/*

 * Copyright (c) 1996, 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package java.util.zip;

import java.io.InputStream;

import java.io.IOException;

import java.io.EOFException;

import java.io.PushbackInputStream;

import java.nio.charset.Charset;

import java.nio.charset.StandardCharsets;

import static java.util.zip.ZipConstants64.*;

import static java.util.zip.ZipUtils.*;

/**

 * This class implements an input stream filter for reading files in the

 * ZIP file format. Includes support for both compressed and uncompressed

 * entries.

 *

 * @author      David Connelly

 * @since 1.1

 */

public

class ZipInputStream extends InflaterInputStream implements ZipConstants {

    private ZipEntry entry;

    private int flag;

    private CRC32 crc = new CRC32();

    private long remaining;

    private byte[] tmpbuf = new byte[512];

    private static final int STORED = ZipEntry.STORED;

    private static final int DEFLATED = ZipEntry.DEFLATED;

    private boolean closed = false;

    // this flag is set to true after EOF has reached for

    // one entry

    private boolean entryEOF = false;

    private ZipCoder zc;

    /**

     * Check to make sure that this stream has not been closed

     */

    private void ensureOpen() throws IOException {

        if (closed) {

            throw new IOException("Stream closed");

        }

    }

    /**

     * Creates a new ZIP input stream.

     *

     * <p>The UTF-8 {@link java.nio.charset.Charset charset} is used to

     * decode the entry names.

     *

     * @param in the actual input stream

     */

    public ZipInputStream(InputStream in) {

        this(in, StandardCharsets.UTF_8);

    }

    /**

     * Creates a new ZIP input stream.

     *

     * @param in the actual input stream

     *

     * @param charset

     *        The {@linkplain java.nio.charset.Charset charset} to be

     *        used to decode the ZIP entry name (ignored if the

     *        <a href="package-summary.html#lang_encoding"> language

     *        encoding bit</a> of the ZIP entry's general purpose bit

     *        flag is set).

     *

     * @since 1.7

     */

    public ZipInputStream(InputStream in, Charset charset) {

        super(new PushbackInputStream(in, 512), new Inflater(true), 512);

        usesDefaultInflater = true;

        if (in == null) {

            throw new NullPointerException("in is null");

        }

        if (charset == null)

            throw new NullPointerException("charset is null");

        this.zc = ZipCoder.get(charset);

    }

    /**

     * Reads the next ZIP file entry and positions the stream at the

     * beginning of the entry data.

     * @return the next ZIP file entry, or null if there are no more entries

     * @throws    ZipException if a ZIP file error has occurred

     * @throws    IOException if an I/O error has occurred

     */

    public ZipEntry getNextEntry() throws IOException {

        ensureOpen();

        if (entry != null) {

            closeEntry();

        }

        crc.reset();

        inf.reset();

        if ((entry = readLOC()) == null) {

            return null;

        }

        if (entry.method == STORED) {

            remaining = entry.size;

        }

        entryEOF = false;

        return entry;

    }

    /**

     * Closes the current ZIP entry and positions the stream for reading the

     * next entry.

     * @throws    ZipException if a ZIP file error has occurred

     * @throws    IOException if an I/O error has occurred

     */

    public void closeEntry() throws IOException {

        ensureOpen();

        while (read(tmpbuf, 0, tmpbuf.length) != -1) ;

        entryEOF = true;

    }

    /**

     * Returns 0 after EOF has reached for the current entry data,

     * otherwise always return 1.

     * <p>

     * Programs should not count on this method to return the actual number

     * of bytes that could be read without blocking.

     *

     * @return     1 before EOF and 0 after EOF has reached for current entry.

     * @throws     IOException  if an I/O error occurs.

     *

     */

    public int available() throws IOException {

        ensureOpen();

        if (entryEOF) {

            return 0;

        } else {

            return 1;

        }

    }

    /**

     * Reads from the current ZIP entry into an array of bytes.

