dom/media/BitWriter.h

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #ifndef BIT_WRITER_H_
   6 #define BIT_WRITER_H_
   7
   8 #include "mozilla/RefPtr.h"
   9
  10 namespace mozilla {
  11
  12 class MediaByteBuffer;
  13
  14 class BitWriter {
  15  public:
  16   explicit BitWriter(MediaByteBuffer* aBuffer);
  17   virtual ~BitWriter();
  18   void WriteBits(uint64_t aValue, size_t aBits);
  19   void WriteBit(bool aValue) { WriteBits(aValue, 1); }
  20   void WriteU8(uint8_t aValue) { WriteBits(aValue, 8); }
  21   void WriteU32(uint32_t aValue) { WriteBits(aValue, 32); }
  22   void WriteU64(uint64_t aValue) { WriteBits(aValue, 64); }
  23
  24   // Write unsigned integer into Exp-Golomb-coded. 2^32-2 at most
  25   void WriteUE(uint32_t aValue);
  26   // Write unsigned integer Little Endian Base 128 coded.
  27   void WriteULEB128(uint64_t aValue);
  28
  29   // Write RBSP trailing bits.
  30   void CloseWithRbspTrailing();
  31
  32   // Advance position forward without modifying buffer, which is usually used
  33   // along with the case when directly appending a byte array to the
  34   // MediaByteBuffer for the efficiency, instead of writing bits one by one.
  35   // So this can only be called when the bit index is zero.
  36   void AdvanceBytes(uint32_t aByteOffset);
  37
  38   // Return the number of bits written so far;
  39   size_t BitCount() const { return mPosition * 8 + mBitIndex; }
  40
  41  private:
  42   RefPtr<MediaByteBuffer> mBuffer;
  43   size_t mPosition = 0;
  44   uint8_t mBitIndex = 0;
  45 };
  46
  47 }  // namespace mozilla
  48
  49 #endif  // BIT_WRITER_H_