1 /* llist.c - Linked list functions
2 *
3 * Linked list structures have a next pointer as their first element.
4 */
5
6 #include "toys.h"
7
8 // Callback function to free data pointer of double_list or arg_list
9
llist_free_arg(void * node)10 void llist_free_arg(void *node)
11 {
12 struct arg_list *d = node;
13
14 free(d->arg);
15 free(d);
16 }
17
llist_free_double(void * node)18 void llist_free_double(void *node)
19 {
20 struct double_list *d = node;
21
22 free(d->data);
23 free(d);
24 }
25
26 // Call a function (such as free()) on each element of a linked list.
llist_traverse(void * list,void (* using)(void * node))27 void llist_traverse(void *list, void (*using)(void *node))
28 {
29 void *old = list;
30
31 while (list) {
32 void *pop = llist_pop(&list);
33 using(pop);
34
35 // End doubly linked list too.
36 if (old == list) break;
37 }
38 }
39
40 // Return the first item from the list, advancing the list (which must be called
41 // as &list)
llist_pop(void * list)42 void *llist_pop(void *list)
43 {
44 // I'd use a void ** for the argument, and even accept the typecast in all
45 // callers as documentation you need the &, except the stupid compiler
46 // would then scream about type-punned pointers. Screw it.
47 void **llist = (void **)list;
48 void **next = (void **)*llist;
49 *llist = *next;
50
51 return (void *)next;
52 }
53
dlist_pop(void * list)54 void *dlist_pop(void *list)
55 {
56 struct double_list **pdlist = (struct double_list **)list, *dlist = *pdlist;
57
58 if (dlist->next == dlist) *pdlist = 0;
59 else {
60 dlist->next->prev = dlist->prev;
61 dlist->prev->next = *pdlist = dlist->next;
62 }
63
64 return dlist;
65 }
66
dlist_add_nomalloc(struct double_list ** list,struct double_list * new)67 void dlist_add_nomalloc(struct double_list **list, struct double_list *new)
68 {
69 if (*list) {
70 new->next = *list;
71 new->prev = (*list)->prev;
72 (*list)->prev->next = new;
73 (*list)->prev = new;
74 } else *list = new->next = new->prev = new;
75 }
76
77
78 // Add an entry to the end of a doubly linked list
dlist_add(struct double_list ** list,char * data)79 struct double_list *dlist_add(struct double_list **list, char *data)
80 {
81 struct double_list *new = xmalloc(sizeof(struct double_list));
82
83 new->data = data;
84 dlist_add_nomalloc(list, new);
85
86 return new;
87 }
88
89 // Terminate circular list for traversal in either direction. Returns end *.
dlist_terminate(void * list)90 void *dlist_terminate(void *list)
91 {
92 struct double_list *end = list;
93
94 if (!list) return 0;
95
96 end = end->prev;
97 end->next->prev = 0;
98 end->next = 0;
99
100 return end;
101 }
102