libcamera: flags: Add type-safe enum-based flags
Add a Flags template class that provide type-safe bitwise operators on enum values. This allows using enum types for bit fields, without giving away type-safety as usually done when storing combined flags in integer variables. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se> Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
This commit is contained in:
Laurent Pinchart
parent
a792512496
commit
87c18aab8c
4 changed files with 389 additions and 0 deletions
195
include/libcamera/base/flags.h
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195
include/libcamera/base/flags.h
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
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/*
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* Copyright (C) 2020, Google Inc.
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*
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* flags.h - Type-safe enum-based bitfields
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*/
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#ifndef __LIBCAMERA_BASE_FLAGS_H__
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#define __LIBCAMERA_BASE_FLAGS_H__
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#include <type_traits>
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namespace libcamera {
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template<typename E>
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class Flags
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{
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public:
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static_assert(std::is_enum<E>::value,
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"Flags<> template parameter must be an enum");
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using Type = std::underlying_type_t<E>;
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constexpr Flags()
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: value_(0)
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{
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}
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constexpr Flags(E flag)
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: value_(static_cast<Type>(flag))
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{
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}
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constexpr Flags &operator&=(E flag)
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{
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value_ &= static_cast<Type>(flag);
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return *this;
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}
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constexpr Flags &operator&=(Flags other)
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{
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value_ &= other.value_;
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return *this;
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}
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constexpr Flags &operator|=(E flag)
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{
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value_ |= static_cast<Type>(flag);
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return *this;
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}
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constexpr Flags &operator|=(Flags other)
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{
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value_ |= other.value_;
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return *this;
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}
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constexpr Flags &operator^=(E flag)
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{
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value_ ^= static_cast<Type>(flag);
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return *this;
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}
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constexpr Flags &operator^=(Flags other)
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{
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value_ ^= other.value_;
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return *this;
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}
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constexpr bool operator==(E flag)
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{
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return value_ == static_cast<Type>(flag);
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}
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constexpr bool operator==(Flags other)
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{
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return value_ == static_cast<Type>(other);
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}
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constexpr bool operator!=(E flag)
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{
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return value_ != static_cast<Type>(flag);
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}
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constexpr bool operator!=(Flags other)
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{
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return value_ != static_cast<Type>(other);
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}
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constexpr explicit operator Type() const
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{
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return value_;
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}
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constexpr explicit operator bool() const
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{
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return !!value_;
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}
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constexpr Flags operator&(E flag) const
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{
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return Flags(static_cast<E>(value_ & static_cast<Type>(flag)));
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}
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constexpr Flags operator&(Flags other) const
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{
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return Flags(static_cast<E>(value_ & other.value_));
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}
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constexpr Flags operator|(E flag) const
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{
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return Flags(static_cast<E>(value_ | static_cast<Type>(flag)));
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}
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constexpr Flags operator|(Flags other) const
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{
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return Flags(static_cast<E>(value_ | other.value_));
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}
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constexpr Flags operator^(E flag) const
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{
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return Flags(static_cast<E>(value_ ^ static_cast<Type>(flag)));
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}
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constexpr Flags operator^(Flags other) const
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{
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return Flags(static_cast<E>(value_ ^ other.value_));
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}
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constexpr Flags operator~() const
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{
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return Flags(static_cast<E>(~value_));
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}
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constexpr bool operator!() const
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{
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return !value_;
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}
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private:
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Type value_;
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};
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#ifndef __DOXYGEN__
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template<typename E>
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struct flags_enable_operators {
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static const bool enable = false;
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};
