1 // Copyright 2016 Google Inc. All rights reserved. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 package com.google.archivepatcher.applier; 16 17 import java.io.FilterInputStream; 18 import java.io.IOException; 19 import java.io.InputStream; 20 21 /** 22 * A stream that simulates EOF after a specified numToRead of bytes has been reached. 23 */ 24 public class LimitedInputStream extends FilterInputStream { 25 /** 26 * Current numToRead. 27 */ 28 private long numToRead; 29 30 /** 31 * Buffer used for one-byte reads to keep all code on the same path. 32 */ 33 private byte[] ONE_BYTE = new byte[1]; 34 35 /** 36 * Creates a new limited stream that delegates operations to the specified stream. 37 * @param in the stream to limit 38 * @param numToRead the number of reads to allow before returning EOF 39 */ 40 public LimitedInputStream(InputStream in, long numToRead) { 41 super(in); 42 if (numToRead < 0) { 43 throw new IllegalArgumentException("numToRead must be >= 0: " + numToRead); 44 } 45 this.numToRead = numToRead; 46 } 47 48 @Override 49 public int read() throws IOException { 50 if (read(ONE_BYTE, 0, 1) == 1) { 51 return ONE_BYTE[0]; 52 } 53 return -1; 54 } 55 56 @Override 57 public int read(byte[] b) throws IOException { 58 return read(b, 0, b.length); 59 } 60 61 @Override 62 public int read(byte[] b, int off, int len) throws IOException { 63 if (numToRead == 0) { 64 return -1; // Simulate EOF 65 } 66 int maxRead = (int) Math.min(len, numToRead); 67 int numRead = in.read(b, off, maxRead); 68 if (numRead > 0) { 69 numToRead -= numRead; 70 } 71 return numRead; 72 } 73 } 74
