ResourceQueue.h - mozsearch

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/* -*- 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/. */

#ifndef MOZILLA_RESOURCEQUEUE_H_

#define MOZILLA_RESOURCEQUEUE_H_

#include "nsDeque.h"

#include "MediaSpan.h"

namespace mozilla {

class ErrorResult;

// A SourceBufferResource has a queue containing the data that is appended

// to it. The queue holds instances of ResourceItem which is an array of the

// bytes. Appending data to the SourceBufferResource pushes this onto the

// queue.

// Data is evicted once it reaches a size threshold. This pops the items off

// the front of the queue and deletes it.  If an eviction happens then the

// MediaSource is notified (done in SourceBuffer::AppendData) which then

// requests all SourceBuffers to evict data up to approximately the same

// timepoint.

struct ResourceItem {

  ResourceItem(const MediaSpan& aData, uint64_t aOffset);

  size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const;

  MediaSpan mData;

  uint64_t mOffset;

};

class ResourceQueue : private nsDeque<ResourceItem> {

 public:

  ResourceQueue();

  // Returns the logical byte offset of the start of the data.

  uint64_t GetOffset();

  // Returns the length of all items in the queue plus the offset.

  // This is the logical length of the resource.

  uint64_t GetLength();

  // Copies aCount bytes from aOffset in the queue into aDest.

  void CopyData(uint64_t aOffset, uint32_t aCount, char* aDest);

  void AppendItem(const MediaSpan& aData);

  // Tries to evict at least aSizeToEvict from the queue up until

  // aOffset. Returns amount evicted.

  uint32_t Evict(uint64_t aOffset, uint32_t aSizeToEvict);

  uint32_t EvictBefore(uint64_t aOffset);

  uint32_t EvictAll();

  size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const;

#if defined(DEBUG)

  void Dump(const char* aPath);

#endif

  const uint8_t* GetContiguousAccess(int64_t aOffset, size_t aSize);

 private:

  ResourceItem* ResourceAt(uint32_t aIndex) const;

  // Returns the index of the resource that contains the given

  // logical offset. aResourceOffset will contain the offset into

  // the resource at the given index returned if it is not null.  If

  // no such resource exists, returns GetSize() and aOffset is

  // untouched.

  uint32_t GetAtOffset(uint64_t aOffset, uint32_t* aResourceOffset) const;

  ResourceItem* PopFront();

  // Logical length of the resource.

  uint64_t mLogicalLength;

  // Logical offset into the resource of the first element in the queue.

  uint64_t mOffset;

};

}  // namespace mozilla

#endif /* MOZILLA_RESOURCEQUEUE_H_ */