/*

 File: memory.c

 Description: Uses malloc to dynamically create an array of n ints. The
 user enters n. The program allocates the memory, fills it with random integers
 scaled between 18 and -9, displays the array and frees the memory. It does
 this forever

 Input: User enters size of the array.

 Output: Displays the contents of the full array and sums up all the elements.

 This problem is adapted from A Book on C (Kelly, Pohl) pg. 261.

*/

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#include<string.h>

// local header file for memory with various useful macros. 
// We use MALLOC_CHECK(), BZERO(), MY_ASSERT(), LOG() 

#include "header.h"

// prototypes

void initArray(int *, int );
int  sumArray(int *, int );
void displayArray(int *, int );

int main (void) {

  int *ip, n;

  srand(time(NULL));

  printf("\n%s\n", 
	 "This program does the following repeatedly:\n"
	 "\n"
	 "     1) Create space for an array of size n\n"
	 "     2) Fill the array with randomly distributed digits\n"
	 "     3) Prints the array and the sum of its elements\n"
	 "     4) Frees the allocated memory\n");

  for ( ; ; ) { // do forever

    printf("Input the size of array you want created. n: ");
    if (scanf("%d", &n) !=1 || n < 1) {
      LOG("Usage: n has to be > 0\n\n");
      continue;  // try again
    }

    // User enters size of array. We dynamically allocate memory using the 
    // MALLOC_CHECK and display the array. Note, that malloc() allocate 
    // unused space for an object whose size in bytes is specified by n
    // and whose value is unspecified. Because of that it is a good idea 
    //to zeroise the returned memory.

    putchar('\n');

    // allocate memory - n bytes; that is n*sizeof(int) bytes
   
    ip = malloc(n*sizeof(int));
    MALLOC_CHECK(ip);

    // display malloc'd array, recall memory not specified could be any value

    displayArray(ip, n);  

    // display BZERO'd array

    BZERO(ip, n*sizeof(int));
    displayArray(ip, n);  

    // display initialed array and sum

    initArray(ip, n);
    displayArray(ip, n);  
    printf("Sum = %d\n\n", sumArray(ip, n));

    // don't forget to free the memory or we will have memory leaks

    free(ip);

  }
  printf("\nLater!\n\n");
  return 0;
}

void initArray(int *a, int n) {

  int i;

  for (i = 0; i < n; i++)
    a[i] = rand()%19 - 9; // scales between 18 and - 9
  
}


int sumArray(int *a, int n) {

  int i, sum =0;
  
  for (i = 0; i < n; i++)
    sum += a[i];  
  
  return(sum);

}

void displayArray(int *a, int n) {

  int i;

  printf("a = [");
  
  for (i = 0; i < n; i++)
    printf("%d%s", a[i], ((i < n - 1) ? ", " : "]\n"));

}