matrix.h

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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2024, Paul Elder <paul.elder@ideasonboard.com>
 *
 * Matrix and related operations
 */
#pragma once

#include <algorithm>
#include <sstream>
#include <vector>

#include <libcamera/base/log.h>
#include <libcamera/base/span.h>

#include "libcamera/internal/yaml_parser.h"

namespace libcamera {

LOG_DECLARE_CATEGORY(Matrix)

#ifndef __DOXYGEN__
template<typename T, unsigned int Rows, unsigned int Cols,
     std::enable_if_t<std::is_arithmetic_v<T>> * = nullptr>
#else
template<typename T, unsigned int Rows, unsigned int Cols>
#endif /* __DOXYGEN__ */
class Matrix
{
public:
    Matrix()
    {
        data_.fill(static_cast<T>(0));
    }

    Matrix(const std::array<T, Rows * Cols> &data)
    {
        std::copy(data.begin(), data.end(), data_.begin());
    }

    static Matrix identity()
    {
        Matrix ret;
        for (size_t i = 0; i < std::min(Rows, Cols); i++)
            ret[i][i] = static_cast<T>(1);
        return ret;
    }

    ~Matrix() = default;

    const std::string toString() const
    {
        std::stringstream out;

        out << "Matrix { ";
        for (unsigned int i = 0; i < Rows; i++) {
            out << "[ ";
            for (unsigned int j = 0; j < Cols; j++) {
                out << (*this)[i][j];
                out << ((j + 1 < Cols) ? ", " : " ");
            }
            out << ((i + 1 < Rows) ? "], " : "]");
        }
        out << " }";

        return out.str();
    }

    Span<const T, Cols> operator[](size_t i) const
    {
        return Span<const T, Cols>{ &data_.data()[i * Cols], Cols };
    }

    Span<T, Cols> operator[](size_t i)
    {
        return Span<T, Cols>{ &data_.data()[i * Cols], Cols };
    }

#ifndef __DOXYGEN__
    template<typename U, std::enable_if_t<std::is_arithmetic_v<U>>>
#else
    template<typename U>
#endif /* __DOXYGEN__ */
    Matrix<T, Rows, Cols> &operator*=(U d)
    {
        for (unsigned int i = 0; i < Rows * Cols; i++)
            data_[i] *= d;
        return *this;
    }

private:
    std::array<T, Rows * Cols> data_;
};

#ifndef __DOXYGEN__
template<typename T, typename U, unsigned int Rows, unsigned int Cols,
     std::enable_if_t<std::is_arithmetic_v<T>> * = nullptr>
#else
template<typename T, typename U, unsigned int Rows, unsigned int Cols>
#endif /* __DOXYGEN__ */
Matrix<U, Rows, Cols> operator*(T d, const Matrix<U, Rows, Cols> &m)
{
    Matrix<U, Rows, Cols> result;

    for (unsigned int i = 0; i < Rows; i++) {
        for (unsigned int j = 0; j < Cols; j++)
            result[i][j] = d * m[i][j];
    }

    return result;
}

#ifndef __DOXYGEN__
template<typename T, typename U, unsigned int Rows, unsigned int Cols,
     std::enable_if_t<std::is_arithmetic_v<T>> * = nullptr>
#else
template<typename T, typename U, unsigned int Rows, unsigned int Cols>
#endif /* __DOXYGEN__ */
Matrix<U, Rows, Cols> operator*(const Matrix<U, Rows, Cols> &m, T d)
{
    return d * m;
}

#ifndef __DOXYGEN__
template<typename T,
     unsigned int R1, unsigned int C1,
     unsigned int R2, unsigned int C2,
     std::enable_if_t<C1 == R2> * = nullptr>
#else
template<typename T, unsigned int R1, unsigned int C1, unsigned int R2, unsigned in C2>
#endif /* __DOXYGEN__ */
Matrix<T, R1, C2> operator*(const Matrix<T, R1, C1> &m1, const Matrix<T, R2, C2> &m2)
{
    Matrix<T, R1, C2> result;

    for (unsigned int i = 0; i < R1; i++) {
        for (unsigned int j = 0; j < C2; j++) {
            T sum = 0;

            for (unsigned int k = 0; k < C1; k++)
                sum += m1[i][k] * m2[k][j];

            result[i][j] = sum;
        }
    }

    return result;
}

template<typename T, unsigned int Rows, unsigned int Cols>
Matrix<T, Rows, Cols> operator+(const Matrix<T, Rows, Cols> &m1, const Matrix<T, Rows, Cols> &m2)
{
    Matrix<T, Rows, Cols> result;

    for (unsigned int i = 0; i < Rows; i++) {
        for (unsigned int j = 0; j < Cols; j++)
            result[i][j] = m1[i][j] + m2[i][j];
    }

    return result;
}

#ifndef __DOXYGEN__
bool matrixValidateYaml(const YamlObject &obj, unsigned int size);
#endif /* __DOXYGEN__ */

#ifndef __DOXYGEN__
template<typename T, unsigned int Rows, unsigned int Cols>
std::ostream &operator<<(std::ostream &out, const Matrix<T, Rows, Cols> &m)
{
    out << m.toString();
    return out;
}

template<typename T, unsigned int Rows, unsigned int Cols>
struct YamlObject::Getter<Matrix<T, Rows, Cols>> {
    std::optional<Matrix<T, Rows, Cols>> get(const YamlObject &obj) const
    {
        if (!matrixValidateYaml(obj, Rows * Cols))
            return std::nullopt;

        Matrix<T, Rows, Cols> matrix;
        T *data = &matrix[0][0];

        unsigned int i = 0;
        for (const YamlObject &entry : obj.asList()) {
            const auto value = entry.get<T>();
            if (!value)
                return std::nullopt;

            data[i++] = *value;
        }

        return matrix;
    }
};
#endif /* __DOXYGEN__ */

} /* namespace libcamera */