libc-top-half/musl/src/malloc/oldmalloc/aligned_alloc.c

   1 #include <stdlib.h>
   2 #include <stdint.h>
   3 #include <errno.h>
   4 #include "malloc_impl.h"
   5
   6 void *aligned_alloc(size_t align, size_t len)
   7 {
   8         unsigned char *mem, *new;
   9
  10         if ((align & -align) != align) {
  11                 errno = EINVAL;
  12                 return 0;
  13         }
  14
  15         if (len > SIZE_MAX - align ||
  16             (__malloc_replaced && !__aligned_alloc_replaced)) {
  17                 errno = ENOMEM;
  18                 return 0;
  19         }
  20
  21         if (align <= SIZE_ALIGN)
  22                 return malloc(len);
  23
  24         if (!(mem = malloc(len + align-1)))
  25                 return 0;
  26
  27         new = (void *)((uintptr_t)mem + align-1 & -align);
  28         if (new == mem) return mem;
  29
  30         struct chunk *c = MEM_TO_CHUNK(mem);
  31         struct chunk *n = MEM_TO_CHUNK(new);
  32
  33         if (IS_MMAPPED(c)) {
  34                 /* Apply difference between aligned and original
  35                  * address to the "extra" field of mmapped chunk. */
  36                 n->psize = c->psize + (new-mem);
  37                 n->csize = c->csize - (new-mem);
  38                 return new;
  39         }
  40
  41         struct chunk *t = NEXT_CHUNK(c);
  42
  43         /* Split the allocated chunk into two chunks. The aligned part
  44          * that will be used has the size in its footer reduced by the
  45          * difference between the aligned and original addresses, and
  46          * the resulting size copied to its header. A new header and
  47          * footer are written for the split-off part to be freed. */
  48         n->psize = c->csize = C_INUSE | (new-mem);
  49         n->csize = t->psize -= new-mem;
  50
  51         __bin_chunk(c);
  52         return new;
  53 }