libavcodec/unary.h

   1 /*
   2  * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
   3  *
   4  * This file is part of FFmpeg.
   5  *
   6  * FFmpeg is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * FFmpeg is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with FFmpeg; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #ifndef AVCODEC_UNARY_H
  22 #define AVCODEC_UNARY_H
  23
  24 #include "get_bits.h"
  25
  26 /**
  27  * Get unary code of limited length
  28  * @param gb GetBitContext
  29  * @param[in] stop The bitstop value (unary code of 1's or 0's)
  30  * @param[in] len Maximum length
  31  * @return unary 0 based code index. This is also the length in bits of the
  32  * code excluding the stop bit.
  33  * (in case len=1)
  34  * 1            0
  35  * 0            1
  36  * (in case len=2)
  37  * 1            0
  38  * 01           1
  39  * 00           2
  40  * (in case len=3)
  41  * 1            0
  42  * 01           1
  43  * 001          2
  44  * 000          3
  45  */
  46 static inline int get_unary(GetBitContext *gb, int stop, int len)
  47 {
  48     int i;
  49
  50     for(i = 0; i < len && get_bits1(gb) != stop; i++);
  51     return i;
  52 }
  53
  54 /**
  55  * Get unary code terminated by a 0 with a maximum length of 33
  56  * @param gb GetBitContext
  57  * @return Unary length/index
  58  */
  59 static inline int get_unary_0_33(GetBitContext *gb)
  60 {
  61     return get_unary(gb, 0, 33);
  62 }
  63
  64 static inline int get_unary_0_9(GetBitContext *gb)
  65 {
  66     return get_unary(gb, 0, 9);
  67 }
  68
  69 #endif /* AVCODEC_UNARY_H */