libcamera: controls: Support array controls in ControlValue

Add array controls support to the ControlValue class. The polymorphic
class can now store more than a single element and supports access and
creation through the use of Span<>.

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

include/libcamera/controls.h

@@ -9,6 +9,7 @@
 #define __LIBCAMERA_CONTROLS_H__
 
 #include <assert.h>
+#include <stdint.h>
 #include <string>
 #include <unordered_map>
 
@@ -51,6 +52,10 @@ struct control_type<int64_t> {
 	static constexpr ControlType value = ControlTypeInteger64;
 };
 
+template<typename T, std::size_t N>
+struct control_type<Span<T, N>> : public control_type<std::remove_cv_t<T>> {
+};
+
 } /* namespace details */
 
 class ControlValue
@@ -58,15 +63,35 @@ class ControlValue
 public:
 	ControlValue();
 
-	template<typename T>
+#ifndef __DOXYGEN__
-	ControlValue(T value)
+	template<typename T, typename std::enable_if_t<!details::is_span<T>::value, std::nullptr_t> = nullptr>
-		: type_(details::control_type<std::remove_cv_t<T>>::value)
+	ControlValue(const T &value)
+		: type_(ControlTypeNone), numElements_(0)
 	{
-		*reinterpret_cast<T *>(&bool_) = value;
+		set(details::control_type<std::remove_cv_t<T>>::value, false,
+		    &value, 1, sizeof(T));
 	}
 
+	template<typename T, typename std::enable_if_t<details::is_span<T>::value, std::nullptr_t> = nullptr>
+#else
+	template<typename T>
+#endif
+	ControlValue(const T &value)
+		: type_(ControlTypeNone), numElements_(0)
+	{
+		set(details::control_type<std::remove_cv_t<T>>::value, true,
+		    value.data(), value.size(), sizeof(typename T::value_type));
+	}
+
+	~ControlValue();
+
+	ControlValue(const ControlValue &other);
+	ControlValue &operator=(const ControlValue &other);
+
 	ControlType type() const { return type_; }
 	bool isNone() const { return type_ == ControlTypeNone; }
+	bool isArray() const { return isArray_; }
+	std::size_t numElements() const { return numElements_; }
 	Span<const uint8_t> data() const;
 
 	std::string toString() const;
@@ -77,31 +102,61 @@ public:
 		return !(*this == other);
 	}
 
-	template<typename T>
+#ifndef __DOXYGEN__
+	template<typename T, typename std::enable_if_t<!details::is_span<T>::value, std::nullptr_t> = nullptr>
 	T get() const
 	{
 		assert(type_ == details::control_type<std::remove_cv_t<T>>::value);
+		assert(!isArray_);
 
-		return *reinterpret_cast<const T *>(&bool_);
+		return *reinterpret_cast<const T *>(data().data());
 	}
 
+	template<typename T, typename std::enable_if_t<details::is_span<T>::value, std::nullptr_t> = nullptr>
+#else
 	template<typename T>
+#endif
+	T get() const
+	{
+		assert(type_ == details::control_type<std::remove_cv_t<T>>::value);
+		assert(isArray_);
+
+		using V = typename T::value_type;
+		const V *value = reinterpret_cast<const V *>(data().data());
+		return { value, numElements_ };
+	}
+
+#ifndef __DOXYGEN__
+	template<typename T, typename std::enable_if_t<!details::is_span<T>::value, std::nullptr_t> = nullptr>
 	void set(const T &value)
 	{
-		type_ = details::control_type<std::remove_cv_t<T>>::value;
+		set(details::control_type<std::remove_cv_t<T>>::value, false,
-		*reinterpret_cast<T *>(&bool_) = value;
+		    reinterpret_cast<const void *>(&value), 1, sizeof(T));
+	}
+
+	template<typename T, typename std::enable_if_t<details::is_span<T>::value, std::nullptr_t> = nullptr>
+#else
+	template<typename T>
+#endif
+	void set(const T &value)
+	{
+		set(details::control_type<std::remove_cv_t<T>>::value, true,
+		    value.data(), value.size(), sizeof(typename T::value_type));
 	}
 
 private:
-	ControlType type_;
+	ControlType type_ : 8;
+	bool isArray_ : 1;
+	std::size_t numElements_ : 16;
+	uint64_t storage_;
 
