--- ray/src/common/urand.c	1991/06/07 10:50:14	1.5
+++ ray/src/common/urand.c	1991/07/11 16:25:58	1.6
@@ -60,3 +60,55 @@ register int  n;
 		hval += *d++ * tab[n&7];
 	return(hval);
 }
+
+
+static char  bctab[256] = {
+		0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
+		1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
+		1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
+		2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+		1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
+		2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+		2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+		3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
+		1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
+		2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+		2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+		3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
+		2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
+		3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
+		3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
+		4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8,
+	};
+
+
+#define NBITS		32
+
+#if NBITS==32
+#define  bitcount(i)	(bctab[(i)>>24&0xff]+bctab[(i)>>16&0xff]+ \
+				bctab[(i)>>8&0xff]+bctab[(i)&0xff])
+#endif
+#if  NBITS==16
+#define  bitcount(i)	(bctab[(i)>>8&0xff]+bctab[(i)&0xff])
+#endif
+
+
+int
+urind(s, i)			/* compute i'th index from seed s */
+int	s, i;
+{
+	register int  ss, k;
+	int  left;
+
+	ss = s*1103515245 + 12345;
+	left = 0;
+	for (k = i/NBITS; k--; ) {
+		left += bitcount(ss);
+		ss = ss*1103515245 + 12345;
+	}
+	for (k = i&(NBITS-1); k--; ss >>= 1)
+		left += ss & 1;
+	if (ss & 1)
+		return(s-left-1);
+	return(s-left+i);
+}