media/codec2/core/include/C2ParamDef.h

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/** \file
 * Templates used to declare parameters.
 */
#ifndef C2PARAM_DEF_H_
#define C2PARAM_DEF_H_

#include <type_traits>

#include <C2Param.h>

/// \addtogroup Parameters
/// @{

/* ======================== UTILITY TEMPLATES FOR PARAMETER DEFINITIONS ======================== */

/// \addtogroup internal
/// @{

/// Helper class that checks if a type has equality and inequality operators.
struct C2_HIDE _C2Comparable_impl
{
    template<typename S, typename=decltype(S() == S())>
    static std::true_type TestEqual(int);
    template<typename>
    static std::false_type TestEqual(...);

    template<typename S, typename=decltype(S() != S())>
    static std::true_type TestNotEqual(int);
    template<typename>
    static std::false_type TestNotEqual(...);
};

/**
 * Helper template that returns if a type has equality and inequality operators.
 *
 * Use as _C2Comparable<typename S>::value.
 */
template<typename S>
struct C2_HIDE _C2Comparable
    : public std::integral_constant<bool, decltype(_C2Comparable_impl::TestEqual<S>(0))::value
                        || decltype(_C2Comparable_impl::TestNotEqual<S>(0))::value> {
};

///  Helper class that checks if a type has a CORE_INDEX constant.
struct C2_HIDE _C2CoreIndexHelper_impl
{
    template<typename S, int=S::CORE_INDEX>
    static std::true_type TestCoreIndex(int);
    template<typename>
    static std::false_type TestCoreIndex(...);
};

/// Macro that defines and thus overrides a type's CORE_INDEX for a setting
#define _C2_CORE_INDEX_OVERRIDE(coreIndex) \
public: \
    enum : uint32_t { CORE_INDEX = coreIndex };


/// Helper template that adds a CORE_INDEX to a type if it does not have one (for testing)
template<typename S, int CoreIndex>
struct C2_HIDE _C2AddCoreIndex : public S {
    _C2_CORE_INDEX_OVERRIDE(CoreIndex)
};

/**
 * \brief Helper class to check struct requirements for parameters.
 *
 * Features:
 *  - verify default constructor, no virtual methods, and no equality operators.
 *  - expose PARAM_TYPE, and non-flex FLEX_SIZE.
 */
template<typename S, int CoreIndex, unsigned TypeFlags>
struct C2_HIDE _C2StructCheck {
    static_assert(
            std::is_default_constructible<S>::value, "C2 structure must have default constructor");
    static_assert(!std::is_polymorphic<S>::value, "C2 structure must not have virtual methods");
    static_assert(!_C2Comparable<S>::value, "C2 structure must not have operator== or !=");

public:
    enum : uint32_t {
        PARAM_TYPE = CoreIndex | TypeFlags
    };

protected:
    enum : uint32_t {
        FLEX_SIZE = 0,
    };
};

/// Helper class that checks if a type has an integer FLEX_SIZE member.
struct C2_HIDE _C2Flexible_impl {
    /// specialization for types that have a FLEX_SIZE member
    template<typename S, unsigned=S::FLEX_SIZE>
    static std::true_type TestFlexSize(int);
    template<typename>
    static std::false_type TestFlexSize(...);
};

/// Helper template that returns if a type has an integer FLEX_SIZE member.
template<typename S>
struct C2_HIDE _C2Flexible
    : public std::integral_constant<bool, decltype(_C2Flexible_impl::TestFlexSize<S>(0))::value> {
};

/// Macro to test if a type is flexible (has a FLEX_SIZE member).
#define IF_FLEXIBLE(S) ENABLE_IF(_C2Flexible<S>::value)
/// Shorthand for std::enable_if
#define ENABLE_IF(cond) typename std::enable_if<cond>::type

template<typename T, typename V=void>
struct C2_HIDE _c2_enable_if_type {
    typedef V type;
};

/// Helper template that exposes the flexible subtype of a struct.
template<typename S, typename E=void>
struct C2_HIDE _C2FlexHelper {
    typedef void FlexType;
    enum : uint32_t { FLEX_SIZE = 0 };
};

/// Specialization for flexible types. This only works if _FlexMemberType is public.
template<typename S>
struct C2_HIDE _C2FlexHelper<S,
        typename _c2_enable_if_type<typename S::_FlexMemberType>::type> {
    typedef typename _C2FlexHelper<typename S::_FlexMemberType>::FlexType FlexType;
    enum : uint32_t { FLEX_SIZE = _C2FlexHelper<typename S::_FlexMemberType>::FLEX_SIZE };
};

/// Specialization for flex arrays.
template<typename S>
struct C2_HIDE _C2FlexHelper<S[],
        typename std::enable_if<std::is_void<typename _C2FlexHelper<S>::FlexType>::value>::type> {
    typedef S FlexType;
    enum : uint32_t { FLEX_SIZE = sizeof(S) };
};

