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Apache Commons Compress software 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.
/*
* 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;
import java.util.zip.CRC32;
import java.util.zip.ZipException;
/**
* Adds Unix file permission and UID/GID fields as well as symbolic
* link handling.
*
* This class uses the ASi extra field in the format:
*
* Value Size Description
* ----- ---- -----------
* (Unix3) 0x756e Short tag for this extra block type
* TSize Short total data size for this block
* CRC Long CRC-32 of the remaining data
* Mode Short file permissions
* SizDev Long symlink'd size OR major/minor dev num
* UID Short user ID
* GID Short group ID
* (var.) variable symbolic link filename
*
* taken from appnote.iz (Info-ZIP note, 981119) found at ftp://ftp.uu.net/pub/archiving/zip/doc/
*
* Short is two bytes and Long is four bytes in big endian byte and
* word order, device numbers are currently not supported.
* @NotThreadSafe
*
* Since the documentation this class is based upon doesn't mention
* the character encoding of the file name at all, it is assumed that
* it uses the current platform's default encoding.
*/
public class AsiExtraField implements ZipExtraField, UnixStat, Cloneable {
private static final ZipShort HEADER_ID = new ZipShort(0x756E);
private static final int WORD = 4;
/**
* Standard Unix stat(2) file mode.
*/
private int mode = 0;
/**
* User ID.
*/
private int uid = 0;
/**
* Group ID.
*/
private int gid = 0;
/**
* File this entry points to, if it is a symbolic link.
*
* empty string - if entry is not a symbolic link.
*/
private String link = "";
/**
* Is this an entry for a directory?
*/
private boolean dirFlag = false;
/**
* Instance used to calculate checksums.
*/
private CRC32 crc = new CRC32();
/** Constructor for AsiExtraField. */
public AsiExtraField() {
}
/**
* The Header-ID.
* @return the value for the header id for this extrafield
*/
public ZipShort getHeaderId() {
return HEADER_ID;
}
/**
* Length of the extra field in the local file data - without
* Header-ID or length specifier.
* @return a ZipShort for the length of the data of this extra field
*/
public ZipShort getLocalFileDataLength() {
return new ZipShort(WORD // CRC
+ 2 // Mode
+ WORD // SizDev
+ 2 // UID
+ 2 // GID
+ getLinkedFile().getBytes().length);
// Uses default charset - see class Javadoc
}
/**
* Delegate to local file data.
* @return the centralDirectory length
*/
public ZipShort getCentralDirectoryLength() {
return getLocalFileDataLength();
}
/**
* The actual data to put into local file data - without Header-ID
* or length specifier.
* @return get the data
*/
public byte[] getLocalFileDataData() {
// CRC will be added later
byte[] data = new byte[getLocalFileDataLength().getValue() - WORD];
System.arraycopy(ZipShort.getBytes(getMode()), 0, data, 0, 2);
byte[] linkArray = getLinkedFile().getBytes(); // Uses default charset - see class Javadoc
// CheckStyle:MagicNumber OFF
System.arraycopy(ZipLong.getBytes(linkArray.length),
0, data, 2, WORD);
System.arraycopy(ZipShort.getBytes(getUserId()),
0, data, 6, 2);
System.arraycopy(ZipShort.getBytes(getGroupId()),
0, data, 8, 2);
System.arraycopy(linkArray, 0, data, 10, linkArray.length);
// CheckStyle:MagicNumber ON
crc.reset();
crc.update(data);
long checksum = crc.getValue();
byte[] result = new byte[data.length + WORD];
System.arraycopy(ZipLong.getBytes(checksum), 0, result, 0, WORD);
System.arraycopy(data, 0, result, WORD, data.length);
return result;
}
/**
* Delegate to local file data.
* @return the local file data
*/
public byte[] getCentralDirectoryData() {
return getLocalFileDataData();
}
/**
* Set the user id.
* @param uid the user id
*/
public void setUserId(int uid) {
this.uid = uid;
}
/**
* Get the user id.
* @return the user id
*/
public int getUserId() {
return uid;
}
/**
* Set the group id.
* @param gid the group id
*/
public void setGroupId(int gid) {
this.gid = gid;
}
/**
* Get the group id.
* @return the group id
*/
public int getGroupId() {
return gid;
}
/**
* Indicate that this entry is a symbolic link to the given filename.
*
* @param name Name of the file this entry links to, empty String
* if it is not a symbolic link.
*/
public void setLinkedFile(String name) {
link = name;
mode = getMode(mode);
}
/**
* Name of linked file
*
* @return name of the file this entry links to if it is a
* symbolic link, the empty string otherwise.
*/
public String getLinkedFile() {
return link;
}
/**
* Is this entry a symbolic link?
* @return true if this is a symbolic link
*/
public boolean isLink() {
return getLinkedFile().length() != 0;
}
/**
* File mode of this file.
* @param mode the file mode
*/
public void setMode(int mode) {
this.mode = getMode(mode);
}
/**
* File mode of this file.
* @return the file mode
*/
public int getMode() {
return mode;
}
/**
* Indicate whether this entry is a directory.
* @param dirFlag if true, this entry is a directory
*/
public void setDirectory(boolean dirFlag) {
this.dirFlag = dirFlag;
mode = getMode(mode);
}
/**
* Is this entry a directory?
* @return true if this entry is a directory
*/
public boolean isDirectory() {
return dirFlag && !isLink();
}
/**
* Populate data from this array as if it was in local file data.
* @param data an array of bytes
* @param offset the start offset
* @param length the number of bytes in the array from offset
* @throws ZipException on error
*/
public void parseFromLocalFileData(byte[] data, int offset, int length)
throws ZipException {
long givenChecksum = ZipLong.getValue(data, offset);
byte[] tmp = new byte[length - WORD];
System.arraycopy(data, offset + WORD, tmp, 0, length - WORD);
crc.reset();
crc.update(tmp);
long realChecksum = crc.getValue();
if (givenChecksum != realChecksum) {
throw new ZipException("bad CRC checksum "
+ Long.toHexString(givenChecksum)
+ " instead of "
+ Long.toHexString(realChecksum));
}
int newMode = ZipShort.getValue(tmp, 0);
// CheckStyle:MagicNumber OFF
byte[] linkArray = new byte[(int) ZipLong.getValue(tmp, 2)];
uid = ZipShort.getValue(tmp, 6);
gid = ZipShort.getValue(tmp, 8);
if (linkArray.length == 0) {
link = "";
} else {
System.arraycopy(tmp, 10, linkArray, 0, linkArray.length);
link = new String(linkArray); // Uses default charset - see class Javadoc
}
// CheckStyle:MagicNumber ON
setDirectory((newMode & DIR_FLAG) != 0);
setMode(newMode);
}
/**
* Doesn't do anything special since this class always uses the
* same data in central directory and local file data.
*/
public void parseFromCentralDirectoryData(byte[] buffer, int offset,
int length)
throws ZipException {
parseFromLocalFileData(buffer, offset, length);
}
/**
* Get the file mode for given permissions with the correct file type.
* @param mode the mode
* @return the type with the mode
*/
protected int getMode(int mode) {
int type = FILE_FLAG;
if (isLink()) {
type = LINK_FLAG;
} else if (isDirectory()) {
type = DIR_FLAG;
}
return type | (mode & PERM_MASK);
}
@Override
public Object clone() {
try {
AsiExtraField cloned = (AsiExtraField) super.clone();
cloned.crc = new CRC32();
return cloned;
} catch (CloneNotSupportedException cnfe) {
// impossible
throw new RuntimeException(cnfe);
}
}
}