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template<typename E>
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typename std::enable_if_t<flags_enable_operators<E>::enable, Flags<E>>
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operator|(E lhs, E rhs)
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{
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using type = std::underlying_type_t<E>;
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return Flags<E>(static_cast<E>(static_cast<type>(lhs) | static_cast<type>(rhs)));
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}
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template<typename E>
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typename std::enable_if_t<flags_enable_operators<E>::enable, Flags<E>>
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operator&(E lhs, E rhs)
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{
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using type = std::underlying_type_t<E>;
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return Flags<E>(static_cast<E>(static_cast<type>(lhs) & static_cast<type>(rhs)));
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}
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template<typename E>
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typename std::enable_if_t<flags_enable_operators<E>::enable, Flags<E>>
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operator^(E lhs, E rhs)
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{
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using type = std::underlying_type_t<E>;
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return Flags<E>(static_cast<E>(static_cast<type>(lhs) ^ static_cast<type>(rhs)));
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}
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template<typename E>
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typename std::enable_if_t<flags_enable_operators<E>::enable, Flags<E>>
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operator~(E rhs)
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{
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using type = std::underlying_type_t<E>;
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return Flags<E>(static_cast<E>(~static_cast<type>(rhs)));
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}
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#define LIBCAMERA_FLAGS_ENABLE_OPERATORS(_enum) \
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template<> \
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struct flags_enable_operators<_enum> { \
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static const bool enable = true; \
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};
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#else /* __DOXYGEN__ */
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#define LIBCAMERA_FLAGS_ENABLE_OPERATORS(_enum)
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#endif /* __DOXYGEN__ */
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} /* namespace libcamera */
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#endif /* __LIBCAMERA_BASE_FLAGS_H__ */
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@ -9,6 +9,7 @@ libcamera_base_headers = files([
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'event_dispatcher_poll.h',
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'event_notifier.h',
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'file.h',
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'flags.h',
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'log.h',
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'message.h',
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'object.h',
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192
src/libcamera/base/flags.cpp
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192
src/libcamera/base/flags.cpp
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@ -0,0 +1,192 @@
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
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/*
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* Copyright (C) 2020, Google Inc.
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*
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* flags.cpp - Type-safe enum-based bitfields
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*/
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#include <libcamera/base/flags.h>
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/**
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* \file base/flags.h
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* \brief Enum-based bit fields
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*/
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namespace libcamera {
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/**
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* \class Flags
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* \brief Type-safe container for enum-based bitfields
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*
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* The Flags template class provides type-safe bitwise operators on enum values.
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* It allows using enum types for bitfields, while preventing unsafe casts from
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* integer types and mixing of flags from different enum types.
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*
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* To use the Flags class, declare an enum containing the desired bit flags, and
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* use the Flags<enum> class to store bitfields based on the enum. If bitwise
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* operators on the underlying enum are also desired, they can be enabled with
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* the LIBCAMERA_FLAGS_ENABLE_OPERATORS(enum) macro.
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*/
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/**
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* \typedef Flags::Type
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* \brief The underlying data type of the enum
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*/
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/**
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* \fn Flags::Flags()
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* \brief Construct a Flags instance with a zero value
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*/
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/**
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* \fn Flags::Flags(E flag)
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* \brief Construct a Flags instance storing the \a flag
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* \param[in] flag The initial value
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*/
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/**
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* \fn Flags &Flags::operator&=(E flag)
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* \brief Store the bitwise AND of this Flags and the \a flag in this Flags
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* \param[in] flag The second operand
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* \return A reference to this Flags
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*/
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/**
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* \fn Flags &Flags::operator&=(Flags other)
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* \brief Store the bitwise AND of this Flags and the \a other Flags in this Flags
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* \param[in] other The second operand
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* \return A reference to this Flags
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*/
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/**
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* \fn Flags &Flags::operator|=(E flag)
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* \brief Store the bitwise OR of this Flags and the \a flag in this Flags
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* \param[in] flag The second operand
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* \return A reference to this Flags
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*/
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/**
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* \fn Flags &Flags::operator|=(Flags other)
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* \brief Store the bitwise OR of this Flags and the \a other Flags in this Flags
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* \param[in] other The second operand
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* \return A reference to this Flags
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*/
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/**
