1 /* 2 * Copyright (c) 2011, 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package com.oracle.ipack.util; 27 28 import java.io.FilterOutputStream; 29 import java.io.IOException; 30 import java.io.OutputStream; 31 import java.security.MessageDigest; 32 import java.security.NoSuchAlgorithmException; 33 import java.util.ArrayList; 34 import java.util.Collections; 35 import java.util.List; 36 37 /** 38 * Similar to HashingOutputStream, but calculates and stores a hash for each 39 * page of the input stream. 40 */ 41 public final class PageHashingOutputStream extends FilterOutputStream { 42 private final MessageDigest messageDigest; 43 private final List<byte[]> pageHashes; 44 private final int pageSize; 45 46 private int pageRemaining; 47 48 public PageHashingOutputStream(final OutputStream out) { 49 this(out, 4096); 50 } 51 52 public PageHashingOutputStream(final OutputStream out, final int pageSize) { 53 super(out); 54 try { 55 messageDigest = MessageDigest.getInstance("SHA1"); 56 } catch (final NoSuchAlgorithmException e) { 57 throw new IllegalStateException("Can't create message digest", e); 58 } 59 pageHashes = new ArrayList<byte[]>(); 60 this.pageSize = pageSize; 61 this.pageRemaining = pageSize; 62 } 63 64 public List<byte[]> getPageHashes() { 65 return Collections.unmodifiableList(pageHashes); 66 } 67 68 @Override 69 public void write(final int byteValue) throws IOException { 70 out.write(byteValue); 71 messageDigest.update((byte) byteValue); 72 --pageRemaining; 73 if (pageRemaining == 0) { 74 commitPageHashImpl(); 75 } 76 } 77 78 @Override 79 public void write(final byte[] buffer, final int offset, final int length) 80 throws IOException { 81 out.write(buffer, offset, length); 82 83 int hashRemaining = length; 84 int hashOffset = offset; 85 while (hashRemaining > 0) { 86 final int chunkLength = 87 (pageRemaining < hashRemaining) ? pageRemaining 88 : hashRemaining; 89 90 messageDigest.update(buffer, hashOffset, chunkLength); 91 92 hashOffset += chunkLength; 93 hashRemaining -= chunkLength; 94 pageRemaining -= chunkLength; 95 96 if (pageRemaining == 0) { 97 commitPageHashImpl(); 98 } 99 } 100 } 101 102 /** 103 * Creates a new page hash from the remaining data. 104 * 105 * If there are some data which haven't been included in the previous page 106 * hash, this methods adds a new page hash for them even if they don't 107 * fill up a complete page. 108 */ 109 public void commitPageHash() { 110 if (pageRemaining != pageSize) { 111 // we do have some data for hashing 112 commitPageHashImpl(); 113 } 114 } 115 116 private void commitPageHashImpl() { 117 pageHashes.add(messageDigest.digest()); 118 pageRemaining = pageSize; 119 } 120 }