1 files changed, 179 insertions, 0 deletions
diff --git a/src/cmd/venti/srv/unwhack.c b/src/cmd/venti/srv/unwhack.c
new file mode 100644
index 00000000..5530bd07
--- /dev/null
+++ b/src/cmd/venti/srv/unwhack.c
@@ -0,0 +1,179 @@
+#include "stdinc.h"
+#include "whack.h"
+
+enum
+{
+	DMaxFastLen	= 7,
+	DBigLenCode	= 0x3c,		/* minimum code for large lenth encoding */
+	DBigLenBits	= 6,
+	DBigLenBase	= 1		/* starting items to encode for big lens */
+};
+
+static uchar lenval[1 << (DBigLenBits - 1)] =
+{
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	3, 3, 3, 3, 3, 3, 3, 3,
+	4, 4, 4, 4,
+	5,
+	6,
+	255,
+	255
+};
+
+static uchar lenbits[] =
+{
+	0, 0, 0,
+	2, 3, 5, 5,
+};
+
+static uchar offbits[16] =
+{
+	5, 5, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 12, 13
+};
+
+static ushort offbase[16] =
+{
+	0, 0x20,
+	0x40, 0x60,
+	0x80, 0xc0,
+	0x100, 0x180,
+	0x200, 0x300,
+	0x400, 0x600,
+	0x800, 0xc00,
+	0x1000,
+	0x2000
+};
+
+void
+unwhackinit(Unwhack *uw)
+{
+	uw->err[0] = '\0';
+}
+
+int
+unwhack(Unwhack *uw, uchar *dst, int ndst, uchar *src, int nsrc)
+{
+	uchar *s, *d, *dmax, *smax, lit;
+	ulong uwbits, lithist;
+	int i, off, len, bits, use, code, uwnbits, overbits;
+
+	d = dst;
+	dmax = d + ndst;
+
+	smax = src + nsrc;
+	uwnbits = 0;
+	uwbits = 0;
+	overbits = 0;
+	lithist = ~0;
+	while(src < smax || uwnbits - overbits >= MinDecode){
+		while(uwnbits <= 24){
+			uwbits <<= 8;
+			if(src < smax)
+				uwbits |= *src++;
+			else
+				overbits += 8;
+			uwnbits += 8;
+		}
+
+		/*
+		 * literal
+		 */
+		len = lenval[(uwbits >> (uwnbits - 5)) & 0x1f];
+		if(len == 0){
+			if(lithist & 0xf){
+				uwnbits -= 9;
+				lit = (uwbits >> uwnbits) & 0xff;
+				lit &= 255;
+			}else{
+				uwnbits -= 8;
+				lit = (uwbits >> uwnbits) & 0x7f;
+				if(lit < 32){
+					if(lit < 24){
+						uwnbits -= 2;
+						lit = (lit << 2) | ((uwbits >> uwnbits) & 3);
+					}else{
+						uwnbits -= 3;
+						lit = (lit << 3) | ((uwbits >> uwnbits) & 7);
+					}
+					lit = (lit - 64) & 0xff;
+				}
+			}
+			if(d >= dmax){
+				snprint(uw->err, WhackErrLen, "too much output");
+				return -1;
+			}
+			*d++ = lit;
+			lithist = (lithist << 1) | (lit < 32) | (lit > 127);
+			continue;
+		}
+
+		/*
+		 * length
+		 */
+		if(len < 255)
+			uwnbits -= lenbits[len];
+		else{
+			uwnbits -= DBigLenBits;
+			code = ((uwbits >> uwnbits) & ((1 << DBigLenBits) - 1)) - DBigLenCode;
+			len = DMaxFastLen;
+			use = DBigLenBase;
+			bits = (DBigLenBits & 1) ^ 1;
+			while(code >= use){
+				len += use;
+				code -= use;
+				code <<= 1;
+				uwnbits--;
+				if(uwnbits < 0){
+					snprint(uw->err, WhackErrLen, "len out of range");
+					return -1;
+				}
+				code |= (uwbits >> uwnbits) & 1;
+				use <<= bits;
+				bits ^= 1;
+			}
+			len += code;
+
+			while(uwnbits <= 24){
+				uwbits <<= 8;
+				if(src < smax)
+					uwbits |= *src++;
+				else
+					overbits += 8;
+				uwnbits += 8;
+			}
+		}
+
+		/*
+		 * offset
+		 */
+		uwnbits -= 4;
+		bits = (uwbits >> uwnbits) & 0xf;
+		off = offbase[bits];
+		bits = offbits[bits];
+
+		uwnbits -= bits;
+		off |= (uwbits >> uwnbits) & ((1 << bits) - 1);
+		off++;
+
+		if(off > d - dst){
+			snprint(uw->err, WhackErrLen, "offset out of range: off=%d d=%ld len=%d nbits=%d", off, d - dst, len, uwnbits);
+			return -1;
+		}
+		if(d + len > dmax){
+			snprint(uw->err, WhackErrLen, "len out of range");
+			return -1;
+		}
+		s = d - off;
+		for(i = 0; i < len; i++)
+			d[i] = s[i];
+		d += len;
+	}
+	if(uwnbits < overbits){
+		snprint(uw->err, WhackErrLen, "compressed data overrun");
+		return -1;
+	}
+
+	len = d - dst;
+
+	return len;
+}