/*
 * fileseek3.c - ftell(), fread(), fseek()
 */
#include <stdio.h>
#include <stdlib.h>

int main(void)
{
  FILE * fp;
  int count;
  float num;
  long position;

  if( (fp=fopen("numbers", "r+b")) == NULL )
  {
    printf("fileseek1 cant open file numbers\n");
    exit(1);
  }
  
  printf("This program moves the pointer\n");
  printf("and reads the number at each location.\n\n");

  position=ftell(fp); // takes file pointer, returns number of bites
                      // address is the postiion in the file
  
  printf("After opening, position is: %d bytes", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);

  fseek(fp, 0, 1); // move pointer address 0 bites from its current location.
  position=ftell(fp);
  printf("After fseek(0,1), position is: %d bytes", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);

  fseek(fp, 0, 1);
  position=ftell(fp);
  printf("After fseek(0,1), position is: %d bytes", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);

  fseek(fp, 0, 1);
  position=ftell(fp);
  printf("After fseek(0,1), position is: %d bytes", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);
  
  // seekfile2.c Addition: 
  fseek(fp, 0,0);
  position=ftell(fp);
  printf("After fseek(0,0), position is: %d bytes", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);

  fseek(fp, 0,0);
  position=ftell(fp);
  printf("After fseek(0,0), position is: %d bytes", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);

  fseek(fp, sizeof(float), 0);
  position=ftell(fp);
  printf("After fseek(sizeof(float),0), position is: %d bytes", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);

  fseek(fp, 2*sizeof(float),0);
  position=ftell(fp);
  printf("After fseek(2*sizeof(float),1), position is: %d bytes", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);

  fseek(fp, sizeof(float),0);
  position=ftell(fp);
  printf("After fseek(sizeof(float),0), position is: %d bytes", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);

  // seekfile3.c Addition: Address memory reletive to position
  fseek(fp, sizeof(float),1);
  position=ftell(fp);
  printf("After fseek(sizeof(float),1), position is: %d bytes", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);

  fseek(fp, 2*sizeof(float),1);
  position=ftell(fp);
  printf("After fseek(2*sizeof(float),1), position is: %d bytes", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);

  fseek(fp, -2*sizeof(float),1);
  position=ftell(fp);
  printf("After fseek(-2*sizeof(float),1), position is: %d bytes", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);

  fseek(fp, -2*sizeof(float),1);
  position=ftell(fp);
  printf("After fseek(-2*sizeof(float),1), position is: %d bytes", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);

  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);
 
  // seekfile4.c Addition: Moving pointer toward the beginning
  fseek(fp, -sizeof(float), 2);
  position=ftell(fp);
  printf("After fseek(-sizeof(float), 2) position is: %d bytes. ", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);

  fseek(fp, -2*sizeof(float), 1);
  position=ftell(fp);
  printf("After fseek(-2*sizeof(float), 1) position is: %d bytes. ", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);
  
  fseek(fp, -2*sizeof(float), 1);
  position=ftell(fp);
  printf("After fseek(-2*sizeof(float), 1) position is: %d bytes. ", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);

  fseek(fp, -2*sizeof(float), 1);
  position=ftell(fp);
  printf("After fseek(-2*sizeof(float), 1) position is: %d bytes. ", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);
    
  fseek(fp, -sizeof(float), 1);
  position=ftell(fp);
  printf("After fseek(-sizeof(float), 2) position is: %d bytes. ", position);
  fread(&num, sizeof(float), 1, fp);
  printf("Value: %f\n\n", num);


  fclose(fp);

  return 0;
}