/
malloc.c
executable file
·83 lines (63 loc) · 1.53 KB
/
malloc.c
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#include <errno.h>
#include <limits.h>
#include <string.h>
#include "malloc.h"
#include "memreq.h"
struct header {
size_t size;
header* next;
int freed;
} header;
struct header* tail;
void *malloc(size_t size) {
if (size == 0) {
return (void*) 0;
}
struct header* ptr = (struct header*) get_memory(size + sizeof(struct header));
ptr->size = size;
ptr->freed = 0;
if (tail == NULL) {
}
return (void*) (ptr + 1);
}
static size_t highest(size_t in) {
size_t num_bits = 0;
while (in != 0) {
++num_bits;
in >>= 1;
}
return num_bits;
}
void* calloc(size_t number, size_t size) {
size_t number_size = 0;
/* This prevents an integer overflow. A size_t is a typedef to an integer
* large enough to index all of memory. If we cannot fit in a size_t, then
* we need to fail.
*/
if (highest(number) + highest(size) > sizeof(size_t) * CHAR_BIT) {
errno = ENOMEM;
return NULL;
}
number_size = number * size;
void* ret = malloc(number_size);
if (ret) {
memset(ret, 0, number_size);
}
return ret;
}
void* realloc(void *ptr, size_t size) {
size_t old_size = 0; /* XXX Set this to the size of the buffer pointed to by ptr */
void* ret = malloc(size);
if (ret) {
if (ptr) {
memmove(ret, ptr, old_size < size ? old_size : size);
free(ptr);
}
return ret;
} else {
errno = ENOMEM;
return NULL;
}
}
void free(void* ptr) {
}