windows-server-2003/shell/shdocvw/mime64.txt

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README.1ST:


                   MIME64 Encoder/Decoder

WHAT MIME64 IS:  MIME64 is an encoding described in RFC1341 as MIME base64.
Its purpose is to encode binary files into ASCII so that they may be passed
through e-mail gates.  In this regard, MIME64 is similar to UUENCODE.
Although most binaries these days are transmitted using UUENCODE, I
have seen a few using MIME64, and I have had requests from friends that
I decode MIME64 files that have fallen into their hands.  As long as
some MIME64 continues to exist, a package such as this one is useful
to have.


WHAT THIS PACKAGE CONTAINS:  This package contains both executable
and ANSI-C source code for a MIME64 encoder/decoder (MIME.EXE and
MIME.C respecively).  It also contains this README file, and a MIME64
encoded file called MIME.64.  The latter will decode to MIME.ZIP if
you issue the DOS command line:

   MIME64 MIME.64 MIME.ZIP

If you unzip the zip file, you will get an essay by Mark Grand about
MIME.


HOW TO USE THIS PACKAGE:  To decode a MIME64 file you may type:

   MIME64 infile outfile

If you leave out the outfile specification, the output file will
overwrite the input file.

To encode a file into MIME64 format, type:

   MIME64 infile outfile -e

Again, if you leave off the outfile specification, the output will
overwrite the input.


STATUS OF THIS PACKAGE:  This package is freeware.  As author, I
claim no copyright.  If you change the source code and intend to
propogate that change to other users, please include a comment to
that effect at the top that states:  The date of the change, the
nature of the change, and who made the change.  As a courtesy, I also
ask that you retain the comment that acknowledges me as the original
author.


SEND QUESTIONS ABOUT THIS PACKAGE TO:  [email protected]

Karl Hahn

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MIME64.C:

/* mime64 */
/* MIME base64 encoder/decoder by Karl Hahn  [email protected]  3-Aug-94 */
#include <stdio.h>
#include <stdlib.h>

char alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
                  "0123456789+/";

void fputch( char blivit, FILE *f )
{
/*   if (blivit == '\n') fputc( '\r', f );*/
   fputc( blivit, f );
}

int classify_args( int narg,
                   char *rawargs[], char *fileargs[], char *optargs[] )
{
   int index, jndex, kndex;
   char *argptr;

   for ( index = 0, jndex = 0, kndex = 0; index < narg; index++ )
   {
      argptr = rawargs[index];
      if (*argptr == '-')
      {
         argptr++;
         optargs[kndex++] = argptr;
      }
      else
      {
         fileargs[jndex++] = argptr;
      }
   }

   return kndex;
}

int cvt_ascii( unsigned char alpha )
{
   if      ( (alpha >= 'A') && (alpha <= 'Z') ) return (int)(alpha - 'A');
   else if ( (alpha >= 'a') && (alpha <= 'z') )
        return 26 + (int)(alpha - 'a');
   else if ( (alpha >= '0') && (alpha <= '9' ) )
        return 52 + (int)(alpha - '0');
   else if ( alpha == '+' ) return 62;
   else if ( alpha == '/' ) return 63;
   else if ( alpha == '=' ) return -2;
   else                     return -1;
}

char *fileargs[64], *optargs[64];

struct STATE64 {
                  unsigned long int accum;
                  int               shift;
               };


int main( int nargs, char *cargs[] )
{
   int n_options, n_files, index, jndex, shift, save_shift;
   enum { ENCODE, DECODE } whattodo = DECODE;
   int help_flag = 0, replace_flag = 0, quit = 0;
   FILE *fin, *fout;
   unsigned char blivit;
   unsigned long accum, value;
   char buf[80];
   char *cptr, *altptr;
   int decode_state;

   n_options = classify_args( nargs, cargs, fileargs, optargs );

   n_files = nargs - n_options;

   if ( n_files < 2 ) help_flag = 1;

   for ( index = 0; index < n_options; index++ )
   {
      if ( ( optargs[index][0] == 'e' ) ||
           ( optargs[index][0] == 'E' ) ) whattodo = ENCODE;
      if ( optargs[index][0] == '?' ) help_flag = 1;
   }

   if ( help_flag )
   {
      printf( "mime64 infile [outfile] [-option] [-option] etc.\n\n"
              "convert between binary and MIME BASE64 format\n\n"
              "        -e       MIME base64 encode (default is decode)\n"
              "        -?       display help message\n\n"
              "if no outfile given, output file replaces infile\n" );
   }

   if ( n_files < 2 ) exit(0);

   if ( whattodo == DECODE )
   {
      fin = fopen( fileargs[1], "r" );
   }
   else
   {
      fin = fopen( fileargs[1], "rb" );
   }

   if ( fin == 0 )
   {
      printf( "%s file not found\n", fileargs[1] );
      exit(-1);
   }

