gecko-dev/dom/media/BufferMediaResource.h

/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* 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/. */

#if !defined(BufferMediaResource_h_)
#  define BufferMediaResource_h_

#  include "MediaResource.h"
#  include "nsISeekableStream.h"
#  include <algorithm>

namespace mozilla {

DDLoggedTypeDeclNameAndBase(BufferMediaResource, MediaResource);

// A simple MediaResource based on an in memory buffer.  This class accepts
// the address and the length of the buffer, and simulates a read/seek API
// on top of it.  The Read implementation involves copying memory, which is
// unfortunate, but the MediaResource interface mandates that.
class BufferMediaResource
    : public MediaResource,
      public DecoderDoctorLifeLogger<BufferMediaResource> {
 public:
  BufferMediaResource(const uint8_t* aBuffer, uint32_t aLength)
      : mBuffer(aBuffer), mLength(aLength) {}

 protected:
  virtual ~BufferMediaResource() = default;

 private:
  // These methods are called off the main thread.
  nsresult ReadAt(int64_t aOffset, char* aBuffer, uint32_t aCount,
                  uint32_t* aBytes) override {
    if (aOffset < 0 || aOffset > mLength) {
      return NS_ERROR_FAILURE;
    }
    *aBytes = std::min(mLength - static_cast<uint32_t>(aOffset), aCount);
    memcpy(aBuffer, mBuffer + aOffset, *aBytes);
    return NS_OK;
  }
  // Memory-based and no locks, caching discouraged.
  bool ShouldCacheReads() override { return false; }

  void Pin() override {}
  void Unpin() override {}
  int64_t GetLength() override { return mLength; }
  int64_t GetNextCachedData(int64_t aOffset) override { return aOffset; }
  int64_t GetCachedDataEnd(int64_t aOffset) override {
    return std::max(aOffset, int64_t(mLength));
  }
  bool IsDataCachedToEndOfResource(int64_t aOffset) override { return true; }
  nsresult ReadFromCache(char* aBuffer, int64_t aOffset,
                         uint32_t aCount) override {
    if (aOffset < 0) {
      return NS_ERROR_FAILURE;
    }

    uint32_t bytes = std::min(mLength - static_cast<uint32_t>(aOffset), aCount);
    memcpy(aBuffer, mBuffer + aOffset, bytes);
    return NS_OK;
  }

  nsresult GetCachedRanges(MediaByteRangeSet& aRanges) override {
    aRanges += MediaByteRange(0, int64_t(mLength));
    return NS_OK;
  }

 private:
  const uint8_t* mBuffer;
  uint32_t mLength;
};

}  // namespace mozilla

#endif