-	union {
+	void release();
-		bool bool_;
+	void set(ControlType type, bool isArray, const void *data,
-		int32_t integer32_;
+		 std::size_t numElements, std::size_t elementSize);
-		int64_t integer64_;
-	};
 };
 
+static_assert(sizeof(ControlValue) == 16, "Invalid size of ControlValue class");
+
 class ControlId
 {
 public:

src/libcamera/controls.cpp

@@ -10,6 +10,7 @@
 #include <iomanip>
 #include <sstream>
 #include <string>
+#include <string.h>
 
 #include "control_validator.h"
 #include "log.h"
@@ -50,7 +51,7 @@ LOG_DEFINE_CATEGORY(Controls)
 namespace {
 
 static constexpr size_t ControlValueSize[] = {
-	[ControlTypeNone]		= 1,
+	[ControlTypeNone]		= 0,
 	[ControlTypeBool]		= sizeof(bool),
 	[ControlTypeInteger32]		= sizeof(int32_t),
 	[ControlTypeInteger64]		= sizeof(int64_t),
@@ -80,16 +81,60 @@ static constexpr size_t ControlValueSize[] = {
  * \brief Construct an empty ControlValue.
  */
 ControlValue::ControlValue()
-	: type_(ControlTypeNone)
+	: type_(ControlTypeNone), isArray_(false), numElements_(0)
 {
 }
 
 /**
- * \fn template<typename T> T ControlValue::ControlValue(T value)
+ * \fn template<typename T> T ControlValue::ControlValue(const T &value)
  * \brief Construct a ControlValue of type T
  * \param[in] value Initial value
+ *
+ * This function constructs a new instance of ControlValue and stores the \a
+ * value inside it. If the type \a T is equivalent to Span<R>, the instance
+ * stores an array of values of type \a R. Otherwise the instance stores a
+ * single value of type \a T. The numElements() and type() are updated to
+ * reflect the stored value.
  */
 
+void ControlValue::release()
+{
+	std::size_t size = numElements_ * ControlValueSize[type_];
+
+	if (size > sizeof(storage_)) {
+		delete[] *reinterpret_cast<char **>(&storage_);
+		storage_ = 0;
+	}
+}
+
+ControlValue::~ControlValue()
+{
+	release();
+}
+
+/**
+ * \brief Construct a ControlValue with the content of \a other
+ * \param[in] other The ControlValue to copy content from
+ */
+ControlValue::ControlValue(const ControlValue &other)
+	: type_(ControlTypeNone), numElements_(0)
+{
+	*this = other;
+}
+
+/**
+ * \brief Replace the content of the ControlValue with a copy of the content
+ * of \a other
+ * \param[in] other The ControlValue to copy content from
+ * \return The ControlValue with its content replaced with the one of \a other
+ */
+ControlValue &ControlValue::operator=(const ControlValue &other)
+{
+	set(other.type_, other.isArray_, other.data().data(),
+	    other.numElements_, ControlValueSize[other.type_]);
+	return *this;
+}
+
 /**
  * \fn ControlValue::type()
  * \brief Retrieve the data type of the value
@@ -102,16 +147,33 @@ ControlValue::ControlValue()
  * \return True if the value type is ControlTypeNone, false otherwise
  */
 
+/**
+ * \fn ControlValue::isArray()
+ * \brief Determine if the value stores an array
+ * \return True if the value stores an array, false otherwise
+ */
+
+/**
+ * \fn ControlValue::numElements()
+ * \brief Retrieve the number of elements stored in the ControlValue
+ *
+ * For instances storing an array, this function returns the number of elements
+ * in the array. Otherwise, it returns 1.
+ *
+ * \return The number of elements stored in the ControlValue
+ */
+
 /**
  * \brief Retrieve the raw data of a control value
  * \return The raw data of the control value as a span of uint8_t
  */
 Span<const uint8_t> ControlValue::data() const
 {
-	return {
+	std::size_t size = numElements_ * ControlValueSize[type_];
-		reinterpret_cast<const uint8_t *>(&bool_),
+	const uint8_t *data = size > sizeof(storage_)
-		ControlValueSize[type_]
+			    ? *reinterpret_cast<const uint8_t * const *>(&storage_)
-	};
+			    : reinterpret_cast<const uint8_t *>(&storage_);
+	return { data, size };
 }
 
