1/* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 18package java.util.zip; 19 20 21/** 22 * The CRC32 class is used to compute a CRC32 checksum from data provided as 23 * input value. 24 * 25 * @since Android 1.0 26 */ 27public class CRC32 implements java.util.zip.Checksum { 28 29 private long crc = 0L; 30 31 long tbytes = 0L; 32 33 /** 34 * Returns the CRC32 checksum for all input received. 35 * 36 * @return The checksum for this instance. 37 * @since Android 1.0 38 */ 39 public long getValue() { 40 return crc; 41 } 42 43 /** 44 * Resets the CRC32 checksum to it initial state. 45 * 46 * @since Android 1.0 47 */ 48 public void reset() { 49 tbytes = crc = 0; 50 51 } 52 53 /** 54 * Updates this checksum with the byte value provided as integer. 55 * 56 * @param val 57 * represents the byte to update the checksum. 58 * @since Android 1.0 59 */ 60 public void update(int val) { 61 crc = updateByteImpl((byte) val, crc); 62 } 63 64 /** 65 * Updates this checksum with the bytes contained in buffer {@code buf}. 66 * 67 * @param buf 68 * the buffer holding the data to update the checksum with. 69 * @since Android 1.0 70 */ 71 public void update(byte[] buf) { 72 update(buf, 0, buf.length); 73 } 74 75 /** 76 * Updates this checksum with n bytes of data obtained from buffer {@code 77 * buf}, starting at offset {@code off}. 78 * 79 * @param buf 80 * the buffer to update the checksum. 81 * @param off 82 * the offset in {@code buf} to obtain data from. 83 * @param nbytes 84 * the number of bytes to read from {@code buf}. 85 * @since Android 1.0 86 */ 87 public void update(byte[] buf, int off, int nbytes) { 88 // avoid int overflow, check null buf 89 if (off <= buf.length && nbytes >= 0 && off >= 0 90 && buf.length - off >= nbytes) { 91 tbytes += nbytes; 92 crc = updateImpl(buf, off, nbytes, crc); 93 } else { 94 throw new ArrayIndexOutOfBoundsException(); 95 } 96 } 97 98 private native long updateImpl(byte[] buf, int off, int nbytes, long crc1); 99 100 private native long updateByteImpl(byte val, long crc1); 101} 102