     * blocks until some input is available; otherwise, no

     * @param b the buffer into which the data is read

     * @param len the maximum number of bytes read

     * @return the actual number of bytes read, or -1 if the end of the

     *         entry is reached

     * @throws    ZipException if a ZIP file error has occurred

     * @throws    IOException if an I/O error has occurred

     */

    public int read(byte[] b, int off, int len) throws IOException {

        ensureOpen();

        if (off < 0 || len < 0 || off > b.length - len) {

            throw new IndexOutOfBoundsException();

        } else if (len == 0) {

            return 0;

        }

        if (entry == null) {

            return -1;

        }

        switch (entry.method) {

        case DEFLATED:

            len = super.read(b, off, len);

            if (len == -1) {

                readEnd(entry);

                entryEOF = true;

                entry = null;

            } else {

                crc.update(b, off, len);

            }

            return len;

        case STORED:

            if (remaining <= 0) {

                entryEOF = true;

                entry = null;

                return -1;

            }

            if (len > remaining) {

                len = (int)remaining;

            }

            len = in.read(b, off, len);

            if (len == -1) {

                throw new ZipException("unexpected EOF");

            }

            crc.update(b, off, len);

            remaining -= len;

            if (remaining == 0 && entry.crc != crc.getValue()) {

                throw new ZipException(

                    "invalid entry CRC (expected 0x" + Long.toHexString(entry.crc) +

                    " but got 0x" + Long.toHexString(crc.getValue()) + ")");

            }

            return len;

        default:

            throw new ZipException("invalid compression method");

        }

    }

    /**

     * Skips specified number of bytes in the current ZIP entry.

     * @param n the number of bytes to skip

     * @return the actual number of bytes skipped

     * @throws    ZipException if a ZIP file error has occurred

     * @throws    IOException if an I/O error has occurred

     * @throws    IllegalArgumentException if {@code n < 0}

     */

    public long skip(long n) throws IOException {

        if (n < 0) {

            throw new IllegalArgumentException("negative skip length");

        }

        ensureOpen();

        int max = (int)Math.min(n, Integer.MAX_VALUE);

        int total = 0;

        while (total < max) {

            int len = max - total;

            if (len > tmpbuf.length) {

                len = tmpbuf.length;

            }

            len = read(tmpbuf, 0, len);

            if (len == -1) {

                entryEOF = true;

                break;

            }

            total += len;

        }

        return total;

    }

    /**

     * Closes this input stream and releases any system resources associated

     * with the stream.

     * @throws    IOException if an I/O error has occurred

     */

    public void close() throws IOException {

        if (!closed) {

            super.close();

            closed = true;

        }

    }

    private byte[] b = new byte[256];

    /*

     * Reads local file (LOC) header for next entry.

     */

    private ZipEntry readLOC() throws IOException {

        try {

            readFully(tmpbuf, 0, LOCHDR);

        } catch (EOFException e) {

            return null;

        }

        if (get32(tmpbuf, 0) != LOCSIG) {

            return null;

        }

        // get flag first, we need check USE_UTF8.

        flag = get16(tmpbuf, LOCFLG);

        // get the entry name and create the ZipEntry first

        int len = get16(tmpbuf, LOCNAM);

        int blen = b.length;

        if (len > blen) {

            do {

                blen = blen * 2;

            } while (len > blen);

            b = new byte[blen];

        }

        readFully(b, 0, len);

        // Force to use UTF-8 if the USE_UTF8 bit is ON

        ZipEntry e = createZipEntry(((flag & USE_UTF8) != 0)

                                    ? zc.toStringUTF8(b, len)

                                    : zc.toString(b, len));

        // now get the remaining fields for the entry

        if ((flag & 1) == 1) {

            throw new ZipException("encrypted ZIP entry not supported");

        }

        e.method = get16(tmpbuf, LOCHOW);

        e.xdostime = get32(tmpbuf, LOCTIM);

        if ((flag & 8) == 8) {

            /* "Data Descriptor" present */

            if (e.method != DEFLATED) {

                throw new ZipException(

                        "only DEFLATED entries can have EXT descriptor");

            }

        } else {

            e.crc = get32(tmpbuf, LOCCRC);

            e.csize = get32(tmpbuf, LOCSIZ);

            e.size = get32(tmpbuf, LOCLEN);

        }

        len = get16(tmpbuf, LOCEXT);

        if (len > 0) {

            byte[] extra = new byte[len];

            readFully(extra, 0, len);

            e.setExtra0(extra,

                        e.csize == ZIP64_MAGICVAL || e.size == ZIP64_MAGICVAL, true);

        }

        return e;

    }

    /**

     * entry name.

