001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 * 017 */ 018package org.apache.commons.compress.utils; 019 020import java.io.IOException; 021import java.io.InputStream; 022import java.util.zip.Checksum; 023 024/** 025 * A stream that calculates the checksum of the data read. 026 * @NotThreadSafe 027 * @since 1.14 028 */ 029public class ChecksumCalculatingInputStream extends InputStream { 030 private final InputStream in; 031 private final Checksum checksum; 032 033 public ChecksumCalculatingInputStream(final Checksum checksum, final InputStream in) { 034 this.checksum = checksum; 035 this.in = in; 036 } 037 038 /** 039 * Reads a single byte from the stream 040 * @throws IOException if the underlying stream throws or the 041 * stream is exhausted and the Checksum doesn't match the expected 042 * value 043 */ 044 @Override 045 public int read() throws IOException { 046 final int ret = in.read(); 047 if (ret >= 0) { 048 checksum.update(ret); 049 } 050 return ret; 051 } 052 053 /** 054 * Reads a byte array from the stream 055 * @throws IOException if the underlying stream throws or the 056 * stream is exhausted and the Checksum doesn't match the expected 057 * value 058 */ 059 @Override 060 public int read(final byte[] b) throws IOException { 061 return read(b, 0, b.length); 062 } 063 064 /** 065 * Reads from the stream into a byte array. 066 * @throws IOException if the underlying stream throws or the 067 * stream is exhausted and the Checksum doesn't match the expected 068 * value 069 */ 070 @Override 071 public int read(final byte[] b, final int off, final int len) throws IOException { 072 final int ret = in.read(b, off, len); 073 if (ret >= 0) { 074 checksum.update(b, off, ret); 075 } 076 return ret; 077 } 078 079 @Override 080 public long skip(final long n) throws IOException { 081 // Can't really skip, we have to hash everything to verify the checksum 082 if (read() >= 0) { 083 return 1; 084 } 085 return 0; 086 } 087 088 /** 089 * Returns the calculated checksum. 090 * @return the calculated checksum. 091 */ 092 public long getValue() { 093 return checksum.getValue(); 094 } 095 096}