libjava/java/util/zip/GZIPInputStream.java

   1 /* GZIPInputStream.java - Input filter for reading gzip file
   2    Copyright (C) 1999, 2000, 2002 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38 package java.util.zip;
  39
  40 import java.io.InputStream;
  41 import java.io.IOException;
  42
  43 /**
  44  * @author Tom Tromey
  45  * @date May 17, 1999
  46  */
  47
  48 /* Written using on-line Java Platform 1.2 API Specification
  49  * and JCL book.
  50  * Believed complete and correct.
  51  */
  52
  53 public class GZIPInputStream extends InflaterInputStream
  54 {
  55   public static final int GZIP_MAGIC = 0x8b1f;
  56
  57   public void close () throws IOException
  58   {
  59     // Nothing to do here.
  60     super.close();
  61   }
  62
  63   public GZIPInputStream (InputStream istream) throws IOException
  64   {
  65     this (istream, 512);
  66   }
  67
  68   private final int eof_read () throws IOException
  69   {
  70     int r = in.read();
  71     if (r == -1)
  72       throw new ZipException ("gzip header corrupted");
  73     return r & 0xff;
  74   }
  75
  76   public GZIPInputStream (InputStream istream, int readsize)
  77     throws IOException
  78   {
  79     super (istream, new Inflater (true), readsize);
  80
  81     // NOTE: header reading code taken from zlib's gzio.c.
  82
  83     // Read the magic number.
  84     int magic = eof_read () | (eof_read () << 8);
  85     if (magic != GZIP_MAGIC)
  86       throw new ZipException ("gzip header corrupted");
  87
  88     int method = eof_read ();
  89     int flags = eof_read ();
  90     // Test from zlib.
  91     if (method != Z_DEFLATED || (flags & RESERVED) != 0)
  92       throw new ZipException ("gzip header corrupted");
  93
  94     // Discard time, xflags, OS code.
  95     for (int i = 0; i < 6; ++i)
  96       eof_read ();
  97
  98     // Skip the extra field.
  99     if ((flags & EXTRA_FIELD) != 0)
 100       {
 101         int len = eof_read () | (eof_read () << 8);
 102         while (len-- != 0)
 103           eof_read ();
 104       }
 105
 106     if ((flags & ORIG_NAME) != 0)
 107       {
 108         while (true)
 109           {
 110             int c = eof_read ();
 111             if (c == 0)
 112               break;
 113           }
 114       }
 115
 116     if ((flags & COMMENT) != 0)
 117       {
 118         while (true)
 119           {
 120             int c = eof_read ();
 121             if (c == 0)
 122               break;
 123           }
 124       }
 125
 126     if ((flags & HEAD_CRC) != 0)
 127       {
 128         // FIXME: consider checking CRC of the header.
 129         eof_read ();
 130         eof_read ();
 131       }
 132
 133     crc = new CRC32 ();
 134   }
 135
 136   public int read (byte[] buf, int off, int len) throws IOException
 137   {
 138     if (eos)
 139       return -1;
 140     int r = super.read(buf, off, len);
 141     if (r == -1)
 142       {
 143         eos = true;
 144
 145         byte[] tmp = new byte[8];
 146         // First copy remaining bytes from inflater input buffer.
 147         int avail = inf.getRemaining ();
 148         System.arraycopy (this.buf, this.len - avail, tmp, 0, avail);
 149
 150         // Now read remaining bytes from wrapped input stream.
 151         for (int i = avail; i < 8; ++i)
 152           {
 153             tmp[i] = (byte) eof_read ();
 154           }
 155
 156         int header_crc = read4 (tmp, 0);
 157         if (crc.getValue() != header_crc)
 158           throw new ZipException ("corrupted gzip file - crc mismatch");
 159         int isize = read4 (tmp, 4);
 160         if (inf.getTotalOut() != isize)
 161           throw new ZipException ("corrupted gzip file - size mismatch");
 162         return -1;
 163       }
 164     crc.update(buf, off, r);
 165     return r;
 166   }
 167
 168   private final int read4 (byte[] buf, int offset) throws IOException
 169   {
 170     return (((buf[offset + 3] & 0xFF) << 24) + ((buf[offset + 2] & 0xFF) << 16)
 171             + ((buf[offset + 1] & 0xFF) << 8) + (buf[offset] & 0xFF));
 172   }
 173
 174   // Checksum used by this input stream.
 175   protected CRC32 crc;
 176
 177   // Indicates whether end-of-stream has been reached.
 178   protected boolean eos;
 179
 180   // Some constants from zlib.
 181   static final int Z_DEFLATED = 8;
 182   static final int HEAD_CRC    = 0x02;
 183   static final int EXTRA_FIELD = 0x04;
 184   static final int ORIG_NAME   = 0x08;
 185   static final int COMMENT     = 0x10;
 186   static final int RESERVED    = 0xe0;
 187 }