--- ray/src/common/urand.c	1991/05/17 12:55:27	1.1
+++ ray/src/common/urand.c	2015/05/27 08:42:06	2.11
@@ -1,35 +1,47 @@
-/* Copyright (c) 1991 Regents of the University of California */
-
 #ifndef lint
-static char SCCSid[] = "$SunId$ LBL";
+static const char	RCSid[] = "$Id: urand.c,v 2.11 2015/05/27 08:42:06 greg Exp $";
 #endif
-
 /*
- * Uncorrelated (anticorrelated) random function
+ * Anticorrelated random function due to Christophe Schlick
  */
 
+#include "copyright.h"
+
+#include  "standard.h"
 #include  "random.h"
 
-#define  NULL		0
+#undef initurand
 
-extern char  *malloc();
+#define  MAXORDER	(8*sizeof(unsigned short))
 
-short  *urperm;		/* urand() permutation */
-int  urmask;		/* bits used in permutation */
+static unsigned short  empty_tab = 0;
 
+unsigned short  *urperm = &empty_tab;	/* urand() permutation */
+int  urmask = 0;			/* bits used in permutation */
 
-initurand(size)		/* initialize urand() for size entries */
-int  size;
+
+int
+initurand(			/* initialize urand() for size entries */
+	int  size
+)
 {
 	int  order, n;
-	register int  i, offset;
+	int  i, offset;
 
-	size--;
-	for (i = 1; size >>= 1; i++)
-		;
+	if ((urperm != NULL) & (urperm != &empty_tab))
+		free((void *)urperm);
+	if (--size <= 0) {
+		empty_tab = 0;
+		urperm = &empty_tab;
+		urmask = 0;
+		return(0);
+	}
+	for (i = 1; (size >>= 1); i++)
+		if (i == MAXORDER)
+			break;
 	order = i;
-	urmask = (1<<i) - 1;
-	urperm = (short *)malloc((urmask+1)*sizeof(short));
+	urmask = (1<<order) - 1;
+	urperm = (unsigned short *)malloc((urmask+1)*sizeof(unsigned short));
 	if (urperm == NULL) {
 		eputs("out of memory in initurand\n");
 		quit(1);
@@ -37,11 +49,27 @@ int  size;
 	urperm[0] = 0;
 	for (n = 1, offset = 1; n <= order; n++, offset <<= 1)
 		for (i = offset; i--; ) {
-			urperm[i] =
-			urperm[i+offset] = 2*urperm[i];
+			urperm[i+offset] = urperm[i] <<= 1;
 			if (random() & 0x4000)
 				urperm[i]++;
 			else
 				urperm[i+offset]++;
 		}
+	return(urmask+1);
+}
+
+
+int
+ilhash(				/* hash a set of integer values */
+	int  *d,
+	int  n
+)
+{
+	static int  tab[8] = {103699,96289,73771,65203,81119,87037,92051,98899};
+	int  hval;
+
+	hval = 0;
+	while (n-- > 0)
+		hval ^= *d++ * tab[n&7];
+	return(hval & 0x7fffffff);
 }