archie/prospero/user/menu/bub.c

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2024-05-27 16:13:40 +02:00
/*
* Copyright (c) 1993 by the University of Southern California
*
* For copying and distribution information, please see the file
* <usc-copyr.h>.
*
* The menu API and client were written by Kwynn Buess (buess@isi.edu)
*/
#include <usc-copyr.h>
#include <pfs.h>
#include "menu.h"
static VLINK swap(VLINK,VLINK);
/* This prototype of the function performs a bubble sort; this will soon be
changed. */
VLINK
vlink_list_sort(VLINK list)
{
VLINK temp;
int compare_collation_ord(VLINK,VLINK);
VLINK head = list; /* use the variable 'list' to do final
rearranging. */
VLINK next; /* used to do final rearranging. --swa */
int all_in_order = 0;
if (!head || !head->next) all_in_order = 1; /* singleton or empty list is
always in order. */
while (!all_in_order) {
all_in_order = 1;
if (compare_collation_ord(head,head->next) == -1)
head = swap(head,head->next);
temp = head;
all_in_order = 1;
while (temp->next->next != NULL) {
if (compare_collation_ord(temp -> next,temp -> next -> next) == -1) {
all_in_order = 0;
temp -> next = swap(temp->next,temp->next->next);
}
temp = temp -> next;
}
}
/* We now have a singly-linked list of VLINKs rooted at 'head'. */
/* Now reorder the list of links, so that it meets the standard
doubly-linked-list conventions. --swa */
list = NULL;
for (temp = head ; temp; temp = next) {
next = temp->next;
APPEND_ITEM(temp, list);
}
return list;
}
static VLINK
swap(VLINK vl1,VLINK vl2) {
vl1 -> next = vl2 -> next;
vl2 -> next = vl1;
vl1 -> previous = vl2;
vl2 -> previous = vl1 -> previous;
return vl2;
}