1 files changed, 153 insertions, 0 deletions
diff --git a/dom/media/systemservices/ShmemPool.h b/dom/media/systemservices/ShmemPool.h
new file mode 100644
index 000000000..95901ffa0
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+++ b/dom/media/systemservices/ShmemPool.h
@@ -0,0 +1,153 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set sw=2 ts=8 et ft=cpp : */
+/* 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/. */
+
+#ifndef mozilla_ShmemPool_h
+#define mozilla_ShmemPool_h
+
+#include "mozilla/ipc/Shmem.h"
+#include "mozilla/Mutex.h"
+
+#undef LOG
+#undef LOG_ENABLED
+extern mozilla::LazyLogModule gCamerasParentLog;
+#define LOG(args) MOZ_LOG(gCamerasParentLog, mozilla::LogLevel::Debug, args)
+#define LOG_ENABLED() MOZ_LOG_TEST(gCamerasParentLog, mozilla::LogLevel::Debug)
+
+namespace mozilla {
+
+class ShmemPool;
+
+class ShmemBuffer {
+public:
+  ShmemBuffer() : mInitialized(false) {}
+  explicit ShmemBuffer(mozilla::ipc::Shmem aShmem) {
+    mInitialized = true;
+    mShmem = aShmem;
+  }
+
+  ShmemBuffer(ShmemBuffer&& rhs) {
+    mInitialized = rhs.mInitialized;
+    mShmem = Move(rhs.mShmem);
+  }
+
+  ShmemBuffer& operator=(ShmemBuffer&& rhs) {
+    MOZ_ASSERT(&rhs != this, "self-moves are prohibited");
+    mInitialized = rhs.mInitialized;
+    mShmem = Move(rhs.mShmem);
+    return *this;
+  }
+
+  // No copies allowed
+  ShmemBuffer(const ShmemBuffer&) = delete;
+  ShmemBuffer& operator=(const ShmemBuffer&) = delete;
+
+  bool Valid() {
+    return mInitialized;
+  }
+
+  char* GetBytes() {
+    return mShmem.get<char>();
+  }
+
+  mozilla::ipc::Shmem& Get() {
+    return mShmem;
+  }
+
+private:
+  friend class ShmemPool;
+
+  bool mInitialized;
+  mozilla::ipc::Shmem mShmem;
+};
+
+class ShmemPool {
+public:
+  explicit ShmemPool(size_t aPoolSize);
+  ~ShmemPool();
+  // Get/GetIfAvailable differ in what thread they can run on. GetIfAvailable
+  // can run anywhere but won't allocate if the right size isn't available.
+  ShmemBuffer GetIfAvailable(size_t aSize);
+  void Put(ShmemBuffer&& aShmem);
+
+  // We need to use the allocation/deallocation functions
+  // of a specific IPC child/parent instance.
+  template <class T>
+  void Cleanup(T* aInstance)
+  {
+    MutexAutoLock lock(mMutex);
+    for (size_t i = 0; i < mShmemPool.Length(); i++) {
+      if (mShmemPool[i].mInitialized) {
+        aInstance->DeallocShmem(mShmemPool[i].Get());
+        mShmemPool[i].mInitialized = false;
+      }
+    }
+  }
+
+  template <class T>
+  ShmemBuffer Get(T* aInstance, size_t aSize)
+  {
+    MutexAutoLock lock(mMutex);
+
+    // Pool is empty, don't block caller.
+    if (mPoolFree == 0) {
+      // This isn't initialized, so will be understood as an error.
+      return ShmemBuffer();
+    }
+
+    ShmemBuffer& res = mShmemPool[mPoolFree - 1];
+
+    if (!res.mInitialized) {
+      LOG(("Initializing new Shmem in pool"));
+      if (!aInstance->AllocShmem(aSize, ipc::SharedMemory::TYPE_BASIC, &res.mShmem)) {
+        LOG(("Failure allocating new Shmem buffer"));
+        return ShmemBuffer();
+      }
+      res.mInitialized = true;
+    }
+
+    MOZ_ASSERT(res.mShmem.IsWritable(), "Shmem in Pool is not writable?");
+
+    // Prepare buffer, increase size if needed (we never shrink as we don't
+    // maintain seperate sized pools and we don't want to keep reallocating)
+    if (res.mShmem.Size<char>() < aSize) {
+      LOG(("Size change/increase in Shmem Pool"));
+      aInstance->DeallocShmem(res.mShmem);
+      res.mInitialized = false;
+      // this may fail; always check return value
+      if (!aInstance->AllocShmem(aSize, ipc::SharedMemory::TYPE_BASIC, &res.mShmem)) {
+        LOG(("Failure allocating resized Shmem buffer"));
+        return ShmemBuffer();
+      } else {
+        res.mInitialized = true;
+      }
+    }
+
+    MOZ_ASSERT(res.mShmem.IsWritable(), "Shmem in Pool is not writable post resize?");
+
+    mPoolFree--;
+#ifdef DEBUG
+    size_t poolUse = mShmemPool.Length() - mPoolFree;
+    if (poolUse > mMaxPoolUse) {
+      mMaxPoolUse = poolUse;
+      LOG(("Maximum ShmemPool use increased: %d buffers", mMaxPoolUse));
+    }
+#endif
+    return Move(res);
+  }
+
+private:
+  Mutex mMutex;
+  size_t mPoolFree;
+#ifdef DEBUG
+  size_t mMaxPoolUse;
+#endif
+  nsTArray<ShmemBuffer> mShmemPool;
+};
+
+
+} // namespace mozilla
+
+#endif  // mozilla_ShmemPool_h