corrade-vassal – Blame information for rev 1
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1 | vero | 1 | /* |
2 | * CVS identifier: |
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3 | * |
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4 | * $Id: BitOutputBuffer.java,v 1.9 2002/07/19 12:40:05 grosbois Exp $ |
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5 | * |
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6 | * Class: BitOutputBuffer |
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7 | * |
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8 | * Description: <short description of class> |
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9 | * |
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10 | * |
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11 | * |
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12 | * COPYRIGHT: |
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13 | * |
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14 | * This software module was originally developed by Raphaël Grosbois and |
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15 | * Diego Santa Cruz (Swiss Federal Institute of Technology-EPFL); Joel |
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16 | * Askelöf (Ericsson Radio Systems AB); and Bertrand Berthelot, David |
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17 | * Bouchard, Félix Henry, Gerard Mozelle and Patrice Onno (Canon Research |
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18 | * Centre France S.A) in the course of development of the JPEG2000 |
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19 | * standard as specified by ISO/IEC 15444 (JPEG 2000 Standard). This |
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20 | * software module is an implementation of a part of the JPEG 2000 |
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21 | * Standard. Swiss Federal Institute of Technology-EPFL, Ericsson Radio |
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22 | * Systems AB and Canon Research Centre France S.A (collectively JJ2000 |
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23 | * Partners) agree not to assert against ISO/IEC and users of the JPEG |
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24 | * 2000 Standard (Users) any of their rights under the copyright, not |
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25 | * including other intellectual property rights, for this software module |
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26 | * with respect to the usage by ISO/IEC and Users of this software module |
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27 | * or modifications thereof for use in hardware or software products |
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28 | * claiming conformance to the JPEG 2000 Standard. Those intending to use |
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29 | * this software module in hardware or software products are advised that |
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30 | * their use may infringe existing patents. The original developers of |
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31 | * this software module, JJ2000 Partners and ISO/IEC assume no liability |
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32 | * for use of this software module or modifications thereof. No license |
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33 | * or right to this software module is granted for non JPEG 2000 Standard |
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34 | * conforming products. JJ2000 Partners have full right to use this |
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35 | * software module for his/her own purpose, assign or donate this |
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36 | * software module to any third party and to inhibit third parties from |
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37 | * using this software module for non JPEG 2000 Standard conforming |
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38 | * products. This copyright notice must be included in all copies or |
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39 | * derivative works of this software module. |
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40 | * |
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41 | * Copyright (c) 1999/2000 JJ2000 Partners. |
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42 | * */ |
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43 | using System; |
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44 | using CSJ2K.j2k.util; |
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45 | namespace CSJ2K.j2k.codestream.writer |
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46 | { |
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47 | |||
48 | /// <summary> This class implements a buffer for writing bits, with the required bit |
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49 | /// stuffing policy for the packet headers. The bits are stored in a byte array |
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50 | /// in the order in which they are written. The byte array is automatically |
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51 | /// reallocated and enlarged whenever necessary. A BitOutputBuffer object may |
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52 | /// be reused by calling its 'reset()' method. |
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53 | /// |
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54 | /// <P>NOTE: The methods implemented in this class are intended to be used only |
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55 | /// in writing packet heads, since a special bit stuffing procedure is used, as |
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56 | /// required for the packet heads. |
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57 | /// |
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58 | /// </summary> |
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59 | public class BitOutputBuffer |
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60 | { |
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61 | /// <summary> Returns the current length of the buffer, in bytes. |
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62 | /// |
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63 | /// <P>This method is declared final to increase performance. |
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64 | /// |
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65 | /// </summary> |
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66 | /// <returns> The currebt length of the buffer in bytes. |
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67 | /// |
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68 | /// </returns> |
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69 | virtual public int Length |
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70 | { |
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71 | get |
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72 | { |
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73 | if (avbits == 8) |
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74 | { |
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75 | // A integral number of bytes |
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76 | return curbyte; |
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77 | } |
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78 | else |
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79 | { |
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80 | // Some bits in last byte |
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81 | return curbyte + 1; |
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82 | } |
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83 | } |
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84 | |||
85 | } |
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86 | /// <summary> Returns the byte buffer. This is the internal byte buffer so it should |
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87 | /// not be modified. Only the first N elements have valid data, where N is |
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88 | /// the value returned by 'getLength()' |
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89 | /// |
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90 | /// <P>This method is declared final to increase performance. |
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91 | /// |
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92 | /// </summary> |
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93 | /// <returns> The internal byte buffer. |
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94 | /// |
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95 | /// </returns> |
