ben-scans/solidify/matrix.c

/*
 * matrix.c - 2D matrix operations
 *
 * Written 2010 by Werner Almesberger
 * Copyright 2010 by Werner Almesberger
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */


#include <assert.h>

#include "matrix.h"


void matrix_identity(struct matrix *m)
{
	m->a[0][0] = m->a[1][1] = 1;
	m->a[0][1] = m->a[1][0] = 0;
	m->b[0] = m->b[1] = 0;
}


void matrix_invert(const double m[2][2], double res[2][2])
{
	double det = m[0][0]*m[1][1]-m[0][1]*m[1][0];

	assert(res != (void *) m);
	res[0][0] = m[1][1]/det;
	res[0][1] = -m[0][1]/det;
	res[1][0] = -m[1][0]/det;
	res[1][1] = m[0][0]/det;
}


void matrix_mult(double a[2][2], double b[2][2], double res[2][2])
{
	assert(res != a);
	assert(res != b);
	res[0][0] = a[0][0]*b[0][0]+a[0][1]*b[1][0];
	res[0][1] = a[0][0]*b[0][1]+a[0][1]*b[1][1];
	res[1][0] = a[1][0]*b[0][0]+a[1][1]*b[1][0];
	res[1][1] = a[1][0]*b[0][1]+a[1][1]*b[1][1];
}


void matrix_multv(const double v[2], double m[2][2], double res[2])
{
	double tmp;

	tmp = v[0]*m[0][0]+v[1]*m[0][1];
	res[1] = v[0]*m[1][0]+v[1]*m[1][1];
	res[0] = tmp;
}


void matrix_copy(double from[2][2], double to[2][2])
{
	to[0][0] = from[0][0];
	to[0][1] = from[0][1];
	to[1][0] = from[1][0];
	to[1][1] = from[1][1];
}