codesburner · March 30, 2012 10:26 · Mar 23, 2012
diff --git a/hash_algo.c b/hash_algo.c
@@ -0,0 +1,157 @@
+//PHP中出现的字符串Hash函数
+
+static unsigned long hashpjw(char *arKey, unsigned int nKeyLength)
+{
+	unsigned long h = 0, g;
+	char *arEnd=arKey+nKeyLength;
+
+	while (arKey < arEnd)
+	{
+		h = (h << 4) + *arKey++;
+		if ((g = (h & 0xF0000000)))
+		{
+			h = h ^ (g >> 24);
+			h = h ^ g;
+		}
+	}
+	return h;
+}
+
+//OpenSSL中出现的字符串Hash函数
+
+unsigned long lh_strhash(char *str)
+{
+	int i,l;
+	unsigned long ret=0;
+	unsigned short *s;
+
+	if (str == NULL) return(0);
+	l=(strlen(str)+1)/2;
+	s=(unsigned short *)str;
+
+	for (i=0; i
+	        ret^=(s[i]<<(i&0x0f));
+	        return(ret);
+}
+
+        /* The following hash seems to work very well on normal text strings
+        * no collisions on /usr/dict/words and it distributes on %2^n quite
+        * well, not as good as MD5, but still good.
+        */
+        unsigned long lh_strhash(const char *c)
+{
+	unsigned long ret=0;
+	long n;
+	unsigned long v;
+	int r;
+
+	if ((c == NULL) || (*c == '\0'))
+		return(ret);
+	/*
+	unsigned char b[16];
+	MD5(c,strlen(c),b);
+	return(b[0]|(b[1]<<8)|(b[2]<<16)|(b[3]<<24));
+	*/
+
+	n=0x100;
+	while (*c)
+	{
+		v=n|(*c);
+		n+=0x100;
+		r= (int)((v>>2)^v)&0x0f;
+		ret=(ret(32-r));
+		ret&=0xFFFFFFFFL;
+		ret^=v*v;
+		c++;
+	}
+
+	return((ret>>16)^ret);
+}
+
+//MySql中出现的字符串Hash函数
+
+#ifndef NEW_HASH_FUNCTION
+
+/* Calc hashvalue for a key */
+static uint calc_hashnr(const byte *key,uint length)
+{
+	register uint nr=1, nr2=4;
+
+	while (length--)
+	{
+		nr^= (((nr & 63)+nr2)*((uint) (uchar) *key++))+ (nr << 8);
+		nr2+=3;
+	}
+
+	return((uint) nr);
+}
+
+/* Calc hashvalue for a key, case indepenently */
+static uint calc_hashnr_caseup(const byte *key,uint length)
+{
+	register uint nr=1, nr2=4;
+
+	while (length--)
+	{
+		nr^= (((nr & 63)+nr2)*((uint) (uchar) toupper(*key++)))+ (nr << 8);
+		nr2+=3;
+	}
+
+	return((uint) nr);
+}
+#else
+/*
+* Fowler/Noll/Vo hash
+*
+* The basis of the hash algorithm was taken from an idea sent by email to the
+* IEEE Posix P1003.2 mailing list from Phong Vo ([email protected]) and
+* Glenn Fowler ([email protected]). Landon Curt Noll ([email protected])
+* later improved on their algorithm.
+*
+* The magic is in the interesting relationship between the special prime
+* 16777619 (2^24 + 403) and 2^32 and 2^8.
+*
+* This hash produces the fewest collisions of any function that we've seen so
+* far, and works well on both numbers and strings.
+*/
+uint calc_hashnr(const byte *key, uint len)
+{
+	const byte *end=key+len;
+	uint hash;
+
+	for (hash = 0; key < end; key++)
+	{
+		hash *= 16777619;
+		hash ^= (uint) *(uchar*) key;
+	}
+
+	return (hash);
+}
+
+uint calc_hashnr_caseup(const byte *key, uint len)
+{
+	const byte *end=key+len;
+	uint hash;
+
+	for (hash = 0; key < end; key++)
+	{
+		hash *= 16777619;
+		hash ^= (uint) (uchar) toupper(*key);
+	}
+
+	return (hash);
+}
+#endif
+
+//Mysql中对字符串Hash函数还区分了大小写
+//另一个经典字符串Hash函数
+unsigned int hash(char *str)
+{
+	register unsigned int h;
+	register unsigned char *p;
+
+	for(h=0, p = (unsigned char *)str; *p ; p++)
+		h = 31 * h + *p;
+
+	return h;
+}