cam: options: Avoid copies of OptionvValue and KeyValueParser::Options

The OptionValue toKeyValues() and toArray() functions return a copy of
the values. This is unnecessary, and can cause use-after-free issues
when taking references to the return values. Return references instead
to optimize the implementation and avoid issues.

The behaviour of the two functions is now undefined in case of an option
type mismatch. The current implementation catches this with an
assertion.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

2 files changed, 14 insertions, 14 deletions

diff --git a/src/cam/options.cpp b/src/cam/options.cpp
index 481ac189..6e0d802c 100644
--- a/src/cam/options.cpp
+++ b/src/cam/options.cpp
@@ -638,27 +638,27 @@ std::string OptionValue::toString() const
 
 /**
  * \brief Retrieve the value as a key-value list
- * \return The option value as a KeyValueParser::Options, or an empty list if
- * the value type isn't ValueType::ValueKeyValue
+ *
+ * The behaviour is undefined if the value type isn't ValueType::ValueKeyValue.
+ *
+ * \return The option value as a KeyValueParser::Options
  */
-KeyValueParser::Options OptionValue::toKeyValues() const
+const KeyValueParser::Options &OptionValue::toKeyValues() const
 {
-	if (type_ != ValueKeyValue)
-		return KeyValueParser::Options();
-
+	assert(type_ == ValueKeyValue);
 	return keyValues_;
 }
 
 /**
  * \brief Retrieve the value as an array
- * \return The option value as a std::vector of OptionValue, or an empty vector
- * if the value type isn't ValueType::ValueArray
+ *
+ * The behaviour is undefined if the value type isn't ValueType::ValueArray.
+ *
+ * \return The option value as a std::vector of OptionValue
  */
-std::vector<OptionValue> OptionValue::toArray() const
+const std::vector<OptionValue> &OptionValue::toArray() const
 {
-	if (type_ != ValueArray)
-		return std::vector<OptionValue>{};
-
+	assert(type_ == ValueArray);
 	return array_;
 }
 
diff --git a/src/cam/options.h b/src/cam/options.h
index 83c409ae..0047b4f2 100644
--- a/src/cam/options.h
+++ b/src/cam/options.h
@@ -142,8 +142,8 @@ public:
 
 	int toInteger() const;
 	std::string toString() const;
-	KeyValueParser::Options toKeyValues() const;
-	std::vector<OptionValue> toArray() const;
+	const KeyValueParser::Options &toKeyValues() const;
+	const std::vector<OptionValue> &toArray() const;
 
 	const OptionsParser::Options &children() const;