/*
Copyright (C) Magna Carta Software, Inc. 1991.  All Rights Reserved
C COMMUNICATIONS TOOLKIT
LL.C -- Routines for handling linked lists of the form:
struct mclink {
    struct mclink   *next;
    struct mclink   *prev;
    ...
};
Note the ordering of 'next' and 'prev'. The 'mc' refers to 'Magna Carta'
and exists solely to prevent name conflicts with your other code.
Note: We call a function called 'memfree()' here. If you use these these
routines outside CCT, just '#define memfree(a) free(a)'
*/

#include <compat.h>
#include <stdio.h>
#include <stdlib.h>
#include <ll.h>

struct mclink {
    struct mclink   *next;
    struct mclink   *prev;
};

typedef struct mclink * MCLINK;


/*
LL_APPEND_LINK -- Append a node to a linked list.
Note that node->next is initialized to NULL;
Parameters:
    void *base  -- any node in the list;
    void *node  -- the address of the node to append;
Return Value:
    0           -- success;
    EOF         -- base is NULL;
*/
short ll_append_link(void *base, void *node)
{
    MCLINK p;

    if (base == NULL) return (EOF);
    else {
        p = base;
        while (p->next != NULL) p = p->next;
        p->next    = node;
        ((MCLINK) node)->prev = p;
        ((MCLINK) node)->next = NULL;
    }

    return (0);
}



/*
LL_COUNT_LINKS -- Count the number of links in a linked list, starting
at (but not including) the specified link.
Parameters:
    void *base -- starting link;
*/
unsigned long ll_count_links(void *base)
{
    MCLINK l = base;
    unsigned long i;

    for (i=0; l != NULL; i++) l = l->next;

    return (i);
}



/*
LL_DELETE_LINK -- Delete a node from a linked list in the structure "mclink".
The surrounding nodes are joined.
Parameters:
    void **base -- the address of the beginning of the list;
    void *node  -- the address of the node to append;
Return Value:
    0           -- success;
    EOF         -- attempt to delete node at beginning of list;
*/
short ll_delete_link(void *node)
{
    MCLINK p;

    if (node != NULL) {
        p = node;
        if (p->prev != NULL) {
            p->prev->next = p->next;
            if (p->next != NULL) p->next->prev = p->prev;
            memfree(p);
        }
        else return (EOF);
    }

    return (0);
}



/*
LL_DELETE_LIST -- Delete all node from the present one to the end of the
list.
Parameters:
    void **base -- the address of the beginning of the list;
    void *node  -- the address of the node to append;
Return Value:
    0           -- success;
    EOF         -- attempt to delete node at beginning of list;
*/
short ll_delete_list(void *node)
{
    MCLINK p;

    if (node != NULL) {
        p = node;
        if (p->next != NULL) do {
            p = p->next;
            memfree(p->prev);
        } while (p->next != NULL);
        memfree(p);
    }

    return (0);
}



/*
LL_FIND_LINK -- Search forward for a specific link.
Return value:
    *   -- address of link number "pos";
    NULL-- link not found;
*/
void * ll_find_link(void *base, void *node)
{
    MCLINK l = base;

    while (l != NULL && l != node) l = l->next;

    return ((l == node) ? l : NULL);
}



/*
LL_FIND_LINKNUM -- Search for link number "pos".
Return value:
    *   -- address of link number "pos";
    NULL-- link not found;
*/
void * ll_find_linknum(void *base, unsigned short pos)
{
    MCLINK l = base;
    unsigned short i = 0;

    if (l == NULL) return (NULL);
    while (l->next != NULL && i++ < pos) l = l->next;

    return ((i == pos) ? l : NULL);
}



/*
LL_INSERT_LINK -- Insert a node into a linked list after the designated node.
Parameters:
    void *base  -- any node in the list;
    void *node  -- the address of the node to append;
Return Value:
    0           -- success;
    EOF         -- base is NULL;
*/
short ll_insert_link(void *base, void *node)
{
    MCLINK p;

    if (base == NULL) return (EOF);
    else {
        p = base;
        ((MCLINK) node)->prev = p;
        ((MCLINK) node)->next = p->next;
        if (p->next != NULL) p->next->prev = node;
        p->next = node;
    }

    return (0);
}


#if 0
/*
LL_SEARCH_LINK -- Search forward for a specific link based on a condition
that applies to a link structure member.
When condition is met, condition() should return 0. Else it should
return a non-zero value.
Return value:
    *   -- address of link that meets "condition";
    NULL-- link not found;
*/
void * ll_search_link(void *base, short (*condition)(void *node, char *s))
{
    MCLINK l = base;

    while (l != NULL) {
        if ((*condition)(l, s)) return (l);
        l = l->next;
    }

    return (NULL);
}
#endif