/usr/include/pj/math.h is in libpjproject-dev 2.7.2~dfsg-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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/*
* Copyright (C) 2008-2011 Teluu Inc. (http://www.teluu.com)
* Copyright (C) 2003-2008 Benny Prijono <benny@prijono.org>
*
* 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.
*
* 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 __PJ_MATH_H__
#define __PJ_MATH_H__
/**
* @file math.h
* @brief Mathematics and Statistics.
*/
#include <pj/string.h>
#include <pj/compat/high_precision.h>
PJ_BEGIN_DECL
/**
* @defgroup pj_math Mathematics and Statistics
* @ingroup PJ_MISC
* @{
*
* Provides common mathematics constants and operations, and also standard
* statistics calculation (min, max, mean, standard deviation). Statistics
* calculation is done in realtime (statistics state is updated on time each
* new sample comes).
*/
/**
* Mathematical constants
*/
#define PJ_PI 3.14159265358979323846 /* pi */
#define PJ_1_PI 0.318309886183790671538 /* 1/pi */
/**
* Mathematical macro
*/
#define PJ_ABS(x) ((x) > 0 ? (x) : -(x))
#define PJ_MAX(x, y) ((x) > (y)? (x) : (y))
#define PJ_MIN(x, y) ((x) < (y)? (x) : (y))
/**
* This structure describes statistics state.
*/
typedef struct pj_math_stat
{
int n; /* number of samples */
int max; /* maximum value */
int min; /* minimum value */
int last; /* last value */
int mean; /* mean */
/* Private members */
#if PJ_HAS_FLOATING_POINT
float fmean_; /* mean(floating point) */
#else
int mean_res_; /* mean residu */
#endif
pj_highprec_t m2_; /* variance * n */
} pj_math_stat;
/**
* Calculate integer square root of an integer.
*
* @param i Integer to be calculated.
*
* @return Square root result.
*/
PJ_INLINE(unsigned) pj_isqrt(unsigned i)
{
unsigned res = 1, prev;
/* Rough guess, calculate half bit of input */
prev = i >> 2;
while (prev) {
prev >>= 2;
res <<= 1;
}
/* Babilonian method */
do {
prev = res;
res = (prev + i/prev) >> 1;
} while ((prev+res)>>1 != res);
return res;
}
/**
* Initialize statistics state.
*
* @param stat Statistic state.
*/
PJ_INLINE(void) pj_math_stat_init(pj_math_stat *stat)
{
pj_bzero(stat, sizeof(pj_math_stat));
}
/**
* Update statistics state as a new sample comes.
*
* @param stat Statistic state.
* @param val The new sample data.
*/
PJ_INLINE(void) pj_math_stat_update(pj_math_stat *stat, int val)
{
#if PJ_HAS_FLOATING_POINT
float delta;
#else
int delta;
#endif
stat->last = val;
if (stat->n++) {
if (stat->min > val)
stat->min = val;
if (stat->max < val)
stat->max = val;
} else {
stat->min = stat->max = val;
}
#if PJ_HAS_FLOATING_POINT
delta = val - stat->fmean_;
stat->fmean_ += delta/stat->n;
/* Return mean value with 'rounding' */
stat->mean = (int) (stat->fmean_ + 0.5);
stat->m2_ += (int)(delta * (val-stat->fmean_));
#else
delta = val - stat->mean;
stat->mean += delta/stat->n;
stat->mean_res_ += delta % stat->n;
if (stat->mean_res_ >= stat->n) {
++stat->mean;
stat->mean_res_ -= stat->n;
} else if (stat->mean_res_ <= -stat->n) {
--stat->mean;
stat->mean_res_ += stat->n;
}
stat->m2_ += delta * (val-stat->mean);
#endif
}
/**
* Get the standard deviation of specified statistics state.
*
* @param stat Statistic state.
*
* @return The standard deviation.
*/
PJ_INLINE(unsigned) pj_math_stat_get_stddev(const pj_math_stat *stat)
{
if (stat->n == 0) return 0;
return (pj_isqrt((unsigned)(stat->m2_/stat->n)));
}
/**
* Set the standard deviation of statistics state. This is useful when
* the statistic state is operated in 'read-only' mode as a storage of
* statistical data.
*
* @param stat Statistic state.
*
* @param dev The standard deviation.
*/
PJ_INLINE(void) pj_math_stat_set_stddev(pj_math_stat *stat, unsigned dev)
{
if (stat->n == 0)
stat->n = 1;
stat->m2_ = dev*dev*stat->n;
}
/** @} */
PJ_END_DECL
#endif /* __PJ_MATH_H__ */
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