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/*
* Copyright (c) Flux Capacitor IP B.V. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* http://www.apache.org/licenses/LICENSE-2.0
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.fluxcapacitor.common;
/**
* The MurmurHash3 algorithm was created by Austin Appleby and placed in the public domain. This java port was authored
* by Yonik Seeley and also placed into the public domain.
*
* This produces exactly the same hash values as the final C++ version of MurmurHash3 and is thus suitable for producing
* the same hash values across platforms.
*
* See ... for future updates to this file.
*/
public class Murmur3 {
/**
* Returns the MurmurHash3_x86_32 hash of the UTF-8 bytes of the String using seed of 0 without actually encoding
* the string to a temporary buffer.
*
* @param data string to hash
* @return the hash code
*/
public static int murmurhash3_x86_32(CharSequence data) {
return murmurhash3_x86_32(data, 0, data.length(), 0);
}
/**
* Returns the MurmurHash3_x86_32 hash of the UTF-8 bytes of the String without actually encoding the string to a
* temporary buffer.
*
* @param data string to hash
* @param offset start in substring to hash
* @param len length of substring to hash
* @param seed algorithm seed
* @return the hash code
*/
public static int murmurhash3_x86_32(CharSequence data, int offset, int len, int seed) {
final int c1 = 0xcc9e2d51;
final int c2 = 0x1b873593;
int h1 = seed;
int pos = offset;
int end = offset + len;
int k1 = 0;
int k2 = 0;
int shift = 0;
int bits = 0;
int nBytes = 0; // length in UTF8 bytes
while (pos < end) {
int code = data.charAt(pos++);
if (code < 0x80) {
k2 = code;
bits = 8;
} else if (code < 0x800) {
k2 = (0xC0 | (code >> 6))
| ((0x80 | (code & 0x3F)) << 8);
bits = 16;
} else if (code < 0xD800 || code > 0xDFFF || pos >= end) {
// we check for pos>=end to encode an unpaired surrogate as 3 bytes.
k2 = (0xE0 | (code >> 12))
| ((0x80 | ((code >> 6) & 0x3F)) << 8)
| ((0x80 | (code & 0x3F)) << 16);
bits = 24;
} else {
// surrogate pair
// int utf32 = pos < end ? (int) data.charAt(pos++) : 0;
int utf32 = (int) data.charAt(pos++);
utf32 = ((code - 0xD7C0) << 10) + (utf32 & 0x3FF);
k2 = (0xff & (0xF0 | (utf32 >> 18)))
| ((0x80 | ((utf32 >> 12) & 0x3F))) << 8
| ((0x80 | ((utf32 >> 6) & 0x3F))) << 16
| (0x80 | (utf32 & 0x3F)) << 24;
bits = 32;
}
k1 |= k2 << shift;
// int used_bits = 32 - shift; // how many bits of k2 were used in k1.
// int unused_bits = bits - used_bits; // (bits-(32-shift)) == bits+shift-32 == bits-newshift
shift += bits;
if (shift >= 32) {
// mix after we have a complete word
k1 *= c1;
k1 = (k1 << 15) | (k1 >>> 17); // ROTL32(k1,15);
k1 *= c2;
h1 ^= k1;
h1 = (h1 << 13) | (h1 >>> 19); // ROTL32(h1,13);
h1 = h1 * 5 + 0xe6546b64;
shift -= 32;
// unfortunately, java won't let you shift 32 bits off, so we need to check for 0
if (shift != 0) {
k1 = k2 >>> (bits - shift); // bits used == bits - newshift
} else {
k1 = 0;
}
nBytes += 4;
}
} // inner
// handle tail
if (shift > 0) {
nBytes += shift >> 3;
k1 *= c1;
k1 = (k1 << 15) | (k1 >>> 17); // ROTL32(k1,15);
k1 *= c2;
h1 ^= k1;
}
// finalization
h1 ^= nBytes;
// fmix(h1);
h1 ^= h1 >>> 16;
h1 *= 0x85ebca6b;
h1 ^= h1 >>> 13;
h1 *= 0xc2b2ae35;
h1 ^= h1 >>> 16;
return h1;
}
}