/**
 * \brief Helper class to check flexible struct requirements and add common operations.
 *
 * Features:
 *  - expose CORE_INDEX and FieldList (this is normally inherited from the struct, but flexible
 *    structs cannot be base classes and thus inherited from)
 *  - disable copy assignment and construction (TODO: this is already done in the FLEX macro for the
 *    flexible struct, so may not be needed here)
 */
template<typename S, int ParamIndex, unsigned TypeFlags>
struct C2_HIDE _C2FlexStructCheck :
// add flexible flag as _C2StructCheck defines PARAM_TYPE
        public _C2StructCheck<S, ParamIndex | C2Param::CoreIndex::IS_FLEX_FLAG, TypeFlags> {
public:
    enum : uint32_t {
        /// \hideinitializer
        CORE_INDEX = ParamIndex | C2Param::CoreIndex::IS_FLEX_FLAG, ///< flexible struct core-index
    };

    inline static const std::vector<C2FieldDescriptor> FieldList() { return S::FieldList(); }

    // default constructor needed because of the disabled copy constructor
    inline _C2FlexStructCheck() = default;

protected:
    // cannot copy flexible params
    _C2FlexStructCheck(const _C2FlexStructCheck<S, ParamIndex, TypeFlags> &) = delete;
    _C2FlexStructCheck& operator= (const _C2FlexStructCheck<S, ParamIndex, TypeFlags> &) = delete;

    // constants used for helper methods
    enum : uint32_t {
        /// \hideinitializer
        FLEX_SIZE = _C2FlexHelper<S>::FLEX_SIZE, ///< size of flexible type
        /// \hideinitializer
        MAX_SIZE = (uint32_t)std::min((size_t)UINT32_MAX, SIZE_MAX), // TODO: is this always u32 max?
        /// \hideinitializer
        BASE_SIZE = sizeof(S) + sizeof(C2Param), ///< size of the base param
    };

    /// returns the allocated size of this param with flexCount, or 0 if it would overflow.
    inline static size_t CalcSize(size_t flexCount, size_t size = BASE_SIZE) {
        if (flexCount <= (MAX_SIZE - size) / S::FLEX_SIZE) {
            return size + S::FLEX_SIZE * flexCount;
        }
        return 0;
    }

    /// dynamic new operator usable for params of type S
    inline void* operator new(size_t size, size_t flexCount) noexcept {
        // TODO: assert(size == BASE_SIZE);
        size = CalcSize(flexCount, size);
        if (size > 0) {
            return ::operator new(size);
        }
        return nullptr;
    }
};

/// Define From() cast operators for params.
#define DEFINE_CAST_OPERATORS(_Type) \
    inline static _Type* From(C2Param *other) { \
        return (_Type*)C2Param::IfSuitable( \
                other, sizeof(_Type), _Type::PARAM_TYPE, _Type::FLEX_SIZE, \
                (_Type::PARAM_TYPE & T::Index::DIR_UNDEFINED) != T::Index::DIR_UNDEFINED); \
    } \
    inline static const _Type* From(const C2Param *other) { \
        return const_cast<const _Type*>(From(const_cast<C2Param *>(other))); \
    } \
    inline static _Type* From(std::nullptr_t) { return nullptr; } \

/**
 * Define flexible allocators (AllocShared or AllocUnique) for flexible params.
 *  - P::AllocXyz(flexCount, args...): allocate for given flex-count. This maps to
 *          T(flexCount, args...)\
 *
 * Clang does not support args... followed by templated param as args... eats it. Hence,
 * provide specializations where the initializer replaces the flexCount.
 *
 * Specializations that deduce flexCount:
 *  - P::AllocXyz(T[], args...): allocate for size of (and with) init array.
 *  - P::AllocXyz(std::initializer_list<T>, args...): allocate for size of (and with) initializer
 *            list.
 *  - P::AllocXyz(std::vector<T>, args...): allocate for size of (and with) init vector.
 *  These specializations map to T(flexCount = size-of-init, args..., init)
 */
#define DEFINE_FLEXIBLE_ALLOC(_Type, S, ptr, Ptr) \
    template<typename ...Args> \
    inline static std::ptr##_ptr<_Type> Alloc##Ptr(size_t flexCount, const Args(&... args)) { \
        return std::ptr##_ptr<_Type>(new(flexCount) _Type(flexCount, args...)); \
    } \
    template<typename ...Args, typename U=typename S::FlexType> \
    inline static std::ptr##_ptr<_Type> Alloc##Ptr( \
            const std::initializer_list<U> &init, const Args(&... args)) { \
        return std::ptr##_ptr<_Type>(new(init.size()) _Type(init.size(), args..., init)); \
    } \
    template<typename ...Args, typename U=typename S::FlexType> \
    inline static std::ptr##_ptr<_Type> Alloc##Ptr( \
            const std::vector<U> &init, const Args(&... args)) { \
        return std::ptr##_ptr<_Type>(new(init.size()) _Type(init.size(), args..., init)); \
    } \
    template<typename ...Args, typename U=typename S::FlexType, unsigned N> \
    inline static std::ptr##_ptr<_Type> Alloc##Ptr(const U(&init)[N], const Args(&... args)) { \
        return std::ptr##_ptr<_Type>(new(N) _Type(N, args..., init)); \
    } \

