mcs/class/System.Web/System.Web.Mail/ToUUEncodingTransform.cs

   1 //
   2 // System.Web.Mail.ToUUEncodingTransform.cs
   3 //
   4 // Author(s):
   5 //   Per Arneng <pt99par@student.bth.se>
   6 //
   7 //
   8 using System;
   9 using System.Security.Cryptography;
  10
  11 namespace System.Web.Mail {
  12
  13     // This class transforms blocks of plaintext to UU encoding
  14     internal class ToUUEncodingTransform : ICryptoTransform {
  15
  16         public int InputBlockSize { get { return 45; } }
  17         public int OutputBlockSize { get { return 61; } }
  18
  19         public bool CanTransformMultipleBlocks { get { return true; } }
  20         public bool CanReuseTransform { get { return true; } }
  21
  22         // transforms a block of bytes to UU encoding
  23         public int TransformBlock( byte[] inputBuffer,
  24                                    int inputOffset,
  25                                    int inputCount,
  26                                    byte[] outputBuffer,
  27                                    int outputOffset
  28                                    ) {
  29
  30             // write the line length length+0x20
  31             outputBuffer[ 0 ] = (byte)'M';
  32
  33             // transform the block 3bytes at a time
  34             for( int i=0;i<15;i++ ) {
  35
  36                 TransformTriplet( inputBuffer , inputOffset + i * 3 , 3,
  37                                   outputBuffer , outputOffset + i * 4 + 1);
  38
  39             }
  40
  41
  42             return OutputBlockSize;
  43         }
  44
  45         // make a final uu transformations
  46         public byte[] TransformFinalBlock(byte[] inputBuffer,
  47                                           int inputOffset,
  48                                           int inputCount
  49                                           ) {
  50
  51             // calculate how many 4-byte blocks there are
  52             int tripletBlocks = inputCount / 3 + 1;
  53
  54             // create a new buffer and copy the input data into that
  55             byte[] buffer = new byte[ tripletBlocks * 3 ];
  56             Buffer.BlockCopy( inputBuffer,inputOffset, buffer,0,inputCount);
  57
  58             // create the outpur buffer and set the first byte
  59             // to the length+0x20
  60             byte[] outputBuffer = new byte[ tripletBlocks * 4 + 1 ];
  61             outputBuffer[ 0 ] = (byte)(inputCount+0x20);
  62
  63             // transform the block 3bytes at a time
  64             for( int i =0 ; i < tripletBlocks ; i++ ) {
  65                 TransformTriplet( inputBuffer , inputOffset + i * 3 , 3,
  66                                   outputBuffer , i * 4 + 1);
  67             }
  68
  69
  70
  71             return outputBuffer;
  72
  73         }
  74
  75         // transforms a 3byte buffer to a 4byte uuencoded buffer
  76         protected int TransformTriplet( byte[] inputBuffer,
  77                                         int inputOffset,
  78                                         int inputCount,
  79                                         byte[] outputBuffer,
  80                                         int outputOffset
  81                                         ) {
  82
  83             byte a = inputBuffer[ inputOffset + 0 ];
  84             byte b = inputBuffer[ inputOffset + 1 ];
  85             byte c = inputBuffer[ inputOffset + 2 ];
  86
  87             outputBuffer[ outputOffset + 0 ] =
  88                 (byte)(0x20 + (( a >> 2                    ) & 0x3F));
  89
  90             outputBuffer[ outputOffset + 1 ] =
  91                 (byte)(0x20 + (((a << 4) | ((b >> 4) & 0xF)) & 0x3F));
  92
  93             outputBuffer[ outputOffset + 2 ] =
  94                 (byte)(0x20 + (((b << 2) | ((c >> 6) & 0x3)) & 0x3F));
  95
  96             outputBuffer[ outputOffset + 3 ] =
  97                 (byte)(0x20 + (( c                         ) & 0x3F));
  98
  99             // tanslate all 0x20 to 0x60 according to specs
 100             for( int i = 0; i < 4; i++ ) {
 101                 if( outputBuffer[ outputOffset + i ] == 0x20 ) {
 102                     outputBuffer[ outputOffset + i ] = 0x60;
 103                 }
 104             }
 105
 106             return 4;
 107         }
 108
 109         public void Dispose() {}
 110     }
 111
 112 }