aga: Breadth first search

This implements breadth first search for the abstract graph algorithms
module.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

ccan/aga/_info

@@ -32,6 +32,7 @@ int main(int argc, char *argv[])
 		printf("ccan/build_assert\n");
 		printf("ccan/check_type\n");
 		printf("ccan/lstack\n");
+		printf("ccan/lqueue\n");
 		return 0;
 	}
 

ccan/aga/aga.h

@@ -107,13 +107,13 @@
  *
  * - Errors are cleared on aga_finish().
  */
-
 #include "config.h"
 #include <string.h>
 
 #include <ccan/build_assert/build_assert.h>
 #include <ccan/check_type/check_type.h>
 #include <ccan/lstack/lstack.h>
+#include <ccan/lqueue/lqueue.h>
 
 struct aga_graph;
 struct aga_node;
@@ -145,6 +145,10 @@ struct aga_node {
 			struct lstack_link parent;
 			const void *edge;
 		} dfs;
+		struct {
+			struct lqueue_link next;
+			const void *edge;
+		} bfs;
 	} u;
 };
 
@@ -216,4 +220,15 @@ struct aga_node *aga_dfs_explore(struct aga_graph *g, struct aga_node *n);
 #define aga_dfs(_n, _g, _start)					\
 	for ((_n) = (_start); ((_n) = aga_dfs_explore((_g), (_n))) != NULL; )
 
+
+/*
+ * Breadth first search
+ */
+
+int aga_bfs_start(struct aga_graph *g);
+struct aga_node *aga_bfs_explore(struct aga_graph *g, struct aga_node *n);
+
+#define aga_bfs(_n, _g, _start)					\
+	for ((_n) = (_start) ; ((_n) = aga_bfs_explore((_g), (_n))) != NULL; )
+
 #endif /* CCAN_AGA_H */

ccan/aga/bfs.c

+/* Licensed under LGPLv2+ - see LICENSE file for details */
+#include "config.h"
+
+#include <stdbool.h>
+#include <stdlib.h>
+#include <assert.h>
+
+#include <ccan/aga/aga.h>
+#include "private.h"
+
+/*
+ * Breadth first search
+ */
+
+static bool bfs_enqueue(struct aga_graph *g, struct lqueue *queue,
+			struct aga_node *n)
+{
+	if (!aga_update_node(g, n))
+		return false;
+
+	lqueue_enqueue(queue, n, u.bfs.next);
+	n->u.bfs.edge = aga_first_edge(g, n);
+	return true;
+}
+
+static struct aga_node *bfs_front(struct lqueue *queue)
+{
+	return lqueue_front(queue, struct aga_node, u.bfs.next);
+}
+
+static void bfs_dequeue(struct lqueue *queue)
+{
+	lqueue_dequeue(queue, struct aga_node, u.bfs.next);
+}
+
+int aga_bfs_start(struct aga_graph *g)
+{
+	int rc;
+
+	rc = aga_start(g);
+	if (rc < 0)
+		return rc;
+
+	return 0;
+}
+
+struct aga_node *aga_bfs_explore(struct aga_graph *g, struct aga_node *n)
+{
+	LQUEUE(queue);
+
+	if (!aga_check_state(g))
+		return NULL;
+
+	if (!n)
+		return NULL;
+ 
+	if (bfs_enqueue(g, &queue, n))
+		return n;
+
+	lqueue_init_from_back(&queue, n, u.bfs.next);
+
+	while ((n = bfs_front(&queue))) {
+		const void *e = n->u.bfs.edge;
+		int err;
+		struct aga_edge_info ei;
+
+		if (!e) {
+			/* out of edges, back up */
+			bfs_dequeue(&queue);
+			continue;
+		}
+
+		n->u.bfs.edge = aga_next_edge(g, n, e);
+
+		err = aga_edge_info(g, n, e, &ei);
+		if (err < 0) {
+			aga_fail(g, err);
+			return NULL;
+		}
+		if (!ei.to) {
+			/* missing edge */
+			continue;
+		}
+
+		if (!bfs_enqueue(g, &queue, ei.to)) {
+			/* already visited node */
+			continue;
+		}
+
+		return ei.to;
+	}
+	
+	return NULL;
+}

