More efficient BitReader::SkipBits for large numbers of bits.

media/base/bit_reader_core.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_BASE_BIT_READER_CORE_H_
 #define MEDIA_BASE_BIT_READER_CORE_H_
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "media/base/media_export.h"
@@ skipping 67 matching lines @@
   // bits cannot be skipped (not enough bits in the stream), true otherwise.
   // When return false, the stream will enter a state where further
   // ReadBits/ReadFlag/SkipBits operations
   // will always return false unless |num_bits| is 0.
   bool SkipBits(int num_bits);
 
   // Returns the number of bits read so far.
   int bits_read() const;
 
  private:
+  // This function can skip any number of bits but is more efficient
+  // for small numbers. Return false if the given number of bits cannot be
+  // skipped (not enough bits in the stream), true otherwise.
+  bool SkipBitsSmall(int num_bits);
+
   // Help function used by ReadBits to avoid inlining the bit reading logic.
   bool ReadBitsInternal(int num_bits, uint64* out);
 
   // Refill bit registers to have at least |min_nbits| bits available.
   // Return true if the mininimum bit count condition is met after the refill.
   bool Refill(int min_nbits);
 
   // Refill the current bit register from the next bit register.
   void RefillCurrentRegister();
 
@@ skipping 11 matching lines @@
   // Note: bits are consumed from MSB to LSB.
   int nbits_next_;
   uint64 reg_next_;
 
   DISALLOW_COPY_AND_ASSIGN(BitReaderCore);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_BIT_READER_CORE_H_