常用的Hash算法
/*
**************************************************************************
* *
* General Purpose Hash Function Algorithms Library *
* *
* Author: Arash Partow - 2002 *
* URL: http://www.partow.net *
* URL: http://www.partow.net/programming/hashfunctions/index.html *
* *
* Copyright notice: *
* Free use of the General Purpose Hash Function Algorithms Library is *
* permitted under the guidelines and in accordance with the most current *
* version of the Common Public License. *
* http://www.opensource.org/licenses/cpl1.0.php *
* *
**************************************************************************
*/
class GeneralHashFunctionLibrary
{
public long RSHash(String str)
{
int b = 378551;
int a = 63689;
long hash = 0;
for(int i = 0; i < str.length(); i++)
{
hash = hash * a + str.charAt(i);
a = a * b;
}
return hash;
}
/* End Of RS Hash Function */
public long JSHash(String str)
{
long hash = 1315423911;
for(int i = 0; i < str.length(); i++)
{
hash ^= ((hash << 5) + str.charAt(i) + (hash >> 2));
}
return hash;
}
/* End Of JS Hash Function */
public long PJWHash(String str)
{
long BitsInUnsignedInt = (long)(4 * 8);
long ThreeQuarters = (long)((BitsInUnsignedInt * 3) / 4);
long OneEighth = (long)(BitsInUnsignedInt / 8);
long HighBits = (long)(0xFFFFFFFF) << (BitsInUnsignedInt - OneEighth);
long hash = 0;
long test = 0;
for(int i = 0; i < str.length(); i++)
{
hash = (hash << OneEighth) + str.charAt(i);
if((test = hash & HighBits) != 0)
{
hash = (( hash ^ (test >> ThreeQuarters)) & (~HighBits));
}
}
return hash;
}
/* End Of P. J. Weinberger Hash Function */
public long ELFHash(String str)
{
long hash = 0;
long x = 0;
for(int i = 0; i < str.length(); i++)
{
hash = (hash << 4) + str.charAt(i);
if((x = hash & 0xF0000000L) != 0)
{
hash ^= (x >> 24);
}
hash &= ~x;
}
return hash;
}
/* End Of ELF Hash Function */
public long BKDRHash(String str)
{
long seed = 131; // 31 131 1313 13131 131313 etc..
long hash = 0;
for(int i = 0; i < str.length(); i++)
{
hash = (hash * seed) + str.charAt(i);
}
return hash;
}
/* End Of BKDR Hash Function */
public long SDBMHash(String str)
{
long hash = 0;
for(int i = 0; i < str.length(); i++)
{
hash = str.charAt(i) + (hash << 6) + (hash << 16) - hash;
}
return hash;
}
/* End Of SDBM Hash Function */
public long DJBHash(String str)
{
long hash = 5381;
for(int i = 0; i < str.length(); i++)
{
hash = ((hash << 5) + hash) + str.charAt(i);
}
return hash;
}
/* End Of DJB Hash Function */
public long DEKHash(String str)
{
long hash = str.length();
for(int i = 0; i < str.length(); i++)
{
hash = ((hash << 5) ^ (hash >> 27)) ^ str.charAt(i);
}
return hash;
}
/* End Of DEK Hash Function */
public long BPHash(String str)
{
long hash = 0;
for(int i = 0; i < str.length(); i++)
{
hash = hash << 7 ^ str.charAt(i);
}
return hash;
}
/* End Of BP Hash Function */
public long FNVHash(String str)
{
long fnv_prime = 0x811C9DC5;
long hash = 0;
for(int i = 0; i < str.length(); i++)
{
hash *= fnv_prime;
hash ^= str.charAt(i);
}
return hash;
}
/* End Of FNV Hash Function */
public long APHash(String str)
{
long hash = 0xAAAAAAAA;
for(int i = 0; i < str.length(); i++)
{
if ((i & 1) == 0)
{
hash ^= ((hash << 7) ^ str.charAt(i) * (hash >> 3));
}
else
{
hash ^= (~((hash << 11) + str.charAt(i) ^ (hash >> 5)));
}
}
return hash;
}
/* End Of AP Hash Function */
}
/*
**************************************************************************
* *
* General Purpose Hash Function Algorithms Test *
* *
* Author: Arash Partow - 2002 *
* URL: http://www.partow.net *
* URL: http://www.partow.net/programming/hashfunctions/index.html *
* *
* Copyright notice: *
* Free use of the General Purpose Hash Function Algorithms Library is *
* permitted under the guidelines and in accordance with the most current *
* version of the Common Public License. *
* http://www.opensource.org/licenses/cpl1.0.php *
* *
**************************************************************************
*/
import java.io.*;
import java.lang.*;
public class GeneralHashTest
{
public static void main(String args[]) throws IOException
{
GeneralHashFunctionLibrary ghl = new GeneralHashFunctionLibrary();
String key = "abcdefghijklmnopqrstuvwxyz1234567890";
System.out.println("General Purpose Hash Function Algorithms Test");
System.out.println("By Arash Partow - 2002\n");
System.out.println("Key: " + key);
System.out.println(" 1. RS-Hash Function Value: " + ghl.RSHash(key));
System.out.println(" 2. JS-Hash Function Value: " + ghl.JSHash(key));
System.out.println(" 3. PJW-Hash Function Value: " + ghl.PJWHash(key));
System.out.println(" 4. ELF-Hash Function Value: " + ghl.ELFHash(key));
System.out.println(" 5. BKDR-Hash Function Value: " + ghl.BKDRHash(key));
System.out.println(" 6. SDBM-Hash Function Value: " + ghl.SDBMHash(key));
System.out.println(" 7. DJB-Hash Function Value: " + ghl.DJBHash(key));
System.out.println(" 8. DEK-Hash Function Value: " + ghl.DEKHash(key));
System.out.println(" 9. BP-Hash Function Value: " + ghl.BPHash(key));
System.out.println(" 9. FNV-Hash Function Value: " + ghl.FNVHash(key));
System.out.println("10. AP-Hash Function Value: " + ghl.APHash(key));
System.out.println("Press 'ENTER' to exit...");
BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
stdin.readLine();
}
}
#
# General Hash Function Algorithms Master MakeFile
# By Arash Partow - 2000
#
# URL: http://www.partow.net/programming/hashfunctions/index.html
#
# Copyright Notice:
# Free use of this library is permitted under the
# guidelines and in accordance with the most
# current version of the Common Public License.
# http://www.opensource.org/licenses/cpl1.0.php
#
COMPILER = javac
all: GeneralHashFunctionLibrary GeneralHashTest
GeneralHashFunctionLibrary: GeneralHashFunctionLibrary.java
$(COMPILER) GeneralHashFunctionLibrary.java
GeneralHashTest: GeneralHashTest.java GeneralHashFunctionLibrary
$(COMPILER) GeneralHashTest.java
clean:
rm -f core *.o *.bak *stackdump *#
#
# The End !
#