整理自本人的有道历史云笔记
一. 常用hash方法列举
加法hash:
/**
* 加法hash
*
* @param str
* @return
*/
public int addHash(String str) {
int hash = 0;
if (str != null && str.length() > 0) {
byte[] bytes;
try {
bytes = str.getBytes("UTF-8");
for (byte b : bytes) {
hash += Math.abs(b);
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
return hash;
}
乘法hash:
/**
* 乘法hash
*
* @param str
* @return
*/
public int multiHash(String str) {
int hash = 0;
if (str != null && str.length() > 0) {
byte[] bytes;
try {
bytes = str.getBytes("UTF-8");
for (byte b : bytes) {
hash *= Math.abs(b);
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
return hash;
}
位移hash:
/**
* 位移hash
*
* @param str
* @return
*/
public int displaceHash(String str) {
int hash = 0;
if (str != null && str.length() > 0) {
byte[] bytes;
try {
bytes = str.getBytes("UTF-8");
for (byte b : bytes) {
hash = hash << 5 ^ Math.abs(b) << 2;
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
return hash;
}
RS Hash Function:
/**
* RS Hash Function
*
* @param str
* @return
*/
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;
}
JS Hash Function:
/**
* JS Hash Function
*
* @param str
* @return
*/
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;
}
P. J. Weinberger Hash Function:
/**
* P. J. Weinberger Hash Function
*
* @param str
* @return
*/
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;
}
ELF Hash Function:
/**
* ELF Hash Function
*
* @param str
* @return
*/
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;
}
BKDR Hash Function:
/**
* BKDR Hash Function
*
* @param str
* @return
*/
public long bkdrHash(String str) {
// 31 131 1313 13131 131313 etc..
long seed = 131;
long hash = 0;
for (int i = 0; i < str.length(); i++) {
hash = (hash * seed) + str.charAt(i);
}
return hash;
}
SDBM Hash Function:
/**
* SDBM Hash Function
*
* @param str
* @return
*/
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;
}
DJB Hash Function:
/**
* DJB Hash Function
*
* @param str
* @return
*/
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;
}
DEK Hash Function:
/**
* DEK Hash Function
*
* @param str
* @return
*/
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;
}
BP Hash Function:
/**
* BP Hash Function
*
* @param str
* @return
*/
public long bpHash(String str) {
long hash = 0;
for (int i = 0; i < str.length(); i++) {
hash = hash << 7 ^ str.charAt(i);
}
return hash;
}
FNV Hash Function:
/**
* FNV Hash Function
*
* @param str
* @return
*/
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;
}
AP Hash Function:
/**
* AP Hash Function
*
* @param str
* @return
*/
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;
}
二. Guava Hashing 简单例子
Google 出的 Guava 是 Java 核心增强的库，应用非常广泛。
Guava 常用 Hash function 如下例子
package com.dbyz.base.guava;
import com.google.common.hash.HashFunction;
import com.google.common.hash.Hashing;
import lombok.extern.slf4j.Slf4j;
import java.nio.charset.StandardCharsets;
/**
* HashingTest
*
* @author fangzheng
* @version v0.1 2017-05-13 14:21
*/
@Slf4j
@SuppressWarnings("UnstableApiUsage")
public class HashingTest {
public static void main(String[] args) {
byte[] bytes = "123456".getBytes(StandardCharsets.UTF_8);
// SIP
HashFunction function = Hashing.sipHash24();
log.info("SIP {}", function.hashBytes(bytes).toString());
// MD5
function = Hashing.md5();
log.info("MD5 {}", function.hashBytes(bytes).toString());
// SHA
function = Hashing.sha256();
log.info("SHA256 {}", function.hashBytes(bytes).toString());
function = Hashing.sha512();
log.info("SHA512 {}", function.hashBytes(bytes).toString());
// CRC
function = Hashing.crc32();
log.info("CRC32 {}", function.hashBytes(bytes).toString());
function = Hashing.crc32c();
log.info("CRC32C {}", function.hashBytes(bytes).toString());
//MURMUR3
function = Hashing.murmur3_32();
log.info("MURMUR3_32 {}", function.hashBytes(bytes).toString());
function = Hashing.murmur3_32(0);
log.info("MURMUR3_32 {}", function.hashBytes(bytes).toString());
function = Hashing.murmur3_128();
log.info("MURMUR3_128 {}", function.hashBytes(bytes).toString());
function = Hashing.murmur3_128(0);
log.info("MURMUR3_128 {}", function.hashBytes(bytes).toString());
// GFH 每次启动都不同随机性(启动时间的毫秒值)
function = Hashing.goodFastHash(32);
log.info("GFH 32 {}", function.hashBytes(bytes).toString());
function = Hashing.goodFastHash(128);
log.info("GFH 128 {}", function.hashBytes(bytes).toString());
// HMAC_SHA256
function = Hashing.hmacSha256("key".getBytes());
log.info("HMAC_SHA256 {}", function.hashBytes(bytes).toString());
function = Hashing.hmacSha512("key".getBytes());
log.info("HMAC_SHA512 {}", function.hashBytes(bytes).toString());
// HMAC_MD5
function = Hashing.hmacMd5("key".getBytes());
log.info("HMAC_MD5 {}", function.hashBytes(bytes).toString());
}
}
