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/*
dsp/util.h
Copyright 2002-4 Tim Goetze <tim@quitte.de>
http://quitte.de/dsp/
common math utility functions.
*/
/*
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 or point your web browser to http://www.gnu.org.
*/
#ifndef _DSP_UTIL_H_
#define _DSP_UTIL_H_
namespace DSP {
inline int next_power_of_2 (int n)
{
assert (n <= 0x40000000);
int m = 1;
while (m < n)
m <<= 1;
return m;
}
/* courtesy of Andrew Simper (vellocet.com) */
inline float
exp2_approx (float x)
{
long * px = (long *) (&x); // store address of float as long pointer
const float tx = (x - .5f) + (3 << 22); // temporary value for truncation
const long lx = *((long *) &tx) - 0x4b400000; // integer power of 2
const float dx = x - (float) (lx); // float remainder of power of 2
x = 1.f + dx * (0.6960656421638072f + // cubic apporoximation of 2^x
dx * (0.224494337302845f + // for x in the range [0, 1]
dx * (0.07944023841053369f)));
*px += (lx << 23); // add integer power of 2 to exponent
return x;
}
inline bool
isprime (int v)
{
if (v <= 3)
return true;
if (!(v & 1))
return false;
for (int i = 3; i < (int) sqrt (v) + 1; i += 2)
if ((v % i) == 0)
return false;
return true;
}
inline double
db2lin (double db)
{
return pow (10., db * .05);
}
inline double
lin2db (double lin)
{
return 20. * log10 (lin);
}
} /* namespace DSP */
#endif /* _DSP_UTIL_H_ */
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