Initial import of the CDE 2.1.30 sources from the Open Group.

cde/lib/DtSvc/DtCodelibs/strhash.C

@@ -0,0 +1,112 @@
+/*
+ * $XConsortium: strhash.C /main/5 1996/06/21 17:36:23 ageorge $
+ *
+ * (c) Copyright 1996 Digital Equipment Corporation.
+ * (c) Copyright 1993,1994,1996 Hewlett-Packard Company.
+ * (c) Copyright 1993,1994,1996 International Business Machines Corp.
+ * (c) Copyright 1993,1994,1996 Sun Microsystems, Inc.
+ * (c) Copyright 1993,1994,1996 Novell, Inc. 
+ * (c) Copyright 1996 FUJITSU LIMITED.
+ * (c) Copyright 1996 Hitachi.
+ */
+
+#include <codelibs/nl_hack.h>
+#include <codelibs/stringx.h>
+
+
+/**************************************************
+// This is quick but does a pretty crummy job
+unsigned strhash(register const unsigned char *key)
+{
+	register unsigned hash = 0;
+	while (*key != '\0')
+		hash = (hash << 3) + *key++;
+	return hash;
+}
+**************************************************/
+
+
+#include <limits.h>
+
+#define BITS(type) 	(CHAR_BIT * (int)sizeof(type))
+
+// This is from the "dragon" Compilers book.
+// It is much better than the above but somewhat slower.
+//
+unsigned strhash(register const char *p)
+{
+	register unsigned h = 0;
+	register unsigned g;
+	wchar_t __nlh_char[1];
+
+	if (p != NULL)
+		while (*p != '\0')
+		{
+			h = (h << 4) + (unsigned)CHARADV(p);
+			if (g = h & ((unsigned)0xF << BITS(unsigned) - 4))
+			{
+				h ^= g >> BITS(unsigned) - 4;
+				h ^= g;
+			}
+		}
+	return h;
+}
+
+// Same as above but case insensitive.  Returns the same value as the
+// above function if there are no upper case letters in the string.
+//
+unsigned strhashi(register const char *p)
+{
+	register unsigned h = 0;
+	register unsigned g;
+	wchar_t __nlh_char[1];
+
+	if (p != NULL)
+		while (*p != '\0')
+		{
+			if (mblen(p, MB_CUR_MAX) > 1)
+				h = (h << 4) + (unsigned)CHARADV(p);
+			else
+			{
+				h = (h << 4) + (unsigned)tolower(*p++);
+			}
+
+			if (g = h & ((unsigned)0xF << BITS(unsigned) - 4))
+			{
+				h ^= g >> BITS(unsigned) - 4;
+				h ^= g;
+			}
+		}
+	return h;
+}
+
+
+/**************************************************
+// This is about twice as slow as the above but 
+// does a slightly better hash.
+// by  TJ Merritt
+
+unsigned int
+hashfunc(buf, len)
+register unsigned char *buf;
+register int len;
+{
+	register unsigned int in;
+	register unsigned int xor;
+	register unsigned int t;
+
+	xor = len << 8;
+	in = 0;
+
+	while (len-- > 0)
+	{
+		in <<= 8;
+		in += *buf++;
+		xor ^= in;
+		t = ((xor & 0x3) << 29) | (xor >> 3);
+		xor ^= t;
+	}
+
+	return xor ^ (xor >> 16);
+}
+**************************************************/