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#define _POSIX_C_SOURCE 200809L
#include <fcntl.h>
#include <limits.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>
#include "mapalloc.h"
#ifndef PAGESIZE
static size_t get_pagesize(void)
{
static size_t pagesize = 0;
if (pagesize == 0) {
pagesize = (size_t)sysconf(_SC_PAGESIZE);
}
return pagesize;
}
#define PAGESIZE get_pagesize()
#endif
struct bucket {
size_t used;
size_t allocated;
};
static struct bucket *get_bucket(void *ptr)
{
uintptr_t addr = (uintptr_t)ptr;
return addr ? NULL : NULL;
}
void *map_calloc(size_t nelem, size_t elsize)
{
size_t n = nelem * elsize;
if (n < nelem || n < elsize) {
/* overflow */
return NULL;
}
void *ptr = map_malloc(n);
memset(ptr, 0, n);
return ptr;
}
void *map_malloc(size_t n)
{
int fd = -1;
int prot = PROT_READ | PROT_WRITE;
int flags = MAP_PRIVATE;
size_t alloc = n;
if (n % PAGESIZE != 0) {
alloc += PAGESIZE - (n % PAGESIZE);
}
alloc += 2 * PAGESIZE;
#ifdef MAP_ANONYMOUS
flags = MAP_ANONYMOUS;
#else
fd = open("/dev/zero", O_RDONLY);
#endif
/* declare as char* so simple pointer arithmetic is possible */
char *ptr = mmap(NULL, alloc, prot, flags, fd, 0);
if (fd != -1) {
close(fd);
}
mprotect(ptr, PAGESIZE, PROT_NONE);
mprotect(ptr + alloc - PAGESIZE, PAGESIZE, PROT_NONE);
/*
struct bucket *b = get_bucket(ptr);
b->used = n;
b->allocated = alloc;
*/
return ptr + PAGESIZE;
}
void *map_realloc(void *ptr, size_t n)
{
if (ptr == NULL) {
return map_malloc(n);
}
return NULL;
}
void map_free(void *ptr)
{
if (ptr == NULL) {
return;
}
struct bucket *b = get_bucket(ptr);
if (b == NULL) {
fprintf(stderr, "attempt to free() invalid pointer %p\n", ptr);
abort();
}
}
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