dom/media/BitReader.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_READER_H_
   6 #define BIT_READER_H_
   7
   8 #include "MediaData.h"
   9
  10 namespace mozilla {
  11
  12 class BitReader {
  13  public:
  14   explicit BitReader(const MediaByteBuffer* aBuffer);
  15   BitReader(const MediaByteBuffer* aBuffer, size_t aBits);
  16   BitReader(const uint8_t* aBuffer, size_t aBits);
  17   ~BitReader();
  18   uint32_t ReadBits(size_t aNum);
  19   bool ReadBit() { return ReadBits(1) != 0; }
  20   uint32_t ReadU32() { return ReadBits(32); }
  21   uint64_t ReadU64();
  22
  23   // Read the UTF-8 sequence and convert it to its 64-bit UCS-4 encoded form.
  24   // Return 0xfffffffffffffff if sequence was invalid.
  25   uint64_t ReadUTF8();
  26   // Read unsigned integer Exp-Golomb-coded.
  27   uint32_t ReadUE();
  28   // Read signed integer Exp-Golomb-coded.
  29   int32_t ReadSE();
  30
  31   // Return the number of bits parsed so far;
  32   size_t BitCount() const;
  33   // Return the number of bits left.
  34   size_t BitsLeft() const;
  35
  36   // Return RBSP bit length.
  37   static uint32_t GetBitLength(const MediaByteBuffer* aNAL);
  38
  39  private:
  40   void FillReservoir();
  41   const uint8_t* mData;
  42   const size_t mOriginalBitSize;
  43   size_t mTotalBitsLeft;
  44   size_t mSize;         // Size left in bytes
  45   uint32_t mReservoir;  // Left-aligned bits
  46   size_t mNumBitsLeft;  // Number of bits left in reservoir.
  47 };
  48
  49 }  // namespace mozilla
  50
  51 #endif  // BIT_READER_H_