mcs/class/I18N/CJK/CodeTable.cs

   1 /*
   2  * CodeTable.cs - Implementation of the "System.Text.CodeTable" class.
   3  *
   4  * Copyright (c) 2002  Southern Storm Software, Pty Ltd
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining
   7  * a copy of this software and associated documentation files (the "Software"),
   8  * to deal in the Software without restriction, including without limitation
   9  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  10  * and/or sell copies of the Software, and to permit persons to whom the
  11  * Software is furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included
  14  * in all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  17  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  20  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  21  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  22  * OTHER DEALINGS IN THE SOFTWARE.
  23  */
  24
  25 namespace I18N.CJK
  26 {
  27
  28 using System;
  29 using System.IO;
  30 using System.Reflection;
  31 using System.Runtime.CompilerServices;
  32 using I18N.Common;
  33
  34 // This class assists encoding classes for the large CJK character
  35 // sets by providing pointer access to table data in the resource
  36 // section of the current assembly.
  37 //
  38 // Code tables are named by their resource (e.g. "jis.table") and
  39 // contain one or more sections.  Each section has an 8-byte header,
  40 // consisting of a 32-bit section number and a 32-bit section length.
  41 // The alignment of the data in the table is not guaranteed.
  42
  43 internal unsafe sealed class CodeTable : IDisposable
  44 {
  45         // Internal state.
  46         private Stream stream;
  47
  48         // Load a code table from the resource section of this assembly.
  49         public CodeTable(String name)
  50                         {
  51                                 stream = (Assembly.GetExecutingAssembly()
  52                                                          .GetManifestResourceStream(name));
  53                                 if(stream == null)
  54                                 {
  55                                         throw new NotSupportedException
  56                                                 (String.Format
  57                                                         (Strings.GetString("NotSupp_MissingCodeTable"),
  58                                                          name));
  59                                 }
  60                         }
  61
  62         // Implement the IDisposable interface.
  63         public void Dispose()
  64                         {
  65                                 if(stream != null)
  66                                 {
  67                                         stream.Close();
  68                                         stream = null;
  69                                 }
  70                         }
  71
  72         // Get the starting address for a particular section within
  73         // the code table.  This address is guaranteed to persist
  74         // after "Dispose" is called.
  75 #if __PNET__
  76         public byte *GetSection(int num)
  77 #else
  78         public byte[] GetSection(int num)
  79 #endif
  80                         {
  81                                 // If the table has been disposed, then bail out.
  82                                 if(stream == null)
  83                                 {
  84                                         return null;
  85                                 }
  86
  87                                 // Scan through the stream looking for the section.
  88                                 long posn = 0;
  89                                 long length = stream.Length;
  90                                 byte[] header = new byte [8];
  91                                 int sectNum, sectLen;
  92                                 while((posn + 8) <= length)
  93                                 {
  94                                         // Read the next header block.
  95                                         stream.Position = posn;
  96                                         if(stream.Read(header, 0, 8) != 8)
  97                                         {
  98                                                 break;
  99                                         }
 100
 101                                         // Decode the fields in the header block.
 102                                         sectNum = ((int)(header[0])) |
 103                                                           (((int)(header[1])) << 8) |
 104                                                           (((int)(header[2])) << 16) |
 105                                                           (((int)(header[3])) << 24);
 106                                         sectLen = ((int)(header[4])) |
 107                                                           (((int)(header[5])) << 8) |
 108                                                           (((int)(header[6])) << 16) |
 109                                                           (((int)(header[7])) << 24);
 110
 111                                         // Is this the section we are looking for?
 112                                         if(sectNum == num)
 113                                         {
 114 #if __PNET__
 115                                                 return GetAddress(stream, posn + 8);
 116 #else
 117                                                 byte[] buf = new byte [sectLen];
 118                                                 if(stream.Read(buf, 0, sectLen) != sectLen)
 119                                                 {
 120                                                         break;
 121                                                 }
 122                                                 return buf;
 123 #endif
 124                                         }
 125
 126                                         // Advance to the next section.
 127                                         posn += 8 + sectLen;
 128                                 }
 129
 130                                 // We were unable to find the requested section.
 131                                 return null;
 132                         }
 133
 134 #if __PNET__
 135         // Back door access into the engine to get the address of
 136         // an offset within a manifest resource stream.
 137         [MethodImpl(MethodImplOptions.InternalCall)]
 138         extern private static byte *GetAddress(Stream stream, long position);
 139 #endif
 140
 141 }; // class CodeTable
 142
 143 }; // namespace I18N.CJK