2 * Copyright © 2012 Keith Packard <keithp@keithp.com>
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; version 2 of the License.
8 * This program is distributed in the hope that it will be useful, but
9 * WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * General Public License for more details.
13 * You should have received a copy of the GNU General Public License along
14 * with this program; if not, write to the Free Software Foundation, Inc.,
15 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
18 #if !defined(AO_CONVERT_TEST) && !defined(AO_FLIGHT_TEST)
22 static const int32_t altitude_table[] = {
23 #include "altitude-pa.h"
26 #define ALT_SCALE (1 << ALT_SHIFT)
27 #define ALT_MASK (ALT_SCALE - 1)
30 ao_pa_to_altitude(int32_t pa)
43 low = (int32_t) altitude_table[o] * (ALT_SCALE - part);
44 high = (int32_t) altitude_table[o+1] * part + (ALT_SCALE >> 1);
45 return (low + high) >> ALT_SHIFT;
49 ao_altitude_to_pa(int32_t alt)
51 int32_t span, sub_span;
57 while ((h - l) != 1) {
59 if (altitude_table[m] < alt)
64 span = altitude_table[l] - altitude_table[h];
65 sub_span = altitude_table[l] - alt;
66 pa = ((((int32_t) l * (span - sub_span) + (int32_t) h * sub_span) << ALT_SHIFT) + (span >> 1)) / span;