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Diffstat (limited to 'android/guava/src/com/google/common/hash/FarmHashFingerprint64.java')
| -rw-r--r-- | android/guava/src/com/google/common/hash/FarmHashFingerprint64.java | 216 |
1 files changed, 0 insertions, 216 deletions
diff --git a/android/guava/src/com/google/common/hash/FarmHashFingerprint64.java b/android/guava/src/com/google/common/hash/FarmHashFingerprint64.java deleted file mode 100644 index 30eab5fad..000000000 --- a/android/guava/src/com/google/common/hash/FarmHashFingerprint64.java +++ /dev/null @@ -1,216 +0,0 @@ -/* - * Copyright (C) 2015 The Guava Authors - * - * 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 com.google.common.hash; - -import static com.google.common.base.Preconditions.checkPositionIndexes; -import static com.google.common.hash.LittleEndianByteArray.load32; -import static com.google.common.hash.LittleEndianByteArray.load64; -import static java.lang.Long.rotateRight; - -import com.google.common.annotations.VisibleForTesting; - -/** - * Implementation of FarmHash Fingerprint64, an open-source fingerprinting algorithm for strings. - * - * <p>Its speed is comparable to CityHash64, and its quality of hashing is at least as good. - * - * <p>Note to maintainers: This implementation relies on signed arithmetic being bit-wise equivalent - * to unsigned arithmetic in all cases except: - * - * <ul> - * <li>comparisons (signed values can be negative) - * <li>division (avoided here) - * <li>shifting (right shift must be unsigned) - * </ul> - * - * @author Kyle Maddison - * @author Geoff Pike - */ -final class FarmHashFingerprint64 extends AbstractNonStreamingHashFunction { - static final HashFunction FARMHASH_FINGERPRINT_64 = new FarmHashFingerprint64(); - - // Some primes between 2^63 and 2^64 for various uses. - private static final long K0 = 0xc3a5c85c97cb3127L; - private static final long K1 = 0xb492b66fbe98f273L; - private static final long K2 = 0x9ae16a3b2f90404fL; - - @Override - public HashCode hashBytes(byte[] input, int off, int len) { - checkPositionIndexes(off, off + len, input.length); - return HashCode.fromLong(fingerprint(input, off, len)); - } - - @Override - public int bits() { - return 64; - } - - @Override - public String toString() { - return "Hashing.farmHashFingerprint64()"; - } - - // End of public functions. - - @VisibleForTesting - static long fingerprint(byte[] bytes, int offset, int length) { - if (length <= 32) { - if (length <= 16) { - return hashLength0to16(bytes, offset, length); - } else { - return hashLength17to32(bytes, offset, length); - } - } else if (length <= 64) { - return hashLength33To64(bytes, offset, length); - } else { - return hashLength65Plus(bytes, offset, length); - } - } - - private static long shiftMix(long val) { - return val ^ (val >>> 47); - } - - private static long hashLength16(long u, long v, long mul) { - long a = (u ^ v) * mul; - a ^= (a >>> 47); - long b = (v ^ a) * mul; - b ^= (b >>> 47); - b *= mul; - return b; - } - - /** - * Computes intermediate hash of 32 bytes of byte array from the given offset. Results are - * returned in the output array because when we last measured, this was 12% faster than allocating - * new arrays every time. - */ - private static void weakHashLength32WithSeeds( - byte[] bytes, int offset, long seedA, long seedB, long[] output) { - long part1 = load64(bytes, offset); - long part2 = load64(bytes, offset + 8); - long part3 = load64(bytes, offset + 16); - long part4 = load64(bytes, offset + 24); - - seedA += part1; - seedB = rotateRight(seedB + seedA + part4, 21); - long c = seedA; - seedA += part2; - seedA += part3; - seedB += rotateRight(seedA, 44); - output[0] = seedA + part4; - output[1] = seedB + c; - } - - private static long