lineholder.c

String Pointers to explore how the pointer work

/* lineholder.c
- Bob Wilson  */

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

#include "lineholder.h"

void *malloc(int);
void free(void*);

static char *lines[MAXLINE];
static int first, last, end, wrapped;

void init_lineholder(int nlines)
{
        if (nlines > MAXLINE)
                nlines = MAXLINE;

	first = last = 0;
	end = nlines-1;
	wrapped = 0;
}

void insert_line(char *line)
{
	if (lines[last] != NULL)
		free((void *) lines[last]);
	if ((lines[last] =  (char * ) malloc(strlen(line) + 1)) != NULL)
	   strcpy(lines[last], line);

        last++;  
        if (last > end) {
                last = 0;   
                wrapped = 1;
        }

	if (wrapped)
		first = (++first > end)? 0 : first;
}

void print_lines(void)
{
        int i;
        for (i = 0; i <= end; i++) {
                if (lines[first] != NULL) {
                        printf("%s", lines[first]);
                        free ((void *) lines[first]);
                        lines[first] = NULL;
                }
                first = (++first > end)? 0 : first;
        }
}