IncreaseBitDepth.hpp

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#pragma once
 
#include <AH/STL/type_traits> // enable_if
#include <limits.h>           // CHAR_BIT
#include <stddef.h>           // size_t
 
BEGIN_AH_NAMESPACE
 
namespace detail {
 
template <size_t Bits_out, size_t Bits_in, class T_out, class T_in>
std::enable_if_t<(Bits_out <= 2 * Bits_in) && (Bits_out > Bits_in), T_out>
increaseBitDepthImpl(T_in in) {
    constexpr size_t leftShift = Bits_out - Bits_in;
    constexpr size_t rightShift = Bits_in - leftShift;
    return (static_cast<T_out>(in) << leftShift) | (in >> rightShift);
}
 
template <size_t Bits_out, size_t Bits_in, class T_out, class T_in>
std::enable_if_t<(Bits_out <= Bits_in), T_out> increaseBitDepthImpl(T_in in) {
    constexpr size_t rightShift = Bits_in - Bits_out;
    return static_cast<T_out>(in >> rightShift);
}
 
template <size_t Bits_out, size_t Bits_in, class T_out, class T_in>
std::enable_if_t<(Bits_out > 2 * Bits_in), T_out>
increaseBitDepthImpl(T_in in) {
    constexpr size_t leftShift = Bits_out - Bits_in;
    return (static_cast<T_out>(in) << leftShift) |
           increaseBitDepthImpl<leftShift, Bits_in, T_out>(in);
}
 
} // namespace detail


template <size_t Bits_out, size_t Bits_in, class T_out, class T_in>
T_out increaseBitDepth(T_in in) {
    static_assert(Bits_in <= sizeof(T_in) * CHAR_BIT,
                  "Error: Bits_in > bits(T_in)");
    static_assert(Bits_out <= sizeof(T_out) * CHAR_BIT,
                  "Error: Bits_out > bits(T_out)");
    return detail::increaseBitDepthImpl<Bits_out, Bits_in, T_out>(in);
}

template <size_t Bits_out, size_t Bits_in, class T_out, class T_in>
T_out increaseBitDepthMiddle(T_in in) {
    static_assert(Bits_in <= sizeof(T_in) * CHAR_BIT,
                  "Error: Bits_in > bits(T_in)");
    static_assert(Bits_out <= sizeof(T_out) * CHAR_BIT,
                  "Error: Bits_out > bits(T_out)");
    constexpr size_t leftShift = Bits_out - Bits_in;
    T_in half = T_in {1} << (Bits_in - 1);
    T_out out = static_cast<T_out>(in) << leftShift;
    if (in > half) {
        T_in repeat = in & (half - 1);
        out |= increaseBitDepth<leftShift, Bits_in - 1, T_out>(repeat);
    }
    return out;
}

 
END_AH_NAMESPACE