   if ( n_files > 2 )
   {
      if ( whattodo == DECODE )
      {
         fout = fopen( fileargs[2], "wb" );
      }
      else
      {
         fout = fopen( fileargs[2], "w" );
      }

      if ( fout == 0 )
      {
         printf( "Couldn't open %s for output\n", fileargs[2] );
      }
   }
   else
   {
      if ( whattodo == DECODE )
      {
         fout = fopen( "$$$$$$$$.$$$", "wb" );
      }
      else
      {
         fout = fopen( "$$$$$$$$.$$$", "w" );
      }

      replace_flag = 1;
   }

   if ( whattodo == DECODE )
   {
      shift = 0;
      accum = 0;
      decode_state = 0;

      while ( ( !feof( fin ) ) && (quit == 0) )
      {
         fgets( buf, 80, fin );

         if ( decode_state == 0 )
         {
            for ( index = 0; 
                  (buf[index] != '\n') && (buf[index] != '\0') &&
                  (decode_state >= 0);
                  index++ )
            {
               if ( ( (buf[index] >= 'A') && (buf[index] <= 'Z') ) ||
                    ( (buf[index] >= 'a') && (buf[index] <= 'z') ) ||
                    ( (buf[index] >= '0') && (buf[index] <= '9') ) ||
                    (buf[index] == '+') ||
                    (buf[index] == '/') || 
                    (buf[index] == '=') )
               {
                  decode_state = 1;
               }
               else
               {
                  decode_state = -2;
               }
            }

            if ( decode_state <= 0 )
            {
               decode_state = 0;
               continue;
            }
         }

         if ( feof(fin) )
         {
            quit = 1;
         }

         if ( quit != 0 )
         {
            buf[0] = '\0';
         }

         for ( index = 0; (buf[index] != '\n') && (buf[index] != '\0'); index++)
         {
            value = cvt_ascii( buf[index] );

            if ( value < 64 )
            {
               accum <<= 6;
               shift += 6;
               accum |= value;
               if ( shift >= 8 )
               {
                  shift -= 8;
                  value = accum >> shift;
                  blivit = (unsigned char)value & 0xFFl;
                  fputc( blivit, fout );
               }
            }
            else
            {
               quit = 1;
               break;
            }
         }
      }
   }
   else
   {
      fprintf ( fout,
       "Content-Type: text/plain; charset=US-ASCII\n"
       "Content-transfer-encoding: base64\n\n" );

      shift = 0;
      accum = 0;
      index = 0;
      while ( ( !feof( fin ) ) || (shift != 0) )
      {
         if ( ( !feof( fin ) ) && ( quit == 0 ) )
         {
            blivit = fgetc( fin );

            if ( feof( fin ) )
            {
               quit = 1;
               save_shift = shift;
               blivit = 0;
            }
         }
         else
         {
            quit = 1;
            save_shift = shift;
            blivit = 0;
         }

         if ( (quit == 0) || (shift != 0) )
         {
            value = (unsigned long)blivit;
            accum <<= 8;
            shift += 8;
            accum |= value;
         } /* ENDIF */

         while ( shift >= 6 )
         {
            shift -= 6;
            value = (accum >> shift) & 0x3Fl;
            blivit = alphabet[value];

            buf[index++] = blivit;
            if ( index >= 60 )
            {
               buf[index] = '\0';
               fprintf( fout, "%s\n", buf );
               index = 0;
            }

            if ( quit != 0 )
            {
               shift = 0;
            }
         }
      }

      if      ( save_shift == 2 )
      {
         buf[index++] = '=';
         if ( index >= 60 )
         {
            buf[index] = '\0';
            fprintf( fout, "%s\n", buf );
            index = 0;
         }

         buf[index++] = '=';
         if ( index >= 60 )
         {
            buf[index] = '\0';
            fprintf( fout, "%s\n", buf );
            index = 0;
         }
      }
      else if ( save_shift == 4 )
      {
         buf[index++] = '=';
         if ( index >= 60 )
         {
            buf[index] = '\0';
            fprintf( fout, "%s\n", buf );
            index = 0;
         }
      }

      if ( index != 0 )
      {
         buf[index] = '\0';
         fprintf( fout, "%s\n", buf );
      }
   }

   fclose( fin );
   fclose( fout );

   if ( replace_flag )
   {
      if ( ( whattodo == DECODE ) && ( decode_state <= 0 ) )
      {
         remove( "$$$$$$$$.$$$" );
         printf( "No MIME base64 lines found in %s\n", fileargs[1] );
      }
      else
      {
         remove( fileargs[1] );
         rename( "$$$$$$$$.$$$", fileargs[1] );
      }
   }
   else
   {
      if ( ( whattodo == DECODE ) && ( decode_state <= 0 ) )
      {
         remove( fileargs[2] );
         printf( "No MIME base64 lines found in %s\n", fileargs[1] );
      }
   }
}

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