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#include "stdinc.h"
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#include "whack.h"
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4 
enum
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{
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	DMaxFastLen	= 7,
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	DBigLenCode	= 0x3c,		/* minimum code for large lenth encoding */
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	DBigLenBits	= 6,
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	DBigLenBase	= 1		/* starting items to encode for big lens */
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};
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static uchar lenval[1 << (DBigLenBits - 1)] =
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{
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	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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	3, 3, 3, 3, 3, 3, 3, 3,
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	4, 4, 4, 4,
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	5,
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	6,
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	255,
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	255
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};
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static uchar lenbits[] =
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{
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	0, 0, 0,
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	2, 3, 5, 5,
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};
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static uchar offbits[16] =
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{
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	5, 5, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 12, 13
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};
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static ushort offbase[16] =
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{
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	0, 0x20,
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	0x40, 0x60,
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	0x80, 0xc0,
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	0x100, 0x180,
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	0x200, 0x300,
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	0x400, 0x600,
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	0x800, 0xc00,
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	0x1000,
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	0x2000
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};
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void
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unwhackinit(Unwhack *uw)
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{
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	uw->err[0] = '\0';
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}
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int
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unwhack(Unwhack *uw, uchar *dst, int ndst, uchar *src, int nsrc)
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{
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	uchar *s, *d, *dmax, *smax, lit;
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	ulong uwbits, lithist;
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	int i, off, len, bits, use, code, uwnbits, overbits;
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60 
	d = dst;
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	dmax = d + ndst;
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	smax = src + nsrc;
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	uwnbits = 0;
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	uwbits = 0;
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	overbits = 0;
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	lithist = ~0;
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	while(src < smax || uwnbits - overbits >= MinDecode){
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		while(uwnbits <= 24){
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			uwbits <<= 8;
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			if(src < smax)
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				uwbits |= *src++;
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			else
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				overbits += 8;
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			uwnbits += 8;
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		}
77 
 
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		/*
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		 * literal
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		 */
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		len = lenval[(uwbits >> (uwnbits - 5)) & 0x1f];
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		if(len == 0){
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			if(lithist & 0xf){
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				uwnbits -= 9;
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				lit = (uwbits >> uwnbits) & 0xff;
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				lit &= 255;
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			}else{
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				uwnbits -= 8;
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				lit = (uwbits >> uwnbits) & 0x7f;
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				if(lit < 32){
91 
					if(lit < 24){
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						uwnbits -= 2;
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						lit = (lit << 2) | ((uwbits >> uwnbits) & 3);
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					}else{
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						uwnbits -= 3;
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						lit = (lit << 3) | ((uwbits >> uwnbits) & 7);
97 
					}
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					lit = (lit - 64) & 0xff;
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				}
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			}
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			if(d >= dmax){
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				snprint(uw->err, WhackErrLen, "too much output");
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				return -1;
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			}
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			*d++ = lit;
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			lithist = (lithist << 1) | (lit < 32) | (lit > 127);
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			continue;
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		}
109 
 
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		/*
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		 * length
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		 */
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		if(len < 255)
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			uwnbits -= lenbits[len];
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		else{
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			uwnbits -= DBigLenBits;
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			code = ((uwbits >> uwnbits) & ((1 << DBigLenBits) - 1)) - DBigLenCode;
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			len = DMaxFastLen;
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			use = DBigLenBase;
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			bits = (DBigLenBits & 1) ^ 1;
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			while(code >= use){
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				len += use;
123 
				code -= use;
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				code <<= 1;
125 
				uwnbits--;
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				if(uwnbits < 0){
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					snprint(uw->err, WhackErrLen, "len out of range");
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					return -1;
129 
				}
130 
				code |= (uwbits >> uwnbits) & 1;
131 
				use <<= bits;
132 
				bits ^= 1;
133 
			}
134 
			len += code;
135 
 
136 
			while(uwnbits <= 24){
137 
				uwbits <<= 8;
138 
				if(src < smax)
139 
					uwbits |= *src++;
140 
				else
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					overbits += 8;
142 
				uwnbits += 8;
143 
			}
144 
		}
145 
 
146 
		/*
147 
		 * offset
148 
		 */
149 
		uwnbits -= 4;
150 
		bits = (uwbits >> uwnbits) & 0xf;
151 
		off = offbase[bits];
152 
		bits = offbits[bits];
153 
 
154 
		uwnbits -= bits;
155 
		off |= (uwbits >> uwnbits) & ((1 << bits) - 1);
156 
		off++;
157 
 
158 
		if(off > d - dst){
159 
			snprint(uw->err, WhackErrLen, "offset out of range: off=%d d=%ld len=%d nbits=%d", off, d - dst, len, uwnbits);
160 
			return -1;
161 
		}
162 
		if(d + len > dmax){
163 
			snprint(uw->err, WhackErrLen, "len out of range");
164 
			return -1;
165 
		}
166 
		s = d - off;
167 
		for(i = 0; i < len; i++)
168 
			d[i] = s[i];
169 
		d += len;
170 
	}
171 
	if(uwnbits < overbits){
172 
		snprint(uw->err, WhackErrLen, "compressed data overrun");
173 
		return -1;
174 
	}
175 
 
176 
	len = d - dst;
177 
 
178 
	return len;
179 
}