/*
 * Copyright 1996-2009 Sun Microsystems, Inc.  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.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.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 static java.util.zip.ZipConstants64.*;

/**
 * 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;

    /**
     * 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.
     * @param in the actual input stream
     */
    public ZipInputStream(InputStream in) {
        super(new PushbackInputStream(in, 512), new Inflater(true), 512);
        usesDefaultInflater = true;
        if(in == null) {
            throw new NullPointerException("in is null");
        }
    }

    /**
     * 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 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 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);
        ZipEntry e = createZipEntry(getUTF8String(b, 0, len));
        // now get the remaining fields for the entry
        flag = get16(tmpbuf, LOCFLG);
        if ((flag & 1) == 1) {
            throw new ZipException("encrypted ZIP entry not supported");
        }
        e.method = get16(tmpbuf, LOCHOW);
        e.time = 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[] bb = new byte[len];
            readFully(bb, 0, len);
            e.setExtra(bb);
            // extra fields are in "HeaderID(2)DataSize(2)Data... format
            if (e.csize == ZIP64_MAGICVAL || e.size == ZIP64_MAGICVAL) {
                int off = 0;
	        while (off + 4 < len) {
                    int sz = get16(bb, off + 2);
                    if (get16(bb, off) == ZIP64_EXTID) {
                        off += 4;
                        // LOC extra zip64 entry MUST include BOTH original and
                        // compressed file size fields
                        if (sz < 16 || (off + sz) > len ) {
			    // invalid zip64 extra fields, simply skip.
			    // throw new ZipException("invalid Zip64 extra fields in LOC");
                            return e;
                        }
                        e.size = get64(bb, off);
                        e.csize = get64(bb, off + 8);
                        break;
                    }
                    off += (sz + 4);
	        }
            }
        }
        return e;
    }

    /*
     * Fetches a UTF8-encoded String from the specified byte array.
     */
    private static String getUTF8String(byte[] b, int off, int len) {
        // First, count the number of characters in the sequence
        int count = 0;
        int max = off + len;
        int i = off;
        while (i < max) {
            int c = b[i++] & 0xff;
            switch (c >> 4) {
            case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
                // 0xxxxxxx
                count++;
                break;
            case 12: case 13:
                // 110xxxxx 10xxxxxx
                if ((b[i++] & 0xc0) != 0x80) {
                    throw new IllegalArgumentException();
                }
                count++;
                break;
            case 14:
                // 1110xxxx 10xxxxxx 10xxxxxx
                if (((b[i++] & 0xc0) != 0x80) ||
                    ((b[i++] & 0xc0) != 0x80)) {
                    throw new IllegalArgumentException();
                }
                count++;
                break;
            default:
                // 10xxxxxx, 1111xxxx
                throw new IllegalArgumentException();
            }
        }
        if (i != max) {
            throw new IllegalArgumentException();
        }
        // Now decode the characters...
        char[] cs = new char[count];
        i = 0;
        while (off < max) {
            int c = b[off++] & 0xff;
            switch (c >> 4) {
            case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
                // 0xxxxxxx
                cs[i++] = (char)c;
                break;
            case 12: case 13:
                // 110xxxxx 10xxxxxx
                cs[i++] = (char)(((c & 0x1f) << 6) | (b[off++] & 0x3f));
                break;
            case 14:
                // 1110xxxx 10xxxxxx 10xxxxxx
                int t = (b[off++] & 0x3f) << 6;
                cs[i++] = (char)(((c & 0x0f) << 12) | t | (b[off++] & 0x3f));
                break;
            default:
                // 10xxxxxx, 1111xxxx
                throw new IllegalArgumentException();
            }
        }
        return new String(cs, 0, count);
    }

    /**
     * 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;
        }
    }

    /*
     * Fetches unsigned 16-bit value from byte array at specified offset.
     * The bytes are assumed to be in Intel (little-endian) byte order.
     */
    private static final int get16(byte b[], int off) {
        return (b[off] & 0xff) | ((b[off+1] & 0xff) << 8);
    }

    /*
     * Fetches unsigned 32-bit value from byte array at specified offset.
     * The bytes are assumed to be in Intel (little-endian) byte order.
     */
    private static final long get32(byte b[], int off) {
        return (get16(b, off) | ((long)get16(b, off+2) << 16)) & 0xffffffffL;
    }

    /*
     * Fetches signed 64-bit value from byte array at specified offset.
     * The bytes are assumed to be in Intel (little-endian) byte order.
     */
    private static final long get64(byte b[], int off) {
        return get32(b, off) | (get32(b, off+4) << 32);
    }
}