A small C program to compute Lempel-Ziv complexity of a string

lzcomplexity.c

/* lzcomplexity.c --- 
 * Author: Subhasis Ray
 * Created: Thu Sep 13 11:54:21 2018 (-0400)
 * Last-Updated: Thu Sep 13 14:01:18 2018 (-0400)
 *           By: Subhasis Ray
 * Version: $Id$
/* This implements the algorithm described by Casper and Schu"ster, 1987, Physical Review A:
   "Easily calculable measure for the complexity of spatiotemporal patterns". */
/* Code: */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int lzcomplexity(char *ss){
  int ii = 0, kk = 1, el = 1, kmax = 1, cc = 1, nn;
  nn = strlen(ss);
  while (1){
    if (ss[ii + kk - 1] == ss[el + kk - 1]){
      kk++;
      if ((el + kk) > nn){
        ++cc;
        break;
      }
    } else {
      if ( kk > kmax ){
        kmax = kk;
      }
      ++ii;
      if (ii == el){
        ++cc;
        el += kmax;
        if ((el + 1) > nn){
          break;
        }
        ii = 0;
        kk = 1;
        kmax = 1;
      } else {
        kk = 1;
      }
    }
  }
  return cc;
}


int test(){
  char data[256] = "1001111011000010\0";
  printf("lzc=%d\n", lzcomplexity(data));
  return 0;
}

int main(int argc, char **argv){
  FILE * input;
  char * buffer;
  int size;
  int length;
  if (argc < 2){
    printf("Require an input file. Usage %s filename\n", argv[0]);
    return -1;
  } 
  input = fopen(argv[1], "rb");
  fseek(input, 0L, SEEK_END);
  size = ftell(input);
  printf("File size: %d\n", size);
  fclose(input);
  input = fopen(argv[1], "r");
  buffer = (char*) calloc(size+1, sizeof(char));
  fgets(buffer, size, input);  
  fclose(input);
  printf("Read %s\n", buffer);  
  length = strlen(buffer);
  printf("Length of string including terminal new line: %d\n", length);
  if (buffer[length - 1] == '\n'){
    buffer[length - 1] = '\0';
    length--;
  }
  printf("Length of string without terminal new line: %d\n", length);
  printf("Lempel-Ziv complexity of this string of length %d is %d\n", length, lzcomplexity(buffer));    
    return 0;
}
            
        


/* lzcomplexity.c ends here */