/* encode.c - Don Yang (uguu.org)

   Encode text to variable length data.  Assume each line starts with
   at least one space.

   11/28/01
                                                                           */
/*@ -shiftsigned -type @*/

#include<stdio.h>

#define BITS_PER_GROUP  2
#define BASE64_OFFSET   '0'


static void FlushCode(int byte, FILE *outfile);
static void WriteCode(int code, int *byte, int *bit, int *size, FILE *outfile);

/******************************************************************** main */
int main(int argc, char **argv)
{
   FILE *infile, *outfile;
   int i, c, len, bit, byte, size;

   infile = stdin;
   outfile = stdout;
   if( argc > 1 )
   {
      if( (infile = fopen(argv[1], "rb")) == NULL )
         return printf("Can not open %s\n", argv[1]);
      if( argc > 2 )
      {
         if( (outfile = fopen(argv[2], "wt+")) == NULL )
         {
            (void)fclose(infile);
            return printf("Can not create %s\n", argv[2]);
         }
      }
   }


   c = EOF;
   len = bit = byte = size = 0;
   (void)fputc('\"', outfile);
   do
   {
      i = fgetc(infile);
      if( i != c )
      {
         if( i == '\n' )
         {
            if( len > 0 && c != EOF )
               WriteCode(len, &byte, &bit, &size, outfile);
            WriteCode(0, &byte, &bit, &size, outfile);
            c = EOF;
            len = 0;
         }
         else
         {
            if( len > 0 && c != EOF )
               WriteCode(len, &byte, &bit, &size, outfile);
            c = i;
            len = 1;
         }
      }
      else
      {
         len++;
      }
   } while( i != EOF );

   if( bit > 0 )
      FlushCode(byte, outfile);
   fprintf(outfile, "\"\n/* %d bits */\n", size);


   (void)fclose(infile);
   (void)fclose(outfile);
   return 0;

} /* main() */

/*************************************************************** FlushCode */
static void FlushCode(int byte, FILE *outfile)
{
   if( (byte += BASE64_OFFSET) == '\\' )
      (void)fputc('\\', outfile);
   (void)fputc(byte, outfile);

} /* FlushCode() */

/*************************************************************** WriteCode */
static void WriteCode(int code, int *byte, int *bit, int *size, FILE *outfile)
{
   int i;

   do
   {
      for(i = 0; i < BITS_PER_GROUP; i++)
      {
         *byte |= ((code & (1 << i)) == 0 ? 0 : 1) << (*bit)++;
         if( *bit > 5 )
         {
            FlushCode(*byte, outfile);
            *bit = *byte = 0;
         }
      }
      *byte |= (code >= (1 << BITS_PER_GROUP) ? 1 : 0) << (*bit)++;
      if( *bit > 5 )
      {
         FlushCode(*byte, outfile);
         *bit = *byte = 0;
      }
      code >>= BITS_PER_GROUP;
      *size += BITS_PER_GROUP + 1;
   } while( code > 0 );

} /* WriteCode() */