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LibrePilot/flight/libraries/math/mathmisc.h

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/**
******************************************************************************
* @addtogroup OpenPilot Math Utilities
* @{
* @addtogroup Reuseable math functions
* @{
*
* @file mathmisc.h
* @author The OpenPilot Team, http://www.openpilot.org Copyright (C) 2012.
* @brief Reuseable math functions
*
* @see The GNU Public License (GPL) Version 3
*
*****************************************************************************/
/*
* 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 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifndef MATHMISC_H
#define MATHMISC_H
#include <math.h>
#include <stdint.h>
// returns min(boundary1,boundary2) if val<min(boundary1,boundary2)
// returns max(boundary1,boundary2) if val>max(boundary1,boundary2)
// returns val if min(boundary1,boundary2)<=val<=max(boundary1,boundary2)
static inline float boundf(float val, float boundary1, float boundary2)
{
if (boundary1 > boundary2) {
if (!(val >= boundary2)) {
return boundary2;
} else if (!(val <= boundary1)) {
return boundary1;
}
} else {
if (!(val >= boundary1)) {
return boundary1;
} else if (!(val <= boundary2)) {
return boundary2;
}
}
return val;
}
static inline float squaref(float x)
{
return x * x;
}
static inline float vector_lengthf(float *vector, const uint8_t dim)
{
float length = 0.0f;
for (int t = 0; t < dim; t++) {
length += squaref(vector[t]);
}
return sqrtf(length);
}
static inline void vector_normalizef(float *vector, const uint8_t dim)
{
float length = vector_lengthf(vector, dim);
if (length <= 0.0f || isnan(length)) {
return;
}
for (int t = 0; t < dim; t++) {
vector[t] /= length;
}
}
typedef struct pointf {
float x;
float y;
} pointf;
// Returns the y value, given x, on the line passing through the points p0 and p1.
static inline float y_on_line(float x, const pointf *p0, const pointf *p1)
{
// Setup line y = m * x + b.
const float dY1 = p1->y - p0->y;
const float dX1 = p1->x - p0->x;
const float m = dY1 / dX1; // == dY0 / dX0 == (p0.y - b) / (p0.x - 0.0f) ==>
const float b = p0->y - m * p0->x;
// Get the y value on the line.
return m * x + b;
}
// Returns the y value, given x, on the curve defined by the points array.
// The fist and last line of the curve extends beyond the first resp. last points.
static inline float y_on_curve(float x, const pointf points[], int num_points)
{
// Find the two points x is within.
// If x is smaller than the first point's x value, use the first line of the curve.
// If x is larger than the last point's x value, user the last line of the curve.
int end_point = num_points - 1;
for (int i = 1; i < num_points; i++) {
if (x < points[i].x) {
end_point = i;
break;
}
}
// Find the y value on the selected line.
return y_on_line(x, &points[end_point - 1], &points[end_point]);
}
// Fast inverse square root implementation from "quake3-1.32b/code/game/q_math.c"
// http://en.wikipedia.org/wiki/Fast_inverse_square_root
static inline float fast_invsqrtf(float number)
{
float x2, y;
const float threehalfs = 1.5F;
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union {
float f;
uint32_t u;
} i;
x2 = number * 0.5F;
y = number;
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i.f = y; // evil floating point bit level hacking
i.u = 0x5f3759df - (i.u >> 1); // what the fxck?
y = i.f;
y = y * (threehalfs - (x2 * y * y)); // 1st iteration
// y = y * ( threehalfs - ( x2 * y * y ) ); // 2nd iteration, this can be removed
return y;
}
/**
* Ultrafast pow() aproximation needed for expo
* Based on Algorithm by Martin Ankerl
*/
static inline float fastPow(float a, float b)
{
union {
double d;
int32_t x[2];
} u = { (double)a };
u.x[1] = (int32_t)(b * (u.x[1] - 1072632447) + 1072632447);
u.x[0] = 0;
return (float)u.d;
}
#endif /* MATHMISC_H */