src/malloc/memalign.c

   1 #include <stdlib.h>
   2 #include <stdint.h>
   3 #include <errno.h>
   4 #include "libc.h"
   5
   6 void __internal_free(void *);
   7
   8 void *__memalign(size_t align, size_t len)
   9 {
  10         unsigned char *mem, *new, *end;
  11         size_t header, footer;
  12
  13         if ((align & -align) != align) {
  14                 errno = EINVAL;
  15                 return NULL;
  16         }
  17
  18         if (len > SIZE_MAX - align || free != __internal_free) {
  19                 errno = ENOMEM;
  20                 return NULL;
  21         }
  22
  23         if (align <= 4*sizeof(size_t)) {
  24                 if (!(mem = malloc(len)))
  25                         return NULL;
  26                 return mem;
  27         }
  28
  29         if (!(mem = malloc(len + align-1)))
  30                 return NULL;
  31
  32         new = (void *)((uintptr_t)mem + align-1 & -align);
  33         if (new == mem) return mem;
  34
  35         header = ((size_t *)mem)[-1];
  36
  37         if (!(header & 7)) {
  38                 ((size_t *)new)[-2] = ((size_t *)mem)[-2] + (new-mem);
  39                 ((size_t *)new)[-1] = ((size_t *)mem)[-1] - (new-mem);
  40                 return new;
  41         }
  42
  43         end = mem + (header & -8);
  44         footer = ((size_t *)end)[-2];
  45
  46         ((size_t *)mem)[-1] = header&7 | new-mem;
  47         ((size_t *)new)[-2] = footer&7 | new-mem;
  48         ((size_t *)new)[-1] = header&7 | end-new;
  49         ((size_t *)end)[-2] = footer&7 | end-new;
  50
  51         free(mem);
  52         return new;
  53 }
  54
  55 weak_alias(__memalign, memalign);