/*
    MALLOC DEMO #3 Illustrates:
	declaring an automatic array of pointers
	use of malloc on that array
	use of free on that array
	passing pointers into functions
*/

#include <stdlib.h>  /* string libraries etc */
#include <stdio.h>   /* input output */
#include <string.h>

#define MAX_WORDS 10
#define MAX_WORD_LENGTH 30

void loadArray(char *arr[], char *infileName, int *count);
void printArray(char *arr[], int count);
void freeArray(char *word[], int count);


int main(int argc, char *argv[])
{
    char *wordArray[MAX_WORDS];  /* a.k.a array of Strings */
    int wordCount = 0;

    if (argc < 2)
    {
	printf("Must enter a text input filename on cmd line.\n");
	exit(EXIT_FAILURE);
    }
    
    loadArray(wordArray, argv[1], &wordCount);  /* pass only the array's name: it's already allocated */
    printf("Printing wordArray:\n\n");
    printArray(wordArray, wordCount);  /* again - need only pass array's name */
    freeArray(wordArray, wordCount);  /* same here */

    return 0;
}

/* ------------------------------------------------------------------------
   Takes 3 args: the name of an array of pointers a file name to read from
   and pointer to counter of words read in. Mallocs  each pointer in the and
   copies a string into it.
*/
void loadArray(char *arr[], char *infileName, int *wordCount)
{
    char buffer[MAX_WORD_LENGTH];  /* MAX_WORD_LENGYH - 1 chars plus a null terminator */
    FILE *infile;

    infile = fopen(infileName, "r");
    if (!infile)
    {
	printf("Can't open %s for input.\n", infileName);
	exit(EXIT_FAILURE);
    }

    *wordCount = 0;
    /* DANGER: fscanf of string vulnerable to overflow */
    while ((*wordCount < MAX_WORDS) && fscanf(infile, "%s", buffer) == 1)
    {
	arr[*wordCount] =  malloc((strlen(buffer)+1) * sizeof(char));
	if (arr[*wordCount] == NULL)  /* ALWAYS CHECK FOR NULL AFTER malloc */
	{
	    printf("malloc failed: Exiting Program!\n\n");
	    exit(EXIT_FAILURE);
	}
	strcpy(arr[*wordCount], buffer);
	++(*wordCount);
    }
    fclose(infile);
}

/* Takes 2 args: the name of an array of pointers, and a count of how many 
   pointers have been malloc'd. Prints each string.
*/
void printArray(char *arr[], int wordCount)
{
    int i;
    for(i = 0; i < wordCount; ++i)
	printf("wordArray[%d]: %s\n", i, arr[i]);
}


/* Takes 2 arg: the name of an array of pointers and a count of how many have
   been malloc'd. Visits each pointer in the array and frees the memory
   allocated to it. 
*/
void freeArray(char *arr[], int wordCount)
{
    int i;
    for(i = 0; i < wordCount; ++i)
	free(arr[i]);
}