X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=blobdiff_plain;f=src%2Fcore%2Fao_convert_pa.c;fp=src%2Fcore%2Fao_convert_pa.c;h=0c93caea60550acd80dac0a879453774fd532050;hp=0000000000000000000000000000000000000000;hb=5d8b9d524d6424ff98dcc4155fe8b8bd892b6d8f;hpb=1541fc0bde71f503b1ae5757497e9e1e6d023111

diff --git a/src/core/ao_convert_pa.c b/src/core/ao_convert_pa.c
new file mode 100644
index 00000000..0c93caea
--- /dev/null
+++ b/src/core/ao_convert_pa.c
@@ -0,0 +1,72 @@
+/*
+ * 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
+
+static const int32_t altitude_table[] = {
+#include "altitude-pa.h"
+};
+
+#define ALT_SCALE	(1 << ALT_SHIFT)
+#define ALT_MASK	(ALT_SCALE - 1)
+
+int32_t
+ao_pa_to_altitude(int32_t pa)
+{
+	int16_t	o;
+	int16_t	part;
+	int32_t low, high;
+
+	if (pa < 0)
+		pa = 0;
+	if (pa > 120000)
+		pa = 120000;
+	o = pa >> ALT_SHIFT;
+	part = pa & ALT_MASK;
+
+	low = (int32_t) altitude_table[o] * (ALT_SCALE - part);
+	high = (int32_t) altitude_table[o+1] * part + (ALT_SCALE >> 1);
+	return (low + high) >> ALT_SHIFT;
+}
+
+int32_t
+ao_altitude_to_pa(int32_t alt)
+{
+	int32_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 = ((((int32_t) l * (span - sub_span) + (int32_t) h * sub_span) << ALT_SHIFT) + (span >> 1)) / span;
+	if (pa > 120000)
+		pa = 120000;
+	if (pa < 0)
+		pa = 0;
+	return pa;
+}