discover/grub2: Create 'conditional' statements

Rather than holding the condition and conditional-statements in struct
grub2_statment_if, create a new conditional type that contains these. We
can then use this to implement elif statements.

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

3 files changed, 65 insertions, 31 deletions

diff --git a/discover/grub2/grub2.h b/discover/grub2/grub2.h
index 5b83fad..7f4a834 100644
--- a/discover/grub2/grub2.h
+++ b/discover/grub2/grub2.h
@@ -43,6 +43,7 @@ struct grub2_statement {
 		STMT_TYPE_MENUENTRY,
 		STMT_TYPE_IF,
 		STMT_TYPE_BLOCK,
+		STMT_TYPE_CONDITIONAL,
 	} type;
 	int			(*exec)(struct grub2_script *,
 					struct grub2_statement *);
@@ -59,11 +60,16 @@ struct grub2_statement_menuentry {
 	struct grub2_statements	*statements;
 };
 
-struct grub2_statement_if {
+struct grub2_statement_conditional {
 	struct grub2_statement	st;
 	struct grub2_statement	*condition;
-	struct grub2_statements	*true_case;
-	struct grub2_statements	*false_case;
+	struct grub2_statements	*statements;
+};
+
+struct grub2_statement_if {
+	struct grub2_statement	st;
+	struct grub2_statement	*conditional;
+	struct grub2_statements	*else_case;
 };
 
 struct grub2_statement_block {
@@ -102,10 +108,13 @@ struct grub2_statement *create_statement_simple(struct grub2_parser *parser,
 struct grub2_statement *create_statement_menuentry(struct grub2_parser *parser,
 		struct grub2_argv *argv, struct grub2_statements *stmts);
 
+struct grub2_statement *create_statement_conditional(
+		struct grub2_parser *parser, struct grub2_statement *condition,
+		struct grub2_statements *statements);
+
 struct grub2_statement *create_statement_if(struct grub2_parser *parser,
-		struct grub2_statement *condition,
-		struct grub2_statements *true_case,
-		struct grub2_statements *false_case);
+		struct grub2_statement *conditional,
+		struct grub2_statements *else_case);
 
 struct grub2_statement *create_statement_block(struct grub2_parser *parser,
 		struct grub2_statements *stmts);
diff --git a/discover/grub2/parser.y b/discover/grub2/parser.y
index 0540ff3..52dac9c 100644
--- a/discover/grub2/parser.y
+++ b/discover/grub2/parser.y
@@ -47,6 +47,7 @@ static void yyerror(struct grub2_parser *, char const *s);
 
 %type <statement>	statement
 %type <statements>	statements
+%type <statement>	conditional
 %type <argv>		words
 %type <word>		word
 
@@ -75,6 +76,10 @@ statements: /* empty */ {
 		$$ = $1;
 	}
 
+conditional: statement TOKEN_EOL "then" TOKEN_EOL statements {
+		$$ = create_statement_conditional(parser, $1, $5);
+	}
+
 statement:
 	words {
 		   $$ = create_statement_simple(parser, $1);
@@ -82,19 +87,14 @@ statement:
 	| '{' statements '}' {
 		$$ = create_statement_block(parser, $2);
 	}
-	| "if" TOKEN_DELIM statement
-		"then" TOKEN_EOL
-		statements
-		"fi" {
-		$$ = create_statement_if(parser, $3, $6, NULL);
+	| "if" TOKEN_DELIM conditional "fi" {
+		$$ = create_statement_if(parser, $3, NULL);
 	}
-	| "if" TOKEN_DELIM statement
-		"then" TOKEN_EOL
-		statements
+	| "if" TOKEN_DELIM conditional
 		"else" TOKEN_EOL
 		statements
 		"fi" {
-		$$ = create_statement_if(parser, $3, $6, $9);
+		$$ = create_statement_if(parser, $3, $6);
 	}
 	| "function" TOKEN_DELIM word TOKEN_DELIM '{' statements '}' {
 		$$ = create_statement_function(parser, $3, $6);
@@ -163,18 +163,29 @@ struct grub2_statement *create_statement_menuentry(struct grub2_parser *parser,
 	return &stmt->st;
 }
 
-struct grub2_statement *create_statement_if(struct grub2_parser *parser,
+struct grub2_statement *create_statement_conditional(
+		struct grub2_parser *parser,
 		struct grub2_statement *condition,
-		struct grub2_statements *true_case,
-		struct grub2_statements *false_case)
+		struct grub2_statements *statements)
+{
+	struct grub2_statement_conditional *stmt =
+		talloc(parser, struct grub2_statement_conditional);
+	stmt->st.type = STMT_TYPE_CONDITIONAL;
+	stmt->condition = condition;
+	stmt->statements = statements;
+	return &stmt->st;
+}
+
+struct grub2_statement *create_statement_if(struct grub2_parser *parser,
+		struct grub2_statement *conditional,
+		struct grub2_statements *else_case)
 {
 	struct grub2_statement_if *stmt =
 		talloc(parser, struct grub2_statement_if);
 	stmt->st.type = STMT_TYPE_IF;
 	stmt->st.exec = statement_if_execute;
-	stmt->condition = condition;
-	stmt->true_case = true_case;
-	stmt->false_case = false_case;
+	stmt->conditional = conditional;
+	stmt->else_case = else_case;
 	return &stmt->st;
 }
 
diff --git a/discover/grub2/script.c b/discover/grub2/script.c
index 9c08737..c0d6e1a 100644
--- a/discover/grub2/script.c
+++ b/discover/grub2/script.c
@@ -15,6 +15,8 @@
 	container_of(stmt, struct grub2_statement_menuentry, st)
 #define to_stmt_function(stmt) \
 	container_of(stmt, struct grub2_statement_function, st)
+#define to_stmt_conditional(stmt) \
+	container_of(stmt, struct grub2_statement_conditional, st)
 
 struct env_entry {
 	const char		*name;
@@ -252,24 +254,36 @@ int statement_simple_execute(struct grub2_script *script,
 	return rc;
 }
 
+/* returns 0 if the statement was executed, 1 otherwise */
+static int statement_conditional_execute(struct grub2_script *script,
+		struct grub2_statement *statement, bool *executed)
+{
+	struct grub2_statement_conditional *st = to_stmt_conditional(statement);
+	int rc;
+
+	rc = st->condition->exec(script, st->condition);
+	*executed = (!rc);
+	if (*executed)
+		rc = statements_execute(script, st->statements);
+
+	return rc;
+}
+
 int statement_if_execute(struct grub2_script *script,
 		struct grub2_statement *statement)
 {
 	struct grub2_statement_if *st = to_stmt_if(statement);
-	struct grub2_statements *case_stmts;
+	struct grub2_statement *conditional;
+	bool executed;
 	int rc;
 
-	rc = st->condition->exec(script, st->condition);
+	conditional = st->conditional;
 
-	if (rc == 0)
-		case_stmts = st->true_case;
-	else
-		case_stmts = st->false_case;
+	rc = statement_conditional_execute(script,
+			conditional, &executed);
 
-	if (case_stmts)
-		statements_execute(script, case_stmts);
-	else
-		rc = 0;
+	if (!executed && st->else_case)
+		rc = statements_execute(script, st->else_case);
 
 	return rc;
 }