306 lines
8.8 KiB
C#
306 lines
8.8 KiB
C#
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/*
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* CVS identifier:
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*
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* $Id: BitToByteOutput.java,v 1.16 2001/10/17 16:56:59 grosbois Exp $
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*
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* Class: BitToByteOutput
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*
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* Description: Adapter to perform bit based output on a byte
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* based one.
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*
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*
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*
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* COPYRIGHT:
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*
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* This software module was originally developed by Rapha<EFBFBD>l Grosbois and
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* Diego Santa Cruz (Swiss Federal Institute of Technology-EPFL); Joel
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* Askel<EFBFBD>f (Ericsson Radio Systems AB); and Bertrand Berthelot, David
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* Bouchard, F<EFBFBD>lix Henry, Gerard Mozelle and Patrice Onno (Canon Research
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* Centre France S.A) in the course of development of the JPEG2000
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* standard as specified by ISO/IEC 15444 (JPEG 2000 Standard). This
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* software module is an implementation of a part of the JPEG 2000
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* Standard. Swiss Federal Institute of Technology-EPFL, Ericsson Radio
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* Systems AB and Canon Research Centre France S.A (collectively JJ2000
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* Partners) agree not to assert against ISO/IEC and users of the JPEG
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* 2000 Standard (Users) any of their rights under the copyright, not
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* including other intellectual property rights, for this software module
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* with respect to the usage by ISO/IEC and Users of this software module
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* or modifications thereof for use in hardware or software products
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* claiming conformance to the JPEG 2000 Standard. Those intending to use
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* this software module in hardware or software products are advised that
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* their use may infringe existing patents. The original developers of
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* this software module, JJ2000 Partners and ISO/IEC assume no liability
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* for use of this software module or modifications thereof. No license
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* or right to this software module is granted for non JPEG 2000 Standard
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* conforming products. JJ2000 Partners have full right to use this
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* software module for his/her own purpose, assign or donate this
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* software module to any third party and to inhibit third parties from
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* using this software module for non JPEG 2000 Standard conforming
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* products. This copyright notice must be included in all copies or
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* derivative works of this software module.
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*
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* Copyright (c) 1999/2000 JJ2000 Partners.
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* */
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using System;
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using CSJ2K.j2k.io;
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namespace CSJ2K.j2k.entropy.encoder
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{
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/// <summary> This class provides an adapter to perform bit based output on byte based
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/// output objects that inherit from a 'ByteOutputBuffer' class. This class
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/// implements the bit stuffing policy needed for the 'selective arithmetic
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/// coding bypass' mode of the entropy coder. This class also delays the output
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/// of a trailing 0xFF, since they are synthetized be the decoder.
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///
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/// </summary>
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class BitToByteOutput
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{
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/// <summary> Set the flag according to whether or not the predictable termination is
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/// requested.
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///
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/// </summary>
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/// <param name="isPredTerm">Whether or not predictable termination is requested.
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///
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/// </param>
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virtual internal bool PredTerm
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{
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set
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{
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this.isPredTerm = value;
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}
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}
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/// <summary>Whether or not predictable termination is requested. This value is
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/// important when the last byte before termination is an 0xFF
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/// </summary>
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private bool isPredTerm = false;
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/// <summary>The alternating sequence of 0's and 1's used for byte padding </summary>
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internal const int PAD_SEQ = 0x2A;
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/// <summary>Flag that indicates if an FF has been delayed </summary>
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internal bool delFF = false;
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/// <summary>The byte based output </summary>
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internal ByteOutputBuffer out_Renamed;
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/// <summary>The bit buffer </summary>
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internal int bbuf;
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/// <summary>The position of the next bit to put in the bit buffer. When it is 7
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/// the bit buffer 'bbuf' is empty. The value should always be between 7
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/// and 0 (i.e. if it gets to -1, the bit buffer should be immediately
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/// written to the byte output).
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/// </summary>
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internal int bpos = 7;
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/// <summary>The number of written bytes (excluding the bit buffer) </summary>
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internal int nb = 0;
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/// <summary> Instantiates a new 'BitToByteOutput' object that uses 'out' as the
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/// underlying byte based output.
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///
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/// </summary>
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/// <param name="out">The underlying byte based output
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///
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/// </param>
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internal BitToByteOutput(ByteOutputBuffer out_Renamed)
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{
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this.out_Renamed = out_Renamed;
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}
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/// <summary> Writes to the bit stream the symbols contained in the 'symbuf'
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/// buffer. The least significant bit of each element in 'symbuf'is
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/// written.
