m_matrix_2x2.h

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// Copyright 2023, Collabora, Ltd.
// SPDX-License-Identifier: BSL-1.0
/*!
 * @file
 * @brief  C matrix_2x2 math library.
 * @author Moses Turner <moses@collabora.com>
 *
 * @see xrt_matrix_2x2
 * @ingroup aux_math
 */
 
#pragma once
 
#include "xrt/xrt_defines.h"
 
#ifdef __cplusplus
extern "C" {
#endif
 
static inline void
m_mat2x2_multiply(const struct xrt_matrix_2x2 *left,
                  const struct xrt_matrix_2x2 *right,
                  struct xrt_matrix_2x2 *result_out)
{
        const struct xrt_matrix_2x2 l = *left;
        const struct xrt_matrix_2x2 r = *right;
 
        // Initialisers: struct, union, v[4]
        struct xrt_matrix_2x2 result = {{{
            l.v[0] * r.v[0] + l.v[1] * r.v[2],
            l.v[0] * r.v[1] + l.v[1] * r.v[3],
            l.v[2] * r.v[0] + l.v[3] * r.v[2],
            l.v[2] * r.v[1] + l.v[3] * r.v[3],
        }}};
 
        *result_out = result;
}
 
static inline void
m_mat2x2_transform_vec2(const struct xrt_matrix_2x2 *left, const struct xrt_vec2 *right, struct xrt_vec2 *result_out)
{
        const struct xrt_matrix_2x2 l = *left;
        const struct xrt_vec2 r = *right;
        struct xrt_vec2 result = {l.v[0] * r.x + l.v[1] * r.y, l.v[2] * r.x + l.v[3] * r.y};
        *result_out = result;
}
 
static inline void
m_mat2x2_invert(const struct xrt_matrix_2x2 *matrix, struct xrt_matrix_2x2 *invertedMatrix)
{
        float determinant = matrix->v[0] * matrix->v[3] - matrix->v[1] * matrix->v[2];
        invertedMatrix->v[0] = matrix->v[3] / determinant;
        invertedMatrix->v[1] = -matrix->v[1] / determinant;
        invertedMatrix->v[2] = -matrix->v[2] / determinant;
        invertedMatrix->v[3] = matrix->v[0] / determinant;
}
 
#ifdef __cplusplus
}
#endif