1#include <stdlib.h>
 2#include <errno.h>
 3#include "meta.h"
 4
 5void *aligned_alloc(size_t align, size_t len)
 6{
 7	if ((align & -align) != align) {
 8		errno = EINVAL;
 9		return 0;
10	}
11
12	if (len > SIZE_MAX - align || align >= (1ULL<<31)*UNIT) {
13		errno = ENOMEM;
14		return 0;
15	}
16
17	if (DISABLE_ALIGNED_ALLOC) {
18		errno = ENOMEM;
19		return 0;
20	}
21
22	if (align <= UNIT) align = UNIT;
23
24	unsigned char *p = malloc(len + align - UNIT);
25	if (!p)
26		return 0;
27
28	struct meta *g = get_meta(p);
29	int idx = get_slot_index(p);
30	size_t stride = get_stride(g);
31	unsigned char *start = g->mem->storage + stride*idx;
32	unsigned char *end = g->mem->storage + stride*(idx+1) - IB;
33	size_t adj = -(uintptr_t)p & (align-1);
34
35	if (!adj) {
36		set_size(p, end, len);
37		return p;
38	}
39	p += adj;
40	uint32_t offset = (size_t)(p-g->mem->storage)/UNIT;
41	if (offset <= 0xffff) {
42		*(uint16_t *)(p-2) = offset;
43		p[-4] = 0;
44	} else {
45		// use a 32-bit offset if 16-bit doesn't fit. for this,
46		// 16-bit field must be zero, [-4] byte nonzero.
47		*(uint16_t *)(p-2) = 0;
48		*(uint32_t *)(p-8) = offset;
49		p[-4] = 1;
50	}
51	p[-3] = idx;
52	set_size(p, end, len);
53	// store offset to aligned enframing. this facilitates cycling
54	// offset and also iteration of heap for debugging/measurement.
55	// for extreme overalignment it won't fit but these are classless
56	// allocations anyway.
57	*(uint16_t *)(start - 2) = (size_t)(p-start)/UNIT;
58	start[-3] = 7<<5;
59	return p;
60}