Power-Programmierung/CD2.mdf/c/library/dos/database/avl/dlist.c

C/C++ Source or Header | 1992-02-15 | 11.7 KB | 391 lines

/****************************************************************************
*
*                    Copyright (C) 1991 Kendall Bennett.
*                            All rights reserved.
*
* Filename:        $RCSfile: dlist.c $
* Version:        $Revision: 1.5 $
*
* Language:        ANSI C
* Environment:    any
*
* Description:    Module to implement doubly linked lists. Includes a routine
*                to peform a mergesort on the doubly linked list.
*
* $Id: dlist.c 1.5 91/12/31 19:39:49 kjb Exp $
*
* Revision History:
* -----------------
*
* $Log:    dlist.c $
* Revision 1.5  91/12/31  19:39:49  kjb
* Modified include file directories.
*
* Revision 1.4  91/10/28  03:16:39  kjb
* Ported to the Iris.
*
* Revision 1.3  91/09/27  03:09:18  kjb
* Cosmetic change.
*
* Revision 1.2  91/09/03  18:27:42  ROOT_DOS
* Ported to UNIX.
*
* Revision 1.1  91/09/01  18:35:23  ROOT_DOS
* Initial revision
*
****************************************************************************/

#include <stdio.h>
#include <malloc.h>
#include <signal.h>
#include "debug.h"
#include "dlist.h"

PUBLIC void *dlst_newnode(int size)
/****************************************************************************
*
* Function:        dlst_newnode
* Parameters:    size    - Amount of memory to allocate for node
* Returns:      Pointer to the allocated node's user space.
*
* Description:    Allocates the memory required for a node, adding a small
*                header at the start of the node. We return a reference to
*                the user space of the node, as if it had been allocated via
*                malloc().
*
****************************************************************************/
{
    DLST_BUCKET    *node;

    if ( !(node = (DLST_BUCKET*)malloc(size + sizeof(DLST_BUCKET))) ) {
        fprintf(stderr,"Not enough memory to allocate list node.\n");
        raise(SIGABRT);
        return NULL;
        }

    return DLST_USERSPACE(node);        /* Return pointer to user space */
}

PUBLIC void dlst_freenode(void *node)
/****************************************************************************
*
* Function:        dlst_freenode
* Parameters:    node    - Node to free.
*
* Description:  Frees a node previously allocated with lst_newnode().
*
****************************************************************************/
{
    free(DLST_HEADER(node));
}

PUBLIC DLIST *dlst_init(void)
/****************************************************************************
*
* Function:        dlst_init
* Returns:      Pointer to a newly created list.
*
* Description:    Initialises a list and returns a pointer to it.
*
****************************************************************************/
{
    DLIST    *l;

    if ((l = (DLIST*)malloc(sizeof(DLIST))) != NULL) {
        l->count = 0;
        l->head = &(l->hz[0]);
        l->z = &(l->hz[1]);
        l->head->next = l->z->next = l->z;
        l->z->prev = l->head->prev = l->head;
        }
    else {
        fprintf(stderr,"Insufficient memory to allocate list\n");
        raise(SIGABRT);
        return NULL;
        }

    return l;
}

PUBLIC void dlst_kill(DLIST *l,void (*freeNode)(void *node))
/****************************************************************************
*
* Function:        dlst_kill
* Parameters:    l            - List to kill
*                freeNode    - Pointer to user routine to free a node
*
* Description:    Kills the list l, by deleting all of the elements contained
*                within the list one by one and then deleting the list
*                itself. Note that we call the user supplied routine
*                (*freeNode)() to free each list node. This allows the user
*                program to perform any extra processing needed to kill each
*                node (if each node contains pointers to other items on the
*                heap for example). If no extra processing is required, just
*                pass the address of dlst_freenode(), ie:
*
*                    dlst_kill(myList,dlst_freenode);
*
****************************************************************************/
{
    DLST_BUCKET    *n,*p;

    n = l->head->next;
    while (n != l->z) {            /* Free all nodes in list                */
        p = n;
        n = n->next;
        (*freeNode)(DLST_USERSPACE(p));
        }
    free(l);                    /* Free the list itself                    */
}

