eff1ff4b41
* Fixed a typo in OpenJPEG.J2KLayerInfo (only affected debug display) git-svn-id: http://libopenmetaverse.googlecode.com/svn/libopenmetaverse/trunk@3118 52acb1d6-8a22-11de-b505-999d5b087335
289 lines
8.6 KiB
C#
289 lines
8.6 KiB
C#
/*
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* CVS identifier:
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*
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* $Id: PktHeaderBitReader.java,v 1.10 2001/09/14 09:29:45 grosbois Exp $
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*
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* Class: PktHeaderBitReader
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*
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* Description: Bit based reader for packet headers
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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 Raphaël Grosbois and
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* Diego Santa Cruz (Swiss Federal Institute of Technology-EPFL); Joel
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* Askelöf (Ericsson Radio Systems AB); and Bertrand Berthelot, David
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* Bouchard, Félix 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.codestream.reader
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{
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/// <summary> This class provides a bit based reading facility from a byte based one,
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/// applying the bit unstuffing procedure as required by the packet headers.
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///
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/// </summary>
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//UPGRADE_NOTE: The access modifier for this class or class field has been changed in order to prevent compilation errors due to the visibility level. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1296'"
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public class PktHeaderBitReader
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{
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/// <summary>The byte based source of data </summary>
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internal RandomAccessIO in_Renamed;
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/// <summary>The byte array that is the source of data if the PktHeaderBitReader
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/// is instantiated with a buffer instead of a RandomAccessIO
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/// </summary>
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internal System.IO.MemoryStream bais;
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/// <summary>Flag indicating whether the data should be read from the buffer </summary>
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internal bool usebais;
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/// <summary>The current bit buffer </summary>
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internal int bbuf;
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/// <summary>The position of the next bit to read in the bit buffer (0 means
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/// empty, 8 full)
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/// </summary>
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internal int bpos;
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/// <summary>The next bit buffer, if bit stuffing occurred (i.e. current bit
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/// buffer holds 0xFF)
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/// </summary>
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internal int nextbbuf;
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/// <summary> Instantiates a 'PktHeaderBitReader' that gets the byte data from the
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/// given source.
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///
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/// </summary>
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/// <param name="in">The source of byte data
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///
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/// </param>
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internal PktHeaderBitReader(RandomAccessIO in_Renamed)
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{
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this.in_Renamed = in_Renamed;
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usebais = false;
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}
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/// <summary> Instantiates a 'PktHeaderBitReader' that gets the byte data from the
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/// given source.
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///
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/// </summary>
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/// <param name="bais">The source of byte data
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///
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/// </param>
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internal PktHeaderBitReader(System.IO.MemoryStream bais)
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{
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this.bais = bais;
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usebais = true;
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}
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/// <summary> Reads a single bit from the input.
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///
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/// </summary>
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/// <returns> The read bit (0 or 1)
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///
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/// </returns>
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/// <exception cref="IOException">If an I/O error occurred
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/// </exception>
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/// <exception cref="EOFException">If teh end of file has been reached
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///
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/// </exception>
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internal int readBit()
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{
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if (bpos == 0)
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{
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// Is bit buffer empty?
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if (bbuf != 0xFF)
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{
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// No bit stuffing
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if (usebais)
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{
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bbuf = bais.ReadByte();
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}
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else
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{
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bbuf = in_Renamed.read();
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}
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bpos = 8;
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if (bbuf == 0xFF)
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{
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// If new bit stuffing get next byte
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if (usebais)
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{
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nextbbuf = bais.ReadByte();
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}
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else
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{
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nextbbuf = in_Renamed.read();
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}
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}
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}
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else
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{
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// We had bit stuffing, nextbuf can not be 0xFF
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bbuf = nextbbuf;
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bpos = 7;
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}
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}
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return (bbuf >> --bpos) & 0x01;
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}
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/// <summary> Reads a specified number of bits and returns them in a single
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/// integer. The bits are returned in the 'n' least significant bits of the
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/// returned integer. The maximum number of bits that can be read is 31.
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///
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/// </summary>
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/// <param name="n">The number of bits to read
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///
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/// </param>
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/// <returns> The read bits, packed in the 'n' LSBs.
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///
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/// </returns>
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/// <exception cref="IOException">If an I/O error occurred
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/// </exception>
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/// <exception cref="EOFException">If teh end of file has been reached
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///
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/// </exception>
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internal int readBits(int n)
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{
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int bits; // The read bits
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// Can we get all bits from the bit buffer?
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if (n <= bpos)
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{
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return (bbuf >> (bpos -= n)) & ((1 << n) - 1);
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}
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else
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{
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// NOTE: The implementation need not be recursive but the not
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// recursive one exploits a bug in the IBM x86 JIT and caused
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// incorrect decoding (Diego Santa Cruz).
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bits = 0;
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do
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{
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// Get all the bits we can from the bit buffer
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bits <<= bpos;
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n -= bpos;
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bits |= readBits(bpos);
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// Get an extra bit to load next byte (here bpos is 0)
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if (bbuf != 0xFF)
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{
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// No bit stuffing
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if (usebais)
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{
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bbuf = bais.ReadByte();
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}
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else
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{
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bbuf = in_Renamed.read();
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}
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bpos = 8;
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if (bbuf == 0xFF)
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{
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// If new bit stuffing get next byte
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if (usebais)
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{
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nextbbuf = bais.ReadByte();
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}
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else
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{
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nextbbuf = in_Renamed.read();
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}
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}
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}
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else
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{
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// We had bit stuffing, nextbuf can not be 0xFF
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bbuf = nextbbuf;
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bpos = 7;
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}
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}
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while (n > bpos);
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// Get the last bits, if any
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bits <<= n;
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bits |= (bbuf >> (bpos -= n)) & ((1 << n) - 1);
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// Return result
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return bits;
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}
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}
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/// <summary> Synchronizes this object with the underlying byte based input. It
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/// discards and buffered bits and gets ready to read bits from the current
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/// position in the underlying byte based input.
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///
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/// <p>This method should always be called when some data has been read
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/// directly from the underlying byte based input since the last call to
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/// 'readBits()' or 'readBit()' before a new call to any of those
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/// methods.</p>
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///
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/// </summary>
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internal virtual void sync()
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{
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bbuf = 0;
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bpos = 0;
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}
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/// <summary> Sets the underlying byte based input to the given object. This method
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/// discards any currently buffered bits and gets ready to start reading
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/// bits from 'in'.
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///
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/// <p>This method is equivalent to creating a new 'PktHeaderBitReader'
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/// object.</p>
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///
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/// </summary>
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/// <param name="in">The source of byte data
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///
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/// </param>
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internal virtual void setInput(RandomAccessIO in_Renamed)
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{
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this.in_Renamed = in_Renamed;
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bbuf = 0;
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bpos = 0;
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}
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/// <summary> Sets the underlying byte based input to the given object. This method
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/// discards any currently buffered bits and gets ready to start reading
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/// bits from 'in'.
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///
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/// <p>This method is equivalent to creating a new 'PktHeaderBitReader'
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/// object.</p>
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///
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/// </summary>
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/// <param name="bais">The source of byte data
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///
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/// </param>
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internal virtual void setInput(System.IO.MemoryStream bais)
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{
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this.bais = bais;
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bbuf = 0;
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bpos = 0;
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}
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}
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} |