/*
* Copyright (c) 1996, 2006, 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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*/
package java.util.zip;
import java.io.SequenceInputStream;
import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.io.IOException;
import java.io.EOFException;
/**
* This class implements a stream filter for reading compressed data in
* the GZIP file format.
*
* @see InflaterInputStream
* @author David Connelly
*
*/
public
class GZIPInputStream extends InflaterInputStream {
/**
* CRC-32 for uncompressed data.
*/
protected CRC32 crc = new CRC32();
/**
* Indicates end of input stream.
*/
protected boolean eos;
private boolean closed = 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 input stream with the specified buffer size.
* @param in the input stream
* @param size the input buffer size
* @exception IOException if an I/O error has occurred
* @exception IllegalArgumentException if size is <= 0
*/
public GZIPInputStream(InputStream in, int size) throws IOException {
super(in, new Inflater(true), size);
usesDefaultInflater = true;
readHeader();
crc.reset();
}
/**
* Creates a new input stream with a default buffer size.
* @param in the input stream
* @exception IOException if an I/O error has occurred
*/
public GZIPInputStream(InputStream in) throws IOException {
this(in, 512);
}
/**
* Reads uncompressed data into an array of bytes. If <code>len</code> is not
* zero, the method will block until some input can be decompressed; otherwise,
* no bytes are read and <code>0</code> is returned.
* @param buf 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
* compressed input stream is reached
* @exception NullPointerException If <code>buf</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>buf.length - off</code>
* @exception IOException if an I/O error has occurred or the compressed
* input data is corrupt
*/
public int read(byte[] buf, int off, int len) throws IOException {
ensureOpen();
if (eos) {
return -1;
}
len = super.read(buf, off, len);
if (len == -1) {
readTrailer();
eos = true;
} else {
crc.update(buf, off, len);
}
return len;
}
/**
* 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();
eos = true;
closed = true;
}
}
/**
* GZIP header magic number.
*/
public final static int GZIP_MAGIC = 0x8b1f;
/*
* File header flags.
*/
private final static int FTEXT = 1; // Extra text
private final static int FHCRC = 2; // Header CRC
private final static int FEXTRA = 4; // Extra field
private final static int FNAME = 8; // File name
private final static int FCOMMENT = 16; // File comment
/*
* Reads GZIP member header.
*/
private void readHeader() throws IOException {
CheckedInputStream in = new CheckedInputStream(this.in, crc);
crc.reset();
// Check header magic
if (readUShort(in) != GZIP_MAGIC) {
throw new IOException("Not in GZIP format");
}
// Check compression method
if (readUByte(in) != 8) {
throw new IOException("Unsupported compression method");
}
// Read flags
int flg = readUByte(in);
// Skip MTIME, XFL, and OS fields
skipBytes(in, 6);
// Skip optional extra field
if ((flg & FEXTRA) == FEXTRA) {
skipBytes(in, readUShort(in));
}
// Skip optional file name
if ((flg & FNAME) == FNAME) {
while (readUByte(in) != 0) ;
}
// Skip optional file comment
if ((flg & FCOMMENT) == FCOMMENT) {
while (readUByte(in) != 0) ;
}
// Check optional header CRC
if ((flg & FHCRC) == FHCRC) {
int v = (int)crc.getValue() & 0xffff;
if (readUShort(in) != v) {
throw new IOException("Corrupt GZIP header");
}
}
}
/*
* Reads GZIP member trailer.
*/
private void readTrailer() throws IOException {
InputStream in = this.in;
int n = inf.getRemaining();
if (n > 0) {
in = new SequenceInputStream(
new ByteArrayInputStream(buf, len - n, n), in);
}
// Uses left-to-right evaluation order
if ((readUInt(in) != crc.getValue()) ||
// rfc1952; ISIZE is the input size modulo 2^32
(readUInt(in) != (inf.getBytesWritten() & 0xffffffffL)))
throw new IOException("Corrupt GZIP trailer");
}
/*
* Reads unsigned integer in Intel byte order.
*/
private long readUInt(InputStream in) throws IOException {
long s = readUShort(in);
return ((long)readUShort(in) << 16) | s;
}
/*
* Reads unsigned short in Intel byte order.
*/
private int readUShort(InputStream in) throws IOException {
int b = readUByte(in);
return ((int)readUByte(in) << 8) | b;
}
/*
* Reads unsigned byte.
*/
private int readUByte(InputStream in) throws IOException {
int b = in.read();
if (b == -1) {
throw new EOFException();
}
if (b < -1 || b > 255) {
// Report on this.in, not argument in; see read{Header, Trailer}.
throw new IOException(this.in.getClass().getName()
+ ".read() returned value out of range -1..255: " + b);
}
return b;
}
private byte[] tmpbuf = new byte[128];
/*
* Skips bytes of input data blocking until all bytes are skipped.
* Does not assume that the input stream is capable of seeking.
*/
private void skipBytes(InputStream in, int n) throws IOException {
while (n > 0) {
int len = in.read(tmpbuf, 0, n < tmpbuf.length ? n : tmpbuf.length);
if (len == -1) {
throw new EOFException();
}
n -= len;
}
}
}