/*
 * List Abstract Data Type
 * Copyright (C) 1997 Kaz Kylheku <kaz@ashi.footprints.net>
 *
 * Free Software License:
 *
 * All rights are reserved by the author, with the following exceptions:
 * Permission is granted to freely reproduce and distribute this software,
 * possibly in exchange for a fee, provided that this copyright notice appears
 * intact. Permission is also granted to adapt this software to produce
 * derivative works, as long as the modified versions carry this copyright
 * notice and additional notices stating that the work has been modified.
 * This source code may be translated into executable form and incorporated
 * into proprietary software; there is no requirement for such software to
 * contain a copyright notice related to this source.
 *
 */


#include <stdlib.h>
#include <stddef.h>
#include <assert.h>
#define LIST_IMPLEMENTATION
#include "list.h"

#define next list_next
#define prev list_prev
#define data list_data

#define pool list_pool
#define fre list_free
#define size list_size

#define nilnode list_nilnode
#define nodecount list_nodecount
#define maxcount list_maxcount

#define list_nil(L)		(&(L)->nilnode)
#define list_first_priv(L)	((L)->nilnode.next)
#define list_last_priv(L)	((L)->nilnode.prev)
#define lnode_next(N)		((N)->next)
#define lnode_prev(N)		((N)->prev)

/*
 * Initialize a list object supplied by the client such that it becomes a valid
 * empty list. If the list is to be ``unbounded'', the maxcount should be
 * specified as LISTCOUNT_T_MAX, or, alternately, as -1. The value zero
 * is not permitted.
 */

list_t *list_init(list_t *list, listcount_t maxcount)
{
    assert (maxcount != 0);
    list->nilnode.next = &list->nilnode;
    list->nilnode.prev = &list->nilnode;
    list->nodecount = 0;
    list->maxcount = maxcount;
    return list;
}

/*
 * Dynamically allocate a list object using malloc(), and initialize it so that
 * it is a valid empty list. If the list is to be ``unbounded'', the maxcount
 * should be specified as LISTCOUNT_T_MAX, or, alternately, as -1.
 */

list_t *list_create(listcount_t maxcount)
{
    list_t *new = malloc(sizeof *new);
    if (new) {
	assert (maxcount != 0);
	new->nilnode.next = &new->nilnode;
	new->nilnode.prev = &new->nilnode;
	new->nodecount = 0;
	new->maxcount = maxcount;
    }
    return new;
}

/*
 * Destroy a dynamically allocated list object.
 * The client must remove the nodes first.
 */

void list_destroy(list_t *list)
{
    assert (list_isempty(list));
    free(list);
}

/*
 * Free all of the nodes of a list. The list must contain only 
 * dynamically allocated nodes. After this call, the list
 * is empty.
 */

void list_destroy_nodes(list_t *list)
{
    lnode_t *lnode = list_first_priv(list), *nil = list_nil(list), *tmp;

    while (lnode != nil) {
	tmp = lnode->next;
	lnode->next = NULL;
	lnode->prev = NULL;
	lnode_destroy(lnode);
	lnode = tmp;
    }

    list_init(list, list->maxcount);
}

/*
 * Return all of the nodes of a list to a node pool. The nodes in
 * the list must all have come from the same pool.
 */

void list_return_nodes(list_t *list, lnodepool_t *pool)
{
    lnode_t *lnode = list_first_priv(list), *tmp, *nil = list_nil(list);

    while (lnode != nil) {
	tmp = lnode->next;
	lnode->next = NULL;
	lnode->prev = NULL;
	lnode_return(pool, lnode);
	lnode = tmp;
    }

    list_init(list, list->maxcount);
}

/*
 * Insert the node ``new'' into the list immediately after ``this'' node.
 */

void list_ins_after(list_t *list, lnode_t *new, lnode_t *this)
{
    lnode_t *that = this->next;

    assert (new != NULL);
    assert (!list_contains(list, new));
    assert (!lnode_is_in_a_list(new));
    assert (this == list_nil(list) || list_contains(list, this));
    assert (list->nodecount + 1 > list->nodecount);

    new->prev = this;
    new->next = that;
    that->prev = new;
    this->next = new;
    list->nodecount++;

    assert (list->nodecount <= list->maxcount);
}

/*
 * Insert the node ``new'' into the list immediately before ``this'' node.
 */

void list_ins_before(list_t *list, lnode_t *new, lnode_t *this)
{
    lnode_t *that = this->prev;

