/*
 * 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 file name

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./**
 * Adds Unix file permission and UID/GID fields as well as symbolic
 * link handling.
 *
 * <p>This class uses the ASi extra field in the format:</p>
 * <pre>
 *         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 file name
 * </pre>
 * <p>taken from appnote.iz (Info-ZIP note, 981119) found at <a
 * href="ftp://ftp.uu.net/pub/archiving/zip/doc/">ftp://ftp.uu.net/pub/archiving/zip/doc/</a></p>
 *
 * <p>Short is two bytes and Long is four bytes in big endian byte and
 * word order, device numbers are currently not supported.</p>
 * @NotThreadSafe
 *
 * <p>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.</p>
 */
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.
/**
     * Standard Unix stat(2) file mode.
     */
    private int mode = 0;
    
User ID.
/**
     * User ID.
     */
    private int uid = 0;
    
Group ID.
/**
     * 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.
/**
     * File this entry points to, if it is a symbolic link.
     *
     * <p>empty string - if entry is not a symbolic link.</p>
     */
    private String link = "";
    
Is this an entry for a directory?
/**
     * Is this an entry for a directory?
     */
    private boolean dirFlag = false;

    
Instance used to calculate checksums.
/**
     * Instance used to calculate checksums.
     */
    private CRC32 crc = new CRC32();

    
Constructor for AsiExtraField. /** Constructor for AsiExtraField. */
    public AsiExtraField() {
    }

    
The Header-ID.
Returns:
the value for the header id for this extrafield/**
     * The Header-ID.
     * @return the value for the header id for this extrafield
     */
    @Override
    public ZipShort getHeaderId() {
        return HEADER_ID;
    }

    
Length of the extra field in the local file data - without
Header-ID or length specifier.
Returns:
a ZipShort for the length of the data of this extra field/**
     * Length of the extra field in the local file data - without
     * Header-ID or length specifier.
     * @return a <code>ZipShort</code> for the length of the data of this extra field
     */
    @Override
    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.
Returns:
the centralDirectory length/**
     * Delegate to local file data.
     * @return the centralDirectory length
     */
    @Override
    public ZipShort getCentralDirectoryLength() {
        return getLocalFileDataLength();
    }

    
The actual data to put into local file data - without Header-ID
or length specifier.
Returns:
get the data/**
     * The actual data to put into local file data - without Header-ID
     * or length specifier.
     * @return get the data
     */
    @Override
    public byte[] getLocalFileDataData() {
        // CRC will be added later
        final byte[] data = new byte[getLocalFileDataLength().getValue() - WORD];
        System.arraycopy(ZipShort.getBytes(getMode()), 0, data, 0, 2);

        final 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);
        final long checksum = crc.getValue();

        final 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.
Returns:
the local file data/**
     * Delegate to local file data.
     * @return the local file data
     */
    @Override
    public byte[] getCentralDirectoryData() {
        return getLocalFileDataData();
    }

    
Set the user id.
Params:
uid – the user id/**
     * Set the user id.
     * @param uid the user id
     */
    public void setUserId(final int uid) {
        this.uid = uid;
    }

    
Get the user id.
Returns:
the user id/**
     * Get the user id.
     * @return the user id
     */
    public int getUserId() {
        return uid;
    }

    
Set the group id.
Params:
gid – the group id/**
     * Set the group id.
     * @param gid the group id
     */
    public void setGroupId(final int gid) {
        this.gid = gid;
    }

    
Get the group id.
Returns:
the group id/**
     * Get the group id.
     * @return the group id
     */
    public int getGroupId() {
        return gid;
    }

    
Indicate that this entry is a symbolic link to the given file name.
Params:
name – Name of the file this entry links to, empty String
            if it is not a symbolic link./**
     * Indicate that this entry is a symbolic link to the given file name.
     *
     * @param name Name of the file this entry links to, empty String
     *             if it is not a symbolic link.
     */
    public void setLinkedFile(final String name) {
        link = name;
        mode = getMode(mode);
    }

    
Name of linked file
Returns:
name of the file this entry links to if it is a
        symbolic link, the empty string otherwise./**
     * 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?
Returns:
true if this is a symbolic 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.
Params:
mode – the file mode/**
     * File mode of this file.
     * @param mode the file mode
     */
    public void setMode(final int mode) {
        this.mode = getMode(mode);
    }

    
File mode of this file.
Returns:
the file mode/**
     * File mode of this file.
     * @return the file mode
     */
    public int getMode() {
        return mode;
    }

    
Indicate whether this entry is a directory.
Params:
dirFlag – if true, this entry is a directory/**
     * Indicate whether this entry is a directory.
     * @param dirFlag if true, this entry is a directory
     */
    public void setDirectory(final boolean dirFlag) {
        this.dirFlag = dirFlag;
        mode = getMode(mode);
    }

    
Is this entry a directory?
Returns:
true if this entry is a directory/**
     * 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.
Params:
data – an array of bytes
offset – the start offset
length – the number of bytes in the array from offset
Throws:
ZipException – on error/**
     * 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
     */
    @Override
    public void parseFromLocalFileData(final byte[] data, final int offset, final int length)
        throws ZipException {

        final long givenChecksum = ZipLong.getValue(data, offset);
        final byte[] tmp = new byte[length - WORD];
        System.arraycopy(data, offset + WORD, tmp, 0, length - WORD);
        crc.reset();
        crc.update(tmp);
        final long realChecksum = crc.getValue();
        if (givenChecksum != realChecksum) {
            throw new ZipException("Bad CRC checksum, expected "
                                   + Long.toHexString(givenChecksum)
                                   + " instead of "
                                   + Long.toHexString(realChecksum));
        }

        final int newMode = ZipShort.getValue(tmp, 0);
        // CheckStyle:MagicNumber OFF
        final 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 if (linkArray.length > tmp.length - 10) {
            throw new ZipException("Bad symbolic link name length " + linkArray.length
                + " in ASI extra field");
        } 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.
/**
     * Doesn't do anything special since this class always uses the
     * same data in central directory and local file data.
     */
    @Override
    public void parseFromCentralDirectoryData(final byte[] buffer, final int offset,
                                              final int length)
        throws ZipException {
        parseFromLocalFileData(buffer, offset, length);
    }

    
Get the file mode for given permissions with the correct file type.
Params:
mode – the mode
Returns:
the type with the mode/**
     * 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(final 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 {
            final AsiExtraField cloned = (AsiExtraField) super.clone();
            cloned.crc = new CRC32();
            return cloned;
        } catch (final CloneNotSupportedException cnfe) {
            // impossible
            throw new RuntimeException(cnfe); //NOSONAR
        }
    }
}