/** Get the md5 of the given key. */
public static byte[] computeMd5(String k) {
MessageDigest md5;
try {
md5 = MessageDigest.getInstance("MD5");
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException("MD5 not supported", e);
}
md5.reset();
md5.update(ByteUtils.getBytes(k));
return md5.digest();
}
/**
* Compute the hash for the given key.
*
* @return a positive integer hash
*/
public long hash(final String k) {
long rv = 0;
switch (this) {
case NATIVE_HASH:
rv = k.hashCode();
break;
case CRC32_HASH:
// return (crc32(shift) >> 16) & 0x7fff;
CRC32 crc32 = new CRC32();
crc32.update(ByteUtils.getBytes(k));
rv = crc32.getValue() >> 16 & 0x7fff;
break;
case FNV1_64_HASH:
{
// Thanks to [email protected] for the pointer
rv = FNV_64_INIT;
int len = k.length();
for (int i = 0; i < len; i++) {
rv *= FNV_64_PRIME;
rv ^= k.charAt(i);
}
}
break;
case MurMurHash:
ByteBuffer buf = ByteBuffer.wrap(k.getBytes());
int seed = 0x1234ABCD;
ByteOrder byteOrder = buf.order();
buf.order(ByteOrder.LITTLE_ENDIAN);
long m = 0xc6a4a7935bd1e995L;
int r = 47;
rv = seed ^ (buf.remaining() * m);
long ky;
while (buf.remaining() >= 8) {
ky = buf.getLong();
ky *= m;
ky ^= ky >>> r;
ky *= m;
rv ^= ky;
rv *= m;
}
if (buf.remaining() > 0) {
ByteBuffer finish = ByteBuffer.allocate(8).order(ByteOrder.LITTLE_ENDIAN);
// for big-endian version, do this first:
// finish.position(8-buf.remaining());
finish.put(buf).rewind();
rv ^= finish.getLong();
rv *= m;
}
rv ^= rv >>> r;
rv *= m;
rv ^= rv >>> r;
buf.order(byteOrder);
break;
case FNV1A_64_HASH:
{
rv = FNV_64_INIT;
int len = k.length();
for (int i = 0; i < len; i++) {
rv ^= k.charAt(i);
rv *= FNV_64_PRIME;
}
}
break;
case FNV1_32_HASH:
{
rv = FNV_32_INIT;
int len = k.length();
for (int i = 0; i < len; i++) {
rv *= FNV_32_PRIME;
rv ^= k.charAt(i);
}
}
break;
case FNV1A_32_HASH:
{
rv = FNV_32_INIT;
int len = k.length();
for (int i = 0; i < len; i++) {
rv ^= k.charAt(i);
rv *= FNV_32_PRIME;
}
}
break;
case KETAMA_HASH:
byte[] bKey = computeMd5(k);
rv =
(long) (bKey[3] & 0xFF) << 24
| (long) (bKey[2] & 0xFF) << 16
| (long) (bKey[1] & 0xFF) << 8
| bKey[0] & 0xFF;
break;
case MYSQL_HASH:
int nr2 = 4;
for (int i = 0; i < k.length(); i++) {
rv ^= ((rv & 63) + nr2) * k.charAt(i) + (rv << 8);
nr2 += 3;
}
break;
case ELF_HASH:
long x = 0;
for (int i = 0; i < k.length(); i++) {
rv = (rv << 4) + k.charAt(i);
if ((x = rv & 0xF0000000L) != 0) {
rv ^= x >> 24;
rv &= ~x;
}
}
rv = rv & 0x7FFFFFFF;
break;
case RS_HASH:
long b = 378551;
long a = 63689;
for (int i = 0; i < k.length(); i++) {
rv = rv * a + k.charAt(i);
a *= b;
}
rv = rv & 0x7FFFFFFF;
break;
case LUA_HASH:
int step = (k.length() >> 5) + 1;
rv = k.length();
for (int len = k.length(); len >= step; len -= step) {
rv = rv ^ (rv << 5) + (rv >> 2) + k.charAt(len - 1);
}
case ONE_AT_A_TIME:
try {
int hash = 0;
for (byte bt : k.getBytes("utf-8")) {
hash += (bt & 0xFF);
hash += (hash << 10);
hash ^= (hash >>> 6);
}
hash += (hash << 3);
hash ^= (hash >>> 11);
hash += (hash << 15);
return hash;
} catch (UnsupportedEncodingException e) {
throw new IllegalStateException("Hash function error", e);
}
default:
assert false;
}
return rv & 0xffffffffL; /* Truncate to 32-bits */
}