/**
 * Define flexible methods AllocShared, AllocUnique and flexCount.
 */
#define DEFINE_FLEXIBLE_METHODS(_Type, S) \
    DEFINE_FLEXIBLE_ALLOC(_Type, S, shared, Shared) \
    DEFINE_FLEXIBLE_ALLOC(_Type, S, unique, Unique) \
    inline size_t flexCount() const { \
        static_assert(sizeof(_Type) == _Type::BASE_SIZE, "incorrect BASE_SIZE"); \
        size_t sz = this->size(); \
        if (sz >= sizeof(_Type)) { \
            return (sz - sizeof(_Type)) / _Type::FLEX_SIZE; \
        } \
        return 0; \
    } \

/// Mark flexible member variable and make structure flexible.
#define FLEX(cls, m) \
    C2_DO_NOT_COPY(cls) \
private: \
    C2PARAM_MAKE_FRIENDS \
    /** \if 0 */ \
    template<typename, typename> friend struct _C2FlexHelper; \
public: \
    typedef decltype(m) _FlexMemberType; \
    /* default constructor with flexCount */ \
    inline cls(size_t) : cls() {} \
    /* constexpr static _FlexMemberType cls::* flexMember = &cls::m; */ \
    typedef typename _C2FlexHelper<_FlexMemberType>::FlexType FlexType; \
    static_assert(\
            !std::is_void<FlexType>::value, \
            "member is not flexible, or a flexible array of a flexible type"); \
    enum : uint32_t { FLEX_SIZE = _C2FlexHelper<_FlexMemberType>::FLEX_SIZE }; \
    /** \endif */ \

/// @}

/**
 * Global-parameter template.
 *
 * Base template to define a global setting/tuning or info based on a structure and
 * an optional ParamIndex. Global parameters are not tied to a port (input or output).
 *
 * Parameters wrap structures by prepending a (parameter) header. The fields of the wrapped
 * structure can be accessed directly, and constructors and potential public methods are also
 * wrapped.
 *
 * \tparam T param type C2Setting, C2Tuning or C2Info
 * \tparam S wrapped structure
 * \tparam ParamIndex optional parameter index override. Must be specified for base/reused
 * structures.
 */
template<typename T, typename S, int ParamIndex=S::CORE_INDEX, class Flex=void>
struct C2_HIDE C2GlobalParam : public T, public S,
        public _C2StructCheck<S, ParamIndex, T::PARAM_KIND | T::Type::DIR_GLOBAL> {
    _C2_CORE_INDEX_OVERRIDE(ParamIndex)
private:
    typedef C2GlobalParam<T, S, ParamIndex> _Type;

public:
    /// Wrapper around base structure's constructor.
    template<typename ...Args>
    inline C2GlobalParam(const Args(&... args)) : T(sizeof(_Type), _Type::PARAM_TYPE), S(args...) { }

    DEFINE_CAST_OPERATORS(_Type)
};

/**
 * Global-parameter template for flexible structures.
 *
 * Base template to define a global setting/tuning or info based on a flexible structure and
 * an optional ParamIndex. Global parameters are not tied to a port (input or output).
 *
 * \tparam T param type C2Setting, C2Tuning or C2Info
 * \tparam S wrapped flexible structure
 * \tparam ParamIndex optional parameter index override. Must be specified for base/reused
 *         structures.
 *
 * Parameters wrap structures by prepending a (parameter) header. The fields and methods of flexible
 * structures can be accessed via the m member variable; however, the constructors of the structure
 * are wrapped directly. (This is because flexible types cannot be subclassed.)
 */
template<typename T, typename S, int ParamIndex>
struct C2_HIDE C2GlobalParam<T, S, ParamIndex, IF_FLEXIBLE(S)>
    : public T, public _C2FlexStructCheck<S, ParamIndex, T::PARAM_KIND | T::Type::DIR_GLOBAL> {
private:
    typedef C2GlobalParam<T, S, ParamIndex> _Type;

    /// Wrapper around base structure's constructor.
    template<typename ...Args>
    inline C2GlobalParam(size_t flexCount, const Args(&... args))
        : T(_Type::CalcSize(flexCount), _Type::PARAM_TYPE), m(flexCount, args...) { }

public:
    S m; ///< wrapped flexible structure

    DEFINE_FLEXIBLE_METHODS(_Type, S)
    DEFINE_CAST_OPERATORS(_Type)
};

