/* $XFree86: xc/programs/Xserver/hw/xfree86/loader/loadext.c,v 1.6 2000/02/08 17:19:19 dawes Exp $ */

/* Copyright 2000 by The XFree86 Project, Inc */

/* Maybe this file belongs elsewhere? */

#define LOADERDECLARATIONS
#include "loaderProcs.h"
#include "misc.h"
#include "xf86.h"

ExtensionModule *ExtensionModuleList = NULL;
static int numExtensionModules = 0;


static ExtensionModule *
NewExtensionModule(void)
{
	ExtensionModule *save = ExtensionModuleList;
	int n;

	/* Sanity check */
	if (!ExtensionModuleList)
		numExtensionModules = 0;

	n = numExtensionModules + 1;
	ExtensionModuleList = xrealloc(ExtensionModuleList,
				       (n + 1) * sizeof(ExtensionModule));
	if (ExtensionModuleList == NULL) {
		ExtensionModuleList = save;
		return NULL;
	} else {
		numExtensionModules++;
		ExtensionModuleList[numExtensionModules].name = NULL;
		return ExtensionModuleList + (numExtensionModules - 1);
	}
}

void
LoadExtension(ExtensionModule *e, Bool builtin)
{
	ExtensionModule *newext;

	if (e == NULL || e->name == NULL)
		return;

	if (!(newext = NewExtensionModule()))
		return;

	if (builtin)
		xf86MsgVerb(X_INFO, 2, "Initializing built-in extension %s\n",
				e->name);
	else
		xf86MsgVerb(X_INFO, 2, "Loading extension %s\n", e->name);

	newext->name = e->name;
	newext->initFunc = e->initFunc;
	newext->disablePtr = e->disablePtr;
	newext->setupFunc = e->setupFunc;
	newext->initDependencies = e->initDependencies;

	if (e->setupFunc != NULL)
		e->setupFunc();
}


/*
 * Sort ExtensionModuleList according to the initialisation order
 * dependencies.  The code for this is taken from BSD's tsort,
 * and carries the following copyright/license:
 *
 *
 * Copyright (c) 1989, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Michael Rendell of Memorial University of Newfoundland.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */


#define	NF_MARK		0x1		/* marker for cycle detection */
#define	NF_ACYCLIC	0x2		/* this node is cycle free */
#define	NF_NODEST	0x4		/* Unreachable */

typedef struct node_str NODE;
struct node_str {
	NODE **n_prevp;			/* pointer to previous node's n_next */
	NODE *n_next;			/* next node in graph */
	NODE **n_arcs;			/* array of arcs to other nodes */
	int n_narcs;			/* number of arcs in n_arcs[] */
	int n_arcsize;			/* size of n_arcs[] array */
	int n_refcnt;			/* # of arcs pointing to this node */
	int n_flags;			/* NF_* */
	const char *n_name;		/* name of this node */
};

static NODE *graph = NULL, **cycle_buf = NULL, **longest_cycle = NULL;
static int longest = 0;
static NODE *sorted = NULL, *last = NULL;

/* Find a node in the graph (insert if not found) and return a pointer to it. */
static NODE *
get_node(const char *name)
{
	NODE *n;

	for (n = graph; n && n->n_name && strcmp(n->n_name, name); n = n->n_next)
		;
	if (n)
		return (n);

	n = xnfalloc(sizeof(NODE));

	n->n_narcs = 0;
	n->n_arcsize = 0;
	n->n_arcs = NULL;
	n->n_refcnt = 0;
	n->n_flags = 0;
	n->n_name = name;

	/* Add to linked list. */
	if ((n->n_next = graph) != NULL)
		graph->n_prevp = &n->n_next;
	n->n_prevp = &graph;
	graph = n;

	return (n);
}


/*
 * add an arc from node s1 to node s2 in the graph.  If s1 or s2 are not in
 * the graph, then add them.
 */
static void
add_arc(const char *s1, const char *s2)
{
	NODE *n1;
	NODE *n2;
	int bsize, i;

	n1 = get_node(s1);

	if (!strcmp(s1, s2))
		return;

	n2 = get_node(s2);

	/*
	 * Check if this arc is already here.
	 */
	for (i = 0; i < n1->n_narcs; i++)
		if (n1->n_arcs[i] == n2)
			return;
	/*
	 * Add it.
	 */
	if (n1->n_narcs == n1->n_arcsize) {
		if (!n1->n_arcsize)
			n1->n_arcsize = 10;
		bsize = n1->n_arcsize * sizeof(*n1->n_arcs) * 2;
		n1->n_arcs = xnfrealloc(n1->n_arcs, bsize);
		n1->n_arcsize = bsize / sizeof(*n1->n_arcs);
	}
	n1->n_arcs[n1->n_narcs++] = n2;
	++n2->n_refcnt;
}

/*
 * Clear the NODEST flag from all nodes.
 */
static void
clear_cycle(void)
{
	NODE *n;

	for (n = graph; n != NULL; n = n->n_next)
		n->n_flags &= ~NF_NODEST;
}

/* print node and remove from graph (does not actually free node) */
static void
remove_node(NODE *n)
{
	NODE **np;
	NODE *newnode;
	int i;

