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#include <unistd.h>
#include <stdio.h>
#include "malloc.h"
#define NALLOC 128
#define MAX_BYTES (size_t) 8192
typedef long long Align;
typedef union header {
struct {
union header *ptr;
size_t size;
} s;
Align x;
} Header;
/* see my_free
* static size_t maxalloc; */
static Header base;
static Header *freep = NULL;
/* static Header *my_morecore(size_t nunits); */
void *my_calloc(size_t n ,size_t size)
{
char *p, *temp;
size_t nb;
nb = n * size;
if ((p = temp = my_malloc(nb)) == NULL)
while (nb-- > 0)
*temp++ = '\0';
return p;
}
void *my_malloc(size_t nbytes)
{
Header *prevp, *p;
size_t nunits;
if (nbytes > MAX_BYTES) {
fprintf(stderr, "alloc:can't allocate more than %lu bytes\n",
MAX_BYTES);
return NULL;
}
if ((prevp = freep) == NULL) {
base.s.ptr = prevp = freep = &base;
base.s.size = 0;
}
nunits = (nbytes + sizeof(Header) - 1) / sizeof(Header) + 1;
for (p = freep->s.ptr; ; prevp = p, p = p->s.ptr) {
if (p->s.size >= nunits) {
if (p->s.size == nunits) {
prevp->s.ptr = p->s.ptr;
} else {
p->s.size -= nunits;
p += p->s.size;
p->s.size = nunits;
}
freep = prevp;
return (void *)(p + 1);
}
if (p == freep)
/* if ((p = my_morecore(nunits)) == NULL) \
* we fully rely on mem from stdlib malloc */
return NULL;
}
return NULL;
}
/* see my_free
* static Header *my_morecore(size_t nunits)
*{
* Header *p;
*
* if (nunits < NALLOC)
* nunits = NALLOC;
*
* if ((p = sbrk(nunits * sizeof(Header))) == (Header *) -1)
* return NULL;
*
* p->s.size = nunits;
* if ((p->s.size = nunits) > maxalloc)
* maxalloc = nunits;
*
* my_free (p + 1);
* return freep;
* } */
void my_free(void *ap)
{
Header *bp, *p;
bp = (Header *)ap - 1;
if (freep == NULL) {
base.s.ptr = freep = &base;
base.s.size = 0;
}
/* we accept random values from bfree
* if (bp->s.size == 0 || bp->s.size > maxalloc) {
* fprintf(stderr, "alloc: can't free %lu units\n", bp->s.size);
* return;
* } */
for (p = freep; !(bp > p && bp < p->s.ptr) ; p = p->s.ptr)
if (p >= p->s.ptr && (bp > p || bp < p->s.ptr))
break;
if (bp + bp->s.size == p->s.ptr) {
bp->s.size += p->s.ptr->s.size;
bp->s.ptr = p->s.ptr->s.ptr;
} else {
bp->s.ptr = p->s.ptr;
}
if (p + p->s.size == bp) {
p->s.size += bp->s.size;
p->s.ptr = bp->s.ptr;
} else {
p->s.ptr = bp;
}
freep = p;
}
size_t bfree(void *ap, size_t n)
{
Header *p;
if (n < sizeof(Header) * 2) {
fprintf(stderr, "bfree: can't free %lu bytes\n", n);
return 0;
}
p = (Header *) ap;
p->s.size = (n / sizeof(Header));
my_free(p + 1);
return p->s.size;
}
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