/**
 * Port-parameter template.
 *
 * Base template to define a port setting/tuning or info based on a structure and
 * an optional ParamIndex. Port parameters are tied to a port (input or output), but not to a
 * specific stream.
 *
 * \tparam T param type C2Setting, C2Tuning or C2Info
 * \tparam S wrapped structure
 * \tparam ParamIndex optional parameter index override. Must be specified for base/reused
 *         structures.
 *
 * Parameters wrap structures by prepending a (parameter) header. The fields of the wrapped
 * structure can be accessed directly, and constructors and potential public methods are also
 * wrapped.
 *
 * There are 3 flavors of port parameters: unspecified, input and output. Parameters with
 * unspecified port expose a setPort method, and add an initial port parameter to the constructor.
 */
template<typename T, typename S, int ParamIndex=S::CORE_INDEX, class Flex=void>
struct C2_HIDE C2PortParam : public T, public S,
        private _C2StructCheck<S, ParamIndex, T::PARAM_KIND | T::Index::DIR_UNDEFINED> {
    _C2_CORE_INDEX_OVERRIDE(ParamIndex)
private:
    typedef C2PortParam<T, S, ParamIndex> _Type;

public:
    /// Default constructor.
    inline C2PortParam() : T(sizeof(_Type), _Type::PARAM_TYPE) { }
    template<typename ...Args>
    /// Wrapper around base structure's constructor while specifying port/direction.
    inline C2PortParam(bool _output, const Args(&... args))
        : T(sizeof(_Type), _output ? output::PARAM_TYPE : input::PARAM_TYPE), S(args...) { }
    /// Set port/direction.
    inline void setPort(bool output) { C2Param::setPort(output); }

    DEFINE_CAST_OPERATORS(_Type)

    /// Specialization for an input port parameter.
    struct input : public T, public S,
            public _C2StructCheck<S, ParamIndex, T::PARAM_KIND | T::Index::DIR_INPUT> {
        _C2_CORE_INDEX_OVERRIDE(ParamIndex)
        /// Wrapper around base structure's constructor.
        template<typename ...Args>
        inline input(const Args(&... args)) : T(sizeof(_Type), input::PARAM_TYPE), S(args...) { }

        DEFINE_CAST_OPERATORS(input)

    };

    /// Specialization for an output port parameter.
    struct output : public T, public S,
            public _C2StructCheck<S, ParamIndex, T::PARAM_KIND | T::Index::DIR_OUTPUT> {
        _C2_CORE_INDEX_OVERRIDE(ParamIndex)
        /// Wrapper around base structure's constructor.
        template<typename ...Args>
        inline output(const Args(&... args)) : T(sizeof(_Type), output::PARAM_TYPE), S(args...) { }

        DEFINE_CAST_OPERATORS(output)
    };
};

/**
 * Port-parameter template for flexible structures.
 *
 * Base template to define a port setting/tuning or info based on a flexible structure and
 * an optional ParamIndex. Port parameters are tied to a port (input or output), but not to a
 * specific stream.
 *
 * \tparam T param type C2Setting, C2Tuning or C2Info
 * \tparam S wrapped flexible structure
 * \tparam ParamIndex optional parameter index override. Must be specified for base/reused
 *         structures.
 *
 * Parameters wrap structures by prepending a (parameter) header. The fields and methods of flexible
 * structures can be accessed via the m member variable; however, the constructors of the structure
 * are wrapped directly. (This is because flexible types cannot be subclassed.)
 *
 * There are 3 flavors of port parameters: unspecified, input and output. Parameters with
 * unspecified port expose a setPort method, and add an initial port parameter to the constructor.
 */
template<typename T, typename S, int ParamIndex>
struct C2_HIDE C2PortParam<T, S, ParamIndex, IF_FLEXIBLE(S)>
    : public T, public _C2FlexStructCheck<S, ParamIndex, T::PARAM_KIND | T::Type::DIR_UNDEFINED> {
private:
    typedef C2PortParam<T, S, ParamIndex> _Type;

    /// Default constructor for basic allocation: new(flexCount) P.
    inline C2PortParam(size_t flexCount) : T(_Type::CalcSize(flexCount), _Type::PARAM_TYPE) { }
    template<typename ...Args>
    /// Wrapper around base structure's constructor while also specifying port/direction.
    inline C2PortParam(size_t flexCount, bool _output, const Args(&... args))
        : T(_Type::CalcSize(flexCount), _output ? output::PARAM_TYPE : input::PARAM_TYPE),
          m(flexCount, args...) { }

public:
    /// Set port/direction.
    inline void setPort(bool output) { C2Param::setPort(output); }

    S m; ///< wrapped flexible structure

    DEFINE_FLEXIBLE_METHODS(_Type, S)
    DEFINE_CAST_OPERATORS(_Type)

