SequencingHelpers.h

#pragma once
#include <array>
#include <algorithm>
#include <bit>
#include <cmath>
 
/* generic sequencing functions and defs to help either agnostic or dependent
 * sequencers do their stuff */
 
constexpr float s_init = -5.F;
constexpr float ms_init = 5000.F;
 
constexpr float finalscaler = 3.632F * 1.06F;
 
static const bool ignore_middle_column = true;
 
// outputs 0b1111 for 4, 0b111 for 3, etc
inline auto
keycount_to_bin(const unsigned& keycount) -> unsigned
{
    if (keycount < 2)
        return 0b11;
    return ~(~1u << (keycount - 1u));
}
 
// outputs 0b1100 for 4, 0b100 for 3, etc
inline auto
right_mask(const unsigned& keycount) -> unsigned
{
    if (keycount <= 2)
        return 0b10;
    return keycount_to_bin(keycount) >> (keycount / 2) << (keycount / 2);
}
 
// outputs 0b0011 for 4, 0b001 for 3, etc
inline auto
left_mask(const unsigned& keycount) -> unsigned
{
    const auto m = right_mask(keycount);
    return ~m & static_cast<int>(std::exp2(std::ceil(std::log2(m))) - 1);
}
 
// outputs 0b1111 for 4, 0b101 for 3, etc
inline auto
mask_to_remove_middle_column(const unsigned& keycount) -> unsigned
{
    if (keycount % 2 == 0) {
        return keycount_to_bin(keycount);
    }
    return keycount_to_bin(keycount) ^ (0b1 << (keycount / 2));
}
 
// outputs 0b0000 for 4, 0b010 for 3, etc
inline auto
middle_mask(const unsigned& keycount) -> unsigned
{
    return ~mask_to_remove_middle_column(keycount);
}
 
// count number of 1's in noterow binary
inline auto
column_count(const unsigned& notes) -> int
{
    return std::popcount(notes);
}
 
inline auto
is_only_1_bit(const unsigned& notes) -> bool
{
    return notes && !(notes & (notes - 1));
}
 
// return a vector of which columns are not empty
// 0 is the leftmost column
inline auto
find_non_empty_cols(const unsigned& notes) -> std::vector<unsigned>
{
    std::vector<unsigned> o{};
    for (auto i = 0u; 1u << i <= notes; i++) {
        if (((1u << i) & notes) != 0u) {
            o.push_back(i);
        }
    }
    return o;
}
 
inline auto
ms_from(const float& now, const float& last) -> float
{
    return (now - last) * 1000.F;
}
 
inline auto
ms_to_bpm(const float& x) -> float
{
    return 15000.F / x;
}
 
inline auto
ms_to_nps(const float& x) -> float
{
    return 1000.F / x;
}
 
inline auto
ms_to_scaled_nps(const float& ms) -> float
{
    return ms_to_nps(ms) * finalscaler;
}
 
inline auto
max_val(const std::vector<int>& v) -> int
{
    return *std::max_element(v.begin(), v.end());
}
 
inline auto
max_val(const std::vector<float>& v) -> float
{
    return *std::max_element(v.begin(), v.end());
}
 
inline auto
max_index(const std::vector<float>& v) -> int
{
    return static_cast<int>(
      std::distance(v.begin(), std::max_element(v.begin(), v.end())));
}
 
 
// it's expected that successive row deltas will often be equal,
// but this is not reliable in floating point. so any time you
// want to branch on a comparison you need to assume that very
// close values are supposed to be equal
 
// floats are good to around 1e-5, milliseconds scale that up by 1e3,
// if we stick to small-brain base 10 then 0.1f is all we have left
 
constexpr float any_ms_epsilon = 0.1F;
 
inline auto
any_ms_is_greater(float a, float b) -> bool
{
    return (a - b) > any_ms_epsilon;
}
 
inline auto
any_ms_is_lesser(float a, float b) -> bool
{
    return (b - a) > any_ms_epsilon;
}
 
inline auto
any_ms_is_close(float a, float b) -> bool
{
    return fabsf(a - b) <= any_ms_epsilon;
}
 
inline auto
any_ms_is_zero(float a) -> bool
{
    return any_ms_is_close(a, 0.F);
}