PUBLIC void dlst_insertafter(DLIST *l,void *node,void *after)
/****************************************************************************
*
* Function:        lst_insertafter
* Parameters:    l        - List to insert node into
*                node    - Pointer to user space of node to insert
*                after    - Pointer to user space of node to insert node after
*
* Description:    Inserts a new node into the list after the node 'after'. To
*                insert a new node at the beginning of the list, user the
*                macro DLST_HEAD in place of 'after'. ie:
*
*                    dlst_insertafter(mylist,node,DLST_HEAD(mylist));
*
****************************************************************************/
{
    DLST_BUCKET    *n = DLST_HEADER(node),*a = DLST_HEADER(after);

    n->next = a->next;
    a->next = n;
    n->prev = a;
    n->next->prev = n;
    l->count++;
}

PUBLIC void *dlst_deletenext(DLIST *l,void *node)
/****************************************************************************
*
* Function:        lst_deletenext
* Parameters:    l        - List to delete node from.
*                node    - Node to delete the next node from
* Returns:        Pointer to the deleted node's userspace.
*
* Description:    Removes the node AFTER 'node' from the list l.
*
****************************************************************************/
{
    DLST_BUCKET    *n = DLST_HEADER(node);

    node = DLST_USERSPACE(n->next);
    n->next->next->prev = n;
    n->next = n->next->next;
    l->count--;
    return node;
}

PUBLIC void *dlst_first(DLIST *l)
/****************************************************************************
*
* Function:        dlst_first
* Parameters:    l        - List to obtain first node from
* Returns:        Pointer to first node in list, NULL if list is empty.
*
* Description:    Returns a pointer to the user space of the first node in
*                the list. If the list is empty, we return NULL.
*
****************************************************************************/
{
    DLST_BUCKET    *n;

    n = l->head->next;
    return (n == l->z ? NULL : DLST_USERSPACE(n));
}

PUBLIC void *dlst_last(DLIST *l)
/****************************************************************************
*
* Function:        dlst_last
* Parameters:    l    - List to obtain last node from
* Returns:        Pointer to last node in list, NULL if list is empty.
*
* Description:    Returns a pointer to the user space of the last node in
*                the list. If the list is empty, we return NULL.
*
****************************************************************************/
{
    DLST_BUCKET    *n;

    n = l->z->prev;
    return (n == l->head ? NULL : DLST_USERSPACE(n));
}

PUBLIC void *dlst_next(void *prev)
/****************************************************************************
*
* Function:        dlst_next
* Parameters:    prev    - Previous node in list to obtain next node from
* Returns:        Pointer to the next node in the list, NULL at end of list.
*
* Description:    Returns a pointer to the user space of the next node in the
*                list given a pointer to the user space of the previous node.
*                If we have reached the end of the list, we return NULL. The
*                end of the list is detected when the next pointer of a node
*                points back to itself, as does the dummy last node's next
*                pointer. This enables us to detect the end of the list
*                without needed access to the list data structure itself.
*
*                NOTE:    We do no checking to ensure that 'prev' is NOT a
*                        NULL pointer.
*
****************************************************************************/
{
    DLST_BUCKET    *n = DLST_HEADER(prev);

    n = n->next;
    return (n == n->next ? NULL : DLST_USERSPACE(n));
}

PUBLIC void *dlst_prev(void *next)
/****************************************************************************
*
* Function:        dlst_prev
* Parameters:    next    - Next node in list to obtain previous node from
* Returns:        Pointer to the previous node in the list, NULL at start list.
*
* Description:    Returns a pointer to the user space of the prev node in the
*                list given a pointer to the user space of the next node.
*                If we have reached the start of the list, we return NULL. The
*                start of the list is detected when the prev pointer of a node
*                points back to itself, as does the dummy head node's prev
*                pointer. This enables us to detect the start of the list
*                without needed access to the list data structure itself.
*
*                NOTE:    We do no checking to ensure that 'next' is NOT a
*                        NULL pointer.
*
****************************************************************************/
{
    DLST_BUCKET    *n = DLST_HEADER(next);

