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/*
* Copyright © 2012 Keith Packard <keithp@keithp.com>
*
* 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; version 2 of the License.
*
* 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.
*/
#if !defined(AO_CONVERT_TEST) && !defined(AO_FLIGHT_TEST)
#include "ao.h"
#endif
#ifndef AO_CONST_ATTRIB
#define AO_CONST_ATTRIB
#endif
static const alt_t altitude_table[] AO_CONST_ATTRIB = {
#if AO_SMALL_ALTITUDE_TABLE
#include "altitude-pa-small.h"
#else
#include "altitude-pa.h"
#endif
};
#ifndef FETCH_ALT
#define FETCH_ALT(o) altitude_table[o]
#endif
#define ALT_SCALE (1 << ALT_SHIFT)
#define ALT_MASK (ALT_SCALE - 1)
alt_t
ao_pa_to_altitude(pres_t pa)
{
int16_t o;
int16_t part;
alt_t low, high;
if (pa < 0)
pa = 0;
if (pa > 120000L)
pa = 120000L;
o = pa >> ALT_SHIFT;
part = pa & ALT_MASK;
low = (alt_t) FETCH_ALT(o) * (ALT_SCALE - part);
high = (alt_t) FETCH_ALT(o+1) * part + (ALT_SCALE >> 1);
return (low + high) >> ALT_SHIFT;
}
#ifdef AO_CONVERT_TEST
pres_t
ao_altitude_to_pa(alt_t alt)
{
alt_t span, sub_span;
uint16_t l, h, m;
int32_t pa;
l = 0;
h = NALT - 1;
while ((h - l) != 1) {
m = (l + h) >> 1;
if (altitude_table[m] < alt)
h = m;
else
l = m;
}
span = altitude_table[l] - altitude_table[h];
sub_span = altitude_table[l] - alt;
pa = ((((alt_t) l * (span - sub_span) + (alt_t) h * sub_span) << ALT_SHIFT) + (span >> 1)) / span;
if (pa > 120000)
pa = 120000;
if (pa < 0)
pa = 0;
return pa;
}
#endif
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