All Downloads are FREE. Search and download functionalities are using the official Maven repository.

org.apache.commons.compress.archivers.zip.GeneralPurposeBit Maven / Gradle / Ivy

Go to download

Apache Commons Compress defines an API for working with compression and archive formats. These include bzip2, gzip, pack200, LZMA, XZ, Snappy, traditional Unix Compress, DEFLATE, DEFLATE64, LZ4, Brotli, Zstandard and ar, cpio, jar, tar, zip, dump, 7z, arj.

There is a newer version: 1.27.1
Show newest version
/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */
package org.apache.commons.compress.archivers.zip;

/**
 * Parser/encoder for the "general purpose bit" field in ZIP's local
 * file and central directory headers.
 *
 * @since 1.1
 * @NotThreadSafe
 */
public final class GeneralPurposeBit implements Cloneable {

    /**
     * Indicates that the file is encrypted.
     */
    private static final int ENCRYPTION_FLAG = 1 << 0;

    /**
     * Indicates the size of the sliding dictionary used by the compression method 6 (imploding).
     * 
    *
  • 0: 4096 bytes
  • *
  • 1: 8192 bytes
  • *
*/ private static final int SLIDING_DICTIONARY_SIZE_FLAG = 1 << 1; /** * Indicates the number of Shannon-Fano trees used by the compression method 6 (imploding). *
    *
  • 0: 2 trees (lengths, distances)
  • *
  • 1: 3 trees (literals, lengths, distances)
  • *
*/ private static final int NUMBER_OF_SHANNON_FANO_TREES_FLAG = 1 << 2; /** * Indicates that a data descriptor stored after the file contents * will hold CRC and size information. */ private static final int DATA_DESCRIPTOR_FLAG = 1 << 3; /** * Indicates strong encryption. */ private static final int STRONG_ENCRYPTION_FLAG = 1 << 6; /** * Indicates that filenames are written in UTF-8. * *

The only reason this is public is that {@link * ZipArchiveOutputStream#EFS_FLAG} was public in Apache Commons * Compress 1.0 and we needed a substitute for it.

*/ public static final int UFT8_NAMES_FLAG = 1 << 11; private boolean languageEncodingFlag = false; private boolean dataDescriptorFlag = false; private boolean encryptionFlag = false; private boolean strongEncryptionFlag = false; private int slidingDictionarySize; private int numberOfShannonFanoTrees; public GeneralPurposeBit() { } /** * whether the current entry uses UTF8 for file name and comment. * @return whether the current entry uses UTF8 for file name and comment. */ public boolean usesUTF8ForNames() { return languageEncodingFlag; } /** * whether the current entry will use UTF8 for file name and comment. * @param b whether the current entry will use UTF8 for file name and comment. */ public void useUTF8ForNames(final boolean b) { languageEncodingFlag = b; } /** * whether the current entry uses the data descriptor to store CRC * and size information. * @return whether the current entry uses the data descriptor to store CRC * and size information */ public boolean usesDataDescriptor() { return dataDescriptorFlag; } /** * whether the current entry will use the data descriptor to store * CRC and size information. * @param b whether the current entry will use the data descriptor to store * CRC and size information */ public void useDataDescriptor(final boolean b) { dataDescriptorFlag = b; } /** * whether the current entry is encrypted. * @return whether the current entry is encrypted */ public boolean usesEncryption() { return encryptionFlag; } /** * whether the current entry will be encrypted. * @param b whether the current entry will be encrypted */ public void useEncryption(final boolean b) { encryptionFlag = b; } /** * whether the current entry is encrypted using strong encryption. * @return whether the current entry is encrypted using strong encryption */ public boolean usesStrongEncryption() { return encryptionFlag && strongEncryptionFlag; } /** * whether the current entry will be encrypted using strong encryption. * @param b whether the current entry will be encrypted using strong encryption */ public void useStrongEncryption(final boolean b) { strongEncryptionFlag = b; if (b) { useEncryption(true); } } /** * Returns the sliding dictionary size used by the compression method 6 (imploding). */ int getSlidingDictionarySize() { return slidingDictionarySize; } /** * Returns the number of trees used by the compression method 6 (imploding). */ int getNumberOfShannonFanoTrees() { return numberOfShannonFanoTrees; } /** * Encodes the set bits in a form suitable for ZIP archives. * @return the encoded general purpose bits */ public byte[] encode() { final byte[] result = new byte[2]; encode(result, 0); return result; } /** * Encodes the set bits in a form suitable for ZIP archives. * * @param buf the output buffer * @param offset * The offset within the output buffer of the first byte to be written. * must be non-negative and no larger than buf.length-2 */ public void encode(final byte[] buf, final int offset) { ZipShort.putShort((dataDescriptorFlag ? DATA_DESCRIPTOR_FLAG : 0) | (languageEncodingFlag ? UFT8_NAMES_FLAG : 0) | (encryptionFlag ? ENCRYPTION_FLAG : 0) | (strongEncryptionFlag ? STRONG_ENCRYPTION_FLAG : 0) , buf, offset); } /** * Parses the supported flags from the given archive data. * * @param data local file header or a central directory entry. * @param offset offset at which the general purpose bit starts * @return parsed flags */ public static GeneralPurposeBit parse(final byte[] data, final int offset) { final int generalPurposeFlag = ZipShort.getValue(data, offset); final GeneralPurposeBit b = new GeneralPurposeBit(); b.useDataDescriptor((generalPurposeFlag & DATA_DESCRIPTOR_FLAG) != 0); b.useUTF8ForNames((generalPurposeFlag & UFT8_NAMES_FLAG) != 0); b.useStrongEncryption((generalPurposeFlag & STRONG_ENCRYPTION_FLAG) != 0); b.useEncryption((generalPurposeFlag & ENCRYPTION_FLAG) != 0); b.slidingDictionarySize = (generalPurposeFlag & SLIDING_DICTIONARY_SIZE_FLAG) != 0 ? 8192 : 4096; b.numberOfShannonFanoTrees = (generalPurposeFlag & NUMBER_OF_SHANNON_FANO_TREES_FLAG) != 0 ? 3 : 2; return b; } @Override public int hashCode() { return 3 * (7 * (13 * (17 * (encryptionFlag ? 1 : 0) + (strongEncryptionFlag ? 1 : 0)) + (languageEncodingFlag ? 1 : 0)) + (dataDescriptorFlag ? 1 : 0)); } @Override public boolean equals(final Object o) { if (!(o instanceof GeneralPurposeBit)) { return false; } final GeneralPurposeBit g = (GeneralPurposeBit) o; return g.encryptionFlag == encryptionFlag && g.strongEncryptionFlag == strongEncryptionFlag && g.languageEncodingFlag == languageEncodingFlag && g.dataDescriptorFlag == dataDescriptorFlag; } @Override public Object clone() { try { return super.clone(); } catch (final CloneNotSupportedException ex) { // impossible throw new RuntimeException("GeneralPurposeBit is not Cloneable?", ex); //NOSONAR } } }




© 2015 - 2025 Weber Informatics LLC | Privacy Policy