Index: /pjproject/trunk/pjlib/include/pj/math.h
===================================================================
--- /pjproject/trunk/pjlib/include/pj/math.h	(revision 1960)
+++ /pjproject/trunk/pjlib/include/pj/math.h	(revision 1960)
@@ -0,0 +1,193 @@
+/* $Id$ */
+/* 
+ * 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;
+    stat->mean = (int) stat->fmean_;
+
+    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(pj_math_stat *stat)
+{
+    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__ */