    assert (new != NULL);
    assert (!list_contains(list, new));
    assert (!lnode_is_in_a_list(new));
    assert (this == list_nil(list) || list_contains(list, this));
    assert (list->nodecount + 1 > list->nodecount);

    new->next = this;
    new->prev = that;
    that->next = new;
    this->prev = new;
    list->nodecount++;

    assert (list->nodecount <= list->maxcount);
}

/*
 * Delete the given node from the list.
 */

lnode_t *list_delete(list_t *list, lnode_t *del)
{
    lnode_t *next = del->next;
    lnode_t *prev = del->prev;

    assert (list_contains(list, del));

    prev->next = next;
    next->prev = prev;
    list->nodecount--;

    del->next = del->prev = NULL;

    return del;
}

/*
 * For each node in the list, execute the given function. The list,
 * current node and the given context pointer are passed on each
 * call to the function.
 */

void list_process(list_t *list, void *context,
	void (* function)(list_t *list, lnode_t *lnode, void *context))
{
    lnode_t *node = list_first_priv(list), *next, *nil = list_nil(list);

    while (node != nil) {
	/* check for callback function deleting	*/
	/* the next node from under us		*/
	assert (list_contains(list, node));
	next = node->next;
	function(list, node, context);
	node = next;
    }
}

/*
 * Dynamically allocate a list node and assign it the given piece of data.
 */

lnode_t *lnode_create(void *data)
{
    lnode_t *new = malloc(sizeof *new);
    if (new) {
	new->data = data;
	new->next = NULL;
	new->prev = NULL;
    }
    return new;
}

/*
 * Initialize a user-supplied lnode.
 */

lnode_t *lnode_init(lnode_t *lnode, void *data)
{
    lnode->data = data;
    lnode->next = NULL;
    lnode->prev = NULL;
    return lnode;
}

/*
 * Destroy a dynamically allocated node.
 */

void lnode_destroy(lnode_t *lnode)
{
    assert (!lnode_is_in_a_list(lnode));
    free(lnode);
}

/*
 * Initialize a node pool object to use a user-supplied set of nodes.
 * The ``nodes'' pointer refers to an array of lnode_t objects, containing
 * ``n'' elements.
 */

lnodepool_t *lnode_pool_init(lnodepool_t *pool, lnode_t *nodes, listcount_t n)
{
    listcount_t i;

    assert (n != 0);

    pool->pool = nodes;
    pool->fre = nodes;
    pool->size = n;
    for (i = 0; i < n - 1; i++) {
	nodes[i].next = nodes + i + 1;
    }
    nodes[i].next = NULL;
    nodes[i].prev = nodes;	/* to make sure node is marked ``on list'' */
    return pool;
}

/*
 * Create a dynamically allocated pool of n nodes.
 */

lnodepool_t *lnode_pool_create(listcount_t n)
{
    lnodepool_t *pool;
    lnode_t *nodes;

    assert (n != 0);

    pool = malloc(sizeof *pool);
    if (!pool)
	return NULL;
    nodes = malloc(n * sizeof *nodes);
    if (!nodes) {
	free(pool);
	return NULL;
    }
    lnode_pool_init(pool, nodes, n);
    return pool;
}

/*
 * Determine whether the given pool is from this pool.
 */

int lnode_pool_isfrom(lnodepool_t *pool, lnode_t *node)
{
    listcount_t i;

    /* this is carefully coded this way because ANSI C forbids pointers
       to different objects from being subtracted or compared other
       than for exact equality */

    for (i = 0; i < pool->size; i++) {
	if (pool->pool + i == node)
	    return 1;
    }
    return 0;
}

/*
 * Destroy a dynamically allocated pool of nodes.
 */

void lnode_pool_destroy(lnodepool_t *p)
{
    free(p->pool);
    free(p);
}

/*
 * Borrow a node from a node pool. Returns a null pointer if the pool
 * is exhausted. 
 */

lnode_t *lnode_borrow(lnodepool_t *pool, void *data)
{
    lnode_t *new = pool->fre;
    if (new) {
	pool->fre = new->next;
	new->data = data;
	new->next = NULL;
	new->prev = NULL;
    }
    return new;
}

