ddnet/src/engine/compression.cpp

#include <baselib/system.h>
#include <string.h>

// Format: ESDDDDDD EDDDDDDD EDD...  Extended, Data, Sign
unsigned char *vint_pack(unsigned char *dst, int i) 
{ 
        *dst = (i>>25)&0x40; // set sign bit if i<0
	i = i^(i>>31); // if(i<0) i = ~i
 
        *dst |= i&0x3F; // pack 6bit into dst
        i >>= 6; // discard 6 bits
        if(i)
	{
                *dst |= 0x80; // set extend bit
		while(1)
		{
			dst++;
	                *dst = i&(0x7F); // pack 7bit
        	        i >>= 7; // discard 7 bits
			*dst |= (i!=0)<<7; // set extend bit (may branch)
                	if(!i)
				break;
		}
	}

	dst++;
        return dst; 
} 
 
const unsigned char *vint_unpack(const unsigned char *src, int *i)
{ 
        int sign = (*src>>6)&1; 
        *i = *src&0x3F; 

	while(1)
	{ 
	        if(!(*src&0x80)) break;
		src++;
                *i |= (*src&(0x7F))<<(6);

	        if(!(*src&0x80)) break;
		src++;
                *i |= (*src&(0x7F))<<(6+7);

	        if(!(*src&0x80)) break;
		src++;
                *i |= (*src&(0x7F))<<(6+7+7);

	        if(!(*src&0x80)) break;
		src++;
                *i |= (*src&(0x7F))<<(6+7+7+7);
	}

	src++;
	*i ^= -sign; // if(sign) *i = ~(*i)
        return src; 
} 


long intpack_decompress(const void *src_, int size, void *dst_)
{
	const unsigned char *src = (unsigned char *)src_;
	const unsigned char *end = src + size;
	int *dst = (int *)dst_;
	while(src < end)
	{
		src = vint_unpack(src, dst);
		dst++;
	}
	return (long)((unsigned char *)dst-(unsigned char *)dst_);
}

long intpack_compress(const void *src_, int size, void *dst_)
{
	int *src = (int *)src_;
	unsigned char *dst = (unsigned char *)dst_;
	size /= 4;
	while(size)
	{
		dst = vint_pack(dst, *src);
		size--;
		src++;
	}
	return (long)(dst-(unsigned char *)dst_);
}


long zerobit_compress(const void *src_, int size, void *dst_)
{
	unsigned char *src = (unsigned char *)src_;
	unsigned char *dst = (unsigned char *)dst_;
	
	//int zerocount = 0 ;
	while(size)
	{
		unsigned char bit = 0x80;
		unsigned char mask = 0;
		int dst_move = 1;
		int chunk = size < 8 ? size : 8;
		size -= chunk;
		
		for(int b = 0; b < chunk; b++, bit>>=1)
		{
			if(*src)
			{
				dst[dst_move] = *src;
				mask |= bit;
				dst_move++;
			}
			
			src++;
		}
		
		*dst = mask;
		dst += dst_move;
	}
	
	long l = (long)(dst-(unsigned char *)dst_);
	//dbg_msg("zerobit", "%d", (int)l);
	return l;
}

long zerobit_decompress(const void *src_, int size, void *dst_)
{
	unsigned char *src = (unsigned char *)src_;
	unsigned char *dst = (unsigned char *)dst_;
	unsigned char *end = src + size;
	
	//int zerocount = 0 ;
	while(src != end)
	{
		unsigned char bit = 0x80;
		unsigned char mask = *src++;
		
		for(int b = 0; b < 8; b++, bit>>=1)
		{
			if(mask&bit)
				*dst++ = *src++;
			else
				*dst++ = 0;
		}
	}
	
	long l = (long)(dst-(unsigned char *)dst_);
	//dbg_msg("zerobit", "%d", (int)l);
	return l;
}