1. Doubly-linked list library.
typedef struct dllist {
struct dllist *flink;
struct dllist *blink;
Jval val;
} *Dllist;
Link to next node
Link to previous node
The node’s value
Next node
flink
Previous node
blink
val

2. Dllist library structure
Circular
Doubly-linked
With a sentinel (header) node
list
flink
blink
val
flink
flink
flink
flink …
blink
blink
blink
blink
val
val
val
val

3. Creating a list: new_dllist()
Dllist l;
l = new_dllist(); l
flink
blink
val

4. Augmenting a list: dll_append()
Dllist l;
l = new_dllist();
dll_append(l, new_jval_i(3)); l
flink
flink
blink
blink
val
val.i=3

5. Augmenting a list: dll_append()
Dllist l;
l = new_dllist();
dll_append(l, new_jval_i(3));
dll_append(l, new_jval_i(8)); l
flink
flink
flink
blink
blink
blink
val
val.i=3
val.i=8

6. What will this print? Dllist l; l = new_dllist();
dll_append(l, new_jval_i(3));
dll_append(l, new_jval_i(8));
printf(“%d\n”, l->flink->val.i); l
flink
flink
flink
blink
blink
blink
val
val.i=3
val.i=8

7. What will this print? Dllist l; l = new_dllist();
dll_append(l, new_jval_i(3));
dll_append(l, new_jval_i(8));
printf(“%d\n”, l->flink->val.i); l
flink
flink
flink 3
blink
blink
blink
val
val.i=3
val.i=8

8. Augmenting a list: dll_prepend()
Dllist l;
l = new_dllist();
dll_append(l, new_jval_i(3));
dll_append(l, new_jval_i(8));
dll_prepend(l, new_jval_s(“Jim”)); l
flink
flink
flink
flink
blink
blink
blink
blink
val
val.s
val.i=3
val.i=8
“Jim”

9. What will this print? Dllist l; l = new_dllist();
dll_append(l, new_jval_i(3));
dll_append(l, new_jval_i(8));
dll_prepend(l, new_jval_s(“Jim”));
printf(“%d\n”, l->flink->val.i); l
flink
flink
flink
flink
blink
blink
blink
blink
val
val.s
val.i=3
val.i=8
“Jim”

10. What will this print? Dllist l; 10864 l = new_dllist();
dll_append(l, new_jval_i(3));
dll_append(l, new_jval_i(8));
dll_prepend(l, new_jval_s(“Jim”));
printf(“%d\n”, l->flink->val.i);
10864
(or something
similar) l
flink
flink
flink
flink
blink
blink
blink
blink
val
val.s
val.i=3
val.i=8
“Jim”

11. Augmenting a list: dll_insert_b()
Dllist l;
l = new_dllist();
dll_append(l, new_jval_i(3));
dll_append(l, new_jval_i(8));
dll_insert_b(l->flink->flink,
new_jval_s(“Jim”));
Inserts before a given node. l
flink
flink
flink
flink
blink
blink
blink
blink
val
val.i=3
val.s
val.i=8
“Jim”

12. What will this do? Dllist l; l = new_dllist();
dll_append(l, new_jval_i(3));
dll_append(l, new_jval_i(8));
dll_insert_b(l, new_jval_s(“Jim”); l
flink
flink
flink
blink
blink
blink
val
val.i=3
val.i=8

13. What will this do? Dllist l; l = new_dllist();
dll_append(l, new_jval_i(3));
dll_append(l, new_jval_i(8));
dll_insert_b(l, new_jval_s(“Jim”); l
flink
flink
flink
flink
blink
blink
blink
blink
val
val.i=3
val.i=8
val.s
“Jim”

14. Deleting: dll_delete_node()
Dllist l;
l = new_dllist();
dll_append(l, new_jval_i(3));
dll_append(l, new_jval_i(8));
dll_insert_b(l, new_jval_s(“Jim”);
dll_delete_node(l->blink); l
flink
flink
flink
flink
before
blink
blink
blink
blink
val
val.i=3
val.i=8
val.s
“Jim”

15. Deleting: dll_delete_node()
Dllist l;
l = new_dllist();
dll_append(l, new_jval_i(3));
dll_append(l, new_jval_i(8));
dll_insert_b(l, new_jval_s(“Jim”);
dll_delete_node(l->blink); l
flink
flink
flink
after
blink
blink
blink
val
val.i=3
val.i=8

