mirror of
https://github.com/reactos/reactos.git
synced 2024-11-02 12:53:33 +00:00
246 lines
7.5 KiB
C#
246 lines
7.5 KiB
C#
// StreamManipulator.cs
|
|
// Copyright (C) 2001 Mike Krueger
|
|
//
|
|
// This file was translated from java, it was part of the GNU Classpath
|
|
// Copyright (C) 2001 Free Software Foundation, Inc.
|
|
//
|
|
// This program 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
|
|
// of the License, or (at your option) any later version.
|
|
//
|
|
// This program 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 this program; if not, write to the Free Software
|
|
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
|
|
//
|
|
// Linking this library statically or dynamically with other modules is
|
|
// making a combined work based on this library. Thus, the terms and
|
|
// conditions of the GNU General Public License cover the whole
|
|
// combination.
|
|
//
|
|
// As a special exception, the copyright holders of this library give you
|
|
// permission to link this library with independent modules to produce an
|
|
// executable, regardless of the license terms of these independent
|
|
// modules, and to copy and distribute the resulting executable under
|
|
// terms of your choice, provided that you also meet, for each linked
|
|
// independent module, the terms and conditions of the license of that
|
|
// module. An independent module is a module which is not derived from
|
|
// or based on this library. If you modify this library, you may extend
|
|
// this exception to your version of the library, but you are not
|
|
// obligated to do so. If you do not wish to do so, delete this
|
|
// exception statement from your version.
|
|
|
|
using System;
|
|
|
|
namespace ICSharpCode.SharpZipLib.Zip.Compression.Streams
|
|
{
|
|
|
|
/// <summary>
|
|
/// This class allows us to retrieve a specified amount of bits from
|
|
/// the input buffer, as well as copy big byte blocks.
|
|
///
|
|
/// It uses an int buffer to store up to 31 bits for direct
|
|
/// manipulation. This guarantees that we can get at least 16 bits,
|
|
/// but we only need at most 15, so this is all safe.
|
|
///
|
|
/// There are some optimizations in this class, for example, you must
|
|
/// never peek more then 8 bits more than needed, and you must first
|
|
/// peek bits before you may drop them. This is not a general purpose
|
|
/// class but optimized for the behaviour of the Inflater.
|
|
///
|
|
/// authors of the original java version : John Leuner, Jochen Hoenicke
|
|
/// </summary>
|
|
public class StreamManipulator
|
|
{
|
|
private byte[] window;
|
|
private int window_start = 0;
|
|
private int window_end = 0;
|
|
|
|
private uint buffer = 0;
|
|
private int bits_in_buffer = 0;
|
|
|
|
/// <summary>
|
|
/// Get the next n bits but don't increase input pointer. n must be
|
|
/// less or equal 16 and if you if this call succeeds, you must drop
|
|
/// at least n-8 bits in the next call.
|
|
/// </summary>
|
|
/// <returns>
|
|
/// the value of the bits, or -1 if not enough bits available. */
|
|
/// </returns>
|
|
public int PeekBits(int n)
|
|
{
|
|
if (bits_in_buffer < n) {
|
|
if (window_start == window_end) {
|
|
return -1; // ok
|
|
}
|
|
buffer |= (uint)((window[window_start++] & 0xff |
|
|
(window[window_start++] & 0xff) << 8) << bits_in_buffer);
|
|
bits_in_buffer += 16;
|
|
}
|
|
return (int)(buffer & ((1 << n) - 1));
|
|
}
|
|
|
|
/// <summary>
|
|
/// Drops the next n bits from the input. You should have called peekBits
|
|
/// with a bigger or equal n before, to make sure that enough bits are in
|
|
/// the bit buffer.
|
|
/// </summary>
|
|
public void DropBits(int n)
|
|
{
|
|
buffer >>= n;
|
|
bits_in_buffer -= n;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Gets the next n bits and increases input pointer. This is equivalent
|
|
/// to peekBits followed by dropBits, except for correct error handling.
|
|
/// </summary>
|
|
/// <returns>
|
|
/// the value of the bits, or -1 if not enough bits available.
|
|
/// </returns>
|
|
public int GetBits(int n)
|
|
{
|
|
int bits = PeekBits(n);
|
|
if (bits >= 0) {
|
|
DropBits(n);
|
|
}
|
|
return bits;
|
|
}
|
|
|
|
/// <summary>
|
|
/// Gets the number of bits available in the bit buffer. This must be
|
|
/// only called when a previous peekBits() returned -1.
