discover/grub2: Use subclass-style structs for AST

Use embedded 'struct grub2_statement' data to create a subclass-style
syntax tree of statements.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

2 files changed, 41 insertions, 39 deletions

diff --git a/discover/grub2/grub2.h b/discover/grub2/grub2.h
index cc817ff..0643a72 100644
--- a/discover/grub2/grub2.h
+++ b/discover/grub2/grub2.h
@@ -18,45 +18,43 @@ struct grub2_argv {
 	struct list		words;
 };
 
+struct grub2_statements {
+	struct list		list;
+};
+
+struct grub2_statement {
+	struct list_item	list;
+	enum {
+		STMT_TYPE_SIMPLE,
+		STMT_TYPE_MENUENTRY,
+		STMT_TYPE_IF,
+		STMT_TYPE_BLOCK,
+	} type;
+};
+
 struct grub2_statement_simple {
+	struct grub2_statement	st;
 	struct grub2_argv	*argv;
 };
 
 struct grub2_statement_menuentry {
+	struct grub2_statement	st;
 	struct grub2_argv	*argv;
 	struct grub2_statements	*statements;
 };
 
 struct grub2_statement_if {
+	struct grub2_statement	st;
 	struct grub2_statement	*condition;
 	struct grub2_statements	*true_case;
 	struct grub2_statements	*false_case;
 };
 
 struct grub2_statement_block {
+	struct grub2_statement	st;
 	struct grub2_statements	*statements;
 };
 
-struct grub2_statement {
-	struct list_item	list;
-	enum {
-		STMT_TYPE_SIMPLE,
-		STMT_TYPE_MENUENTRY,
-		STMT_TYPE_IF,
-		STMT_TYPE_BLOCK,
-	} type;
-	union {
-		struct grub2_statement_simple		simple;
-		struct grub2_statement_menuentry	menuentry;
-		struct grub2_statement_if		ifstmt;
-		struct grub2_statement_block		block;
-	};
-};
-
-struct grub2_statements {
-	struct list		list;
-};
-
 struct grub2_parser {
 	void			*scanner;
 	struct grub2_statements	*statements;
diff --git a/discover/grub2/parser-api.c b/discover/grub2/parser-api.c
index 37c88a2..d3bec3d 100644
--- a/discover/grub2/parser-api.c
+++ b/discover/grub2/parser-api.c
@@ -14,20 +14,22 @@ struct grub2_statements *create_statements(struct grub2_parser *parser)
 struct grub2_statement *create_statement_simple(struct grub2_parser *parser,
 		struct grub2_argv *argv)
 {
-	struct grub2_statement *stmt = talloc(parser, struct grub2_statement);
-	stmt->type = STMT_TYPE_SIMPLE;
-	stmt->simple.argv = argv;
-	return stmt;
+	struct grub2_statement_simple *stmt =
+		talloc(parser, struct grub2_statement_simple);
+	stmt->st.type = STMT_TYPE_SIMPLE;
+	stmt->argv = argv;
+	return &stmt->st;
 }
 
 struct grub2_statement *create_statement_menuentry(struct grub2_parser *parser,
 		struct grub2_argv *argv, struct grub2_statements *stmts)
 {
-	struct grub2_statement *stmt = talloc(parser, struct grub2_statement);
-	stmt->type = STMT_TYPE_MENUENTRY;
-	stmt->menuentry.argv = argv;
-	stmt->menuentry.statements = stmts;
-	return stmt;
+	struct grub2_statement_menuentry *stmt =
+		talloc(parser, struct grub2_statement_menuentry);
+	stmt->st.type = STMT_TYPE_MENUENTRY;
+	stmt->argv = argv;
+	stmt->statements = stmts;
+	return &stmt->st;
 }
 
 struct grub2_statement *create_statement_if(struct grub2_parser *parser,
@@ -35,21 +37,23 @@ struct grub2_statement *create_statement_if(struct grub2_parser *parser,
 		struct grub2_statements *true_case,
 		struct grub2_statements *false_case)
 {
-	struct grub2_statement *stmt = talloc(parser, struct grub2_statement);
-	stmt->type = STMT_TYPE_IF;
-	stmt->ifstmt.condition = condition;
-	stmt->ifstmt.true_case = true_case;
-	stmt->ifstmt.false_case = false_case;
-	return stmt;
+	struct grub2_statement_if *stmt =
+		talloc(parser, struct grub2_statement_if);
+	stmt->st.type = STMT_TYPE_IF;
+	stmt->condition = condition;
+	stmt->true_case = true_case;
+	stmt->false_case = false_case;
+	return &stmt->st;
 }
 
 struct grub2_statement *create_statement_block(struct grub2_parser *parser,
 		struct grub2_statements *stmts)
 {
-	struct grub2_statement *stmt = talloc(parser, struct grub2_statement);
-	stmt->type = STMT_TYPE_BLOCK;
-	stmt->block.statements = stmts;
-	return stmt;
+	struct grub2_statement_block *stmt =
+		talloc(parser, struct grub2_statement_block);
+	stmt->st.type = STMT_TYPE_BLOCK;
+	stmt->statements = stmts;
+	return &stmt->st;
 }
 
 void statement_append(struct grub2_statements *stmts,