src/dsutil/GolombBuffer.cpp

   1 /*
   2  * (C) 2006-2012 see Authors.txt
   3  *
   4  * This file is part of MPC-HC.
   5  *
   6  * MPC-HC is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * MPC-HC 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
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  *
  19  */
  20
  21 #include "stdafx.h"
  22 #include "GolombBuffer.h"
  23
  24 CGolombBuffer::CGolombBuffer(BYTE* pBuffer, int nSize)
  25 {
  26     m_pBuffer = pBuffer;
  27     m_nSize   = nSize;
  28
  29     Reset();
  30 }
  31
  32 UINT64 CGolombBuffer::BitRead(int nBits, bool fPeek)
  33 {
  34     //ASSERT(nBits >= 0 && nBits <= 64);
  35
  36     while (m_bitlen < nBits) {
  37         m_bitbuff <<= 8;
  38
  39         if (m_nBitPos >= m_nSize) {
  40             return 0;
  41         }
  42
  43         *(BYTE*)&m_bitbuff = m_pBuffer[m_nBitPos++];
  44         m_bitlen += 8;
  45     }
  46
  47     int bitlen = m_bitlen - nBits;
  48
  49     UINT64 ret = (m_bitbuff >> bitlen) & ((1ui64 << nBits) - 1);
  50
  51     if (!fPeek) {
  52         m_bitbuff &= ((1ui64 << bitlen) - 1);
  53         m_bitlen = bitlen;
  54     }
  55
  56     return ret;
  57 }
  58
  59 UINT64 CGolombBuffer::UExpGolombRead()
  60 {
  61     int n = -1;
  62     for (BYTE b = 0; !b; n++) {
  63         b = (BYTE)BitRead(1);
  64     }
  65     return (1ui64 << n) - 1 + BitRead(n);
  66 }
  67
  68 INT64 CGolombBuffer::SExpGolombRead()
  69 {
  70     UINT64 k = UExpGolombRead();
  71     return ((k & 1) ? 1 : -1) * ((k + 1) >> 1);
  72 }
  73
  74 void CGolombBuffer::BitByteAlign()
  75 {
  76     m_bitlen &= ~7;
  77 }
  78
  79 int CGolombBuffer::GetPos()
  80 {
  81     return m_nBitPos - (m_bitlen >> 3);
  82 }
  83
  84 void CGolombBuffer::ReadBuffer(BYTE* pDest, int nSize)
  85 {
  86     ASSERT(m_nBitPos + nSize <= m_nSize);
  87     ASSERT(m_bitlen == 0);
  88     nSize = min(nSize, m_nSize - m_nBitPos);
  89
  90     memcpy(pDest, m_pBuffer + m_nBitPos, nSize);
  91     m_nBitPos += nSize;
  92 }
  93
  94 void CGolombBuffer::Reset()
  95 {
  96     m_nBitPos = 0;
  97     m_bitlen  = 0;
  98     m_bitbuff = 0;
  99 }
 100
 101 void CGolombBuffer::Reset(BYTE* pNewBuffer, int nNewSize)
 102 {
 103     m_pBuffer = pNewBuffer;
 104     m_nSize   = nNewSize;
 105
 106     Reset();
 107 }
 108
 109 void CGolombBuffer::SkipBytes(int nCount)
 110 {
 111     m_nBitPos += nCount;
 112     m_bitlen   = 0;
 113     m_bitbuff  = 0;
 114 }