16. Deleting: free_dllist()
Destroys a list
Including the sentinel node.
Frees all malloc’d nodes
Does not free jvals!
IS is; Dllist l;
l = new_dllist();
is = new_inputstruct(NULL);
while(get_line(is) >= 0) {
dll_prepend(l, new_jval_s(strdup(is->text1))); }
free_dllist(l);

17. Handy macros (from dllist.h)
#define dll_first(d) ((d)->flink)
#define dll_next(d) ((d)->flink)
#define dll_last(d) ((d)->blink)
#define dll_prev(d) ((d)->blink)
#define dll_nil(d) (d) l
flink
flink
flink
blink
blink
blink
val
val.i=3
val.i=8

18. Traversal macros: weird but useful!
#define dll_traverse(ptr, list) \
for (ptr = (list)->flink; ptr != (list); ptr = ptr->flink)
#define dll_rtraverse(ptr, list) \
for (ptr = (list)->blink; ptr != (list); ptr = ptr->blink) l
flink
flink
flink
blink
blink
blink
val
val.i=3
val.i=8

19. Two programs to reverse stdin:
#include “fields.h”
#include “dllist.h”
main() {
IS is; Dllist l;
is = new_inputstruct(NULL);
l = new_dllist();
while(get_line(is) >= 0) {
dll_prepend(l, new_jval_s(strdup(is->text1))); }
dll_traverse(tmp, l) {
printf(“%s”, tmp->val.s); #1

20. Two programs to reverse stdin:
#include “fields.h”
#include “dllist.h”
main() {
IS is; Dllist l;
is = new_inputstruct(NULL);
l = new_dllist();
while(get_line(is) >= 0) {
dll_append(l, new_jval_s(strdup(is->text1))); }
dll_rtraverse(tmp, l) {
printf(“%s”, tmp->val.s); #2

21. Implementation: new_dllist()
Dllist new_dllist() {
Dllist d;
d = (Dllist) malloc (sizeof(struct dllist));
d->flink = d;
d->blink = d;
return d; } d
flink
blink
val

22. Implementation: dll_insert_b()
void dll_insert_b(Dllist node, Jval v) {
Dllist newnode;
newnode = (Dllist) malloc (sizeof(struct dllist));
newnode->val = v;
newnode->flink = node;
newnode->blink = node->blink;
newnode->flink->blink = newnode;
newnode->blink->flink = newnode; }
e.g. before dll_insert_b(n, new_jval_i(10)); n
flink
flink
flink
blink
blink
blink
val.i=3
val.i=8
val.i=2

23. Implementation: dll_insert_b()
void dll_insert_b(Dllist node, Jval v) {
Dllist newnode;
newnode = (Dllist) malloc (sizeof(struct dllist));
newnode->val = v;
newnode->flink = node;
newnode->blink = node->blink;
newnode->flink->blink = newnode;
newnode->blink->flink = newnode; }
newnode
dll_insert_b(n, new_jval_i(10));
flink
blink n
val
flink
flink
flink
blink
blink
blink
val.i=3
val.i=8
val.i=2

24. Implementation: dll_insert_b()
void dll_insert_b(Dllist node, Jval v) {
Dllist newnode;
newnode = (Dllist) malloc (sizeof(struct dllist));
newnode->val = v;
newnode->flink = node;
newnode->blink = node->blink;
newnode->flink->blink = newnode;
newnode->blink->flink = newnode; }
newnode
dll_insert_b(n, new_jval_i(10));
flink
blink n
val.i=10
flink
flink
flink
blink
blink
blink
val.i=3
val.i=8
val.i=2

25. Implementation: dll_insert_b()
void dll_insert_b(Dllist node, Jval v) {
Dllist newnode;
newnode = (Dllist) malloc (sizeof(struct dllist));
newnode->val = v;
newnode->flink = node;
newnode->blink = node->blink;
newnode->flink->blink = newnode;
newnode->blink->flink = newnode; }
newnode
dll_insert_b(n, new_jval_i(10));
flink
blink n
val.i=10
flink
flink
flink
blink
blink
blink
val.i=3
val.i=8
val.i=2

