/* Primes finder (primes.c) by Cobi */

/*
 * We need this library (printf?).
 */
#include <stdio.h>

/*
 * We need this library for atoi().
 */
#include <stdlib.h>

int main (int argc, char **argv) { /* Our main program. */
	/* Make sure we have the correct arguments. */
	if (argc < 2) {
		/* We don't, complain. */
		fprintf (stderr,"This binary requires the ");
		fprintf (stderr,"stop value as an argument");
		fprintf (stderr,".\n");
		fprintf (stderr,"Example: %s [verbose] <stop>\n",argv[0]);
		return 1;
	}

	/* We initialize our outer loop variables. */
	unsigned long long bigcounter = 2;
	unsigned long long upperbound;

	/* Then we initialize our inner loop variables. */
	unsigned long long to = 0;
	unsigned long long counter = 0;
	unsigned long long halfto = 0;

	/* We initialize our verbose flag. */
	unsigned short verbose;

	/* We initialize our primes array. */
	unsigned long long *primes = (unsigned long long*)malloc(0);
	unsigned long long nprimes = 0;

	/*
	 * And then we initialize our variable to
	 * hold the status of the current check.
	 */
	unsigned short found = 0;

	/* Do we have 2 arguments? */
	if (argc == 3) {
		/*
		 * Yes, initialize our variables
		 * on the assumption that we have
		 * verbose as the first arguement.
		 */
		upperbound = atoi(argv[2]);
		if (strcmp(argv[1],"verbose") == 0) {
			verbose = 1;
		} else {
			verbose = 0;
		}
	} else if (argc == 2) {
		/*
		 * No, we have only 1 argument.
		 * The first arguement is the start
		 * and the second is the end.
		 */
		upperbound = atoi(argv[1]);
		verbose = 0;
	} else {
		/*
		 * We have more than 2 arguments,
		 * we don't know what to do with this.
		 */
		fprintf (stderr,"Uhh, we only need at most 2 arguments.\n");
		return 1;
	}

	/*
	 * We make a big loop through each integer
	 * between argv[1] and argv[2].
	 */
	while (bigcounter <= upperbound) {
		/* Reset any variables for the inner loop. */
		counter = 0;
		to = bigcounter;
		found = 0;
		

		/*
		 * We make an inner loop to loop through
		 * each integer element of the primes array
		 * between 0 and the number of array elements
		 * - 1 integer we are checking for primality.
		 */
		while (counter < nprimes) {
			/* Is verbose on? */
			if (verbose == 1) {
				/* Print verbose data to standard error output. */
				fprintf (stderr,"counter: %d bigcounter: %d upperbound: %d\n",counter,bigcounter,upperbound);
			}

			/*
			 * We check to see if the counter devides
			 * evenly into the integer we are checking
			 * for primality.
			 */
			if (to % primes[counter] == 0) {
				/* It is not prime, set found = 1 */
				found = 1;
				/* and set counter so the loop exits. */
				counter = to;
			}

			/* Increment the counter. */
			counter++;
		}

		/*
		 * Check to see if the loop exited normally
		 * as opposed to prematurely.
		 */
		if (found == 0) {
			/*
			 * If it exited normally, we found
			 * ourselves a prime!  Store it in 
			 * array, and print it out so the 
			 * owner can see.
			 */
			nprimes++;
			if( (primes = (unsigned long long*) realloc (primes, sizeof(unsigned long long) * nprimes)) == NULL) {
				fprintf (stderr,"Insufficient memory");
				return 1;
			}
			primes[nprimes - 1] = to;
			printf("%d\n",to);
		}

		/* Increment the counter. */
		if (bigcounter != 2) { bigcounter++; }
		bigcounter++;
	}

	/* Exit successfully. */
	return 0;
}