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#include <stdlib.h>
#include <stdio.h>
#include "list.h"
#ifdef DEBUG
#define PDEBUG(Args...) \
do { fprintf(stderr, "mcwm: "); fprintf(stderr, ##Args); } while(0)
#define D(x) x
#else
#define PDEBUG(Args...)
#define D(x)
#endif
void movetohead(struct item **mainlist, struct item *item)
{
if (NULL == item || NULL == mainlist || NULL == *mainlist)
{
return;
}
if (*mainlist == item)
{
/* Already at head. Do nothing. */
return;
}
/* Braid together the list where we are now. */
if (NULL != item->prev)
{
item->prev->next = item->next;
}
if (NULL != item->next)
{
item->next->prev = item->prev;
}
/* Now at head. */
item->prev = NULL;
item->next = *mainlist;
/* Remember the new head. */
*mainlist = item;
}
void movetonext(struct item **mainlist, struct item *item, struct item *next)
{
if (NULL == item || NULL == next || NULL == mainlist || NULL == *mainlist)
{
return;
}
if (item->next == next || item == next)
{
/* Already in position. Do nothing. */
return;
}
/* Braid together the list where next used to be. */
if (NULL != next->next)
{
next->next->prev = next->prev;
}
if (NULL != next->prev)
{
next->prev->next = next->next;
}
else
{
/* next is currently head. move head one step further along. */
if (NULL != next->next)
{
*mainlist = next->next;
next->next->prev = NULL;
}
}
/* Position next after item and braid together list again. */
next->prev = item;
next->next = item->next;
if (NULL != next->next)
{
next->next->prev = next;
}
/* Remember where next is now. */
item->next = next;
}
/*
*/
struct item *additem(struct item **mainlist)
{
struct item *item;
if (NULL == (item = (struct item *) malloc(sizeof (struct item))))
{
return NULL;
}
if (NULL == *mainlist)
{
/* First in the list. */
item->prev = NULL;
item->next = NULL;
}
else
{
/* Add to beginning of list. */
item->next = *mainlist;
item->next->prev = item;
item->prev = NULL;
}
*mainlist = item;
return item;
}
void delitem(struct item **mainlist, struct item *item)
{
struct item *ml = *mainlist;
if (NULL == mainlist || NULL == *mainlist || NULL == item)
{
return;
}
if (item == *mainlist)
{
/* First entry was removed. Remember the next one instead. */
*mainlist = ml->next;
}
else
{
item->prev->next = item->next;
if (NULL != item->next)
{
/* This is not the last item in the list. */
item->next->prev = item->prev;
}
}
free(item);
}
void listitems(struct item *mainlist)
{
struct item *item;
int i;
for (item = mainlist, i = 1; item != NULL; item = item->next, i ++)
{
printf("item #%d (stored at %p).\n", i, (void *)item);
}
}
#if 0
void listall(struct item *mainlist)
{
struct item *item;
int i;
printf("Listing all:\n");
for (item = mainlist, i = 1; item != NULL; item = item->next, i ++)
{
printf("%d at %p: %s.\n", i, (void *)item, (char *)item->data);
printf(" prev: %p\n", item->prev);
printf(" next: %p\n", item->next);
}
}
int main(void)
{
struct item *mainlist = NULL;
struct item *item1;
struct item *item2;
struct item *item3;
struct item *item4;
struct item *item;
struct item *nextitem;
int i;
char *foo1 = "1";
char *foo2 = "2";
char *foo3 = "3";
char *foo4 = "4";
item1 = additem(&mainlist);
if (NULL == item1)
{
printf("Couldn't allocate.\n");
exit(1);
}
item1->data = foo1;
printf("Current elements:\n");
listall(mainlist);
item2 = additem(&mainlist);
if (NULL == item2)
{
printf("Couldn't allocate.\n");
exit(1);
}
item2->data = foo2;
printf("Current elements:\n");
listall(mainlist);
item3 = additem(&mainlist);
if (NULL == item3)
{
printf("Couldn't allocate.\n");
exit(1);
}
item3->data = foo3;
printf("Current elements:\n");
listall(mainlist);
item4 = additem(&mainlist);
if (NULL == item4)
{
printf("Couldn't allocate.\n");
exit(1);
}
item4->data = foo4;
printf("Current elements:\n");
listall(mainlist);
printf("----------------------------------------------------------------------\n");
printf("Moving item3 to be after item2\n");
movetonext(&mainlist, item2, item3);
printf("Current elements:\n");
listall(mainlist);
printf("----------------------------------------------------------------------\n");
printf("Moving head! item4 to be after item2\n");
movetonext(&mainlist, item2, item4);
printf("Current elements:\n");
listall(mainlist);
printf("----------------------------------------------------------------------\n");
printf("Moving tail! item1 to be after item2\n");
movetonext(&mainlist, item2, item1);
printf("Current elements:\n");
listall(mainlist);
printf("----------------------------------------------------------------------\n");
printf("Moving head to be after tail.\n");
movetonext(&mainlist, item3, item2);
printf("Current elements:\n");
listall(mainlist);
printf("Moving all the items after each other.\n");
/* item3 is tail. work backwards. */
for (item = mainlist, i = 1;
item != NULL;
item = item->next, i ++)
{
for (nextitem = item2; nextitem != NULL; nextitem = nextitem->prev)
{
movetonext(&mainlist, nextitem, item);
printf("Current elements:\n");
listall(mainlist);
}
}
printf("----------------------------------------------------------------------\n");
#if 0
movetohead(&mainlist, item2);
printf("Current elements:\n");
listall(mainlist);
printf("----------------------------------------------------------------------\n");
#endif
printf("Deleting item stored at %p\n", item3);
delitem(&mainlist, item3);
printf("Current elements:\n");
listall(mainlist);
puts("");
delitem(&mainlist, item2);
printf("Current elements:\n");
listall(mainlist);
puts("");
delitem(&mainlist, item1);
printf("Current elements:\n");
listall(mainlist);
puts("");
printf("----------------------------------------------------------------------\n");
exit(0);
}
#endif
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