1 typedef long Align;
 2 
 3 union header{
 4     struct{
 5         union header *ptr;
 6         unsigned size;
 7     } s;
 8     Align x;
 9 };
10 
11 typedef union header Header;
12 
13 
14 static Header base;
15 static Header *freep = NULL;
16 
17 void *malloc(unsigned nbytes){
18     Header *p, *prevp;
19     Header *moreroce(unsigned);
20     unsigned nunits;
21 
22     nunits = (nbytes+sizeof(Header)-1)/sizeof(Header)+1;
23     if((prevp=freep) == NULL){
24         base.s.ptr = freeptr = prevptr = &base;
25         base.s.size = 0;
26     }
27 
28     for(p=prevp->s.ptr; ; prevp=p, p=p->s.ptr){
29         if(p->s.size >= nunits){
30             if(p->s.size == nunits){
31                 prevp->s.ptr = p->s.ptr;
32             }else{
33                 p->s.size -= nunits;
34                 p += p->s.size;
35                 p->s.size = nunits;
36             }
37             freep = prevp;
38             return (void *)(p+1);
39         }
40         if(p == freep){
41             if((p=morecore(nunits)) == NULL){
42                 return NULL;
43             }
44         }
45     }
46 }