1 /* 2 * Copyright (C) 2011 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 5 * in compliance with the License. You may obtain a copy of the License at 6 * 7 * http://www.apache.org/licenses/LICENSE-2.0 8 * 9 * Unless required by applicable law or agreed to in writing, software distributed under the License 10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 11 * or implied. See the License for the specific language governing permissions and limitations under 12 * the License. 13 */ 14 15 package com.google.common.hash; 16 17 /** 18 * This class generates a CRC32C checksum, defined by RFC 3720, Section 12.1. 19 * The generator polynomial for this checksum is {@code 0x11EDC6F41}. 20 * 21 * @author Kurt Alfred Kluever 22 */ 23 final class Crc32cHashFunction extends AbstractStreamingHashFunction { 24 25 @Override bits()26 public int bits() { 27 return 32; 28 } 29 30 @Override newHasher()31 public Hasher newHasher() { 32 return new Crc32cHasher(); 33 } 34 35 @Override toString()36 public String toString() { 37 return "Hashing.crc32c()"; 38 } 39 40 static final class Crc32cHasher extends AbstractByteHasher { 41 42 // The CRC table, generated from the polynomial 0x11EDC6F41. 43 static final int[] CRC_TABLE = { 44 0x00000000, 0xf26b8303, 0xe13b70f7, 0x1350f3f4, 45 0xc79a971f, 0x35f1141c, 0x26a1e7e8, 0xd4ca64eb, 46 0x8ad958cf, 0x78b2dbcc, 0x6be22838, 0x9989ab3b, 47 0x4d43cfd0, 0xbf284cd3, 0xac78bf27, 0x5e133c24, 48 0x105ec76f, 0xe235446c, 0xf165b798, 0x030e349b, 49 0xd7c45070, 0x25afd373, 0x36ff2087, 0xc494a384, 50 0x9a879fa0, 0x68ec1ca3, 0x7bbcef57, 0x89d76c54, 51 0x5d1d08bf, 0xaf768bbc, 0xbc267848, 0x4e4dfb4b, 52 0x20bd8ede, 0xd2d60ddd, 0xc186fe29, 0x33ed7d2a, 53 0xe72719c1, 0x154c9ac2, 0x061c6936, 0xf477ea35, 54 0xaa64d611, 0x580f5512, 0x4b5fa6e6, 0xb93425e5, 55 0x6dfe410e, 0x9f95c20d, 0x8cc531f9, 0x7eaeb2fa, 56 0x30e349b1, 0xc288cab2, 0xd1d83946, 0x23b3ba45, 57 0xf779deae, 0x05125dad, 0x1642ae59, 0xe4292d5a, 58 0xba3a117e, 0x4851927d, 0x5b016189, 0xa96ae28a, 59 0x7da08661, 0x8fcb0562, 0x9c9bf696, 0x6ef07595, 60 0x417b1dbc, 0xb3109ebf, 0xa0406d4b, 0x522bee48, 61 0x86e18aa3, 0x748a09a0, 0x67dafa54, 0x95b17957, 62 0xcba24573, 0x39c9c670, 0x2a993584, 0xd8f2b687, 63 0x0c38d26c, 0xfe53516f, 0xed03a29b, 0x1f682198, 64 0x5125dad3, 0xa34e59d0, 0xb01eaa24, 0x42752927, 65 0x96bf4dcc, 0x64d4cecf, 0x77843d3b, 0x85efbe38, 66 0xdbfc821c, 0x2997011f, 0x3ac7f2eb, 0xc8ac71e8, 67 0x1c661503, 