/*
 * Return a node to a node pool. A node must be returned to the pool
 * from which it came.
 */

void lnode_return(lnodepool_t *pool, lnode_t *node)
{
    assert (lnode_pool_isfrom(pool, node));
    assert (!lnode_is_in_a_list(node));

    node->next = pool->fre;
    node->prev = node;
    pool->fre = node;
}

/*
 * Determine whether the given list contains the given node.
 * According to this function, a list does not contain its nilnode.
 */

int list_contains(list_t *list, lnode_t *node)
{
    lnode_t *n, *nil = list_nil(list);

    for (n = list_first_priv(list); n != nil; n = lnode_next(n)) {
	if (node == n)
	    return 1;
    }

    return 0;
}

/*
 * A more generalized variant of list_transfer. This one removes a
 * ``slice'' from the source list and appends it to the destination
 * list.
 */

void list_extract(list_t *dest, list_t *source, lnode_t *first, lnode_t *last)
{
    listcount_t moved = 1;

    assert (first == NULL || list_contains(source, first));
    assert (last == NULL || list_contains(source, last));

    if (first == NULL || last == NULL)
	return;

    /* adjust the destination list so that the slice is spliced out */

    first->prev->next = last->next;
    last->next->prev = first->prev;

    /* graft the splice at the end of the dest list */

    last->next = &dest->nilnode;
    first->prev = dest->nilnode.prev;
    dest->nilnode.prev->next = first;
    dest->nilnode.prev = last;

    while (first != last) {
	first = first->next;
	assert (first != list_nil(source));	/* oops, last before first! */
	moved++;
    }
    
    /* assert no overflows */
    assert (source->nodecount - moved <= source->nodecount);
    assert (dest->nodecount + moved >= dest->nodecount);

    /* assert no weirdness */
    assert (moved <= source->nodecount);

    source->nodecount -= moved;
    dest->nodecount += moved;

    /* assert list sanity */
    assert (list_verify(source));
    assert (list_verify(dest));
}


/*
 * Split off a trailing sequence of nodes from the source list and relocate
 * them to the tail of the destination list. The trailing sequence begins
 * with node ``first'' and terminates with the last node of the source
 * list. The nodes are added to the end of the new list in their original
 * order.
 */

void list_transfer(list_t *dest, list_t *source, lnode_t *first)
{
    listcount_t moved = 1;
    lnode_t *last;

    assert (first == NULL || list_contains(source, first));

    if (first == NULL)
	return;

    last = source->nilnode.prev;

    source->nilnode.prev = first->prev;
    first->prev->next = &source->nilnode;

    last->next = &dest->nilnode;
    first->prev = dest->nilnode.prev;
    dest->nilnode.prev->next = first;
    dest->nilnode.prev = last;

    while (first != last) {
	first = first->next;
	moved++;
    }
    
    /* assert no overflows */
    assert (source->nodecount - moved <= source->nodecount);
    assert (dest->nodecount + moved >= dest->nodecount);

    /* assert no weirdness */
    assert (moved <= source->nodecount);

    source->nodecount -= moved;
    dest->nodecount += moved;

    /* assert list sanity */
    assert (list_verify(source));
    assert (list_verify(dest));
}

void list_merge(list_t *dest, list_t *sour,
	int compare (const void *, const void *))
{
    lnode_t *dn, *sn, *tn;
    lnode_t *d_nil = list_nil(dest), *s_nil = list_nil(sour);

    /* Nothing to do if source and destination list are the same. */
    if (dest == sour)
	return;

    /* overflow check */
    assert (list_count(sour) + list_count(dest) >= list_count(sour));

    /* lists must be sorted */
    assert (list_is_sorted(sour, compare));
    assert (list_is_sorted(dest, compare));

    dn = list_first_priv(dest);
    sn = list_first_priv(sour);

    while (dn != d_nil && sn != s_nil) {
	if (compare(lnode_get(dn), lnode_get(sn)) >= 0) {
	    tn = lnode_next(sn);
	    list_delete(sour, sn);
	    list_ins_before(dest, sn, dn);
	    sn = tn;
	} else {
	    dn = lnode_next(dn);
	}
    }

    if (dn != d_nil)
	return;

    if (sn != s_nil)
	list_transfer(dest, sour, sn);
}

void list_sort(list_t *list, int compare(const void *, const void *))
{
    list_t extra;
    listcount_t middle;
    lnode_t *node;

    if (list_count(list) > 1) {
	middle = list_count(list) / 2;
	node = list_first_priv(list);

	list_init(&extra, list_count(list) - middle);

	while (middle--)
	    node = lnode_next(node);
	
	list_transfer(&extra, list, node);
	list_sort(list, compare);
	list_sort(&extra, compare);
	list_merge(list, &extra, compare);
    } 
    assert (list_is_sorted(list, compare));
}

