cppreg/register/RegisterPack.h

//! Register pack implementation.
/**
 * @file      RegisterPack.h
 * @author    Nicolas Clauvelin (nclauvelin@sendyne.com)
 * @copyright Copyright 2010-2019 Sendyne Corp. All rights reserved.
 *
 * This header provides the definitions related to packed register
 * implementation.
 */


#ifndef CPPREG_REGISTERPACK_H
#define CPPREG_REGISTERPACK_H


#include "Internals.h"
#include "Memory.h"
#include "Register.h"


namespace cppreg {


//! Packed register implementation.
/**
 * @tparam RegisterPack Pack to which the register belongs.
 * @tparam reg_size Register size enum value.
 * @tparam bit_offset Offset in bits for the register with respect to base.
 * @tparam reset_value Register reset value (0x0 if unknown).
 * @tparam use_shadow Boolean flag to enable shadow value.
 *
 * This implementation is intended to be used when defining a register
 * that belongs to a peripheral group.
 */
template <typename RegisterPack,
          RegBitSize reg_size,
          std::uint32_t bit_offset,
          typename TypeTraits<reg_size>::type reset_value = 0x0,
          bool use_shadow = false>
struct PackedRegister : Register<RegisterPack::pack_base + (bit_offset / 8u),
                                 reg_size,
                                 reset_value,
                                 use_shadow> {

    //! Register pack.
    using pack = RegisterPack;

    //! Register type.
    using base_reg = Register<RegisterPack::pack_base + (bit_offset / 8u),
                              reg_size,
                              reset_value,
                              use_shadow>;

    //! Memory modifier.
    /**
     * @return A reference to the writable register memory.
     */
    static typename base_reg::MMIO& rw_mem_device() noexcept {
        using mem_device =
            typename RegisterMemoryDevice<RegisterPack>::mem_device;
        return mem_device::template rw_memory<reg_size, (bit_offset / 8u)>();
    }

    //! Memory accessor.
    /**
     * @return A reference to the read-only register memory.
     */
    static const typename base_reg::MMIO& ro_mem_device() noexcept {
        using mem_device =
            typename RegisterMemoryDevice<RegisterPack>::mem_device;
        return mem_device::template ro_memory<reg_size, (bit_offset / 8u)>();
    }

    // Safety check to detect if are overflowing the pack.
    static_assert(TypeTraits<reg_size>::byte_size + (bit_offset / 8u)
                      <= RegisterPack::size_in_bytes,
                  "PackRegister:: packed register is overflowing the pack");

    // A packed register of width N bits requires:
    // - the pack address to be N-bits aligned (N/8 aligned),
    // - the pack address with offset to be N-bits aligned (N/8 aligned).
    static_assert(
        internals::is_aligned<RegisterPack::pack_base,
                              TypeTraits<reg_size>::byte_size>::value,
        "PackedRegister:: pack base address is mis-aligned for register type");
    static_assert(
        internals::is_aligned<RegisterPack::pack_base + (bit_offset / 8u),
                              TypeTraits<reg_size>::byte_size>::value,
        "PackedRegister:: offset address is mis-aligned for register type");
};


//! Pack indexing structure.
/**
 * @tparam T List of types (registers or fields) to index.
 *
 * This can be used to conveniently map indices over packed registers.
 * The order in the variadic parameter pack will define the indexing
 * (starting at zero).
 */
template <typename... T>
struct PackIndexing {

    //! Tuple type.
    using tuple_t = typename std::tuple<T...>;

    //! Number of elements.
    constexpr static const std::size_t n_elems =
        std::tuple_size<tuple_t>::value;

    //! Element accessor.
    template <std::size_t N>
    using elem = typename std::tuple_element<N, tuple_t>::type;
};


//! Template for loop implementation.
/**
 * @tparam start Start index value.
 * @tparam end End index value.
 */
template <std::size_t start, std::size_t end>
struct for_loop {

    //! Loop method.
    /**
     * @tparam Func Function to be called at each iteration.
     *
     * This will call Op for the range [start, end).
     */
    template <typename Func>
    static void apply() noexcept {
        Func().template operator()<start>();
        if (start < end)
            for_loop<start + 1ul, end>::template apply<Func>();
    }

#if __cplusplus >= 201402L
    //! Apply method.
    /**
     * @tparam Op Operator type to be called.
     *
     * This is only available with C++14 and up as this requires polymorphic
     * lambdas to be used in a somewhat useful manner.
     *
     * Typical example:
     * use lambda [](auto index) { index.value will be the loop index};
     */
    template <typename Op>
    static void apply(Op&& f) noexcept {
        if (start < end) {
            f(std::integral_constant<std::size_t, start>{});
            for_loop<start + 1ul, end>::apply(std::forward<Op>(f));
        };
    }
#endif    // __cplusplus 201402L
};
template <std::size_t end>
struct for_loop<end, end> {
    template <typename Func>
    static void apply() noexcept {}
#if __cplusplus >= 201402L
    template <typename Op>
    static void apply(Op&& f) noexcept {}
#endif    // __cplusplus 201402L
};


//! Template range loop implementation.
/**
 * @tparam IndexedPack Indexed pack type.
 */
template <typename IndexedPack>
struct pack_loop : for_loop<0, IndexedPack::n_elems> {};


}    // namespace cppreg


#endif    // CPPREG_REGISTERPACK_H