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106 lines
2.4 KiB
C++
106 lines
2.4 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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#include <array> // std::size
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// Format: ESDDDDDD EDDDDDDD EDD... Extended, Data, Sign
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unsigned char *CVariableInt::Pack(unsigned char *pDst, int i, int DstSize)
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{
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if(DstSize <= 0)
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return 0;
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DstSize--;
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*pDst = 0;
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if(i < 0)
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{
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*pDst |= 0x40; // set sign bit
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i = ~i;
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}
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*pDst |= i & 0x3F; // pack 6bit into dst
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i >>= 6; // discard 6 bits
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while(i)
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{
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if(DstSize <= 0)
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return 0;
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*pDst |= 0x80; // set extend bit
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DstSize--;
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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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}
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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, int SrcSize)
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{
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if(SrcSize <= 0)
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return 0;
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const int Sign = (*pSrc >> 6) & 1;
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*pInOut = *pSrc & 0x3F;
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SrcSize--;
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const static int s_aMasks[] = {0x7F, 0x7F, 0x7F, 0x0F};
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const static int s_aShifts[] = {6, 6 + 7, 6 + 7 + 7, 6 + 7 + 7 + 7};
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for(unsigned i = 0; i < std::size(s_aMasks); i++)
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{
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if(!(*pSrc & 0x80))
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break;
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if(SrcSize <= 0)
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return 0;
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SrcSize--;
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pSrc++;
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*pInOut |= (*pSrc & s_aMasks[i]) << s_aShifts[i];
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}
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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 SrcSize, void *pDst_, int DstSize)
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{
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dbg_assert(DstSize % sizeof(int) == 0, "invalid bounds");
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const unsigned char *pSrc = (unsigned char *)pSrc_;
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const unsigned char *pSrcEnd = pSrc + SrcSize;
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int *pDst = (int *)pDst_;
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const int *pDstEnd = pDst + DstSize / sizeof(int);
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while(pSrc < pSrcEnd)
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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, pSrcEnd - pSrc);
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if(!pSrc)
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return -1;
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pDst++;
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}
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return (long)((unsigned char *)pDst - (unsigned char *)pDst_);
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}
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long CVariableInt::Compress(const void *pSrc_, int SrcSize, void *pDst_, int DstSize)
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{
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dbg_assert(SrcSize % sizeof(int) == 0, "invalid bounds");
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const int *pSrc = (int *)pSrc_;
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unsigned char *pDst = (unsigned char *)pDst_;
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const unsigned char *pDstEnd = pDst + DstSize;
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SrcSize /= sizeof(int);
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while(SrcSize)
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{
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pDst = CVariableInt::Pack(pDst, *pSrc, pDstEnd - pDst);
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if(!pDst)
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return -1;
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SrcSize--;
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pSrc++;
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}
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return (long)(pDst - (unsigned char *)pDst_);
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}
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