hadoop CRC 源码

haddop CRC 代码

文件路径：/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/compress/bzip2/CRC.java

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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.
 *
 */

/*
 * This package is based on the work done by Keiron Liddle, Aftex Software
 * <keiron@aftexsw.com> to whom the Ant project is very grateful for his
 * great code.
 */

package org.apache.hadoop.io.compress.bzip2;

/**
 * A simple class the hold and calculate the CRC for sanity checking of the
 * data.
 *
 */
final class CRC {
  static final int crc32Table[] = { 0x00000000, 0x04c11db7, 0x09823b6e,
      0x0d4326d9, 0x130476dc, 0x17c56b6b, 0x1a864db2, 0x1e475005,
      0x2608edb8, 0x22c9f00f, 0x2f8ad6d6, 0x2b4bcb61, 0x350c9b64,
      0x31cd86d3, 0x3c8ea00a, 0x384fbdbd, 0x4c11db70, 0x48d0c6c7,
      0x4593e01e, 0x4152fda9, 0x5f15adac, 0x5bd4b01b, 0x569796c2,
      0x52568b75, 0x6a1936c8, 0x6ed82b7f, 0x639b0da6, 0x675a1011,
      0x791d4014, 0x7ddc5da3, 0x709f7b7a, 0x745e66cd, 0x9823b6e0,
      0x9ce2ab57, 0x91a18d8e, 0x95609039, 0x8b27c03c, 0x8fe6dd8b,
      0x82a5fb52, 0x8664e6e5, 0xbe2b5b58, 0xbaea46ef, 0xb7a96036,
      0xb3687d81, 0xad2f2d84, 0xa9ee3033, 0xa4ad16ea, 0xa06c0b5d,
      0xd4326d90, 0xd0f37027, 0xddb056fe, 0xd9714b49, 0xc7361b4c,
      0xc3f706fb, 0xceb42022, 0xca753d95, 0xf23a8028, 0xf6fb9d9f,
      0xfbb8bb46, 0xff79a6f1, 0xe13ef6f4, 0xe5ffeb43, 0xe8bccd9a,
      0xec7dd02d, 0x34867077, 0x30476dc0, 0x3d044b19, 0x39c556ae,
      0x278206ab, 0x23431b1c, 0x2e003dc5, 0x2ac12072, 0x128e9dcf,
      0x164f8078, 0x1b0ca6a1, 0x1fcdbb16, 0x018aeb13, 0x054bf6a4,
      0x0808d07d, 0x0cc9cdca, 0x7897ab07, 0x7c56b6b0, 0x71159069,
      0x75d48dde, 0x6b93dddb, 0x6f52c06c, 0x6211e6b5, 0x66d0fb02,
      0x5e9f46bf, 0x5a5e5b08, 0x571d7dd1, 0x53dc6066, 0x4d9b3063,
      0x495a2dd4, 0x44190b0d, 0x40d816ba, 0xaca5c697, 0xa864db20,
      0xa527fdf9, 0xa1e6e04e, 0xbfa1b04b, 0xbb60adfc, 0xb6238b25,
      0xb2e29692, 0x8aad2b2f, 0x8e6c3698, 0x832f1041, 0x87ee0df6,
      0x99a95df3, 0x9d684044, 0x902b669d, 0x94ea7b2a, 0xe0b41de7,
      0xe4750050, 0xe9362689, 0xedf73b3e, 0xf3b06b3b, 0xf771768c,
      0xfa325055, 0xfef34de2, 0xc6bcf05f, 0xc27dede8, 0xcf3ecb31,
      0xcbffd686, 0xd5b88683, 0xd1799b34, 0xdc3abded, 0xd8fba05a,
      0x690ce0ee, 0x6dcdfd59, 0x608edb80, 0x644fc637, 0x7a089632,
      0x7ec98b85, 0x738aad5c, 0x774bb0eb, 0x4f040d56, 0x4bc510e1,
