ast: implement post-order ast traversal

bshell/ast/ast.c

@@ -26,7 +26,7 @@ extern struct ast_node_definition if_ast_node;
 extern struct ast_node_definition if_branch_ast_node;
 extern struct ast_node_definition op_ast_node;
 
-static const struct ast_node_definition *ast_node_defintions[] = {
+static const struct ast_node_definition *ast_node_definitions[] = {
 	[AST_NULL] = &null_ast_node,
 	[AST_INT] = &int_ast_node,
 	[AST_DOUBLE] = &double_ast_node,
@@ -47,14 +47,14 @@ static const struct ast_node_definition *ast_node_defintions[] = {
 	[AST_HASHTABLE_ITEM] = &hashtable_item_ast_node,
 	[AST_OP] = &op_ast_node,
 };
-static const size_t nr_ast_node_definitions
+static const size_t nr_ast_node_definitions = sizeof ast_node_definitions
-	= sizeof ast_node_defintions / sizeof ast_node_defintions[0];
+                                            / sizeof ast_node_definitions[0];
 
 struct ast_node *ast_node_create(enum ast_node_type type)
 {
 	assert(type < nr_ast_node_definitions);
 
-	const struct ast_node_definition *def = ast_node_defintions[type];
+	const struct ast_node_definition *def = ast_node_definitions[type];
 	struct ast_node *out = malloc(def->def_node_size);
 	if (!out) {
 		return NULL;
@@ -80,8 +80,8 @@ void ast_node_destroy(struct ast_node *node)
 			break;
 		}
 
-		const struct ast_node_definition *def
+		const struct ast_node_definition *def = ast_node_definitions
-			= ast_node_defintions[node->n_type];
+			[node->n_type];
 
 		if (def->def_cleanup) {
 			def->def_cleanup(node);
@@ -92,15 +92,10 @@ void ast_node_destroy(struct ast_node *node)
 	}
 }
 
-void ast_node_iterate(struct ast_node *node, struct ast_iterator *it)
-{
-	ast_iterator_enqueue(it, node);
-}
-
 void ast_node_to_string(const struct ast_node *node, fx_bstr *out)
 {
-	const struct ast_node_definition *def
+	const struct ast_node_definition *def = ast_node_definitions
-		= ast_node_defintions[node->n_type];
+		[node->n_type];
 	if (def->def_to_string) {
 		def->def_to_string(node, out);
 	}
@@ -158,8 +153,8 @@ struct ast_node *ast_iterator_dequeue(struct ast_iterator *it)
 	}
 
 	struct ast_node *node = fx_unbox(struct ast_node, cur, n_it.e_entry);
-	const struct ast_node_definition *def
+	const struct ast_node_definition *def = ast_node_definitions
-		= ast_node_defintions[node->n_type];
+		[node->n_type];
 
 	it->it_insert_after = cur;
 	if (def->def_collect_children) {
@@ -176,8 +171,10 @@ void ast_iterator_enqueue(struct ast_iterator *it, struct ast_node *node)
 
 	fx_queue_entry *cur = fx_queue_first(&it->it_queue);
 	if (cur) {
-		struct ast_node *cur_node
+		struct ast_node *cur_node = fx_unbox(
-			= fx_unbox(struct ast_node, cur, n_it.e_entry);
+			struct ast_node,
+			cur,
+			n_it.e_entry);
 		new_depth = cur_node->n_it.e_depth + 1;
 	}
 
