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#include <stdlib.h>
#include <stdint.h>
#include <errno.h>
/* This function should work with most dlmalloc-like chunk bookkeeping
* systems, but it's only guaranteed to work with the native implementation
* used in this library. */
int posix_memalign(void **res, size_t align, size_t len)
{
unsigned char *mem, *new, *end;
size_t header, footer;
if ((align & -align & -sizeof(void *)) != align) return EINVAL;
if (len > SIZE_MAX - align) return ENOMEM;
if (align <= 4*sizeof(size_t)) {
if (!(mem = malloc(len)))
return errno;
*res = mem;
return 0;
}
if (!(mem = malloc(len + align-1)))
return errno;
header = ((size_t *)mem)[-1];
end = mem + (header & -8);
footer = ((size_t *)end)[-2];
new = (void *)((uintptr_t)mem + align-1 & -align);
if (!(header & 7)) {
((size_t *)new)[-2] = ((size_t *)mem)[-2] + (new-mem);
((size_t *)new)[-1] = ((size_t *)mem)[-1] - (new-mem);
*res = new;
return 0;
}
((size_t *)mem)[-1] = header&7 | new-mem;
((size_t *)new)[-2] = footer&7 | new-mem;
((size_t *)new)[-1] = header&7 | end-new;
((size_t *)end)[-2] = footer&7 | end-new;
if (new != mem) free(mem);
*res = new;
return 0;
}
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