1 void *gc_malloc (size_t size)
2 {
3     list_t *list, *newlist;
4     char *addr, *test;
5     long foo, mask;
6     Tree *alloc_tree;
7     int registers[3];
8     int top;
9 
10     /* start by getting the callee-save registers and the top of the program
11      * stack at this point. Doing this here means that we don't have to search
12      * the stack frame for gc_malloc or anything that it calls when we collect
13      * root pointers.
14      */
15     GET_CALLEE_REGS(registers);
16     PGM_STACK_TOP(top);
17 
18     /* round up size to a multiple of 8 */
19     size = (size ? ((size>>3) + !!(size & 7)) << 3 : 8);
20 
21     /* search un-coalesced free list */
22     addr = dseg_lo;
23     list = *(list_t **)addr;
24     if (list != NULL) {
25       do {
26 	if (list->size >= size) {
27 	  break;
28 	}
29 	list = list->next;
30 	if (list == *(list_t **)addr) {
31 	  list = NULL;
32 	}
33       } while (list);
34     }
35       
36     /* if we couldn't find a fit then try sbrk */
37     if(list==NULL) {    
38       mask = mem_pagesize()-1;
39       size += sizeof(Tree);
40       /* number of pages needed, ceil( size/pagesize ) */
41       foo = (size & ~mask) + ((!!(size & mask))*mem_pagesize());
42       size -= sizeof(Tree);
43       list = (list_t *)(dseg_hi+1);
44       test = mem_sbrk(foo);
45       if (!test) 
46 	return NULL;
47       list->size = foo - sizeof(Tree);
48       gc_add_free(dseg_lo, list);
49     }
50 
51 
52     /* found a fit */
53     if (list->size < size + sizeof(list_t) + sizeof(long) ) {
54 	/* give them the whole chunk (we need sizeof(list_t) to hold accounting
55 	 * information, want at least one usable word if we're going to 
56 	 * keep track of this block!) */
57 	gc_remove_free(addr, list);
58 	/* put this block in the allocated tree */
59 	addr = dseg_lo + sizeof(long);
60 	alloc_tree = *(Tree **)addr;
61 	*(Tree **)addr = insert(alloc_tree, (Tree *)list);
62 	return (((void *)list) + sizeof(Tree));
63     }
64 
65     /* give them the beginning of the block */
66     newlist = (list_t *)(((void *)list) + size + sizeof(Tree));
67     newlist->size = list->size - size - sizeof(Tree);
68     list->size = size;
69 
70     if (list->next == list) {
71 	newlist->next = newlist->prev = newlist;
72     } else {
73 	newlist->prev = list->prev;
74 	newlist->next = list->next;
75 	newlist->prev->next = newlist->next->prev = newlist;
76     }
77     if (*(list_t **)addr == list) {
78 	*(list_t **)addr = newlist;
79     }
80 
81     /* put this block in the allocated tree */
82     addr = dseg_lo + sizeof(long);
83     alloc_tree = *(Tree **)addr;
84     *(Tree **)addr = insert(alloc_tree, (Tree *)list);
85 
86     return ((void *)list + sizeof(Tree));
87 }
88