0xee0d9600, 0xfd5d65f4, 0x0f36e6f7, 68 0x61c69362, 0x93ad1061, 0x80fde395, 0x72966096, 69 0xa65c047d, 0x5437877e, 0x4767748a, 0xb50cf789, 70 0xeb1fcbad, 0x197448ae, 0x0a24bb5a, 0xf84f3859, 71 0x2c855cb2, 0xdeeedfb1, 0xcdbe2c45, 0x3fd5af46, 72 0x7198540d, 0x83f3d70e, 0x90a324fa, 0x62c8a7f9, 73 0xb602c312, 0x44694011, 0x5739b3e5, 0xa55230e6, 74 0xfb410cc2, 0x092a8fc1, 0x1a7a7c35, 0xe811ff36, 75 0x3cdb9bdd, 0xceb018de, 0xdde0eb2a, 0x2f8b6829, 76 0x82f63b78, 0x709db87b, 0x63cd4b8f, 0x91a6c88c, 77 0x456cac67, 0xb7072f64, 0xa457dc90, 0x563c5f93, 78 0x082f63b7, 0xfa44e0b4, 0xe9141340, 0x1b7f9043, 79 0xcfb5f4a8, 0x3dde77ab, 0x2e8e845f, 0xdce5075c, 80 0x92a8fc17, 0x60c37f14, 0x73938ce0, 0x81f80fe3, 81 0x55326b08, 0xa759e80b, 0xb4091bff, 0x466298fc, 82 0x1871a4d8, 0xea1a27db, 0xf94ad42f, 0x0b21572c, 83 0xdfeb33c7, 0x2d80b0c4, 0x3ed04330, 0xccbbc033, 84 0xa24bb5a6, 0x502036a5, 0x4370c551, 0xb11b4652, 85 0x65d122b9, 0x97baa1ba, 0x84ea524e, 0x7681d14d, 86 0x2892ed69, 0xdaf96e6a, 0xc9a99d9e, 0x3bc21e9d, 87 0xef087a76, 0x1d63f975, 0x0e330a81, 0xfc588982, 88 0xb21572c9, 0x407ef1ca, 0x532e023e, 0xa145813d, 89 0x758fe5d6, 0x87e466d5, 0x94b49521, 0x66df1622, 90 0x38cc2a06, 0xcaa7a905, 0xd9f75af1, 0x2b9cd9f2, 91 0xff56bd19, 0x0d3d3e1a, 0x1e6dcdee, 0xec064eed, 92 0xc38d26c4, 0x31e6a5c7, 0x22b65633, 0xd0ddd530, 93 0x0417b1db, 0xf67c32d8, 0xe52cc12c, 0x1747422f, 94 0x49547e0b, 0xbb3ffd08, 0xa86f0efc, 0x5a048dff, 95 0x8ecee914, 0x7ca56a17, 0x6ff599e3, 0x9d9e1ae0, 96 0xd3d3e1ab, 0x21b862a8, 0x32e8915c, 0xc083125f, 97 0x144976b4, 0xe622f5b7, 0xf5720643, 0x07198540, 98 0x590ab964, 0xab613a67, 0xb831c993, 0x4a5a4a90, 99 0x9e902e7b, 0x6cfbad78, 0x7fab5e8c, 0x8dc0dd8f, 100 0xe330a81a, 0x115b2b19, 0x020bd8ed, 0xf0605bee, 101 0x24aa3f05, 0xd6c1bc06, 0xc5914ff2, 0x37faccf1, 102 0x69e9f0d5, 0x9b8273d6, 0x88d28022, 0x7ab90321, 103 0xae7367ca, 0x5c18e4c9, 0x4f48173d, 0xbd23943e, 104 0xf36e6f75, 0x0105ec76, 0x12551f82, 0xe03e9c81, 105 0x34f4f86a, 0xc69f7b69, 0xd5cf889d, 0x27a40b9e, 106 0x79b737ba, 0x8bdcb4b9, 0x988c474d, 0x6ae7c44e, 107 0xbe2da0a5, 0x4c4623a6, 0x5f16d052, 0xad7d5351 108 }; 109 110 private int crc = 0; 111 112 @Override update(byte b)113 public void update(byte b) { 114 crc ^= 0xFFFFFFFF; 115 // See Hacker's Delight 2nd Edition, Figure 14-7. 116 crc = ~((crc >>> 8) ^ CRC_TABLE[(crc ^ b) & 0xFF]); 117 } 118 119 @Override hash()120 public HashCode hash() { 121 return HashCode.fromInt(crc); 122 } 123 } 124 } 125