ccan/aga/test/api-bfs.c

+#include "config.h"
+
+#include <stddef.h>
+#include <assert.h>
+
+#include <ccan/tap/tap.h>
+#include <ccan/array_size/array_size.h>
+
+#include <ccan/aga/aga.h>
+
+#include "simple-graph.h"
+
+#define test_bfs_partial(sg, first, ...)				\
+	do {								\
+		int cmp[] = { __VA_ARGS__ };				\
+		bool stillok = true;					\
+		struct aga_node *node;					\
+		int i = 0;						\
+		aga_bfs(node, &(sg)->g, &(sg)->nodes[first]) {	\
+			int index = node - (sg)->nodes;			\
+			diag("Visited %d\n", index);			\
+			if (i >= ARRAY_SIZE(cmp) || (index != cmp[i]))	\
+				stillok = false;			\
+			i++;						\
+		}							\
+		ok1(stillok);						\
+	} while (0)
+
+#define test_bfs(sg, first, ...)					\
+	do {								\
+		ok1(aga_bfs_start(&(sg)->g) == 0);			\
+		test_bfs_partial(sg, first, __VA_ARGS__);		\
+		aga_finish(&(sg)->g);					\
+	} while (0)
+
+int main(void)
+{
+	struct trivial_graph tg;
+	struct parallel_graph pg;
+	struct full_graph fg;
+	struct chain_graph cg;
+	struct grid_graph gg1, gg2;
+	struct error_graph eg;
+	struct traversal1_graph t1g;
+	struct aga_node *node;
+	
+	plan_tests(2 * 13 + 10 + 10);
+
+	trivial_graph_init(&tg);
+	test_bfs(&tg.sg, 1, 1);
+
+	parallel_graph_init(&pg, 3);
+	test_bfs(&pg.sg, 1, 1, 2);
+
+	full_graph_init(&fg, 5);
+	test_bfs(&fg.sg, 1, 1, 2, 3, 4, 5);
+	test_bfs(&fg.sg, 3, 3, 1, 2, 4, 5);
+
+	chain_graph_init(&cg, 8);
+	test_bfs(&cg.fg.sg, 1, 1, 2, 3, 4, 5, 6, 7, 8);
+	test_bfs(&cg.fg.sg, 8, 8, 7, 6, 5, 4, 3, 2, 1);
+	test_bfs(&cg.fg.sg, 5, 5, 4, 6, 3, 7, 2, 8, 1);
+
+	grid_graph_init(&gg1, 3, 3, true, true, false, false);
+	test_bfs(&gg1.sg, 1, 1, 2, 4, 3, 5, 7, 6, 8, 9);
+	test_bfs(&gg1.sg, 5, 5, 6, 8, 9);
+	test_bfs(&gg1.sg, 9, 9);
+
+	grid_graph_init(&gg2, 3, 3, true, true, true, true);
+	test_bfs(&gg2.sg, 1, 1, 2, 4, 3, 5, 7, 6, 8, 9);
+	test_bfs(&gg2.sg, 5, 5, 6, 8, 4, 2, 9, 3, 7, 1);
+	test_bfs(&gg2.sg, 9, 9, 8, 6, 7, 5, 3, 4, 2, 1);
+
+	error_graph_init(&eg);
+	test_bfs(&eg.sg, 1, 1, 2);
+	ok(aga_bfs_start(&eg.sg.g) == 0, "started error traversal");
+	node = aga_bfs_explore(&eg.sg.g, &eg.sg.nodes[3]);
+	ok(node == &eg.sg.nodes[3], "Expected node #3 (%p), actually #%ld (%p)",
+	   &eg.sg.nodes[3], node - eg.sg.nodes, node);
+	node = aga_bfs_explore(&eg.sg.g, node);
+	ok(node == &eg.sg.nodes[4], "Expected node #4 (%p), actually #%ld (%p)",
+	   &eg.sg.nodes[4], node - eg.sg.nodes, node);
+	ok1(aga_bfs_explore(&eg.sg.g, node) == NULL);
+	ok1(aga_error(&eg.sg.g) == -1);
+	ok1(aga_bfs_explore(&eg.sg.g, node) == NULL);
+	aga_finish(&eg.sg.g);
+	test_bfs(&eg.sg, 1, 1, 2);
+
+	traversal1_graph_init(&t1g);
+	test_bfs(&t1g.sg, 1, 1, 2, 3, 4, 5, 6);
+	test_bfs(&t1g.sg, 9, 9, 8, 7, 6, 5, 4);
+
+	ok1(aga_bfs_start(&t1g.sg.g) == 0);
+	test_bfs_partial(&t1g.sg, 1, 1, 2, 3, 4, 5, 6);
+	test_bfs_partial(&t1g.sg, 9, 9, 8, 7);
+	aga_finish(&t1g.sg.g);
+
+	ok1(aga_bfs_start(&t1g.sg.g) == 0);
+	test_bfs_partial(&t1g.sg, 9, 9, 8, 7, 6, 5, 4);
+	test_bfs_partial(&t1g.sg, 1, 1, 2, 3);
+	aga_finish(&t1g.sg.g);
+
+	return exit_status();
+}