {
+  if (OnHeap()) {
+    return 0;
+  }
+
+  unsigned long pagemask = getpagesize() - 1;
+  return (mSize + pagemask) & ~pagemask;
+}
+
+}  // namespace mozilla