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* \fn Flags &Flags::operator^=(E flag)
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* \brief Store the bitwise XOR of this Flags and the \a flag in this Flags
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* \param[in] flag The second operand
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* \return A reference to this Flags
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*/
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/**
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* \fn Flags &Flags::operator^=(Flags other)
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* \brief Store the bitwise XOR of this Flags and the \a other Flags in this Flags
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* \param[in] other The second operand
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* \return A reference to this Flags
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*/
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/**
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* \fn bool Flags::operator==(E flag)
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* \brief Compare flags for equality
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* \param[in] flag The second operand
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* \return True if the Flags and \a flag are equal, false otherwise
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*/
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/**
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* \fn bool Flags::operator==(Flags other)
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* \brief Compare flags for equality
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* \param[in] other The second operand
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* \return True if the Flags and \a other are equal, false otherwise
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*/
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/**
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* \fn bool Flags::operator!=(E flag)
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* \brief Compare flags for non-equality
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* \param[in] flag The second operand
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* \return True if the Flags and \a flag are not equal, false otherwise
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*/
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/**
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* \fn bool Flags::operator!=(Flags other)
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* \brief Compare flags for non-equality
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* \param[in] other The second operand
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* \return True if the Flags and \a other are not equal, false otherwise
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*/
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/**
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* \fn Flags::operator Type() const
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* \brief Convert the Flags to the underlying integer type
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* \return The Flags value as an integer
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*/
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/**
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* \fn Flags::operator bool() const
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* \brief Convert the Flags to a boolean
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* \return True if at least one flag is set, false otherwise
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*/
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/**
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* \fn Flags Flags::operator&(E flag) const
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* \brief Compute the bitwise AND of this Flags and the \a flag
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* \param[in] flag The second operand
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* \return A Flags containing the result of the AND operation
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*/
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/**
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* \fn Flags Flags::operator&(Flags other) const
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* \brief Compute the bitwise AND of this Flags and the \a other Flags
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* \param[in] other The second operand
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* \return A Flags containing the result of the AND operation
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*/
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/**
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* \fn Flags Flags::operator|(E flag) const
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* \brief Compute the bitwise OR of this Flags and the \a flag
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* \param[in] flag The second operand
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* \return A Flags containing the result of the OR operation
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*/
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/**
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* \fn Flags Flags::operator|(Flags other) const
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* \brief Compute the bitwise OR of this Flags and the \a other Flags
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* \param[in] other The second operand
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* \return A Flags containing the result of the OR operation
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*/
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/**
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* \fn Flags Flags::operator^(E flag) const
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* \brief Compute the bitwise XOR of this Flags and the \a flag
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* \param[in] flag The second operand
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* \return A Flags containing the result of the XOR operation
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*/
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/**
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* \fn Flags Flags::operator^(Flags other) const
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* \brief Compute the bitwise XOR of this Flags and the \a other Flags
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* \param[in] other The second operand
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* \return A Flags containing the result of the XOR operation
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*/
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/**
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* \fn Flags Flags::operator~() const
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* \brief Compute the bitwise NOT of this Flags
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* \return A Flags containing the result of the NOT operation
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*/
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/**
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* \fn bool Flags::operator!() const
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* \brief Check if flags are set
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* \return True if no flags is set, false otherwise
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*/
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/**
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* \def LIBCAMERA_FLAGS_ENABLE_OPERATORS(enum)
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* \brief Enable bitwise operations on the \a enum enumeration
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*
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* This macro enables the bitwise AND, OR, XOR and NOT operators on the given
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* \a enum. This allows the enum values to be safely used in bitwise operations
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* with the Flags<> class.
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*/
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} /* namespace libcamera */
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@ -7,6 +7,7 @@ libcamera_base_sources = files([
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'event_dispatcher_poll.cpp',
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'event_notifier.cpp',
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'file.cpp',
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'flags.cpp',
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'log.cpp',
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'message.cpp',
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'object.cpp',
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