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// GZIPInputStream.java - Input tiler for reading gzip file.
/* Copyright (C) 1999 Cygnus Solutions
This file is part of libgcj.
This software is copyrighted work licensed under the terms of the
Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
details. */
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;
}
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