alloc.c

#include "alloc.h"
#include "error.h"
extern char *malloc();
extern void free();

#define ALIGNMENT 16 /* XXX: assuming that this alignment is enough */
#define SPACE 4096 /* must be multiple of ALIGNMENT */

typedef union { char irrelevant[ALIGNMENT]; double d; } aligned;
static aligned realspace[SPACE / ALIGNMENT];
#define space ((char *) realspace)
static unsigned int avail = SPACE; /* multiple of ALIGNMENT; 0<=avail<=SPACE */

char *alloc(n)
unsigned int n;
{
 char *x;

 n = ALIGNMENT + n - (n & (ALIGNMENT - 1)); /* XXX: could overflow */

 if (n <= avail) { avail -= n; return space + avail; }

 x = malloc(n);
 if (!x) errno = error_nomem;
 return x;
}

void alloc_free(x)
char *x;
{
 if (x >= space)
   if (x < space + SPACE)
     return; /* XXX: assuming that pointers are flat */
 free(x);
}