    n = n->prev;
    return (n == n->prev ? NULL : DLST_USERSPACE(n));
}

/* Static globals required by merge()    */

static DLST_BUCKET    *z;
static int             (*cmp)(void*,void*);

PRIVATE DLST_BUCKET *merge(DLST_BUCKET *a,DLST_BUCKET *b,DLST_BUCKET **end)
/****************************************************************************
*
* Function:        merge
* Parameters:    a,b        - Sublist's to merge
* Returns:        Pointer to the merged sublists.
*
* Description:    Merges two sorted lists of nodes together into a single
*                sorted list.
*
****************************************************************************/
{
    DLST_BUCKET    *c;

    /* Go through the lists, merging them together in sorted order    */

    c = z;
    while (a != z && b != z) {
        if ((*cmp)(DLST_USERSPACE(a),DLST_USERSPACE(b)) <= 0) {
            c->next = a; c = a; a = a->next;
            }
        else {
            c->next = b; c = b; b = b->next;
            }
        };

    /* If one of the lists is not exhausted, then re-attach it to the end
     * of the newly merged list
     */

    if (a != z) c->next = a;
    if (b != z) c->next = b;

    /* Set *end to point to the end of the newly merged list    */

    while (c->next != z) c = c->next;
    *end = c;

    /* Determine the start of the merged lists, and reset z to point to
     * itself
     */

    c = z->next; z->next = z;
    return c;
}

PUBLIC void dlst_mergesort(DLIST *l,int (*cmp_func)(void*,void*))
/****************************************************************************
*
* Function:        dlst_mergesort
* Parameters:    l            - List to merge sort
*                cmp_func    - Function to compare two user spaces
*
* Description:    Mergesort's all the nodes in the list. 'cmp' must point to
*                a comparison function that can compare the user spaces of
*                two different nodes. 'cmp' should work the same as
*                strcmp(), in terms of the values it returns. Rather than
*                waste processing time keeping the previous pointers up to
*                date while performing the mergesort, we simply run through
*                the list at the end of the sort to fix the previous pointers.
*
****************************************************************************/
{
    int            i,N;
    DLST_BUCKET    *a,*b;        /* Pointers to sublists to merge            */
    DLST_BUCKET    *c;            /* Pointer to end of sorted sublists        */
    DLST_BUCKET    *head;        /* Pointer to dummy head node for list        */
    DLST_BUCKET    *todo;        /* Pointer to sublists yet to be sorted        */
    DLST_BUCKET    *t;            /* Temporary                                */

    /* Set up globals required by merge() and pointer to head    */

    z = l->z; cmp = cmp_func; head = l->head;

    for (N = 1,a = z; a != head->next; N = N + N) {
        todo = head->next; c = head;
        while (todo != z) {

            /* Build first sublist to be merged, and splice from main list
             */

            a = t = todo;
            for (i = 1; i < N; i++) t = t->next;
            b = t->next; t->next = z; t = b;

            /* Build second sublist to be merged and splice from main list
             */

            for (i = 1; i < N; i++) t = t->next;
            todo = t->next; t->next = z;

            /* Merge the two sublists created, and set 'c' to point to the
             * end of the newly merged sublists.
             */

            c->next = merge(a,b,&t); c = t;
            }
        }

    /* Fix the previous pointers for the list    */

    a = b = l->head;
    b = b->next;
    while (1) {
        b->prev = a;
        if (b == z)
            break;
        a = a->next;
        b = b->next;
        }
}