      0x46863638, 0x42472b8f, 0x5c007b8a, 0x58c1663d, 0x558240e4,
      0x51435d53, 0x251d3b9e, 0x21dc2629, 0x2c9f00f0, 0x285e1d47,
      0x36194d42, 0x32d850f5, 0x3f9b762c, 0x3b5a6b9b, 0x0315d626,
      0x07d4cb91, 0x0a97ed48, 0x0e56f0ff, 0x1011a0fa, 0x14d0bd4d,
      0x19939b94, 0x1d528623, 0xf12f560e, 0xf5ee4bb9, 0xf8ad6d60,
      0xfc6c70d7, 0xe22b20d2, 0xe6ea3d65, 0xeba91bbc, 0xef68060b,
      0xd727bbb6, 0xd3e6a601, 0xdea580d8, 0xda649d6f, 0xc423cd6a,
      0xc0e2d0dd, 0xcda1f604, 0xc960ebb3, 0xbd3e8d7e, 0xb9ff90c9,
      0xb4bcb610, 0xb07daba7, 0xae3afba2, 0xaafbe615, 0xa7b8c0cc,
      0xa379dd7b, 0x9b3660c6, 0x9ff77d71, 0x92b45ba8, 0x9675461f,
      0x8832161a, 0x8cf30bad, 0x81b02d74, 0x857130c3, 0x5d8a9099,
      0x594b8d2e, 0x5408abf7, 0x50c9b640, 0x4e8ee645, 0x4a4ffbf2,
      0x470cdd2b, 0x43cdc09c, 0x7b827d21, 0x7f436096, 0x7200464f,
      0x76c15bf8, 0x68860bfd, 0x6c47164a, 0x61043093, 0x65c52d24,
      0x119b4be9, 0x155a565e, 0x18197087, 0x1cd86d30, 0x029f3d35,
      0x065e2082, 0x0b1d065b, 0x0fdc1bec, 0x3793a651, 0x3352bbe6,
      0x3e119d3f, 0x3ad08088, 0x2497d08d, 0x2056cd3a, 0x2d15ebe3,
      0x29d4f654, 0xc5a92679, 0xc1683bce, 0xcc2b1d17, 0xc8ea00a0,
      0xd6ad50a5, 0xd26c4d12, 0xdf2f6bcb, 0xdbee767c, 0xe3a1cbc1,
      0xe760d676, 0xea23f0af, 0xeee2ed18, 0xf0a5bd1d, 0xf464a0aa,
      0xf9278673, 0xfde69bc4, 0x89b8fd09, 0x8d79e0be, 0x803ac667,
      0x84fbdbd0, 0x9abc8bd5, 0x9e7d9662, 0x933eb0bb, 0x97ffad0c,
      0xafb010b1, 0xab710d06, 0xa6322bdf, 0xa2f33668, 0xbcb4666d,
      0xb8757bda, 0xb5365d03, 0xb1f740b4 };

  CRC() {
    initialiseCRC();
  }

  void initialiseCRC() {
    globalCrc = 0xffffffff;
  }

  int getFinalCRC() {
    return ~globalCrc;
  }

  int getGlobalCRC() {
    return globalCrc;
  }

  void setGlobalCRC(int newCrc) {
    globalCrc = newCrc;
  }

  void updateCRC(int inCh) {
    int temp = (globalCrc >> 24) ^ inCh;
    if (temp < 0) {
      temp = 256 + temp;
    }
    globalCrc = (globalCrc << 8) ^ CRC.crc32Table[temp];
  }

  void updateCRC(int inCh, int repeat) {
    int globalCrcShadow = this.globalCrc;
    while (repeat-- > 0) {
      int temp = (globalCrcShadow >> 24) ^ inCh;
      globalCrcShadow = (globalCrcShadow << 8)
          ^ crc32Table[(temp >= 0) ? temp : (temp + 256)];
    }
    this.globalCrc = globalCrcShadow;
  }

  int globalCrc;
}

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