zipfile.java

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/*
 *  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.tools.zip;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.io.UnsupportedEncodingException;
import java.util.Calendar;
import java.util.Date;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.zip.Inflater;
import java.util.zip.InflaterInputStream;
import java.util.zip.ZipException;

/**
 * Replacement for <code>java.util.ZipFile</code>.
 *
 * <p>This class adds support for file name encodings other than UTF-8
 * (which is required to work on ZIP files created by native zip tools
 * and is able to skip a preamble like the one found in self
 * extracting archives.  Furthermore it returns instances of
 * <code>org.apache.tools.zip.ZipEntry</code> instead of
 * <code>java.util.zip.ZipEntry</code>.</p>
 *
 * <p>It doesn't extend <code>java.util.zip.ZipFile</code> as it would
 * have to reimplement all methods anyway.  Like
 * <code>java.util.ZipFile</code>, it uses RandomAccessFile under the
 * covers and supports compressed and uncompressed entries.</p>
 *
 * <p>The method signatures mimic the ones of
 * <code>java.util.zip.ZipFile</code>, with a couple of exceptions:
 *
 * <ul>
 *   <li>There is no getName method.</li>
 *   <li>entries has been renamed to getEntries.</li>
 *   <li>getEntries and getEntry return
 *   <code>org.apache.tools.zip.ZipEntry</code> instances.</li>
 *   <li>close is allowed to throw IOException.</li>
 * </ul>
 *
 */
public class ZipFile {
    private static final int HASH_SIZE = 509;
    private static final int SHORT     =   2;
    private static final int WORD      =   4;
    private static final int NIBLET_MASK = 0x0f;
    private static final int BYTE_SHIFT = 8;
    private static final int POS_0 = 0;
    private static final int POS_1 = 1;
    private static final int POS_2 = 2;
    private static final int POS_3 = 3;

    /**
     * Maps ZipEntrys to Longs, recording the offsets of the local
     * file headers.
     */
    private Hashtable entries = new Hashtable(HASH_SIZE);

    /**
     * Maps String to ZipEntrys, name -> actual entry.
     */
    private Hashtable nameMap = new Hashtable(HASH_SIZE);

    private static final class OffsetEntry {
        private long headerOffset = -1;
        private long dataOffset = -1;
    }

    /**
     * The encoding to use for filenames and the file comment.
     *
     * <p>For a list of possible values see <a
     * href="http://java.sun.com/j2se/1.5.0/docs/guide/intl/encoding.doc.html">http://java.sun.com/j2se/1.5.0/docs/guide/intl/encoding.doc.html</a>.
     * Defaults to the platform's default character encoding.</p>
     */
    private String encoding = null;

    /**
     * The actual data source.
     */
    private RandomAccessFile archive;

    /**
     * Opens the given file for reading, assuming the platform's
     * native encoding for file names.
     *
     * @param f the archive.
     *
     * @throws IOException if an error occurs while reading the file.
     */
    public ZipFile(File f) throws IOException {
        this(f, null);
    }

    /**
     * Opens the given file for reading, assuming the platform's
     * native encoding for file names.
     *
     * @param name name of the archive.
     *
     * @throws IOException if an error occurs while reading the file.
     */
    public ZipFile(String name) throws IOException {
        this(new File(name), null);
    }

    /**
     * Opens the given file for reading, assuming the specified
     * encoding for file names.
     *
     * @param name name of the archive.
     * @param encoding the encoding to use for file names
     *
     * @throws IOException if an error occurs while reading the file.
     */
    public ZipFile(String name, String encoding) throws IOException {
        this(new File(name), encoding);
    }

    /**
     * Opens the given file for reading, assuming the specified
     * encoding for file names.
     *
     * @param f the archive.
     * @param encoding the encoding to use for file names
     *
     * @throws IOException if an error occurs while reading the file.
     */
    public ZipFile(File f, String encoding) throws IOException {
        this.encoding = encoding;
        archive = new RandomAccessFile(f, "r");
        try {
            populateFromCentralDirectory();
            resolveLocalFileHeaderData();
        } catch (IOException e) {
            try {
                archive.close();
            } catch (IOException e2) {
                // swallow, throw the original exception instead
            }
            throw e;
        }
    }

