java解压缩.Z文件 Uncompress a unix compressed file--.Z
1、跟解压缩gzip,zip不同
2、参考
Java Programming - Uncompress a unix compressed file
How to Inflate a Unix Compressed File .Z
UncompressInputStream.java
/*
* @(#)UncompressInputStream.java 0.3-2 18/06/1999
*
* This file is part of the HTTPClient package
* Copyright (C) 1996-1999 Ronald Tschalr
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free
* Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
* MA 02111-1307, USA
*
* For questions, suggestions, bug-reports, enhancement-requests etc.
* I may be contacted at:
*
* ronald@innovation.ch
*
*/
package HTTPClient;
import java.io.IOException;
import java.io.EOFException;
import java.io.InputStream;
import java.io.FileInputStream;
import java.io.FilterInputStream;
/**
* This class decompresses an input stream containing data compressed with
* the unix "compress" utility (LZC, a LZW variant). This code is based
* heavily on the <var>unlzw.c</var> code in <var>gzip-1.2.4</var> (written
* by Peter Jannesen) and the original compress code.
*
* @version 0.3-2 18/06/1999
* @author Ronald Tschalr
*/
class UncompressInputStream extends FilterInputStream
{
/**
* @param is the input stream to decompress
* @exception IOException if the header is malformed
*/
public UncompressInputStream(InputStream is) throws IOException
{
super(is);
parse_header();
}
byte[] one = new byte[1];
public synchronized int read() throws IOException
{
int b = in.read(one, 0, 1);
if (b == 1)
return (one[0] & 0xff);
else
return -1;
}
// string table stuff
private static final int TBL_CLEAR = 0x100;
private static final int TBL_FIRST = TBL_CLEAR + 1;
private int[] tab_prefix;
private byte[] tab_suffix;
private int[] zeros = new int[256];
private byte[] stack;
// various state
private boolean block_mode;
private int n_bits;
private int maxbits;
private int maxmaxcode;
private int maxcode;
private int bitmask;
private int oldcode;
private byte finchar;
private int stackp;
private int free_ent;
// input buffer
private byte[] data = new byte[10000];
private int bit_pos = 0, end = 0, got = 0;
private boolean eof = false;
private static final int EXTRA = 64;
public synchronized int read(byte[] buf, int off, int len)
throws IOException
{
if (eof) return -1;
int start = off;
/* Using local copies of various variables speeds things up by as
* much as 30% !
*/
int[] l_tab_prefix = tab_prefix;
byte[] l_tab_suffix = tab_suffix;
byte[] l_stack = stack;
int l_n_bits = n_bits;
int l_maxcode = maxcode;
int l_maxmaxcode = maxmaxcode;
int l_bitmask = bitmask;
int l_oldcode = oldcode;
byte l_finchar = finchar;
int l_stackp = stackp;
int l_free_ent = free_ent;
byte[] l_data = data;
int l_bit_pos = bit_pos;
// empty stack if stuff still left
int s_size = l_stack.length - l_stackp;
if (s_size > 0)
{
int num = (s_size >= len) ? len : s_size ;
System.arraycopy(l_stack, l_stackp, buf, off, num);
off += num;
len -= num;
l_stackp += num;
}
if (len == 0)
{
stackp = l_stackp;
return off-start;
}
// loop, filling local buffer until enough data has been decompressed
main_loop: do
{
if (end < EXTRA) fill();
int bit_in = (got > 0) ? (end - end%l_n_bits)<<3 :
(end<<3)-(l_n_bits-1);
while (l_bit_pos < bit_in)
{
// check for code-width expansion
if (l_free_ent > l_maxcode)
{
int n_bytes = l_n_bits << 3;
l_bit_pos = (l_bit_pos-1) +
n_bytes - (l_bit_pos-1+n_bytes) % n_bytes;
l_n_bits++;
l_maxcode = (l_n_bits==maxbits) ? l_maxmaxcode :
(1<<l_n_bits) - 1;
if (debug)
System.err.println("Code-width expanded to " + l_n_bits);
l_bitmask = (1<<l_n_bits)-1;
l_bit_pos = resetbuf(l_bit_pos);
continue main_loop;
}
// read next code
int pos = l_bit_pos>>3;
int code = (((l_data[pos]&0xFF) | ((l_data[pos+1]&0xFF)<<8) |
((l_data[pos+2]&0xFF)<<16))
>> (l_bit_pos & 0x7)) & l_bitmask;
l_bit_pos += l_n_bits;
// handle first iteration
if (l_oldcode == -1)
{
if (code >= 256)
throw new IOException("corrupt input: " + code +
" > 255");
l_finchar = (byte) (l_oldcode = code);
buf[off++] = l_finchar;
len--;
continue;
}
// handle CLEAR code
if (code == TBL_CLEAR && block_mode)
{
System.arraycopy(zeros, 0, l_tab_prefix, 0, zeros.length);
l_free_ent = TBL_FIRST - 1;
int n_bytes = l_n_bits << 3;
l_bit_pos = (l_bit_pos-1) +
n_bytes - (l_bit_pos-1+n_bytes) % n_bytes;
l_n_bits = INIT_BITS;
l_maxcode = (1 << l_n_bits) - 1;
l_bitmask = l_maxcode;
if (debug) System.err.println("Code tables reset");
