mdw@git.distorted.org.uk Git - qmail/blob - alloc.c

   1 #include "alloc.h"
   2 #include "error.h"
   3 extern char *malloc();
   4 extern void free();
   5
   6 #define ALIGNMENT 16 /* XXX: assuming that this alignment is enough */
   7 #define SPACE 4096 /* must be multiple of ALIGNMENT */
   8
   9 typedef union { char irrelevant[ALIGNMENT]; double d; } aligned;
  10 static aligned realspace[SPACE / ALIGNMENT];
  11 #define space ((char *) realspace)
  12 static unsigned int avail = SPACE; /* multiple of ALIGNMENT; 0<=avail<=SPACE */
  13
  14 /*@null@*//*@out@*/char *alloc(n)
  15 unsigned int n;
  16 {
  17   char *x;
  18   n = ALIGNMENT + n - (n & (ALIGNMENT - 1)); /* XXX: could overflow */
  19   if (n <= avail) { avail -= n; return space + avail; }
  20   x = malloc(n);
  21   if (!x) errno = error_nomem;
  22   return x;
  23 }
  24
  25 void alloc_free(x)
  26 char *x;
  27 {
  28   if (x >= space)
  29     if (x < space + SPACE)
  30       return; /* XXX: assuming that pointers are flat */
  31   free(x);
  32 }