@@ -194,3 +191,80 @@ void ast_iterator_enqueue(struct ast_iterator *it, struct ast_node *node)
 		it->it_insert_after);
 	it->it_insert_after = &node->n_it.e_entry;
 }
+
+enum bshell_status ast_node_iterate(
+	struct ast_node *node,
+	struct ast_iterator *it,
+	ast_iterator_callback callback,
+	void *arg)
+{
+	fx_queue_push_back(&it->it_queue, &node->n_it.e_entry);
+	node->n_it.e_depth = 0;
+
+	fx_queue_entry *entry = fx_queue_first(&it->it_queue);
+
+	while (entry) {
+		struct ast_iterator_entry *it_entry = fx_unbox(
+			struct ast_iterator_entry,
+			entry,
+			e_entry);
+		node = fx_unbox(struct ast_node, it_entry, n_it);
+
+		if (!node) {
+			/* this should never happen. */
+			return BSHELL_ERR_INTERNAL_FAILURE;
+		}
+
+		struct ast_iterate_result result = callback(
+			node,
+			AST_ITERATION_PRE,
+			it,
+			arg);
+		if (result.r_status != BSHELL_SUCCESS
+		    || result.r_flags & AST_ITERATE_STOP) {
+			return result.r_status;
+		}
+
+		const struct ast_node_definition *type = ast_node_definitions
+			[node->n_type];
+		if (type->def_collect_children
+		    && result.r_flags & AST_ITERATE_ADD_CHILDREN) {
+			it->it_insert_after = entry;
+			type->def_collect_children(node, it);
+		}
+
+		if (!(result.r_flags & AST_ITERATE_REPEAT)) {
+			entry = fx_queue_next(entry);
+		}
+	}
+
+	while (!fx_queue_empty(&it->it_queue)) {
+		fx_queue_entry *entry = fx_queue_last(&it->it_queue);
+		if (!entry) {
+			break;
+		}
+
+		node = fx_unbox(struct ast_node, entry, n_it);
+
+		if (!node) {
+			/* this should never happen. */
+			return BSHELL_ERR_INTERNAL_FAILURE;
+		}
+
+		struct ast_iterate_result result = callback(
+			node,
+			AST_ITERATION_POST,
+			it,
+			arg);
+		if (result.r_status != BSHELL_SUCCESS
+		    || result.r_flags & AST_ITERATE_STOP) {
+			return result.r_status;
+		}
+
+		if (!(result.r_flags & AST_ITERATE_REPEAT)) {
+			fx_queue_pop_back(&it->it_queue);
+		}
+	}
+
+	return BSHELL_SUCCESS;
+}

bshell/ast/ast.h

@@ -8,6 +8,12 @@
 
 struct lex_token;
 
+#define AST_ITERATE_OK(flags)                                                  \
+	((struct ast_iterate_result) {.r_status = BSHELL_SUCCESS,              \
+	                              .r_flags = (flags)})
+#define AST_ITERATE_ERR(status)                                                \
+	((struct ast_iterate_result) {.r_status = (status)})
+
 enum ast_node_type {
 	AST_NONE = 0x00u,
 	AST_NULL,
@@ -170,6 +176,27 @@ struct ast_iterator {
 	fx_queue_entry *it_insert_after;
 };
 
+struct ast_iterate_result {
+	enum bshell_status r_status;
+	enum {
+		AST_ITERATE_CONTINUE = 0x00u,
+		AST_ITERATE_STOP = 0x01u,
+		AST_ITERATE_ADD_CHILDREN = 0x02u,
+		AST_ITERATE_REPEAT = 0x04u,
+	} r_flags;
+};
+
+enum ast_iteration_type {
+	AST_ITERATION_PRE,
+	AST_ITERATION_POST,
+};
+
+typedef struct ast_iterate_result (*ast_iterator_callback)(
+	struct ast_node *,
+	enum ast_iteration_type,
+	struct ast_iterator *,
+	void *);
+
 struct ast_node_definition {
 	enum ast_node_type def_id;
 	size_t def_node_size;
@@ -182,8 +209,12 @@ struct ast_node_definition {
 
 extern struct ast_node *ast_node_create(enum ast_node_type type);
 extern void ast_node_destroy(struct ast_node *node);
-extern void ast_node_iterate(struct ast_node *node, struct ast_iterator *it);
 extern void ast_node_to_string(const struct ast_node *node, fx_bstr *out);
+extern enum bshell_status ast_node_iterate(
+	struct ast_node *node,
+	struct ast_iterator *it,
+	ast_iterator_callback callback,
+	void *arg);
 
 extern const char *ast_node_type_to_string(enum ast_node_type type);