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95 lines
2 KiB
C++
95 lines
2 KiB
C++
/* (c) Magnus Auvinen. See licence.txt in the root of the distribution for more information. */
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/* If you are missing that file, acquire a complete release at teeworlds.com. */
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#include <base/system.h>
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#include "compression.h"
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// Format: ESDDDDDD EDDDDDDD EDD... Extended, Data, Sign
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unsigned char *CVariableInt::Pack(unsigned char *pDst, int i)
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{
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*pDst = (i>>25)&0x40; // set sign bit if i<0
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i = i^(i>>31); // if(i<0) i = ~i
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*pDst |= i&0x3F; // pack 6bit into dst
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i >>= 6; // discard 6 bits
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if(i)
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{
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*pDst |= 0x80; // set extend bit
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while(1)
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{
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pDst++;
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*pDst = i&(0x7F); // pack 7bit
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i >>= 7; // discard 7 bits
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*pDst |= (i!=0)<<7; // set extend bit (may branch)
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if(!i)
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break;
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}
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}
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pDst++;
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return pDst;
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}
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const unsigned char *CVariableInt::Unpack(const unsigned char *pSrc, int *pInOut)
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{
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int Sign = (*pSrc>>6)&1;
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*pInOut = *pSrc&0x3F;
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do
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{
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if(!(*pSrc&0x80)) break;
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pSrc++;
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*pInOut |= (*pSrc&(0x7F))<<(6);
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if(!(*pSrc&0x80)) break;
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pSrc++;
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*pInOut |= (*pSrc&(0x7F))<<(6+7);
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if(!(*pSrc&0x80)) break;
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pSrc++;
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*pInOut |= (*pSrc&(0x7F))<<(6+7+7);
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if(!(*pSrc&0x80)) break;
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pSrc++;
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*pInOut |= (*pSrc&(0x7F))<<(6+7+7+7);
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} while(0);
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pSrc++;
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*pInOut ^= -Sign; // if(sign) *i = ~(*i)
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return pSrc;
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}
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long CVariableInt::Decompress(const void *pSrc_, int Size, void *pDst_, int DstSize)
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{
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const unsigned char *pSrc = (unsigned char *)pSrc_;
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const unsigned char *pEnd = pSrc + Size;
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int *pDst = (int *)pDst_;
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int *pDstEnd = pDst + DstSize / 4;
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while(pSrc < pEnd)
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{
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if(pDst >= pDstEnd)
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return -1;
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pSrc = CVariableInt::Unpack(pSrc, pDst);
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pDst++;
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}
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return (unsigned char *)pDst-(unsigned char *)pDst_;
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}
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long CVariableInt::Compress(const void *pSrc_, int Size, void *pDst_, int DstSize)
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{
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int *pSrc = (int *)pSrc_;
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unsigned char *pDst = (unsigned char *)pDst_;
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unsigned char *pDstEnd = pDst + DstSize;
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Size /= 4;
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while(Size)
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{
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if(pDstEnd - pDst < 6)
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return -1;
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pDst = CVariableInt::Pack(pDst, *pSrc);
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Size--;
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pSrc++;
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}
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return pDst-(unsigned char *)pDst_;
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}
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