aga: Depth first search

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

ccan/aga/_info

@@ -31,12 +31,14 @@ int main(int argc, char *argv[])
 	if (strcmp(argv[1], "depends") == 0) {
 		printf("ccan/build_assert\n");
 		printf("ccan/check_type\n");
+		printf("ccan/lstack\n");
 		return 0;
 	}
 
 	if (strcmp(argv[1], "testdepends") == 0) {
 		printf("ccan/container_of\n");
 		printf("ccan/ptrint\n");
+		printf("ccan/array_size\n");
 		return 0;
 	}
 

ccan/aga/aga.h

@@ -113,6 +113,7 @@
 
 #include <ccan/build_assert/build_assert.h>
 #include <ccan/check_type/check_type.h>
+#include <ccan/lstack/lstack.h>
 
 struct aga_graph;
 struct aga_node;
@@ -140,7 +141,10 @@ typedef int (*aga_edge_info_fn)(const struct aga_graph *g,
 struct aga_node {
 	int sequence;
 	union {
-		/* Per-algorithm state here */
+		struct {
+			struct lstack_link parent;
+			const void *edge;
+		} dfs;
 	} u;
 };
 
@@ -202,4 +206,14 @@ int aga_edge_info(const struct aga_graph *g, const struct aga_node *n,
 	     (_e) = aga_next_edge((_g), (_n), (_e)))			\
 		if ((_ei).to)
 
+/*
+ * Depth first search
+ */
+
+int aga_dfs_start(struct aga_graph *g);
+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; )
+
 #endif /* CCAN_AGA_H */

ccan/aga/dfs.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"
+
+/*
+ * Depth first search
+ */
+
+static bool dfs_push(struct aga_graph *g, struct lstack *stack,
+		     struct aga_node *n)
+{
+	if (!aga_update_node(g, n))
+		return false;
+
+	lstack_push(stack, n, u.dfs.parent);
+	n->u.dfs.edge = aga_first_edge(g, n);
+	return true;
+}
+
+static void dfs_pop(struct lstack *stack)
+{
+	lstack_pop(stack, struct aga_node, u.dfs.parent);
+}
+
+static struct aga_node *dfs_top(struct lstack *stack)
+{
+	return lstack_top(stack, struct aga_node, u.dfs.parent);
+}
+
+int aga_dfs_start(struct aga_graph *g)
+{
+	int rc;
+
+	rc = aga_start(g);
+	if (rc < 0)
+		return rc;
+
+	return 0;
+}
+
+struct aga_node *aga_dfs_explore(struct aga_graph *g, struct aga_node *n)
+{
+	LSTACK(stack);
+
+	if (!aga_check_state(g))
+		return NULL;
+
+	if (!n)
+		return NULL;
+
+	if (dfs_push(g, &stack, n))
+		return n;
+
+	lstack_init_from_top(&stack, n, u.dfs.parent);
+
+	while ((n = dfs_top(&stack))) {
+		const void *e = n->u.dfs.edge;
+		int err;
+		struct aga_edge_info ei;
+
+		if (!e) {
+			/* out of edges, back up */
+			dfs_pop(&stack);
+			continue;
+		}
+
+		n->u.dfs.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 (!dfs_push(g, &stack, ei.to)) {
+			/* already visited node */
+			continue;
+		}
+
+		return ei.to;
+	}
+	
+	return NULL;
+}

ccan/aga/test/api-dfs.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_dfs_partial(sg, first, ...)				\
+	do {								\
+		int cmp[] = { __VA_ARGS__ };				\
+		bool stillok = true;					\
+		struct aga_node *node;					\
+		int i = 0;						\
+		aga_dfs(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_dfs(sg, first, ...)					\
+	do {								\
+		ok1(aga_dfs_start(&(sg)->g) == 0);			\
+		test_dfs_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_dfs(&tg.sg, 1, 1);
+
+	parallel_graph_init(&pg, 3);
+	test_dfs(&pg.sg, 1, 1, 2);
+
+	full_graph_init(&fg, 5);
+	test_dfs(&fg.sg, 1, 1, 2, 3, 4, 5);
+	test_dfs(&fg.sg, 3, 3, 1, 2, 4, 5);
+
+	chain_graph_init(&cg, 8);
+	test_dfs(&cg.fg.sg, 1, 1, 2, 3, 4, 5, 6, 7, 8);
+	test_dfs(&cg.fg.sg, 8, 8, 7, 6, 5, 4, 3, 2, 1);
+	test_dfs(&cg.fg.sg, 5, 5, 4, 3, 2, 1, 6, 7, 8);
+
+	grid_graph_init(&gg1, 3, 3, true, true, false, false);
+	test_dfs(&gg1.sg, 1, 1, 2, 3, 6, 9, 5, 8, 4, 7);
+	test_dfs(&gg1.sg, 5, 5, 6, 9, 8);
+	test_dfs(&gg1.sg, 9, 9);
+
+	grid_graph_init(&gg2, 3, 3, true, true, true, true);
+	test_dfs(&gg2.sg, 1, 1, 2, 3, 6, 9, 8, 7, 4, 5);
+	test_dfs(&gg2.sg, 5, 5, 6, 9, 8, 7, 4, 1, 2, 3);
+	test_dfs(&gg2.sg, 9, 9, 8, 7, 4, 5, 6, 3, 2, 1);
+
+	error_graph_init(&eg);
+	test_dfs(&eg.sg, 1, 1, 2);
+	ok(aga_dfs_start(&eg.sg.g) == 0, "started error traversal");
+	node = aga_dfs_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_dfs_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_dfs_explore(&eg.sg.g, node) == NULL);
+	ok1(aga_error(&eg.sg.g) == -1);
+	ok1(aga_dfs_explore(&eg.sg.g, node) == NULL);
+	aga_finish(&eg.sg.g);
+	test_dfs(&eg.sg, 1, 1, 2);
+
+	traversal1_graph_init(&t1g);
+	test_dfs(&t1g.sg, 1, 1, 2, 4, 5, 3, 6);
+	test_dfs(&t1g.sg, 9, 9, 8, 6, 5, 7, 4);
+
+	ok1(aga_dfs_start(&t1g.sg.g) == 0);
+	test_dfs_partial(&t1g.sg, 1, 1, 2, 4, 5, 3, 6);
+	test_dfs_partial(&t1g.sg, 9, 9, 8, 7);
+	aga_finish(&t1g.sg.g);
+
+	ok1(aga_dfs_start(&t1g.sg.g) == 0);
+	test_dfs_partial(&t1g.sg, 9, 9, 8, 6, 5, 7, 4);
+	test_dfs_partial(&t1g.sg, 1, 1, 2, 3);
+	aga_finish(&t1g.sg.g);
+
+	return exit_status();
+}