    /// Specialization for an input port parameter.
    struct input : public T,
            public _C2FlexStructCheck<S, ParamIndex, T::PARAM_KIND | T::Index::DIR_INPUT> {
    private:
        /// Wrapper around base structure's constructor while also specifying port/direction.
        template<typename ...Args>
        inline input(size_t flexCount, const Args(&... args))
            : T(_Type::CalcSize(flexCount), input::PARAM_TYPE), m(flexCount, args...) { }

    public:
        S m; ///< wrapped flexible structure

        DEFINE_FLEXIBLE_METHODS(input, S)
        DEFINE_CAST_OPERATORS(input)
    };

    /// Specialization for an output port parameter.
    struct output : public T,
            public _C2FlexStructCheck<S, ParamIndex, T::PARAM_KIND | T::Index::DIR_OUTPUT> {
    private:
        /// Wrapper around base structure's constructor while also specifying port/direction.
        template<typename ...Args>
        inline output(size_t flexCount, const Args(&... args))
            : T(_Type::CalcSize(flexCount), output::PARAM_TYPE), m(flexCount, args...) { }

    public:
        S m; ///< wrapped flexible structure

        DEFINE_FLEXIBLE_METHODS(output, S)
        DEFINE_CAST_OPERATORS(output)
    };
};

/**
 * Stream-parameter template.
 *
 * Base template to define a stream setting/tuning or info based on a structure and
 * an optional ParamIndex. Stream parameters are tied to a specific stream on a port (input or
 * output).
 *
 * \tparam T param type C2Setting, C2Tuning or C2Info
 * \tparam S wrapped structure
 * \tparam ParamIndex optional paramter index override. Must be specified for base/reused
 *         structures.
 *
 * Parameters wrap structures by prepending a (parameter) header. The fields of the wrapped
 * structure can be accessed directly, and constructors and potential public methods are also
 * wrapped.
 *
 * There are 3 flavors of stream parameters: unspecified port, input and output. All of these expose
 * a setStream method and an extra initial streamID parameter for the constructor. Moreover,
 * parameters with unspecified port expose a setPort method, and add an additional initial port
 * parameter to the constructor.
 */
template<typename T, typename S, int ParamIndex=S::CORE_INDEX, class Flex=void>
struct C2_HIDE C2StreamParam : public T, public S,
        private _C2StructCheck<S, ParamIndex,
                T::PARAM_KIND | T::Index::IS_STREAM_FLAG | T::Index::DIR_UNDEFINED> {
    _C2_CORE_INDEX_OVERRIDE(ParamIndex)
private:
    typedef C2StreamParam<T, S, ParamIndex> _Type;

public:
    /// Default constructor. Port/direction and stream-ID is undefined.
    inline C2StreamParam() : T(sizeof(_Type), _Type::PARAM_TYPE) { }
    /// Wrapper around base structure's constructor while also specifying port/direction and
    /// stream-ID.
    template<typename ...Args>
    inline C2StreamParam(bool _output, unsigned stream, const Args(&... args))
        : T(sizeof(_Type), _output ? output::PARAM_TYPE : input::PARAM_TYPE, stream),
          S(args...) { }
    /// Set port/direction.
    inline void setPort(bool output) { C2Param::setPort(output); }
    /// Set stream-id. \retval true if the stream-id was successfully set.
    inline bool setStream(unsigned stream) { return C2Param::setStream(stream); }

    DEFINE_CAST_OPERATORS(_Type)

    /// Specialization for an input stream parameter.
    struct input : public T, public S,
            public _C2StructCheck<S, ParamIndex,
                    T::PARAM_KIND | T::Index::IS_STREAM_FLAG | T::Type::DIR_INPUT> {
        _C2_CORE_INDEX_OVERRIDE(ParamIndex)

        /// Default constructor. Stream-ID is undefined.
        inline input() : T(sizeof(_Type), input::PARAM_TYPE) { }
        /// Wrapper around base structure's constructor while also specifying stream-ID.
        template<typename ...Args>
        inline input(unsigned stream, const Args(&... args))
            : T(sizeof(_Type), input::PARAM_TYPE, stream), S(args...) { }
        /// Set stream-id. \retval true if the stream-id was successfully set.
        inline bool setStream(unsigned stream) { return C2Param::setStream(stream); }

        DEFINE_CAST_OPERATORS(input)
    };

    /// Specialization for an output stream parameter.
    struct output : public T, public S,
            public _C2StructCheck<S, ParamIndex,
                    T::PARAM_KIND | T::Index::IS_STREAM_FLAG | T::Type::DIR_OUTPUT> {
        _C2_CORE_INDEX_OVERRIDE(ParamIndex)

        /// Default constructor. Stream-ID is undefined.
        inline output() : T(sizeof(_Type), output::PARAM_TYPE) { }
        /// Wrapper around base structure's constructor while also specifying stream-ID.
        template<typename ...Args>
        inline output(unsigned stream, const Args(&... args))
            : T(sizeof(_Type), output::PARAM_TYPE, stream), S(args...) { }
        /// Set stream-id. \retval true if the stream-id was successfully set.
        inline bool setStream(unsigned stream) { return C2Param::setStream(stream); }