26. Implementation: dll_insert_b()
void dll_insert_b(Dllist node, Jval v) {
Dllist newnode;
newnode = (Dllist) malloc (sizeof(struct dllist));
newnode->val = v;
newnode->flink = node;
newnode->blink = node->blink;
newnode->flink->blink = newnode;
newnode->blink->flink = newnode; }
newnode
dll_insert_b(n, new_jval_i(10));
flink
blink n
val.i=10
flink
flink
flink
blink
blink
blink
val.i=3
val.i=8
val.i=2

27. Implementation: dll_insert_b()
void dll_insert_b(Dllist node, Jval v) {
Dllist newnode;
newnode = (Dllist) malloc (sizeof(struct dllist));
newnode->val = v;
newnode->flink = node;
newnode->blink = node->blink;
newnode->flink->blink = newnode;
newnode->blink->flink = newnode; }
newnode
dll_insert_b(n, new_jval_i(10));
flink
blink n
val.i=10
flink
flink
flink
blink
blink
blink
val.i=3
val.i=8
val.i=2

28. Implementation: dll_insert_b()
void dll_insert_b(Dllist node, Jval v) {
Dllist newnode;
newnode = (Dllist) malloc (sizeof(struct dllist));
newnode->val = v;
newnode->flink = node;
newnode->blink = node->blink;
newnode->flink->blink = newnode;
newnode->blink->flink = newnode; }
newnode
dll_insert_b(n, new_jval_i(10));
flink
blink n
val.i=10
flink
flink
flink
blink
blink
blink
val.i=3
val.i=8
val.i=2

29. Implementation: dll_insert_b()
void dll_insert_b(Dllist node, Jval v) {
Dllist newnode;
newnode = (Dllist) malloc (sizeof(struct dllist));
newnode->val = v;
newnode->flink = node;
newnode->blink = node->blink;
newnode->flink->blink = newnode;
newnode->blink->flink = newnode; }
dll_insert_b(n, new_jval_i(10)); n
flink
flink
flink
flink
blink
blink
blink
blink
val.i=3
val.i=10
val.i=8
val.i=2

30. Implementation: dll_insert_a()
void dll_insert_a(Dllist n, Jval val) {
dll_insert_b(n->flink, val); } n
flink
flink
flink
blink
blink
blink
val
val.i=3
val.i=8

31. Implementation: dll_append()
void dll_append(Dllist l, Jval val) {
dll_insert_b(l, val); } l
flink
flink
flink
blink
blink
blink
val
val.i=3
val.i=8

32. Implementation: dll_prepend()
void dll_prepend(Dllist l, Jval val) {
dll_insert_a(l, val); } l
flink
flink
flink
blink
blink
blink
val
val.i=3
val.i=8

33. Implementation: dll_delete_node()
void dll_delete_node(Dllist node) {
node->flink->blink = node->blink;
node->blink->flink = node->flink;
free(node); }
e.g. before dll_delete_node(n); n
flink
flink
flink
blink
blink
blink
val.i=3
val.i=8
val.i=2

34. Implementation: dll_delete_node()
void dll_delete_node(Dllist node) {
node->flink->blink = node->blink;
node->blink->flink = node->flink;
free(node); }
dll_delete_node(n); n
flink
flink
flink
blink
blink
blink
val.i=3
val.i=8
val.i=2

35. Implementation: dll_delete_node()
void dll_delete_node(Dllist node) {
node->flink->blink = node->blink;
node->blink->flink = node->flink;
free(node); }
dll_delete_node(n); n
flink
flink
flink
blink
blink
blink
val.i=3
val.i=8
val.i=2

36. Implementation: dll_delete_node()
void dll_delete_node(Dllist node) {
node->flink->blink = node->blink;
node->blink->flink = node->flink;
free(node); }
dll_delete_node(n); n
flink
flink
blink
blink
val.i=3
val.i=2

37. Implementation: dll_delete_node()
void dll_delete_node(Dllist node) {
node->flink->blink = node->blink;
node->blink->flink = node->flink;
free(node); }
dll_delete_node(n); n ?
flink
flink
blink
blink
val.i=3
val.i=2

38. Implementation: free_dllist()
void free_dllist(Dllist l) {
while (!dll_empty(l)) {
dll_delete_node(dll_first(l)); }
free(l); l
flink
flink
flink
blink
blink
blink
val
val.i=3
val.i=8

39. Implementation: dll_empty()
int dll_empty(Dllist l) {
return (l->flink == l); } l
flink
flink
flink
blink
blink
blink
val
val.i=3
val.i=8