    /**
     * The encoding to use for filenames and the file comment.
     *
     * @return null if using the platform's default character encoding.
     */
    public String getEncoding() {
        return encoding;
    }

    /**
     * Closes the archive.
     * @throws IOException if an error occurs closing the archive.
     */
    public void close() throws IOException {
        archive.close();
    }

    /**
     * close a zipfile quietly; throw no io fault, do nothing
     * on a null parameter
     * @param zipfile file to close, can be null
     */
    public static void closeQuietly(ZipFile zipfile) {
        if (zipfile != null) {
            try {
                zipfile.close();
            } catch (IOException e) {
                //ignore
            }
        }
    }

    /**
     * Returns all entries.
     * @return all entries as {@link ZipEntry} instances
     */
    public Enumeration getEntries() {
        return entries.keys();
    }

    /**
     * Returns a named entry - or <code>null</code> if no entry by
     * that name exists.
     * @param name name of the entry.
     * @return the ZipEntry corresponding to the given name - or
     * <code>null</code> if not present.
     */
    public ZipEntry getEntry(String name) {
        return (ZipEntry) nameMap.get(name);
    }

    /**
     * Returns an InputStream for reading the contents of the given entry.
     * @param ze the entry to get the stream for.
     * @return a stream to read the entry from.
     * @throws IOException if unable to create an input stream from the zipenty
     * @throws ZipException if the zipentry has an unsupported compression method
     */
    public InputStream getInputStream(ZipEntry ze)
        throws IOException, ZipException {
        OffsetEntry offsetEntry = (OffsetEntry) entries.get(ze);
        if (offsetEntry == null) {
            return null;
        }
        long start = offsetEntry.dataOffset;
        BoundedInputStream bis =
            new BoundedInputStream(start, ze.getCompressedSize());
        switch (ze.getMethod()) {
            case ZipEntry.STORED:
                return bis;
            case ZipEntry.DEFLATED:
                bis.addDummy();
                return new InflaterInputStream(bis, new Inflater(true));
            default:
                throw new ZipException("Found unsupported compression method "
                                       + ze.getMethod());
        }
    }

    private static final int CFH_LEN =
        /* version made by                 */ SHORT
        /* version needed to extract       */ + SHORT
        /* general purpose bit flag        */ + SHORT
        /* compression method              */ + SHORT
        /* last mod file time              */ + SHORT
        /* last mod file date              */ + SHORT
        /* crc-32                          */ + WORD
        /* compressed size                 */ + WORD
        /* uncompressed size               */ + WORD
        /* filename length                 */ + SHORT
        /* extra field length              */ + SHORT
        /* file comment length             */ + SHORT
        /* disk number start               */ + SHORT
        /* internal file attributes        */ + SHORT
        /* external file attributes        */ + WORD
        /* relative offset of local header */ + WORD;

    /**
     * Reads the central directory of the given archive and populates
     * the internal tables with ZipEntry instances.
     *
     * <p>The ZipEntrys will know all data that can be obtained from
     * the central directory alone, but not the data that requires the
     * local file header or additional data to be read.</p>
     */
    private void populateFromCentralDirectory()
        throws IOException {
        positionAtCentralDirectory();

        byte[] cfh = new byte[CFH_LEN];

        byte[] signatureBytes = new byte[WORD];
        archive.readFully(signatureBytes);
        long sig = ZipLong.getValue(signatureBytes);
        final long cfhSig = ZipLong.getValue(ZipOutputStream.CFH_SIG);
        while (sig == cfhSig) {
            archive.readFully(cfh);
            int off = 0;
            ZipEntry ze = new ZipEntry();

            int versionMadeBy = ZipShort.getValue(cfh, off);
            off += SHORT;
            ze.setPlatform((versionMadeBy >> BYTE_SHIFT) & NIBLET_MASK);

            off += WORD; // skip version info and general purpose byte

            ze.setMethod(ZipShort.getValue(cfh, off));