|
|
/// </summary>
|
|
/// <returns>
|
|
/// the number of bits available.
|
|
/// </returns>
|
|
public int AvailableBits {
|
|
get {
|
|
return bits_in_buffer;
|
|
}
|
|
}
|
|
|
|
/// <summary>
|
|
/// Gets the number of bytes available.
|
|
/// </summary>
|
|
/// <returns>
|
|
/// the number of bytes available.
|
|
/// </returns>
|
|
public int AvailableBytes {
|
|
get {
|
|
return window_end - window_start + (bits_in_buffer >> 3);
|
|
}
|
|
}
|
|
|
|
/// <summary>
|
|
/// Skips to the next byte boundary.
|
|
/// </summary>
|
|
public void SkipToByteBoundary()
|
|
{
|
|
buffer >>= (bits_in_buffer & 7);
|
|
bits_in_buffer &= ~7;
|
|
}
|
|
|
|
public bool IsNeedingInput {
|
|
get {
|
|
return window_start == window_end;
|
|
}
|
|
}
|
|
|
|
/// <summary>
|
|
/// Copies length bytes from input buffer to output buffer starting
|
|
/// at output[offset]. You have to make sure, that the buffer is
|
|
/// byte aligned. If not enough bytes are available, copies fewer
|
|
/// bytes.
|
|
/// </summary>
|
|
/// <param name="output">
|
|
/// the buffer.
|
|
/// </param>
|
|
/// <param name="offset">
|
|
/// the offset in the buffer.
|
|
/// </param>
|
|
/// <param name="length">
|
|
/// the length to copy, 0 is allowed.
|
|
/// </param>
|
|
/// <returns>
|
|
/// the number of bytes copied, 0 if no byte is available.
|
|
/// </returns>
|
|
public int CopyBytes(byte[] output, int offset, int length)
|
|
{
|
|
if (length < 0) {
|
|
throw new ArgumentOutOfRangeException("length negative");
|
|
}
|
|
if ((bits_in_buffer & 7) != 0) {
|
|
/* bits_in_buffer may only be 0 or 8 */
|
|
throw new InvalidOperationException("Bit buffer is not aligned!");
|
|
}
|
|
|
|
int count = 0;
|
|
while (bits_in_buffer > 0 && length > 0) {
|
|
output[offset++] = (byte) buffer;
|
|
buffer >>= 8;
|
|
bits_in_buffer -= 8;
|
|
length--;
|
|
count++;
|
|
}
|
|
if (length == 0) {
|
|
return count;
|
|
}
|
|
|
|
int avail = window_end - window_start;
|
|
if (length > avail) {
|
|
length = avail;
|
|
}
|
|
System.Array.Copy(window, window_start, output, offset, length);
|
|
window_start += length;
|
|
|
|
if (((window_start - window_end) & 1) != 0) {
|
|
/* We always want an even number of bytes in input, see peekBits */
|
|
buffer = (uint)(window[window_start++] & 0xff);
|
|
bits_in_buffer = 8;
|
|
}
|
|
return count + length;
|
|
}
|
|
|
|
public StreamManipulator()
|
|
{
|
|
}
|
|
|
|
public void Reset()
|
|
{
|
|
buffer = (uint)(window_start = window_end = bits_in_buffer = 0);
|
|
}
|
|
|
|
public void SetInput(byte[] buf, int off, int len)
|
|
{
|
|
if (window_start < window_end) {
|
|
throw new InvalidOperationException("Old input was not completely processed");
|
|
}
|
|
|
|
int end = off + len;
|
|
|
|
/* We want to throw an ArrayIndexOutOfBoundsException early. The
|
|
* check is very tricky: it also handles integer wrap around.
|
|
*/
|
|
if (0 > off || off > end || end > buf.Length) {
|
|
throw new ArgumentOutOfRangeException();
|
|
}
|
|
|
|
if ((len & 1) != 0) {
|
|
/* We always want an even number of bytes in input, see peekBits */
|
|
buffer |= (uint)((buf[off++] & 0xff) << bits_in_buffer);
|
|
bits_in_buffer += 8;
|
|
}
|
|
|
|
window = buf;
|
|
window_start = off;
|
|
window_end = end;
|
|
}
|
|
}
|
|
}
|