        DEFINE_CAST_OPERATORS(output)
    };
};

/**
 * Stream-parameter template for flexible structures.
 *
 * Base template to define a stream setting/tuning or info based on a flexible structure and
 * an optional ParamIndex. Stream parameters are tied to a specific stream on a port (input or
 * output).
 *
 * \tparam T param type C2Setting, C2Tuning or C2Info
 * \tparam S wrapped flexible structure
 * \tparam ParamIndex optional parameter index override. Must be specified for base/reused
 *         structures.
 *
 * Parameters wrap structures by prepending a (parameter) header. The fields and methods of flexible
 * structures can be accessed via the m member variable; however, the constructors of the structure
 * are wrapped directly. (This is because flexible types cannot be subclassed.)
 *
 * There are 3 flavors of stream parameters: unspecified port, input and output. All of these expose
 * a setStream method and an extra initial streamID parameter for the constructor. Moreover,
 * parameters with unspecified port expose a setPort method, and add an additional initial port
 * parameter to the constructor.
 */
template<typename T, typename S, int ParamIndex>
struct C2_HIDE C2StreamParam<T, S, ParamIndex, IF_FLEXIBLE(S)>
    : public T,
      public _C2FlexStructCheck<S, ParamIndex,
              T::PARAM_KIND | T::Index::IS_STREAM_FLAG | T::Index::DIR_UNDEFINED> {
private:
    typedef C2StreamParam<T, S, ParamIndex> _Type;
    /// Default constructor. Port/direction and stream-ID is undefined.
    inline C2StreamParam(size_t flexCount) : T(_Type::CalcSize(flexCount), _Type::PARAM_TYPE, 0u) { }
    /// Wrapper around base structure's constructor while also specifying port/direction and
    /// stream-ID.
    template<typename ...Args>
    inline C2StreamParam(size_t flexCount, bool _output, unsigned stream, const Args(&... args))
        : T(_Type::CalcSize(flexCount), _output ? output::PARAM_TYPE : input::PARAM_TYPE, stream),
          m(flexCount, args...) { }

public:
    S m; ///< wrapped flexible structure

    /// Set port/direction.
    inline void setPort(bool output) { C2Param::setPort(output); }
    /// Set stream-id. \retval true if the stream-id was successfully set.
    inline bool setStream(unsigned stream) { return C2Param::setStream(stream); }

    DEFINE_FLEXIBLE_METHODS(_Type, S)
    DEFINE_CAST_OPERATORS(_Type)

    /// Specialization for an input stream parameter.
    struct input : public T,
            public _C2FlexStructCheck<S, ParamIndex,
                    T::PARAM_KIND | T::Index::IS_STREAM_FLAG | T::Type::DIR_INPUT> {
    private:
        /// Default constructor. Stream-ID is undefined.
        inline input(size_t flexCount) : T(_Type::CalcSize(flexCount), input::PARAM_TYPE) { }
        /// Wrapper around base structure's constructor while also specifying stream-ID.
        template<typename ...Args>
        inline input(size_t flexCount, unsigned stream, const Args(&... args))
            : T(_Type::CalcSize(flexCount), input::PARAM_TYPE, stream), m(flexCount, args...) { }

    public:
        S m; ///< wrapped flexible structure

        /// Set stream-id. \retval true if the stream-id was successfully set.
        inline bool setStream(unsigned stream) { return C2Param::setStream(stream); }

        DEFINE_FLEXIBLE_METHODS(input, S)
        DEFINE_CAST_OPERATORS(input)
    };

    /// Specialization for an output stream parameter.
    struct output : public T,
            public _C2FlexStructCheck<S, ParamIndex,
                    T::PARAM_KIND | T::Index::IS_STREAM_FLAG | T::Type::DIR_OUTPUT> {
    private:
        /// Default constructor. Stream-ID is undefined.
        inline output(size_t flexCount) : T(_Type::CalcSize(flexCount), output::PARAM_TYPE) { }
        /// Wrapper around base structure's constructor while also specifying stream-ID.
        template<typename ...Args>
        inline output(size_t flexCount, unsigned stream, const Args(&... args))
            : T(_Type::CalcSize(flexCount), output::PARAM_TYPE, stream), m(flexCount, args...) { }

    public:
        S m; ///< wrapped flexible structure

        /// Set stream-id. \retval true if the stream-id was successfully set.
        inline bool setStream(unsigned stream) { return C2Param::setStream(stream); }

        DEFINE_FLEXIBLE_METHODS(output, S)
        DEFINE_CAST_OPERATORS(output)
    };
};

/* ======================== SIMPLE VALUE PARAMETERS ======================== */

/**
 * \ingroup internal
 * A structure template encapsulating a single element with default constructors and no core-index.
 */
template<typename T>
struct C2SimpleValueStruct {
    T value; ///< simple value of the structure
    // Default constructor.
    inline C2SimpleValueStruct() = default;
    // Constructor with an initial value.
    inline C2SimpleValueStruct(T value) : value(value) {}
    DEFINE_BASE_C2STRUCT(SimpleValue)
};

