1 #define _GNU_SOURCE
2 #include <stdlib.h>
3 #include <sys/mman.h>
4 #include <string.h>
5 #include "meta.h"
6
realloc(void * p,size_t n)7 void *realloc(void *p, size_t n)
8 {
9 if (!p) return malloc(n);
10 if (size_overflows(n)) return 0;
11
12 struct meta *g = get_meta(p);
13 int idx = get_slot_index(p);
14 size_t stride = get_stride(g);
15 unsigned char *start = g->mem->storage + stride*idx;
16 unsigned char *end = start + stride - IB;
17 size_t old_size = get_nominal_size(p, end);
18 size_t avail_size = end-(unsigned char *)p;
19 void *new;
20
21 // only resize in-place if size class matches
22 if (n <= avail_size && n<MMAP_THRESHOLD
23 && size_to_class(n)+1 >= g->sizeclass) {
24 set_size(p, end, n);
25 return p;
26 }
27
28 // use mremap if old and new size are both mmap-worthy
29 if (g->sizeclass>=48 && n>=MMAP_THRESHOLD) {
30 assert(g->sizeclass==63);
31 size_t base = (unsigned char *)p-start;
32 size_t needed = (n + base + UNIT + IB + 4095) & -4096;
33 new = g->maplen*4096UL == needed ? g->mem :
34 mremap(g->mem, g->maplen*4096UL, needed, MREMAP_MAYMOVE);
35 if (new!=MAP_FAILED) {
36 g->mem = new;
37 g->maplen = needed/4096;
38 p = g->mem->storage + base;
39 end = g->mem->storage + (needed - UNIT) - IB;
40 *end = 0;
41 set_size(p, end, n);
42 return p;
43 }
44 }
45
46 new = malloc(n);
47 if (!new) return 0;
48 memcpy(new, p, n < old_size ? n : old_size);
49 free(p);
50 return new;
51 }
52