/*
* 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.
*/
package com.alipay.sofa.rpc.codec.snappy;
import java.util.zip.Checksum;
/**
* A pure-java implementation of the CRC32 checksum that uses
* the CRC32-C polynomial, the same polynomial used by iSCSI
* and implemented on many Intel chipsets supporting SSE4.2.
*/
// this code was taken from Apache Hadoop
class Crc32C implements Checksum {
private static final int MASK_DELTA = 0xa282ead8;
public static int maskedCrc32c(byte[] data) {
return maskedCrc32c(data, 0, data.length);
}
public static int maskedCrc32c(byte[] data, int offset, int length) {
Crc32C crc32c = new Crc32C();
crc32c.update(data, offset, length);
return crc32c.getMaskedValue();
}
/**
* Return a masked representation of crc.
*
* Motivation: it is problematic to compute the CRC of a string that
* contains embedded CRCs. Therefore we recommend that CRCs stored
* somewhere (e.g., in files) should be masked before being stored.
*/
public static int mask(int crc) {
// Rotate right by 15 bits and add a constant.
return ((crc >>> 15) | (crc << 17)) + MASK_DELTA;
}
/**
* Return the crc whose masked representation is masked_crc.
*/
public static int unmask(int maskedCrc) {
int rot = maskedCrc - MASK_DELTA;
return ((rot >>> 17) | (rot << 15));
}
/**
* the current CRC value, bit-flipped
*/
private int crc;
/**
* Create a new PureJavaCrc32 object.
*/
public Crc32C() {
reset();
}
public int getMaskedValue() {
return mask(getIntValue());
}
public int getIntValue() {
return ~crc;
}
@Override
public long getValue() {
long ret = crc;
return (~ret) & 0xffffffffL;
}
@Override
public void reset() {
crc = 0xffffffff;
}
@Override
public void update(byte[] b, int off, int len) {
int localCrc = crc;
while (len > 7) {
int c0 = b[off++] ^ localCrc;
int c1 = b[off++] ^ (localCrc >>>= 8);
int c2 = b[off++] ^ (localCrc >>>= 8);
int c3 = b[off++] ^ (localCrc >>>= 8);
localCrc = (T8_7[c0 & 0xff] ^ T8_6[c1 & 0xff])
^ (T8_5[c2 & 0xff] ^ T8_4[c3 & 0xff]);
localCrc ^= (T8_3[b[off++] & 0xff] ^ T8_2[b[off++] & 0xff])
^ (T8_1[b[off++] & 0xff] ^ T8_0[b[off++] & 0xff]);
len -= 8;
}
while (len > 0) {
localCrc = (localCrc >>> 8) ^ T8_0[(localCrc ^ b[off++]) & 0xff];
len--;
}
// Publish crc out to object
crc = localCrc;
}
@Override
public void update(int b) {
crc = (crc >>> 8) ^ T8_0[(crc ^ b) & 0xff];
}
// CRC polynomial tables generated by:
// java -cp build/test/classes/:build/classes/ \
// org.apache.hadoop.util.TestPureJavaCrc32\$Table 82F63B78
static final int[] T8_0 = new int[] {
0x00000000, 0xF26B8303, 0xE13B70F7, 0x1350F3F4,
