1 files changed, 93 insertions, 0 deletions
diff --git a/gfx/layers/ipc/RefCountedShmem.cpp b/gfx/layers/ipc/RefCountedShmem.cpp
new file mode 100644
index 0000000000..8eec82dc9a
--- /dev/null
+++ b/gfx/layers/ipc/RefCountedShmem.cpp
@@ -0,0 +1,93 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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 "RefCountedShmem.h"
+
+#include "mozilla/Atomics.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "mozilla/layers/WebRenderMessages.h"
+
+#define SHM_REFCOUNT_HEADER_SIZE 16
+
+namespace mozilla {
+namespace layers {
+
+uint8_t* RefCountedShm::GetBytes(const RefCountedShmem& aShm) {
+  uint8_t* data = aShm.buffer().get<uint8_t>();
+  if (!data) {
+    return nullptr;
+  }
+  return data + SHM_REFCOUNT_HEADER_SIZE;
+}
+
+size_t RefCountedShm::GetSize(const RefCountedShmem& aShm) {
+  if (!IsValid(aShm)) {
+    return 0;
+  }
+  size_t totalSize = aShm.buffer().Size<uint8_t>();
+  if (totalSize < SHM_REFCOUNT_HEADER_SIZE) {
+    return 0;
+  }
+
+  return totalSize - SHM_REFCOUNT_HEADER_SIZE;
+}
+
+bool RefCountedShm::IsValid(const RefCountedShmem& aShm) {
+  return aShm.buffer().IsWritable() &&
+         aShm.buffer().Size<uint8_t>() > SHM_REFCOUNT_HEADER_SIZE;
+}
+
+int32_t RefCountedShm::GetReferenceCount(const RefCountedShmem& aShm) {
+  if (!IsValid(aShm)) {
+    return 0;
+  }
+
+  return *aShm.buffer().get<Atomic<int32_t>>();
+}
+
+int32_t RefCountedShm::AddRef(const RefCountedShmem& aShm) {
+  if (!IsValid(aShm)) {
+    return 0;
+  }
+
+  auto* counter = aShm.buffer().get<Atomic<int32_t>>();
+  if (counter) {
+    return (*counter)++;
+  }
+  return 0;
+}
+
+int32_t RefCountedShm::Release(const RefCountedShmem& aShm) {
+  if (!IsValid(aShm)) {
+    return 0;
+  }
+
+  auto* counter = aShm.buffer().get<Atomic<int32_t>>();
+  if (counter) {
+    return --(*counter);
+  }
+
+  return 0;
+}
+
+bool RefCountedShm::Alloc(mozilla::ipc::IProtocol* aAllocator, size_t aSize,
+                          RefCountedShmem& aShm) {
+  MOZ_ASSERT(!IsValid(aShm));
+  auto size = aSize + SHM_REFCOUNT_HEADER_SIZE;
+  if (!aAllocator->AllocUnsafeShmem(size, &aShm.buffer())) {
+    return false;
+  }
+  return true;
+}
+
+void RefCountedShm::Dealloc(mozilla::ipc::IProtocol* aAllocator,
+                            RefCountedShmem& aShm) {
+  aAllocator->DeallocShmem(aShm.buffer());
+  aShm.buffer() = ipc::Shmem();
+}
+
+}  // namespace layers
+}  // namespace mozilla