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
10void llist_free_arg(void *node)
11{
12  struct arg_list *d = node;
13
14  free(d->arg);
15  free(d);
16}
17
18void 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.
27void 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)
42void *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
54void *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
67void 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
79struct 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 *.
90void *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