     *

     * @param name the ZIP file entry name

     * @return the ZipEntry just created

     */

    protected ZipEntry createZipEntry(String name) {

        return new ZipEntry(name);

    }

    /**

     * Reads end of deflated entry as well as EXT descriptor if present.

     *

     * Local headers for DEFLATED entries may optionally be followed by a

     * data descriptor, and that data descriptor may optionally contain a

     * leading signature (EXTSIG).

     *

     * From the zip spec http://www.pkware.com/documents/casestudies/APPNOTE.TXT

     *

     * """Although not originally assigned a signature, the value 0x08074b50

     * has commonly been adopted as a signature value for the data descriptor

     * record.  Implementers should be aware that ZIP files may be

     * encountered with or without this signature marking data descriptors

     * and should account for either case when reading ZIP files to ensure

     * compatibility."""

     */

    private void readEnd(ZipEntry e) throws IOException {

        int n = inf.getRemaining();

        if (n > 0) {

            ((PushbackInputStream)in).unread(buf, len - n, n);

        }

        if ((flag & 8) == 8) {

            /* "Data Descriptor" present */

            if (inf.getBytesWritten() > ZIP64_MAGICVAL ||

                inf.getBytesRead() > ZIP64_MAGICVAL) {

                // ZIP64 format

                readFully(tmpbuf, 0, ZIP64_EXTHDR);

                long sig = get32(tmpbuf, 0);

                if (sig != EXTSIG) { // no EXTSIG present

                    e.crc = sig;

                    e.csize = get64(tmpbuf, ZIP64_EXTSIZ - ZIP64_EXTCRC);

                    e.size = get64(tmpbuf, ZIP64_EXTLEN - ZIP64_EXTCRC);

                    ((PushbackInputStream)in).unread(

                        tmpbuf, ZIP64_EXTHDR - ZIP64_EXTCRC, ZIP64_EXTCRC);

                } else {

                    e.crc = get32(tmpbuf, ZIP64_EXTCRC);

                    e.csize = get64(tmpbuf, ZIP64_EXTSIZ);

                    e.size = get64(tmpbuf, ZIP64_EXTLEN);

                }

            } else {

                readFully(tmpbuf, 0, EXTHDR);

                long sig = get32(tmpbuf, 0);

                if (sig != EXTSIG) { // no EXTSIG present

                    e.crc = sig;

                    e.csize = get32(tmpbuf, EXTSIZ - EXTCRC);

                    e.size = get32(tmpbuf, EXTLEN - EXTCRC);

                    ((PushbackInputStream)in).unread(

                                               tmpbuf, EXTHDR - EXTCRC, EXTCRC);

                } else {

                    e.crc = get32(tmpbuf, EXTCRC);

                    e.csize = get32(tmpbuf, EXTSIZ);

                    e.size = get32(tmpbuf, EXTLEN);

                }

            }

        }

        if (e.size != inf.getBytesWritten()) {

            throw new ZipException(

                "invalid entry size (expected " + e.size +

                " but got " + inf.getBytesWritten() + " bytes)");

        }

        if (e.csize != inf.getBytesRead()) {

            throw new ZipException(

                "invalid entry compressed size (expected " + e.csize +

                " but got " + inf.getBytesRead() + " bytes)");

        }

        if (e.crc != crc.getValue()) {

            throw new ZipException(

                "invalid entry CRC (expected 0x" + Long.toHexString(e.crc) +

                " but got 0x" + Long.toHexString(crc.getValue()) + ")");

        }

    }

    /*

     * Reads bytes, blocking until all bytes are read.

     */

    private void readFully(byte[] b, int off, int len) throws IOException {

        while (len > 0) {

            int n = in.read(b, off, len);

            if (n == -1) {

                throw new EOFException();

            }

            off += n;

            len -= n;

        }

    }

}