src/dsutil/GolombBuffer.cpp

   1 /*
   2  * $Id: GolombBuffer.cpp 3526 2011-08-01 15:46:29Z XhmikosR $
   3  *
   4  * (C) 2006-2010 see AUTHORS
   5  *
   6  * This file is part of mplayerc.
   7  *
   8  * Mplayerc is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 3 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * Mplayerc is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20  *
  21  */
  22
  23
  24 #include "stdafx.h"
  25 #include "GolombBuffer.h"
  26
  27 CGolombBuffer::CGolombBuffer(BYTE* pBuffer, int nSize)
  28 {
  29         m_pBuffer       = pBuffer;
  30         m_nSize         = nSize;
  31
  32         Reset();
  33 }
  34
  35 UINT64 CGolombBuffer::BitRead(int nBits, bool fPeek)
  36 {
  37         //      ASSERT(nBits >= 0 && nBits <= 64);
  38
  39         while(m_bitlen < nBits) {
  40                 m_bitbuff <<= 8;
  41
  42                 if (m_nBitPos >= m_nSize) {
  43                         return 0;
  44                 }
  45
  46                 *(BYTE*)&m_bitbuff = m_pBuffer[m_nBitPos++];
  47                 m_bitlen += 8;
  48         }
  49
  50         int bitlen = m_bitlen - nBits;
  51
  52         UINT64 ret = (m_bitbuff >> bitlen) & ((1ui64 << nBits) - 1);
  53
  54         if(!fPeek) {
  55                 m_bitbuff &= ((1ui64 << bitlen) - 1);
  56                 m_bitlen = bitlen;
  57         }
  58
  59         return ret;
  60 }
  61
  62 UINT64 CGolombBuffer::UExpGolombRead()
  63 {
  64         int n = -1;
  65         for(BYTE b = 0; !b; n++) {
  66                 b = (BYTE)BitRead(1);
  67         }
  68         return (1ui64 << n) - 1 + BitRead(n);
  69 }
  70
  71 INT64 CGolombBuffer::SExpGolombRead()
  72 {
  73         UINT64 k = UExpGolombRead();
  74         return ((k&1) ? 1 : -1) * ((k + 1) >> 1);
  75 }
  76
  77 void CGolombBuffer::BitByteAlign()
  78 {
  79         m_bitlen &= ~7;
  80 }
  81
  82 __int64 CGolombBuffer::GetPos()
  83 {
  84         return m_nBitPos - (m_bitlen>>3);
  85 }
  86
  87 void CGolombBuffer::ReadBuffer(BYTE* pDest, int nSize)
  88 {
  89         ASSERT (m_nBitPos + nSize <= m_nSize);
  90         ASSERT (m_bitlen == 0);
  91         nSize = min (nSize, m_nSize - m_nBitPos);
  92
  93         memcpy (pDest, m_pBuffer+m_nBitPos, nSize);
  94         m_nBitPos += nSize;
  95 }
  96
  97 void CGolombBuffer::Reset()
  98 {
  99         m_nBitPos       = 0;
 100         m_bitlen        = 0;
 101         m_bitbuff       = 0;
 102 }
 103
 104 void CGolombBuffer::Reset(BYTE* pNewBuffer, int nNewSize)
 105 {
 106         m_pBuffer       = pNewBuffer;
 107         m_nSize         = nNewSize;
 108
 109         Reset();
 110 }
 111
 112 void CGolombBuffer::SkipBytes(int nCount)
 113 {
 114         m_nBitPos  += nCount;
 115         m_bitlen        = 0;
 116         m_bitbuff       = 0;
 117 }