Help with runlength coding

[edesign]

#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <assert.h>

#define         INPUTFILENAME           "input.rle"
#define         OUTPUTFILENAME          "output.rle"
#define         TEMPFILENAME            "rle.tmp"

FILE    *f;
long     fsize;

/////////////////////////////////
//  Return file size in bytes  //
/////////////////////////////////
long filesize(FILE *f)
{
  long pos, fsize;

  pos = ftell(f);
  fseek(f, 0L, SEEK_END);
  fsize = ftell(f);
  fseek(f, pos, SEEK_SET);

  return fsize;
}

/////////////////////////////////////////////////////////
//  Read input file to memory to speed up compression  //
/////////////////////////////////////////////////////////
char *rle_readinputstream(char *inputstream)
{
  char *stream;

  f = fopen(inputstream,"r+b");
  assert(f != NULL);
  fsize = filesize(f);

  stream = (char *)calloc(fsize, sizeof(char));
  assert(stream != NULL);

  fread(stream, fsize, 1, f);
  fclose(f);

  return stream;
}

///////////////////////////////////////////////////////
//  Encode input stream and write it to output file  //
///////////////////////////////////////////////////////
void rle_encode(char *stream)
{
  int   k;
  char  byte, freq;

  f = fopen(TEMPFILENAME,"w+b");
  assert(f != NULL);

  k = 0;
  while (k < fsize) {
    byte = stream[k];
    freq = 0;

    while (stream[k++] == byte && freq < 63) freq++;
    --k;

    if (freq == 1 && byte < 0xC0)
      fwrite(&byte, sizeof(byte), 1, f);
    else {
      freq |= 0xC0;
      fwrite(&freq, sizeof(char), 1, f);
      fwrite(&byte, sizeof(char), 1, f);
    }

  }

  fclose(f);

}


///////////////////////////////////////////////////////
//  Decode input stream and write it to output file  //
///////////////////////////////////////////////////////
void rle_decode(char *stream)
{
  int   k, l;
  char  byte, freq;

  f = fopen(OUTPUTFILENAME,"w+b");
  assert(f != NULL);

  k = 0;
  while (k < fsize) {

    byte = stream[k++];

    if ((byte & 0xC0) == 0xC0) {
      freq = byte & 0x3F;
      byte = stream[k++];
    }
    else freq = 1;

    for (l = 0; l < freq; l++)
      fwrite(&byte, sizeof(byte), 1, f);


  }

  fclose(f);
}

////////////////////
//  Main program  //
////////////////////
void main()
{
  char *stream;

  printf("RLE compression\n");
  printf("Copyright (c) 1997 by Matjaz Trtnik\n");

  stream = rle_readinputstream(INPUTFILENAME);
  rle_encode(stream);

  stream = rle_readinputstream(TEMPFILENAME);
  rle_decode(stream);
}

This code does runlength coding ...but as it uses 2 MSB's as indicator of counter it can only code .txt files...what should i do if Iwant to do it for any other type of data as well.


Thanks,
Edesign

[edesign]

I thought of it and now I have decided to to make a buffer having information that this particular byte is count and rest is value..and mention this at the end of the file...for that I have modified the encode function as follows..writing all the data & then info...

void rle_encode(char *stream)
{
  long int k;
  int *p;
  int j,cntf,i;
  char  byte, freq;

  f = fopen(TEMPFILENAME,"wb");
  assert(f != NULL);

  k = 0;
  i = 0;
  while (k < fsize) {
    byte = stream[k];
    freq = 0;
	j=k;

	while (stream[k++] == byte && freq < 255) {
		freq++;
	}
    --k;
	if(freq>0)
	{
		p[cntf]=j;
		cntf++;
		fwrite(&freq, sizeof(char), 1, f);
		fwrite(&byte, sizeof(char), 1, f);
	}
	else 
	{
      fwrite(&byte, sizeof(byte), 1, f);
    }

  }
  for(int h=0;h<cntf;h++)
	  fwrite(p[h],sizeof(p[h]),1,f);
  fwrite(&cntf,sizeof(cntf),1,f);

  fclose(f);
}

This is how I modified it for my purpose, p has to hold value of byte number which holds count & not data..but I don't know how I can do that...[because..int *p can't be used as I used it..but I don't know how I can accomplish this..]

at last I have mentioned total no of bytes which holds info about byte numbers..so decoder can identify them