0xC79A971F, 0x35F1141C, 0x26A1E7E8, 0xD4CA64EB,
0x8AD958CF, 0x78B2DBCC, 0x6BE22838, 0x9989AB3B,
0x4D43CFD0, 0xBF284CD3, 0xAC78BF27, 0x5E133C24,
0x105EC76F, 0xE235446C, 0xF165B798, 0x030E349B,
0xD7C45070, 0x25AFD373, 0x36FF2087, 0xC494A384,
0x9A879FA0, 0x68EC1CA3, 0x7BBCEF57, 0x89D76C54,
0x5D1D08BF, 0xAF768BBC, 0xBC267848, 0x4E4DFB4B,
0x20BD8EDE, 0xD2D60DDD, 0xC186FE29, 0x33ED7D2A,
0xE72719C1, 0x154C9AC2, 0x061C6936, 0xF477EA35,
0xAA64D611, 0x580F5512, 0x4B5FA6E6, 0xB93425E5,
0x6DFE410E, 0x9F95C20D, 0x8CC531F9, 0x7EAEB2FA,
0x30E349B1, 0xC288CAB2, 0xD1D83946, 0x23B3BA45,
0xF779DEAE, 0x05125DAD, 0x1642AE59, 0xE4292D5A,
0xBA3A117E, 0x4851927D, 0x5B016189, 0xA96AE28A,
0x7DA08661, 0x8FCB0562, 0x9C9BF696, 0x6EF07595,
0x417B1DBC, 0xB3109EBF, 0xA0406D4B, 0x522BEE48,
0x86E18AA3, 0x748A09A0, 0x67DAFA54, 0x95B17957,
0xCBA24573, 0x39C9C670, 0x2A993584, 0xD8F2B687,
0x0C38D26C, 0xFE53516F, 0xED03A29B, 0x1F682198,
0x5125DAD3, 0xA34E59D0, 0xB01EAA24, 0x42752927,
0x96BF4DCC, 0x64D4CECF, 0x77843D3B, 0x85EFBE38,
0xDBFC821C, 0x2997011F, 0x3AC7F2EB, 0xC8AC71E8,
0x1C661503, 0xEE0D9600, 0xFD5D65F4, 0x0F36E6F7,
0x61C69362, 0x93AD1061, 0x80FDE395, 0x72966096,
0xA65C047D, 0x5437877E, 0x4767748A, 0xB50CF789,
0xEB1FCBAD, 0x197448AE, 0x0A24BB5A, 0xF84F3859,
0x2C855CB2, 0xDEEEDFB1, 0xCDBE2C45, 0x3FD5AF46,
0x7198540D, 0x83F3D70E, 0x90A324FA, 0x62C8A7F9,
0xB602C312, 0x44694011, 0x5739B3E5, 0xA55230E6,
0xFB410CC2, 0x092A8FC1, 0x1A7A7C35, 0xE811FF36,
0x3CDB9BDD, 0xCEB018DE, 0xDDE0EB2A, 0x2F8B6829,
0x82F63B78, 0x709DB87B, 0x63CD4B8F, 0x91A6C88C,
0x456CAC67, 0xB7072F64, 0xA457DC90, 0x563C5F93,
0x082F63B7, 0xFA44E0B4, 0xE9141340, 0x1B7F9043,
0xCFB5F4A8, 0x3DDE77AB, 0x2E8E845F, 0xDCE5075C,
0x92A8FC17, 0x60C37F14, 0x73938CE0, 0x81F80FE3,
0x55326B08, 0xA759E80B, 0xB4091BFF, 0x466298FC,
0x1871A4D8, 0xEA1A27DB, 0xF94AD42F, 0x0B21572C,
0xDFEB33C7, 0x2D80B0C4, 0x3ED04330, 0xCCBBC033,
0xA24BB5A6, 0x502036A5, 0x4370C551, 0xB11B4652,
0x65D122B9, 0x97BAA1BA, 0x84EA524E, 0x7681D14D,
0x2892ED69, 0xDAF96E6A, 0xC9A99D9E, 0x3BC21E9D,
0xEF087A76, 0x1D63F975, 0x0E330A81, 0xFC588982,
0xB21572C9, 0x407EF1CA, 0x532E023E, 0xA145813D,
0x758FE5D6, 0x87E466D5, 0x94B49521, 0x66DF1622,
0x38CC2A06, 0xCAA7A905, 0xD9F75AF1, 0x2B9CD9F2,
0xFF56BD19, 0x0D3D3E1A, 0x1E6DCDEE, 0xEC064EED,
0xC38D26C4, 0x31E6A5C7, 0x22B65633, 0xD0DDD530,
0x0417B1DB, 0xF67C32D8, 0xE52CC12C, 0x1747422F,
0x49547E0B, 0xBB3FFD08, 0xA86F0EFC, 0x5A048DFF,
0x8ECEE914, 0x7CA56A17, 0x6FF599E3, 0x9D9E1AE0,
0xD3D3E1AB, 0x21B862A8, 0x32E8915C, 0xC083125F,
0x144976B4, 0xE622F5B7, 0xF5720643, 0x07198540,
0x590AB964, 0xAB613A67, 0xB831C993, 0x4A5A4A90,