| /* GZIPInputStream.java - Input filter for reading gzip file |
| Copyright (C) 1999, 2000 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath 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 for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
| 02111-1307 USA. |
| |
| As a special exception, if you link this library with other files to |
| produce an executable, this library does not by itself cause the |
| resulting executable to be covered by the GNU General Public License. |
| This exception does not however invalidate any other reasons why the |
| executable file might be covered by the GNU General Public License. */ |
| |
| package java.util.zip; |
| |
| import java.io.InputStream; |
| import java.io.IOException; |
| |
| /** |
| * @author Tom Tromey |
| * @date May 17, 1999 |
| */ |
| |
| /* Written using on-line Java Platform 1.2 API Specification |
| * and JCL book. |
| * Believed complete and correct. |
| */ |
| |
| public class GZIPInputStream extends InflaterInputStream |
| { |
| public static final int GZIP_MAGIC = 0x8b1f; |
| |
| public void close () throws IOException |
| { |
| // Nothing to do here. |
| super.close(); |
| } |
| |
| public GZIPInputStream (InputStream istream) throws IOException |
| { |
| this (istream, 512); |
| } |
| |
| private final int eof_read () throws IOException |
| { |
| int r = in.read(); |
| if (r == -1) |
| throw new ZipException ("gzip header corrupted"); |
| return r & 0xff; |
| } |
| |
| public GZIPInputStream (InputStream istream, int readsize) |
| throws IOException |
| { |
| super (istream, new Inflater (true), readsize); |
| |
| // NOTE: header reading code taken from zlib's gzio.c. |
| |
| // Read the magic number. |
| int magic = eof_read () | (eof_read () << 8); |
| if (magic != GZIP_MAGIC) |
| throw new ZipException ("gzip header corrupted"); |
| |
| int method = eof_read (); |
| int flags = eof_read (); |
| // Test from zlib. |
| if (method != Z_DEFLATED || (flags & RESERVED) != 0) |
| throw new ZipException ("gzip header corrupted"); |
| |
| // Discard time, xflags, OS code. |
| for (int i = 0; i < 6; ++i) |
| eof_read (); |
| |
| // Skip the extra field. |
| if ((flags & EXTRA_FIELD) != 0) |
| { |
| int len = eof_read () | (eof_read () << 8); |
| while (len-- != 0) |
| eof_read (); |
| } |
| |
| if ((flags & ORIG_NAME) != 0) |
| { |
| while (true) |
| { |
| int c = eof_read (); |
| if (c == 0) |
| break; |
| } |
| } |
| |
| if ((flags & COMMENT) != 0) |
| { |
| while (true) |
| { |
| int c = eof_read (); |
| if (c == 0) |
| break; |
| } |
| } |
| |
| if ((flags & HEAD_CRC) != 0) |
| { |
| // FIXME: consider checking CRC of the header. |
| eof_read (); |
| eof_read (); |
| } |
| |
| crc = new CRC32 (); |
| } |
| |
| public int read (byte[] buf, int off, int len) throws IOException |
| { |
| if (eos) |
| return -1; |
| int r = super.read(buf, off, len); |
| if (r == -1) |
| { |
| eos = true; |
| int header_crc = read4 (); |
| if (crc.getValue() != header_crc) |
| throw new ZipException ("corrupted gzip file"); |
| // Read final `ISIZE' field. |
| // FIXME: should we check this length? |
| read4 (); |
| return -1; |
| } |
| crc.update(buf, off, r); |
| return r; |
| } |
| |
| private final int read4 () throws IOException |
| { |
| int byte0 = in.read(); |
| int byte1 = in.read(); |
| int byte2 = in.read(); |
| int byte3 = in.read(); |
| if (byte3 < 0) |
| throw new ZipException (".zip archive ended prematurely"); |
| return ((byte3 & 0xFF) << 24) + ((byte2 & 0xFF) << 16) |
| + ((byte1 & 0xFF) << 8) + (byte0 & 0xFF); |
| } |
| |
| // Checksum used by this input stream. |
| protected CRC32 crc; |
| |
| // Indicates whether end-of-stream has been reached. |
| protected boolean eos; |
| |
| // Some constants from zlib. |
| static final int Z_DEFLATED = 8; |
| static final int HEAD_CRC = 0x02; |
| static final int EXTRA_FIELD = 0x04; |
| static final int ORIG_NAME = 0x08; |
| static final int COMMENT = 0x10; |
| static final int RESERVED = 0xe0; |
| } |