// TODO: move this and next to some generic place
/**
 * Interface to a block of (mapped) memory containing an array of some type (T).
 */
template<typename T>
struct C2MemoryBlock {
    /// \returns the number of elements in this block.
    virtual size_t size() const = 0;
    /// \returns a const pointer to the start of this block. Care must be taken to not read outside
    /// the block.
    virtual const T *data() const = 0; // TODO: should this be friend access only in some C2Memory module?
    /// \returns a pointer to the start of this block. Care must be taken to not read or write
    /// outside the block.
    inline T *data() { return const_cast<T*>(const_cast<const C2MemoryBlock*>(this)->data()); }

protected:
    // TODO: for now it should never be deleted as C2MemoryBlock
    virtual ~C2MemoryBlock() = default;
};

/**
 * Interface to a block of memory containing a constant (constexpr) array of some type (T).
 */
template<typename T>
struct C2ConstMemoryBlock : public C2MemoryBlock<T> {
    virtual const T * data() const { return _mData; }
    virtual size_t size() const { return _mSize; }

    /// Constructor.
    template<unsigned N>
    inline constexpr C2ConstMemoryBlock(const T(&init)[N]) : _mData(init), _mSize(N) {}

private:
    const T *_mData;
    const size_t _mSize;
};

/// \addtogroup internal
/// @{

/// Helper class to initialize flexible arrays with various initalizers.
struct _C2ValueArrayHelper {
    // char[]-s are used as null terminated strings, so the last element is never inited.

    /// Initialize a flexible array using a constexpr memory block.
    template<typename T>
    static void init(T(&array)[], size_t arrayLen, const C2MemoryBlock<T> &block) {
        // reserve last element for terminal 0 for strings
        if (arrayLen && std::is_same<T, char>::value) {
            --arrayLen;
        }
        if (block.data()) {
            memcpy(array, block.data(), std::min(arrayLen, block.size()) * sizeof(T));
        }
    }

    /// Initialize a flexible array using an initializer list.
    template<typename T>
    static void init(T(&array)[], size_t arrayLen, const std::initializer_list<T> &init) {
        size_t ix = 0;
        // reserve last element for terminal 0 for strings
        if (arrayLen && std::is_same<T, char>::value) {
            --arrayLen;
        }
        for (const T &item : init) {
            if (ix == arrayLen) {
                break;
            }
            array[ix++] = item;
        }
    }

    /// Initialize a flexible array using a vector.
    template<typename T>
    static void init(T(&array)[], size_t arrayLen, const std::vector<T> &init) {
        size_t ix = 0;
        // reserve last element for terminal 0 for strings
        if (arrayLen && std::is_same<T, char>::value) {
            --arrayLen;
        }
        for (const T &item : init) {
            if (ix == arrayLen) {
                break;
            }
            array[ix++] = item;
        }
    }

    /// Initialize a flexible array using another flexible array.
    template<typename T, unsigned N>
    static void init(T(&array)[], size_t arrayLen, const T(&str)[N]) {
        // reserve last element for terminal 0 for strings
        if (arrayLen && std::is_same<T, char>::value) {
            --arrayLen;
        }
        if (arrayLen) {
            memcpy(array, str, std::min(arrayLen, (size_t)N) * sizeof(T));
        }
    }
};

/**
 * Specialization for a flexible blob and string arrays. A structure template encapsulating a single
 * flexible array member with default flexible constructors and no core-index. This type cannot be
 * constructed on its own as it's size is 0.
 *
 * \internal This is different from C2SimpleArrayStruct<T[]> simply because its member has the name
 * as value to reflect this is a single value.
 */
template<typename T>
struct C2SimpleValueStruct<T[]> {
    static_assert(std::is_same<T, char>::value || std::is_same<T, uint8_t>::value,
                  "C2SimpleValueStruct<T[]> is only for BLOB or STRING");
    T value[];

    inline C2SimpleValueStruct() = default;
    DEFINE_BASE_C2STRUCT(SimpleValue)
    FLEX(C2SimpleValueStruct, value)

private:
    inline C2SimpleValueStruct(size_t flexCount, const C2MemoryBlock<T> &block) {
        _C2ValueArrayHelper::init(value, flexCount, block);
    }

    inline C2SimpleValueStruct(size_t flexCount, const std::initializer_list<T> &init) {
        _C2ValueArrayHelper::init(value, flexCount, init);
    }

    inline C2SimpleValueStruct(size_t flexCount, const std::vector<T> &init) {
        _C2ValueArrayHelper::init(value, flexCount, init);
    }

    template<unsigned N>
    inline C2SimpleValueStruct(size_t flexCount, const T(&init)[N]) {
        _C2ValueArrayHelper::init(value, flexCount, init);
    }
};

