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// Mtf8.h
#ifndef __MTF8_H
#define __MTF8_H
#include "Common/Types.h"
namespace NCompress {
class CMtf8Encoder
{
public:
Byte Buffer[256];
int FindAndMove(Byte v)
{
int pos;
for (pos = 0; Buffer[pos] != v; pos++);
int resPos = pos;
for (; pos >= 8; pos -= 8)
{
Buffer[pos] = Buffer[pos - 1];
Buffer[pos - 1] = Buffer[pos - 2];
Buffer[pos - 2] = Buffer[pos - 3];
Buffer[pos - 3] = Buffer[pos - 4];
Buffer[pos - 4] = Buffer[pos - 5];
Buffer[pos - 5] = Buffer[pos - 6];
Buffer[pos - 6] = Buffer[pos - 7];
Buffer[pos - 7] = Buffer[pos - 8];
}
for (; pos > 0; pos--)
Buffer[pos] = Buffer[pos - 1];
Buffer[0] = v;
return resPos;
}
};
/*
class CMtf8Decoder
{
public:
Byte Buffer[256];
void Init(int) {};
Byte GetHead() const { return Buffer[0]; }
Byte GetAndMove(int pos)
{
Byte res = Buffer[pos];
for (; pos >= 8; pos -= 8)
{
Buffer[pos] = Buffer[pos - 1];
Buffer[pos - 1] = Buffer[pos - 2];
Buffer[pos - 2] = Buffer[pos - 3];
Buffer[pos - 3] = Buffer[pos - 4];
Buffer[pos - 4] = Buffer[pos - 5];
Buffer[pos - 5] = Buffer[pos - 6];
Buffer[pos - 6] = Buffer[pos - 7];
Buffer[pos - 7] = Buffer[pos - 8];
}
for (; pos > 0; pos--)
Buffer[pos] = Buffer[pos - 1];
Buffer[0] = res;
return res;
}
};
*/
#ifdef _WIN64
#define MODE_64BIT
#endif
#ifdef MODE_64BIT
typedef UInt64 CMtfVar;
#define MTF_MOVS 3
#else
typedef UInt32 CMtfVar;
#define MTF_MOVS 2
#endif
#define MTF_MASK ((1 << MTF_MOVS) - 1)
class CMtf8Decoder
{
public:
CMtfVar Buffer[256 >> MTF_MOVS];
void StartInit() { memset(Buffer, 0, sizeof(Buffer)); }
void Add(unsigned int pos, Byte val) { Buffer[pos >> MTF_MOVS] |= ((CMtfVar)val << ((pos & MTF_MASK) << 3)); }
Byte GetHead() const { return (Byte)Buffer[0]; }
Byte GetAndMove(unsigned int pos)
{
UInt32 lim = ((UInt32)pos >> MTF_MOVS);
pos = (pos & MTF_MASK) << 3;
CMtfVar prev = (Buffer[lim] >> pos) & 0xFF;
UInt32 i = 0;
if ((lim & 1) != 0)
{
CMtfVar next = Buffer[0];
Buffer[0] = (next << 8) | prev;
prev = (next >> (MTF_MASK << 3));
i = 1;
lim -= 1;
}
for (; i < lim; i += 2)
{
CMtfVar next = Buffer[i];
Buffer[i] = (next << 8) | prev;
prev = (next >> (MTF_MASK << 3));
next = Buffer[i + 1];
Buffer[i + 1] = (next << 8) | prev;
prev = (next >> (MTF_MASK << 3));
}
CMtfVar next = Buffer[i];
CMtfVar mask = (((CMtfVar)0x100 << pos) - 1);
Buffer[i] = (next & ~mask) | (((next << 8) | prev) & mask);
return (Byte)Buffer[0];
}
};
/*
const int kSmallSize = 64;
class CMtf8Decoder
{
Byte SmallBuffer[kSmallSize];
int SmallSize;
Byte Counts[16];
int Size;
public:
Byte Buffer[256];
Byte GetHead() const
{
if (SmallSize > 0)
return SmallBuffer[kSmallSize - SmallSize];
return Buffer[0];
}
void Init(int size)
{
Size = size;
SmallSize = 0;
for (int i = 0; i < 16; i++)
{
Counts[i] = ((size >= 16) ? 16 : size);
size -= Counts[i];
}
}
Byte GetAndMove(int pos)
{
if (pos < SmallSize)
{
Byte *p = SmallBuffer + kSmallSize - SmallSize;
Byte res = p[pos];
for (; pos > 0; pos--)
p[pos] = p[pos - 1];
SmallBuffer[kSmallSize - SmallSize] = res;
return res;
}
if (SmallSize == kSmallSize)
{
int i = Size - 1;
int g = 16;
do
{
g--;
int offset = (g << 4);
for (int t = Counts[g] - 1; t >= 0; t--, i--)
Buffer[i] = Buffer[offset + t];
}
while(g != 0);
for (i = kSmallSize - 1; i >= 0; i--)
Buffer[i] = SmallBuffer[i];
Init(Size);
}
pos -= SmallSize;
int g;
for (g = 0; pos >= Counts[g]; g++)
pos -= Counts[g];
int offset = (g << 4);
Byte res = Buffer[offset + pos];
for (pos; pos < 16 - 1; pos++)
Buffer[offset + pos] = Buffer[offset + pos + 1];
SmallSize++;
SmallBuffer[kSmallSize - SmallSize] = res;
Counts[g]--;
return res;
}
};
*/
}
#endif
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