lnode_t *list_find(list_t *list, const void *key, int compare(const void *, const void *))
{
    lnode_t *node;

    for (node = list_first_priv(list); node != list_nil(list); node = node->next) {
	if (compare(lnode_get(node), key) == 0)
	    return node;
    }
    
    return 0;
}


/*
 * Return 1 if the list is in sorted order, 0 otherwise
 */

int list_is_sorted(list_t *list, int compare(const void *, const void *))
{
    lnode_t *node, *next, *nil;

    next = nil = list_nil(list);
    node = list_first_priv(list);

    if (node != nil)
	next = lnode_next(node);

    for (; next != nil; node = next, next = lnode_next(next)) {
	if (compare(lnode_get(node), lnode_get(next)) > 0)
	    return 0;
    }

    return 1;
}

/*
 * Get rid of macro functions definitions so they don't interfere
 * with the actual definitions
 */

#undef list_isempty
#undef list_isfull
#undef lnode_pool_isempty
#undef list_append
#undef list_prepend
#undef list_first
#undef list_last
#undef list_next
#undef list_prev
#undef list_count
#undef list_del_first
#undef list_del_last
#undef lnode_put
#undef lnode_get

/*
 * Return 1 if the list is empty, 0 otherwise
 */

int list_isempty(list_t *list)
{
    return list->nodecount == 0;
}

/*
 * Return 1 if the list is full, 0 otherwise
 * Permitted only on bounded lists. 
 */

int list_isfull(list_t *list)
{
    return list->nodecount == list->maxcount;
}

/*
 * Check if the node pool is empty.
 */

int lnode_pool_isempty(lnodepool_t *pool)
{
    return (pool->fre == NULL);
}

/*
 * Add the given node at the end of the list
 */

void list_append(list_t *list, lnode_t *node)
{
    list_ins_before(list, node, &list->nilnode);
}

/*
 * Add the given node at the beginning of the list.
 */

void list_prepend(list_t *list, lnode_t *node)
{
    list_ins_after(list, node, &list->nilnode);
}

/*
 * Retrieve the first node of the list
 */

lnode_t *list_first(list_t *list)
{
    if (list->nilnode.next == &list->nilnode)
	return NULL;
    return list->nilnode.next;
}

/*
 * Retrieve the last node of the list
 */

lnode_t *list_last(list_t *list)
{
    if (list->nilnode.prev == &list->nilnode)
	return NULL;
    return list->nilnode.prev;
}

/*
 * Retrieve the count of nodes in the list
 */

listcount_t list_count(list_t *list)
{
    return list->nodecount;
}

/*
 * Remove the first node from the list and return it.
 */

lnode_t *list_del_first(list_t *list)
{
    return list_delete(list, list->nilnode.next);
}

/*
 * Remove the last node from the list and return it.
 */

lnode_t *list_del_last(list_t *list)
{
    return list_delete(list, list->nilnode.prev);
}


/*
 * Associate a data item with the given node.
 */

void lnode_put(lnode_t *lnode, void *data)
{
    lnode->data = data;
}

/*
 * Retrieve the data item associated with the node.
 */

void *lnode_get(lnode_t *lnode)
{
    return lnode->data;
}

/*
 * Retrieve the node's successor. If there is no successor, 
 * NULL is returned.
 */

lnode_t *list_next(list_t *list, lnode_t *lnode)
{
    assert (list_contains(list, lnode));

    if (lnode->next == list_nil(list))
	return NULL;
    return lnode->next;
}

/*
 * Retrieve the node's predecessor. See comment for lnode_next().
 */

lnode_t *list_prev(list_t *list, lnode_t *lnode)
{
    assert (list_contains(list, lnode));

    if (lnode->prev == list_nil(list))
	return NULL;
    return lnode->prev;
}

/*
 * Return 1 if the lnode is in some list, otherwise return 0.
 */

int lnode_is_in_a_list(lnode_t *lnode)
{
    return (lnode->next != NULL || lnode->prev != NULL);
}


int list_verify(list_t *list)
{
    lnode_t *node = list_first_priv(list), *nil = list_nil(list);
    listcount_t count = list_count(list);

    if (node->prev != nil)
	return 0;

    if (count > list->maxcount)
	return 0;

    while (node != nil && count--) {
	if (node->next->prev != node)
	    return 0;
	node = node->next;
    }

    if (count != 0 || node != nil)
	return 0;
    
    return 1;
}