 /**
@@ -120,18 +182,43 @@ Span<const uint8_t> ControlValue::data() const
  */
 std::string ControlValue::toString() const
 {
-	switch (type_) {
+	if (type_ == ControlTypeNone)
-	case ControlTypeNone:
+		return "<ValueType Error>";
-		return "<None>";
+
-	case ControlTypeBool:
+	const uint8_t *data = ControlValue::data().data();
-		return bool_ ? "True" : "False";
+	std::string str(isArray_ ? "[ " : "");
-	case ControlTypeInteger32:
+
-		return std::to_string(integer32_);
+	for (unsigned int i = 0; i < numElements_; ++i) {
-	case ControlTypeInteger64:
+		switch (type_) {
-		return std::to_string(integer64_);
+		case ControlTypeBool: {
+			const bool *value = reinterpret_cast<const bool *>(data);
+			str += *value ? "True" : "False";
+			break;
+		}
+		case ControlTypeInteger32: {
+			const int32_t *value = reinterpret_cast<const int32_t *>(data);
+			str += std::to_string(*value);
+			break;
+		}
+		case ControlTypeInteger64: {
+			const int64_t *value = reinterpret_cast<const int64_t *>(data);
+			str += std::to_string(*value);
+			break;
+		}
+		case ControlTypeNone:
+			break;
+		}
+
+		if (i + 1 != numElements_)
+			str += ", ";
+
+		data += ControlValueSize[type_];
 	}
 
-	return "<ValueType Error>";
+	if (isArray_)
+		str += " ]";
+
+	return str;
 }
 
 /**
@@ -143,16 +230,13 @@ bool ControlValue::operator==(const ControlValue &other) const
 	if (type_ != other.type_)
 		return false;
 
-	switch (type_) {
+	if (numElements_ != other.numElements())
-	case ControlTypeBool:
-		return bool_ == other.bool_;
-	case ControlTypeInteger32:
-		return integer32_ == other.integer32_;
-	case ControlTypeInteger64:
-		return integer64_ == other.integer64_;
-	default:
 		return false;
-	}
+
+	if (isArray_ != other.isArray_)
+		return false;
+
+	return memcmp(data().data(), other.data().data(), data().size()) == 0;
 }
 
 /**
@@ -165,8 +249,16 @@ bool ControlValue::operator==(const ControlValue &other) const
  * \fn template<typename T> T ControlValue::get() const
  * \brief Get the control value
  *
- * The control value type shall match the type T, otherwise the behaviour is
+ * This function returns the contained value as an instance of \a T. If the
- * undefined.
+ * ControlValue instance stores a single value, the type \a T shall match the
+ * stored value type(). If the instance stores an array of values, the type
+ * \a T should be equal to Span<const R>, and the type \a R shall match the
+ * stored value type(). The behaviour is undefined otherwise.
+ *
+ * Note that a ControlValue instance that stores a non-array value is not
+ * equivalent to an instance that stores an array value containing a single
+ * element. The latter shall be accessed through a Span<const R> type, while
+ * the former shall be accessed through a type \a T corresponding to type().
  *
  * \return The control value
  */
@@ -175,8 +267,41 @@ bool ControlValue::operator==(const ControlValue &other) const
  * \fn template<typename T> void ControlValue::set(const T &value)
  * \brief Set the control value to \a value
  * \param[in] value The control value
+ *
+ * This function stores the \a value in the instance. If the type \a T is
+ * equivalent to Span<R>, the instance stores an array of values of type \a R.
+ * Otherwise the instance stores a single value of type \a T. The numElements()
+ * and type() are updated to reflect the stored value.
+ *
+ * The entire content of \a value is copied to the instance, no reference to \a
+ * value or to the data it references is retained. This may be an expensive
+ * operation for Span<> values that refer to large arrays.
  */
 
+void ControlValue::set(ControlType type, bool isArray, const void *data,
+		       std::size_t numElements, std::size_t elementSize)
+{
+	ASSERT(elementSize == ControlValueSize[type]);
+
+	release();
+
+	type_ = type;
+	numElements_ = numElements;
+	isArray_ = isArray;
+
+	std::size_t size = elementSize * numElements;
+	void *storage;
+
+	if (size > sizeof(storage_)) {
+		storage = reinterpret_cast<void *>(new char[size]);
+		*reinterpret_cast<void **>(&storage_) = storage;
+	} else {
+		storage = reinterpret_cast<void *>(&storage_);
+	}
+
+	memcpy(storage, data, size);
+}
+
 /**
  * \class ControlId
  * \brief Control static metadata