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; 022 023/** 024 * A stream that limits reading from a wrapped stream to a given number of bytes. 025 * @NotThreadSafe 026 * @since 1.6 027 */ 028public class BoundedInputStream extends InputStream { 029 private final InputStream in; 030 private long bytesRemaining; 031 032 /** 033 * Creates the stream that will at most read the given amount of 034 * bytes from the given stream. 035 * @param in the stream to read from 036 * @param size the maximum amount of bytes to read 037 */ 038 public BoundedInputStream(final InputStream in, final long size) { 039 this.in = in; 040 bytesRemaining = size; 041 } 042 043 @Override 044 public int read() throws IOException { 045 if (bytesRemaining > 0) { 046 --bytesRemaining; 047 return in.read(); 048 } 049 return -1; 050 } 051 052 @Override 053 public int read(final byte[] b, final int off, final int len) throws IOException { 054 if (len == 0) { 055 return 0; 056 } 057 if (bytesRemaining == 0) { 058 return -1; 059 } 060 int bytesToRead = len; 061 if (bytesToRead > bytesRemaining) { 062 bytesToRead = (int) bytesRemaining; 063 } 064 final int bytesRead = in.read(b, off, bytesToRead); 065 if (bytesRead >= 0) { 066 bytesRemaining -= bytesRead; 067 } 068 return bytesRead; 069 } 070 071 @Override 072 public void close() { 073 // there isn't anything to close in this stream and the nested 074 // stream is controlled externally 075 } 076 077 /** 078 * @since 1.20 079 */ 080 @Override 081 public long skip(final long n) throws IOException { 082 long bytesToSkip = Math.min(bytesRemaining, n); 083 long bytesSkipped = in.skip(bytesToSkip); 084 bytesRemaining -= bytesSkipped; 085 086 return bytesSkipped; 087 } 088}