/// @}

/**
 * A structure template encapsulating a single flexible array element of a specific type (T) with
 * default constructors and no core-index. This type cannot be constructed on its own as it's size
 * is 0. Instead, it is meant to be used as a parameter, e.g.
 *
 *   typedef C2StreamParam<C2Info, C2SimpleArrayStruct<C2MyFancyStruct>,
 *           kParamIndexMyFancyArrayStreamParam> C2MyFancyArrayStreamInfo;
 */
template<typename T>
struct C2SimpleArrayStruct {
    static_assert(!std::is_same<T, char>::value && !std::is_same<T, uint8_t>::value,
                  "use C2SimpleValueStruct<T[]> is for BLOB or STRING");

    T values[]; ///< array member
    /// Default constructor
    inline C2SimpleArrayStruct() = default;
    DEFINE_BASE_FLEX_C2STRUCT(SimpleArray, values)
    //FLEX(C2SimpleArrayStruct, values)

private:
    /// Construct from a C2MemoryBlock.
    /// Used only by the flexible parameter allocators (AllocUnique & AllocShared).
    inline C2SimpleArrayStruct(size_t flexCount, const C2MemoryBlock<T> &block) {
        _C2ValueArrayHelper::init(values, flexCount, block);
    }

    /// Construct from an initializer list.
    /// Used only by the flexible parameter allocators (AllocUnique & AllocShared).
    inline C2SimpleArrayStruct(size_t flexCount, const std::initializer_list<T> &init) {
        _C2ValueArrayHelper::init(values, flexCount, init);
    }

    /// Construct from an vector.
    /// Used only by the flexible parameter allocators (AllocUnique & AllocShared).
    inline C2SimpleArrayStruct(size_t flexCount, const std::vector<T> &init) {
        _C2ValueArrayHelper::init(values, flexCount, init);
    }

    /// Construct from another flexible array.
    /// Used only by the flexible parameter allocators (AllocUnique & AllocShared).
    template<unsigned N>
    inline C2SimpleArrayStruct(size_t flexCount, const T(&init)[N]) {
        _C2ValueArrayHelper::init(values, flexCount, init);
    }
};

/**
 * \addtogroup simplevalue Simple value and array structures.
 * @{
 *
 * Simple value structures.
 *
 * Structures containing a single simple value. These can be reused to easily define simple
 * parameters of various types:
 *
 *   typedef C2PortParam<C2Tuning, C2Int32Value, kParamIndexMyIntegerPortParam>
 *           C2MyIntegerPortParamTuning;
 *
 * They contain a single member (value or values) that is described as "value" or "values".
 *
 * These structures don't define a core index, and as such, they cannot be used in structure
 * declarations. Use type[] instead, such as int32_t field[].
 */
/// A 32-bit signed integer parameter in value, described as "value"
typedef C2SimpleValueStruct<int32_t> C2Int32Value;
/// A 32-bit signed integer array parameter in values, described as "values"
typedef C2SimpleArrayStruct<int32_t> C2Int32Array;
/// A 32-bit unsigned integer parameter in value, described as "value"
typedef C2SimpleValueStruct<uint32_t> C2Uint32Value;
/// A 32-bit unsigned integer array parameter in values, described as "values"
typedef C2SimpleArrayStruct<uint32_t> C2Uint32Array;
/// A 64-bit signed integer parameter in value, described as "value"
typedef C2SimpleValueStruct<int64_t> C2Int64Value;
/// A 64-bit signed integer array parameter in values, described as "values"
typedef C2SimpleArrayStruct<int64_t> C2Int64Array;
/// A 64-bit unsigned integer parameter in value, described as "value"
typedef C2SimpleValueStruct<uint64_t> C2Uint64Value;
/// A 64-bit unsigned integer array parameter in values, described as "values"
typedef C2SimpleArrayStruct<uint64_t> C2Uint64Array;
/// A float parameter in value, described as "value"
typedef C2SimpleValueStruct<float> C2FloatValue;
/// A float array parameter in values, described as "values"
typedef C2SimpleArrayStruct<float> C2FloatArray;
/// A blob flexible parameter in value, described as "value"
typedef C2SimpleValueStruct<uint8_t[]> C2BlobValue;
/// A string flexible parameter in value, described as "value"
typedef C2SimpleValueStruct<char[]> C2StringValue;

template<typename T>
const std::vector<C2FieldDescriptor> C2SimpleValueStruct<T>::FieldList() {
    return { DESCRIBE_C2FIELD(value, "value") };
}
template<typename T>
const std::vector<C2FieldDescriptor> C2SimpleValueStruct<T[]>::FieldList() {
    return { DESCRIBE_C2FIELD(value, "value") };
}
template<typename T>
const std::vector<C2FieldDescriptor> C2SimpleArrayStruct<T>::FieldList() {
    return { DESCRIBE_C2FIELD(values, "values") };
}

/// @}

/// @}

#endif  // C2PARAM_DEF_H_