hashLength0to16(byte[] bytes, int offset, int length) { - if (length >= 8) { - long mul = K2 + length * 2; - long a = load64(bytes, offset) + K2; - long b = load64(bytes, offset + length - 8); - long c = rotateRight(b, 37) * mul + a; - long d = (rotateRight(a, 25) + b) * mul; - return hashLength16(c, d, mul); - } - if (length >= 4) { - long mul = K2 + length * 2; - long a = load32(bytes, offset) & 0xFFFFFFFFL; - return hashLength16(length + (a << 3), load32(bytes, offset + length - 4) & 0xFFFFFFFFL, mul); - } - if (length > 0) { - byte a = bytes[offset]; - byte b = bytes[offset + (length >> 1)]; - byte c = bytes[offset + (length - 1)]; - int y = (a & 0xFF) + ((b & 0xFF) << 8); - int z = length + ((c & 0xFF) << 2); - return shiftMix(y * K2 ^ z * K0) * K2; - } - return K2; - } - - private static long hashLength17to32(byte[] bytes, int offset, int length) { - long mul = K2 + length * 2; - long a = load64(bytes, offset) * K1; - long b = load64(bytes, offset + 8); - long c = load64(bytes, offset + length - 8) * mul; - long d = load64(bytes, offset + length - 16) * K2; - return hashLength16( - rotateRight(a + b, 43) + rotateRight(c, 30) + d, a + rotateRight(b + K2, 18) + c, mul); - } - - private static long hashLength33To64(byte[] bytes, int offset, int length) { - long mul = K2 + length * 2; - long a = load64(bytes, offset) * K2; - long b = load64(bytes, offset + 8); - long c = load64(bytes, offset + length - 8) * mul; - long d = load64(bytes, offset + length - 16) * K2; - long y = rotateRight(a + b, 43) + rotateRight(c, 30) + d; - long z = hashLength16(y, a + rotateRight(b + K2, 18) + c, mul); - long e = load64(bytes, offset + 16) * mul; - long f = load64(bytes, offset + 24); - long g = (y + load64(bytes, offset + length - 32)) * mul; - long h = (z + load64(bytes, offset + length - 24)) * mul; - return hashLength16( - rotateRight(e + f, 43) + rotateRight(g, 30) + h, e + rotateRight(f + a, 18) + g, mul); - } - - /* - * Compute an 8-byte hash of a byte array of length greater than 64 bytes. - */ - private static long hashLength65Plus(byte[] bytes, int offset, int length) { - final int seed = 81; - // For strings over 64 bytes we loop. Internal state consists of 56 bytes: v, w, x, y, and z. - long x = seed; - @SuppressWarnings("ConstantOverflow") - long y = seed * K1 + 113; - long z = shiftMix(y * K2 + 113) * K2; - long[] v = new long[2]; - long[] w = new long[2]; - x = x * K2 + load64(bytes, offset); - - // Set end so that after the loop we have 1 to 64 bytes left to process. - int end = offset + ((length - 1) / 64) * 64; - int last64offset = end + ((length - 1) & 63) - 63; - do { - x = rotateRight(x + y + v[0] + load64(bytes, offset + 8), 37) * K1; - y = rotateRight(y + v[1] + load64(bytes, offset + 48), 42) * K1; - x ^= w[1]; - y += v[0] + load64(bytes, offset + 40); - z = rotateRight(z + w[0], 33) * K1; - weakHashLength32WithSeeds(bytes, offset, v[1] * K1, x + w[0], v); - weakHashLength32WithSeeds(bytes, offset + 32, z + w[1], y + load64(bytes, offset + 16), w); - long tmp = x; - x = z; - z = tmp; - offset += 64; - } while (offset != end); - long mul = K1 + ((z & 0xFF) << 1); - // Operate on the last 64 bytes of input. - offset = last64offset; - w[0] += ((length - 1) & 63); - v[0] += w[0]; - w[0] += v[0]; - x = rotateRight(x + y + v[0] + load64(bytes, offset + 8), 37) * mul; - y = rotateRight(y + v[1] + load64(bytes, offset + 48), 42) * mul; - x ^= w[1] * 9; - y += v[0] * 9 + load64(bytes, offset + 40); - z = rotateRight(z + w[0], 33) * mul; - weakHashLength32WithSeeds(bytes, offset, v[1] * mul, x + w[0], v); - weakHashLength32WithSeeds(bytes, offset + 32, z + w[1], y + load64(bytes, offset + 16), w); - return hashLength16( - hashLength16(v[0], w[0], mul) + shiftMix(y) * K0 + x, - hashLength16(v[1], w[1], mul) + z, - mul); - } -} |