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96 | virtual public byte[] Buffer |
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97 | { |
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98 | get |
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99 | { |
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100 | return buf; |
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101 | } |
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102 | |||
103 | } |
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104 | |||
105 | /// <summary>The buffer where we store the data </summary> |
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106 | internal byte[] buf; |
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107 | |||
108 | /// <summary>The position of the current byte to write </summary> |
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109 | internal int curbyte; |
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110 | |||
111 | /// <summary>The number of available bits in the current byte </summary> |
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112 | internal int avbits = 8; |
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113 | |||
114 | /// <summary>The increment size for the buffer, 16 bytes. This is the |
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115 | /// number of bytes that are added to the buffer each time it is |
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116 | /// needed to enlarge it. |
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117 | /// </summary> |
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118 | // This must be always 6 or larger. |
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119 | public const int SZ_INCR = 16; |
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120 | |||
121 | /// <summary>The initial size for the buffer, 32 bytes. </summary> |
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122 | public const int SZ_INIT = 32; |
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123 | |||
124 | /// <summary> Creates a new BitOutputBuffer width a buffer of length |
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125 | /// 'SZ_INIT'. |
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126 | /// |
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127 | /// </summary> |
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128 | public BitOutputBuffer() |
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129 | { |
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130 | buf = new byte[SZ_INIT]; |
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131 | } |
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132 | |||
133 | /// <summary> Resets the buffer. This rewinds the current position to the start of |
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134 | /// the buffer and sets all tha data to 0. Note that no new buffer is |
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135 | /// allocated, so this will affect any data that was returned by the |
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136 | /// 'getBuffer()' method. |
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137 | /// |
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138 | /// </summary> |
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139 | public virtual void reset() |
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140 | { |
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141 | //int i; |
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142 | // Reinit pointers |
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143 | curbyte = 0; |
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144 | avbits = 8; |
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145 | ArrayUtil.byteArraySet(buf, (byte) 0); |
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146 | } |
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147 | |||
148 | /// <summary> Writes a bit to the buffer at the current position. The value 'bit' |
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149 | /// must be either 0 or 1, otherwise it corrupts the bits that have been |
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150 | /// already written. The buffer is enlarged, by 'SZ_INCR' bytes, if |
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151 | /// necessary. |
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152 | /// |
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153 | /// <P>This method is declared final to increase performance. |
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154 | /// |
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155 | /// </summary> |
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156 | /// <param name="bit">The bit to write, 0 or 1. |
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157 | /// |
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158 | /// </param> |
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159 | public void writeBit(int bit) |
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160 | { |
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161 | buf[curbyte] |= (byte) (bit << --avbits); |
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162 | if (avbits > 0) |
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163 | { |
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164 | // There is still place in current byte for next bit |
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165 | return ; |
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166 | } |
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167 | else |
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168 | { |
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169 | // End of current byte => goto next |
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170 | if (buf[curbyte] != (byte) SupportClass.Identity(0xFF)) |
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171 | { |
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172 | // We don't need bit stuffing |
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173 | avbits = 8; |
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174 | } |
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175 | else |
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176 | { |
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177 | // We need to stuff a bit (next MSBit is 0) |
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178 | avbits = 7; |
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179 | } |
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180 | curbyte++; |
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181 | if (curbyte == buf.Length) |
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182 | { |
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183 | // We are at end of 'buf' => extend it |
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184 | byte[] oldbuf = buf; |
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185 | buf = new byte[oldbuf.Length + SZ_INCR]; |
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186 | Array.Copy(oldbuf, 0, buf, 0, oldbuf.Length); |
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187 | } |
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188 | } |
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189 | } |
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190 | |||
191 | /// <summary> Writes the n least significant bits of 'bits' to the buffer at the |
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192 | /// current position. The least significant bit is written last. The 32-n |
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193 | /// most significant bits of 'bits' must be 0, otherwise corruption of the |
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194 | /// buffer will result. The buffer is enlarged, by 'SZ_INCR' bytes, if |
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195 | /// necessary. |
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196 | /// |
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197 | /// <P>This method is declared final to increase performance. |
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198 | /// |
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199 | /// </summary> |
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200 | /// <param name="bits">The bits to write. |
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201 | /// |
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202 | /// </param> |
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203 | /// <param name="n">The number of LSBs in 'bits' to write. |
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204 | /// |
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205 | /// </param> |
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206 | public void writeBits(int bits, int n) |
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207 | { |
