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Posted By

Zydeco on 10/11/09


Tagged

length run RLE runlength run-length


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RLE Encoding and decoding

 / Published in: C
 

URL: http://en.wikipedia.org/wiki/Run-length_encoding

Encode and decode RLE from files

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  1. int rle_encode_file (FILE * in, FILE * out)
  2. {
  3.     int block_len, block_char, c;
  4.     block_len = 0;
  5.     block_char = -1;
  6.  
  7.     for(;;)
  8.     {
  9.         c = getc(in);
  10.         if (c == EOF) break;
  11.  
  12.         if (c == block_char && block_len < 255)
  13.         {
  14.             /* same block */
  15.             block_len++;
  16.         }
  17.         else
  18.         {
  19.             if (block_len)
  20.             {   /* write block */
  21.                 putc(block_len, out);
  22.                 putc(block_char, out);
  23.             }
  24.             /* start new block */
  25.             block_len = 1;
  26.             block_char = c;
  27.         }
  28.     }
  29.  
  30.     if (block_len)
  31.     {
  32.         /* last block */
  33.         putc(block_len, out);
  34.         putc(block_char, out);
  35.     }
  36.     return 1;
  37. }
  38.  
  39. int rle_decode_file (FILE * in, FILE * out)
  40. {
  41.     int i, len, c;
  42.  
  43.     for(;;)
  44.     {
  45.         len = getc(in); /* block length */
  46.         c = getc(in); /* character */
  47.  
  48.         /* checking */
  49.         if (len == EOF) return 1; /* end of file */
  50.         if (c == EOF) return 0; /* bad format */
  51.  
  52.         /* output */
  53.         for(i = 0; i < len; i++) putc(c, out);
  54.     }
  55. }

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