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// http://www.openwall.com/lists/musl/2015/02/03/1
#include <pthread.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <dlfcn.h>
#include <unistd.h>
#include <stdio.h>
static void *(*real_malloc)(size_t);
static void *initial_brk;
static pthread_once_t once_control[1];
static void once_func()
{
real_malloc = dlsym(RTLD_NEXT, "malloc");
initial_brk = sbrk(0);
}
static int cmp(const void *a, const void *b)
{
void *aa = *(void **)a, *bb = *(void **)b;
return aa < bb ? -1 : aa > bb ? 1 : 0;
}
void *malloc(size_t n)
{
size_t i, j, k;
pthread_once(once_control, once_func);
if (n < 100000 || n > (size_t)-1/2) {
void *p;
do p = real_malloc(n);
while (p > sbrk(0) || (p && p < initial_brk));
return p;
}
size_t cnt = n/16384;
void **list = real_malloc(sizeof *list * cnt);
if (!list) return 0;
for (i=0; i<cnt; i++) list[i] = 0;
for (i=0; i<cnt; i++) {
list[i] = real_malloc(65536 - 2*sizeof(size_t));
if (!list[i]) goto fail;
if (i<cnt/4) continue;
size_t base = 0;
qsort(list, i+1, sizeof(void *), cmp);
for (j=0; j<i; j++) {
char *p = list[base];
char *s = list[j];
char *z = list[j+1];
if (z-s > 65536) {
base = j+1;
continue;
}
if (z-p < n+64) {
continue;
}
for (k=0; k<base; k++) free(list[k]);
*(size_t *)(p-sizeof(size_t)) = z-p | 1;
*(size_t *)(z-2*sizeof(size_t)) = z-p | 1;
for (k=j+1; k<i+1; k++) free(list[k]);
free(list);
return p;
}
}
fail:
for (i=0; i<cnt; i++) free(list[i]);
free(list);
return 0;
}
void *calloc(size_t n, size_t m)
{
if ((size_t)-1/n <= m) n *= m;
else n = (size_t)-1;
void *p = malloc(n);
if (p) memset(p, 0, n);
return p;
}
void *realloc(void *p, size_t n)
{
void *q = malloc(n);
if (!q) return 0;
size_t l = *(size_t *)((char *)p - sizeof(size_t)) & -8;
memcpy(q, p, l<n ? l : n);
free(p);
return q;
}
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