trigonometry.hh

/*

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Copyright (c) 2023 PCSX-Redux authors

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*/

#pragma once

#include <EASTL/array.h>
#include <stdint.h>

#include "psyqo/fixed-point.hh"

namespace psyqo {

namespace TrigInternals {

void generateTable(eastl::array<int32_t, 512>& table, unsigned precisionBits);

}

/**
 * @brief A fixed point angle.
 *
 * @details This is a fixed point angle. Its value is in fractions of Pi.
 * In other words, 1.0 is 180 degrees, 0.5 is 90 degrees, and so on.
 */
typedef FixedPoint<10> Angle;

namespace trig_literals {

/**
 * @brief A user-defined literal for angle values.
 *
 * @param angle The angle in fractions of Pi.
 * @return consteval Angle The constructed angle.
 */
consteval Angle operator""_pi(long double angle) { return angle; }

}  // namespace trig_literals

/**
 * @brief A trigonometry table.
 *
 * @details This is a trigonometry table. It is used to calculate
 * sine and cosine values for angles. It is constructed with a
 * template parameter that specifies the number of bits of
 * precision to use for the table. The default is 12 bits.
 *
 * @tparam precisionBits The number of bits of precision to use
 * for the FixedPoint values in the table.
 */
template <unsigned precisionBits = 12>
class Trig {
  public:
    Trig() { TrigInternals::generateTable(table, precisionBits); }

    /**
     * @brief Calculate the cosine of an angle.
     *
     * @param a The angle to calculate the cosine of.
     * @return FixedPoint<precisionBits> The cosine of the angle.
     */
    constexpr FixedPoint<precisionBits> cos(Angle a) const {
        using namespace trig_literals;
        uint32_t t = a.value;

        t %= (2.0_pi).value;
        a.value = t;
        int32_t r;

        if (a < 0.5_pi) {
            r = table[t];
        } else if (a < 1.0_pi) {
            r = -table[(1.0_pi).value - 1 - t];
        } else if (a < 1.5_pi) {
            r = -table[t - (1.0_pi).value];
        } else {
            r = table[(2.0_pi).value - 1 - t];
        }

        FixedPoint<precisionBits> ret;
        ret.value = r;
        return ret;
    }

    /**
     * @brief Calculate the sine of an angle.
     *
     * @param a The angle to calculate the sine of.
     * @return FixedPoint<precisionBits> The sine of the angle.
     */
    constexpr FixedPoint<precisionBits> sin(Angle a) const {
        using namespace trig_literals;
        return cos(a - 0.5_pi);
    }

  private:
    eastl::array<int32_t, 512> table;
};

}  // namespace psyqo