alloc

5.4 alloc

#define ALLOCSIZE 10000 /* size of available space */

static char allocbuf[ALLOCSIZE];
static char *allocp = allocbuf;

char *alloc(int n)      /* return pointer to n characters */
{
        if(allocbuf + ALLOCSIZE - allocp >= n){
                allocp += n;
                return allocp - n;
        } else          /* not enough room */
                return 0;
}

void afree(char *p)     /* free storage pointed to by p */
{
        if(allocp >= allocbuf && allocp < allocbuf + ALLOCSIZE)
                allocp = p;
}

#include <stdio.h>

int main()
{
        char *p;
        p = alloc(10);
        p[0] = 'u';
        p[1] = '\0';
        printf("%s, %p\n", p, p);
        afree(p);
        printf("%s, %p\n", p, p);
        return 0;
}