#ifdef DEBUG
	ErrorF("%s\n", n->n_name);
#endif
	newnode = xnfalloc(sizeof(NODE));
	memcpy(newnode, n, sizeof(NODE));
	if (last)
		last->n_next = newnode;
	else
		sorted = newnode;
	last = newnode;
	newnode->n_next = NULL;

	for (np = n->n_arcs, i = n->n_narcs; --i >= 0; np++)
		--(*np)->n_refcnt;
	n->n_narcs = 0;
	*n->n_prevp = n->n_next;
	if (n->n_next)
		n->n_next->n_prevp = n->n_prevp;
}


static void
free_nodes(NODE *nodelist)
{
	NODE *n, *nextnode;

	for (n = nodelist; n;) {
		nextnode = n->n_next;
		xfree(n);
		n = nextnode;
	}
}


/* look for the longest? cycle from node from to node to. */
static int
find_cycle(NODE *from, NODE *to, int longest_len, int depth)
{
	NODE **np;
	int i, len;

	/*
	 * avoid infinite loops and ignore portions of the graph known
	 * to be acyclic
	 */
	if (from->n_flags & (NF_NODEST|NF_MARK|NF_ACYCLIC))
		return (0);
	from->n_flags |= NF_MARK;

	for (np = from->n_arcs, i = from->n_narcs; --i >= 0; np++) {
		cycle_buf[depth] = *np;
		if (*np == to) {
			if (depth + 1 > longest_len) {
				longest_len = depth + 1;
				memcpy((char *)longest_cycle,
				    (char *)cycle_buf,
				    longest_len * sizeof(NODE *));
			}
		} else {
			if ((*np)->n_flags & (NF_MARK|NF_ACYCLIC|NF_NODEST))
				continue;
			len = find_cycle(*np, to, longest_len, depth + 1);

#ifdef DEBUG
			ErrorF("%*s %s->%s %d\n", depth, "",
			    from->n_name, to->n_name, len);
#endif

			if (len == 0)
				(*np)->n_flags |= NF_NODEST;

			if (len > longest_len)
				longest_len = len;

			if (len > 0 && !longest)
				break;
		}
	}
	from->n_flags &= ~NF_MARK;
	return (longest_len);
}


/* do topological sort on graph */
static void
tsort(void)
{
	NODE *n, *next;
	int cnt, i;

	while (graph != NULL) {
		/*
		 * Keep getting rid of simple cases until there are none left,
		 * if there are any nodes still in the graph, then there is
		 * a cycle in it.
		 */
		do {
			for (cnt = 0, n = graph; n != NULL; n = next) {
				next = n->n_next;
				if (n->n_refcnt == 0) {
					remove_node(n);
					++cnt;
				}
			}
		} while (graph != NULL && cnt);

		if (graph == NULL)
			break;

		if (!cycle_buf) {
			/*
			 * Allocate space for two cycle logs - one to be used
			 * as scratch space, the other to save the longest
			 * cycle.
			 */
			for (cnt = 0, n = graph; n != NULL; n = n->n_next)
				++cnt;
			cycle_buf = xnfalloc(sizeof(NODE *) * cnt);
			longest_cycle = xnfalloc(sizeof(NODE *) * cnt);
			if (cycle_buf == NULL || longest_cycle == NULL)
				return;
		}
		for (n = graph; n != NULL; n = n->n_next)
			if (!(n->n_flags & NF_ACYCLIC)) {
				if ((cnt = find_cycle(n, n, 0, 0))) {
					ErrorF("tsort: cycle in data");
					for (i = 0; i < cnt; i++)
						ErrorF("%s",
						    longest_cycle[i]->n_name);
					remove_node(n);
					clear_cycle();
					break;
				} else {
					/* to avoid further checks */
					n->n_flags  |= NF_ACYCLIC;
					clear_cycle();
				}
			}

		if (n == NULL)
			ErrorF("tsort: internal error -- could not find cycle");
	}
	if (cycle_buf)
		xfree(cycle_buf);
	if (longest_cycle)
		xfree(longest_cycle);
	if (graph)
		free_nodes(graph);
}

void
LoaderSortExtensions()
{
	int i, j;
	ExtensionModule *ext, *newList;
	NODE *node;

	graph = NULL;
	longest = 0;
	sorted = NULL;
	last = NULL;
	cycle_buf = NULL;
	longest_cycle = NULL;
	
	/*
	 * Parse list and build the graph.  Enter them in reverse order
	 * because tsort() will reverse those that have no depedencies.
	 */
	for (i = numExtensionModules - 1; i >= 0; i--) {
		ext = &ExtensionModuleList[i];
		add_arc(ext->name, ext->name);
#ifdef DEBUG
		ErrorF("Extension %s:\n", ext->name);
#endif
		if (ext->initDependencies)
			for (j = 0; ext->initDependencies[j]; j++) {
				add_arc(ext->initDependencies[j], ext->name);
#ifdef DEBUG
				ErrorF("\t%s\n", ext->initDependencies[j]);
#endif
		}
	}
	tsort();
	newList = xnfalloc((numExtensionModules + 1) * sizeof(ExtensionModule));
	i = 0;
	for (node = sorted; node; node = node->n_next) {
		for (j = 0; j < numExtensionModules; j++)
			if (!strcmp(node->n_name, ExtensionModuleList[j].name))
				break;
		if (j != numExtensionModules)
			newList[i++] = ExtensionModuleList[j];
	}
	if (sorted)
		free_nodes(sorted);
	newList[i].name = NULL;
	xfree(ExtensionModuleList);
	ExtensionModuleList = newList;
#ifdef DEBUG
	for (i = 0; ExtensionModuleList[i].name; i++)
		ErrorF("Extension %s\n", ExtensionModuleList[i].name);
#endif
}

