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// copyright (c) 2007 magnus auvinen, see licence.txt for more info
#include <base/system.h>
#include "compression.h"
// Format: ESDDDDDD EDDDDDDD EDD... Extended, Data, Sign
unsigned char *CVariableInt::Pack(unsigned char *pDst, int i)
{
*pDst = (i>>25)&0x40; // set sign bit if i<0
i = i^(i>>31); // if(i<0) i = ~i
*pDst |= i&0x3F; // pack 6bit into dst
i >>= 6; // discard 6 bits
if(i)
{
*pDst |= 0x80; // set extend bit
while(1)
{
pDst++;
*pDst = i&(0x7F); // pack 7bit
i >>= 7; // discard 7 bits
*pDst |= (i!=0)<<7; // set extend bit (may branch)
if(!i)
break;
}
}
pDst++;
return pDst;
}
const unsigned char *CVariableInt::Unpack(const unsigned char *pSrc, int *pInOut)
{
int Sign = (*pSrc>>6)&1;
*pInOut = *pSrc&0x3F;
do
{
if(!(*pSrc&0x80)) break;
pSrc++;
*pInOut |= (*pSrc&(0x7F))<<(6);
if(!(*pSrc&0x80)) break;
pSrc++;
*pInOut |= (*pSrc&(0x7F))<<(6+7);
if(!(*pSrc&0x80)) break;
pSrc++;
*pInOut |= (*pSrc&(0x7F))<<(6+7+7);
if(!(*pSrc&0x80)) break;
pSrc++;
*pInOut |= (*pSrc&(0x7F))<<(6+7+7+7);
} while(0);
pSrc++;
*pInOut ^= -Sign; // if(sign) *i = ~(*i)
return pSrc;
}
long CVariableInt::Decompress(const void *pSrc_, int Size, void *pDst_)
{
const unsigned char *pSrc = (unsigned char *)pSrc_;
const unsigned char *pEnd = pSrc + Size;
int *pDst = (int *)pDst_;
while(pSrc < pEnd)
{
pSrc = CVariableInt::Unpack(pSrc, pDst);
pDst++;
}
return (long)((unsigned char *)pDst-(unsigned char *)pDst_);
}
long CVariableInt::Compress(const void *pSrc_, int Size, void *pDst_)
{
int *pSrc = (int *)pSrc_;
unsigned char *pDst = (unsigned char *)pDst_;
Size /= 4;
while(Size)
{
pDst = CVariableInt::Pack(pDst, *pSrc);
Size--;
pSrc++;
}
return (long)(pDst-(unsigned char *)pDst_);
}
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