001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, 013 * software distributed under the License is distributed on an 014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 015 * KIND, either express or implied. See the License for the 016 * specific language governing permissions and limitations 017 * under the License. 018 */ 019package org.apache.commons.compress.archivers.zip; 020 021 022import java.util.zip.ZipException; 023 024/** 025 * An extra field who's sole purpose is to align and pad the local file header 026 * so that the entry's data starts at a certain position. 027 * 028 * <p>The padding content of the padding is ignored and not retained 029 * when reading a padding field.</p> 030 * 031 * <p>This enables Commons Compress to create "aligned" archives 032 * similar to Android's zipalign command line tool.</p> 033 * 034 * @since 1.14 035 * @see "https://developer.android.com/studio/command-line/zipalign.html" 036 * @see ZipArchiveEntry#setAlignment 037 */ 038public class ResourceAlignmentExtraField implements ZipExtraField { 039 040 /** 041 * Extra field id used for storing alignment and padding. 042 */ 043 public static final ZipShort ID = new ZipShort(0xa11e); 044 045 public static final int BASE_SIZE = 2; 046 047 private static final int ALLOW_METHOD_MESSAGE_CHANGE_FLAG = 0x8000; 048 049 private short alignment; 050 051 private boolean allowMethodChange; 052 053 private int padding = 0; 054 055 public ResourceAlignmentExtraField() { 056 } 057 058 public ResourceAlignmentExtraField(int alignment) { 059 this(alignment, false); 060 } 061 062 public ResourceAlignmentExtraField(int alignment, boolean allowMethodChange) { 063 this(alignment, allowMethodChange, 0); 064 } 065 066 public ResourceAlignmentExtraField(int alignment, boolean allowMethodChange, int padding) { 067 if (alignment < 0 || alignment > 0x7fff) { 068 throw new IllegalArgumentException("Alignment must be between 0 and 0x7fff, was: " + alignment); 069 } 070 if (padding < 0) { 071 throw new IllegalArgumentException("Padding must not be negative, was: " + padding); 072 } 073 this.alignment = (short) alignment; 074 this.allowMethodChange = allowMethodChange; 075 this.padding = padding; 076 } 077 078 /** 079 * Gets requested alignment. 080 * 081 * @return 082 * requested alignment. 083 */ 084 public short getAlignment() { 085 return alignment; 086 } 087 088 /** 089 * Indicates whether method change is allowed when re-compressing the zip file. 090 * 091 * @return 092 * true if method change is allowed, false otherwise. 093 */ 094 public boolean allowMethodChange() { 095 return allowMethodChange; 096 } 097 098 @Override 099 public ZipShort getHeaderId() { 100 return ID; 101 } 102 103 @Override 104 public ZipShort getLocalFileDataLength() { 105 return new ZipShort(BASE_SIZE + padding); 106 } 107 108 @Override 109 public ZipShort getCentralDirectoryLength() { 110 return new ZipShort(BASE_SIZE); 111 } 112 113 @Override 114 public byte[] getLocalFileDataData() { 115 byte[] content = new byte[BASE_SIZE + padding]; 116 ZipShort.putShort(alignment | (allowMethodChange ? ALLOW_METHOD_MESSAGE_CHANGE_FLAG : 0), 117 content, 0); 118 return content; 119 } 120 121 @Override 122 public byte[] getCentralDirectoryData() { 123 return ZipShort.getBytes(alignment | (allowMethodChange ? ALLOW_METHOD_MESSAGE_CHANGE_FLAG : 0)); 124 } 125 126 @Override 127 public void parseFromLocalFileData(byte[] buffer, int offset, int length) throws ZipException { 128 parseFromCentralDirectoryData(buffer, offset, length); 129 this.padding = length - BASE_SIZE; 130 } 131 132 @Override 133 public void parseFromCentralDirectoryData(byte[] buffer, int offset, int length) throws ZipException { 134 if (length < BASE_SIZE) { 135 throw new ZipException("Too short content for ResourceAlignmentExtraField (0xa11e): " + length); 136 } 137 int alignmentValue = ZipShort.getValue(buffer, offset); 138 this.alignment = (short) (alignmentValue & (ALLOW_METHOD_MESSAGE_CHANGE_FLAG - 1)); 139 this.allowMethodChange = (alignmentValue & ALLOW_METHOD_MESSAGE_CHANGE_FLAG) != 0; 140 } 141}