l_bit_pos = resetbuf(l_bit_pos);
continue main_loop;
}
// setup
int incode = code;
l_stackp = l_stack.length;
// Handle KwK case
if (code >= l_free_ent)
{
if (code > l_free_ent)
throw new IOException("corrupt input: code=" + code +
", free_ent=" + l_free_ent);
l_stack[--l_stackp] = l_finchar;
code = l_oldcode;
}
// Generate output characters in reverse order
while (code >= 256)
{
l_stack[--l_stackp] = l_tab_suffix[code];
code = l_tab_prefix[code];
}
l_finchar = l_tab_suffix[code];
buf[off++] = l_finchar;
len--;
// And put them out in forward order
s_size = l_stack.length - l_stackp;
int num = (s_size >= len) ? len : s_size ;
System.arraycopy(l_stack, l_stackp, buf, off, num);
off += num;
len -= num;
l_stackp += num;
// generate new entry in table
if (l_free_ent < l_maxmaxcode)
{
l_tab_prefix[l_free_ent] = l_oldcode;
l_tab_suffix[l_free_ent] = l_finchar;
l_free_ent++;
}
// Remember previous code
l_oldcode = incode;
// if output buffer full, then return
if (len == 0)
{
n_bits = l_n_bits;
maxcode = l_maxcode;
bitmask = l_bitmask;
oldcode = l_oldcode;
finchar = l_finchar;
stackp = l_stackp;
free_ent = l_free_ent;
bit_pos = l_bit_pos;
return off-start;
}
}
l_bit_pos = resetbuf(l_bit_pos);
} while (got > 0);
n_bits = l_n_bits;
maxcode = l_maxcode;
bitmask = l_bitmask;
oldcode = l_oldcode;
finchar = l_finchar;
stackp = l_stackp;
free_ent = l_free_ent;
bit_pos = l_bit_pos;
eof = true;
return off-start;
}
/**
* Moves the unread data in the buffer to the beginning and resets
* the pointers.
*/
private final int resetbuf(int bit_pos)
{
int pos = bit_pos >> 3;
System.arraycopy(data, pos, data, 0, end-pos);
end -= pos;
return 0;
}
private final void fill() throws IOException
{
got = in.read(data, end, data.length-1-end);
if (got > 0) end += got;
}
public synchronized long skip(long num) throws IOException
{
byte[] tmp = new byte[(int) num];
int got = read(tmp, 0, (int) num);
if (got > 0)
return (long) got;
else
return 0L;
}
public synchronized int available() throws IOException
{
if (eof) return 0;
return in.available();
}
private static final int LZW_MAGIC = 0x1f9d;
private static final int MAX_BITS = 16;
private static final int INIT_BITS = 9;
private static final int HDR_MAXBITS = 0x1f;
private static final int HDR_EXTENDED = 0x20;
private static final int HDR_FREE = 0x40;
private static final int HDR_BLOCK_MODE = 0x80;
private void parse_header() throws IOException
{
// read in and check magic number
int t = in.read();
if (t < 0) throw new EOFException("Failed to read magic number");
int magic = (t & 0xff) << 8;
t = in.read();
if (t < 0) throw new EOFException("Failed to read magic number");
magic += t & 0xff;
if (magic != LZW_MAGIC)
throw new IOException("Input not in compress format (read " +
"magic number 0x" +
Integer.toHexString(magic) + ")");
// read in header byte
int header = in.read();
if (header < 0) throw new EOFException("Failed to read header");
block_mode = (header & HDR_BLOCK_MODE) > 0;
maxbits = header & HDR_MAXBITS;
if (maxbits > MAX_BITS)
throw new IOException("Stream compressed with " + maxbits +
" bits, but can only handle " + MAX_BITS +
" bits");
if ((header & HDR_EXTENDED) > 0)
throw new IOException("Header extension bit set");
if ((header & HDR_FREE) > 0)
throw new IOException("Header bit 6 set");
if (debug)
{
System.err.println("block mode: " + block_mode);
System.err.println("max bits: " + maxbits);
}
// initialize stuff
maxmaxcode = 1 << maxbits;
n_bits = INIT_BITS;
maxcode = (1 << n_bits) - 1;
bitmask = maxcode;
oldcode = -1;
finchar = 0;
free_ent = block_mode ? TBL_FIRST : 256;
tab_prefix = new int[1 << maxbits];
tab_suffix = new byte[1 << maxbits];
stack = new byte[1 << maxbits];
stackp = stack.length;
for (int idx=255; idx>=0; idx--)
tab_suffix[idx] = (byte) idx;
}
private static final boolean debug = false;
public static void main (String args[]) throws Exception
{
if (args.length != 1)
{
System.err.println("Usage: UncompressInputStream <file>");
System.exit(1);
}
InputStream in =
new UncompressInputStream(new FileInputStream(args[0]));
byte[] buf = new byte[100000];
int tot = 0;
long beg = System.currentTimeMillis();
while (true)
{
int got = in.read(buf);
if (got < 0) break;
System.out.write(buf, 0, got);
tot += got;
}
long end = System.currentTimeMillis();
System.err.println("Decompressed " + tot + " bytes");
System.err.println("Time: " + (end-beg)/1000. + " seconds");
}
}