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///
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/// </summary>
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/// <param name="symbuf">The symbols to write
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///
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/// </param>
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/// <param name="nsym">The number of symbols in symbuf
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///
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/// </param>
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internal void writeBits(int[] symbuf, int nsym)
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{
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int i;
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int bbuf, bpos;
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bbuf = this.bbuf;
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bpos = this.bpos;
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// Write symbol by symbol to bit buffer
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for (i = 0; i < nsym; i++)
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{
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bbuf |= (symbuf[i] & 0x01) << (bpos--);
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if (bpos < 0)
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{
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// Bit buffer is full, write it
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if (bbuf != 0xFF)
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{
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// No bit-stuffing needed
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if (delFF)
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{
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// Output delayed 0xFF if any
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out_Renamed.write(0xFF);
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nb++;
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delFF = false;
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}
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out_Renamed.write(bbuf);
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nb++;
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bpos = 7;
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}
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else
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{
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// We need to do bit stuffing on next byte
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delFF = true;
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bpos = 6; // One less bit in next byte
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}
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bbuf = 0;
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}
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}
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this.bbuf = bbuf;
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this.bpos = bpos;
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}
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/// <summary> Write a bit to the output. The least significant bit of 'bit' is
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/// written to the output.
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///
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/// </summary>
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/// <param name="bit">
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/// </param>
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internal void writeBit(int bit)
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{
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bbuf |= (bit & 0x01) << (bpos--);
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if (bpos < 0)
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{
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if (bbuf != 0xFF)
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{
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// No bit-stuffing needed
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if (delFF)
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{
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// Output delayed 0xFF if any
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out_Renamed.write(0xFF);
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nb++;
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delFF = false;
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}
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// Output the bit buffer
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out_Renamed.write(bbuf);
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nb++;
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bpos = 7;
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}
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else
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{
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// We need to do bit stuffing on next byte
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delFF = true;
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bpos = 6; // One less bit in next byte
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}
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bbuf = 0;
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}
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}
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/// <summary> Writes the contents of the bit buffer and byte aligns the output by
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/// filling bits with an alternating sequence of 0's and 1's.
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///
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/// </summary>
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internal virtual void flush()
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{
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if (delFF)
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{
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// There was a bit stuffing
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if (bpos != 6)
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{
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// Bit buffer is not empty
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// Output delayed 0xFF
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out_Renamed.write(0xFF);
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nb++;
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delFF = false;
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// Pad to byte boundary with an alternating sequence of 0's
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// and 1's.
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bbuf |= (SupportClass.URShift(PAD_SEQ, (6 - bpos)));
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// Output the bit buffer
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out_Renamed.write(bbuf);
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nb++;
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bpos = 7;
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bbuf = 0;
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}
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else if (isPredTerm)
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{
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out_Renamed.write(0xFF);
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nb++;
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out_Renamed.write(0x2A);
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nb++;
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bpos = 7;
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bbuf = 0;
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delFF = false;
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}
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}
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else
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{
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// There was no bit stuffing
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if (bpos != 7)
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{
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// Bit buffer is not empty
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// Pad to byte boundary with an alternating sequence of 0's and
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// 1's.
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bbuf |= (SupportClass.URShift(PAD_SEQ, (6 - bpos)));
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// Output the bit buffer (bbuf can not be 0xFF)
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out_Renamed.write(bbuf);
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nb++;
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bpos = 7;
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bbuf = 0;
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}
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}
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}
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/// <summary> Terminates the bit stream by calling 'flush()' and then
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/// 'reset()'. Finally, it returns the number of bytes effectively written.
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///
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/// </summary>
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/// <returns> The number of bytes effectively written.
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///
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/// </returns>
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public virtual int terminate()
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{
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flush();
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int savedNb = nb;
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reset();
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return savedNb;
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}
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/// <summary> Resets the bit buffer to empty, without writing anything to the
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/// underlying byte output, and resets the byte count. The underlying byte
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/// output is NOT reset.
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///
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/// </summary>
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internal virtual void reset()
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{
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delFF = false;
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bpos = 7;
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bbuf = 0;
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nb = 0;
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}
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/// <summary> Returns the length, in bytes, of the output bit stream as written by
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/// this object. If the output bit stream does not have an integer number
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/// of bytes in length then it is rounded to the next integer.
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///
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/// </summary>
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/// <returns> The length, in bytes, of the output bit stream.
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///
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/// </returns>
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internal virtual int length()
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{
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if (delFF)
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{
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// If bit buffer is empty we just need 'nb' bytes. If not we need
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// the delayed FF and the padded bit buffer.
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return nb + 2;
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}
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else
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{
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// If the bit buffer is empty, we just need 'nb' bytes. If not, we
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// add length of the padded bit buffer
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return nb + ((bpos == 7)?0:1);
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}
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}
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}
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}
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