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208 | // Check that we have enough place in 'buf' for n bits, and that we do |
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209 | // not fill last byte, taking into account possibly stuffed bits (max |
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210 | // 2) |
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211 | if (((buf.Length - curbyte) << 3) - 8 + avbits <= n + 2) |
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212 | { |
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213 | // Not enough place, extend it |
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214 | byte[] oldbuf = buf; |
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215 | buf = new byte[oldbuf.Length + SZ_INCR]; |
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216 | Array.Copy(oldbuf, 0, buf, 0, oldbuf.Length); |
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217 | // SZ_INCR is always 6 or more, so it is enough to hold all the |
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218 | // new bits plus the ones to come after |
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219 | } |
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220 | // Now write the bits |
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221 | if (n >= avbits) |
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222 | { |
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223 | // Complete the current byte |
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224 | n -= avbits; |
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225 | buf[curbyte] |= (byte) (bits >> n); |
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226 | if (buf[curbyte] != (byte) SupportClass.Identity(0xFF)) |
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227 | { |
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228 | // We don't need bit stuffing |
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229 | avbits = 8; |
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230 | } |
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231 | else |
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232 | { |
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233 | // We need to stuff a bit (next MSBit is 0) |
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234 | avbits = 7; |
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235 | } |
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236 | curbyte++; |
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237 | // Write whole bytes |
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238 | while (n >= avbits) |
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239 | { |
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240 | n -= avbits; |
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241 | // CONVERSION PROBLEM? |
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242 | buf[curbyte] |= (byte)((bits >> n) & (~ (1 << avbits))); |
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243 | if (buf[curbyte] != (byte) SupportClass.Identity(0xFF)) |
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244 | { |
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245 | // We don't need bit |
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246 | // stuffing |
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247 | avbits = 8; |
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248 | } |
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249 | else |
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250 | { |
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251 | // We need to stuff a bit (next MSBit is 0) |
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252 | avbits = 7; |
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253 | } |
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254 | curbyte++; |
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255 | } |
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256 | } |
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257 | // Finish last byte (we know that now n < avbits) |
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258 | if (n > 0) |
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259 | { |
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260 | avbits -= n; |
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261 | buf[curbyte] |= (byte) ((bits & ((1 << n) - 1)) << avbits); |
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262 | } |
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263 | if (avbits == 0) |
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264 | { |
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265 | // Last byte is full |
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266 | if (buf[curbyte] != (byte) SupportClass.Identity(0xFF)) |
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267 | { |
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268 | // We don't need bit stuffing |
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269 | avbits = 8; |
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270 | } |
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271 | else |
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272 | { |
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273 | // We need to stuff a bit (next MSBit is 0) |
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274 | avbits = 7; |
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275 | } |
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276 | curbyte++; // We already ensured that we have enough place |
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277 | } |
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278 | } |
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279 | |||
280 | /// <summary> Returns the byte buffer data in a new array. This is a copy of the |
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281 | /// internal byte buffer. If 'data' is non-null it is used to return the |
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282 | /// data. This array should be large enough to contain all the data, |
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283 | /// otherwise a IndexOutOfBoundsException is thrown by the Java system. The |
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284 | /// number of elements returned is what 'getLength()' returns. |
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285 | /// |
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286 | /// </summary> |
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287 | /// <param name="data">If non-null this array is used to return the data, which |
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288 | /// mus be large enough. Otherwise a new one is created and returned. |
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289 | /// |
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290 | /// </param> |
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291 | /// <returns> The byte buffer data. |
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292 | /// |
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293 | /// </returns> |
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294 | public virtual byte[] toByteArray(byte[] data) |
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295 | { |
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296 | if (data == null) |
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297 | { |
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298 | data = new byte[(avbits == 8)?curbyte:curbyte + 1]; |
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299 | } |
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300 | Array.Copy(buf, 0, data, 0, (avbits == 8)?curbyte:curbyte + 1); |
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301 | return data; |
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302 | } |
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303 | |||
304 | /// <summary> Prints information about this object for debugging purposes |
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305 | /// |
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306 | /// </summary> |
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307 | /// <returns> Information about the object. |
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308 | /// |
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309 | /// </returns> |
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310 | public override System.String ToString() |
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311 | { |
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312 | return "bits written = " + (curbyte * 8 + (8 - avbits)) + ", curbyte = " + curbyte + ", avbits = " + avbits; |
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313 | } |
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314 | } |
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315 | } |