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#define _GNU_SOURCE
#include <stdlib.h>
#include <sys/mman.h>
#include <string.h>
#include "meta.h"
void *realloc(void *p, size_t n)
{
if (!p) return malloc(n);
if (size_overflows(n)) return 0;
struct meta *g = get_meta(p);
int idx = get_slot_index(p);
size_t stride = get_stride(g);
unsigned char *start = g->mem->storage + stride*idx;
unsigned char *end = start + stride - IB;
size_t old_size = get_nominal_size(p, end);
size_t avail_size = end-(unsigned char *)p;
void *new;
// only resize in-place if size class matches
if (n <= avail_size && n<MMAP_THRESHOLD
&& size_to_class(n)+1 >= g->sizeclass) {
set_size(p, end, n);
return p;
}
// use mremap if old and new size are both mmap-worthy
if (g->sizeclass>=48 && n>=MMAP_THRESHOLD) {
assert(g->sizeclass==63);
size_t base = (unsigned char *)p-start;
size_t needed = (n + base + UNIT + IB + 4095) & -4096;
new = g->maplen*4096UL == needed ? g->mem :
mremap(g->mem, g->maplen*4096UL, needed, MREMAP_MAYMOVE);
if (new!=MAP_FAILED) {
g->mem = new;
g->maplen = needed/4096;
p = g->mem->storage + base;
end = g->mem->storage + (needed - UNIT) - IB;
*end = 0;
set_size(p, end, n);
return p;
}
}
new = malloc(n);
if (!new) return 0;
memcpy(new, p, n < old_size ? n : old_size);
free(p);
return new;
}
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