/*
 * Copyright (c) 1996, 2015, 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
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 * 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
 */
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
     * @exception ZipException if a ZIP file error has occurred
     * @exception 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.
     * @exception ZipException if a ZIP file error has occurred
     * @exception 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.
     * @exception  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.
     * If <code>len</code> is not zero, the method
     * blocks until some input is available; otherwise, no
     * bytes are read and <code>0</code> is returned.
     * @param b the buffer into which the data is read
     * @param off the start offset in the destination array <code>b</code>
     * @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
     * @exception  NullPointerException if <code>b</code> is <code>null</code>.
     * @exception  IndexOutOfBoundsException if <code>off</code> is negative,
     * <code>len</code> is negative, or <code>len</code> is greater than
     * <code>b.length - off</code>
     * @exception ZipException if a ZIP file error has occurred
     * @exception 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
     * @exception ZipException if a ZIP file error has occurred
     * @exception IOException if an I/O error has occurred
     * @exception 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.
     * @exception 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 EFS.
        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 EFS bit is ON, even the cs is NOT UTF-8
        ZipEntry e = createZipEntry(((flag & EFS) != 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);
        }
        return e;
    }

    /**
     * Creates a new <code>ZipEntry</code> object for the specified
     * 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.
     */
    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 - 1, 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 - 1, 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;
        }
    }

}
