From 92a51059b4a1dc19c78331ae34abcab676bcf766 Mon Sep 17 00:00:00 2001
From: Richard Senior <richard.j.senior@gmail.com>
Date: Tue, 5 Apr 2016 11:49:59 +0100
Subject: [PATCH] Fix problems parsing METAR strings that denote temporary
 sensor failures

1. Weather (normally blank, RA, SN, etc.) can be "//"
2. Cloud can be suffixed by "///", e.g. FEW045///

Also updated unit test.
---
 simgear/environment/metar.cxx      | 31 +++++++++++++++++++++++---
 simgear/environment/test_metar.cxx | 35 +++++++++++++++++++++++++++++-
 2 files changed, 62 insertions(+), 4 deletions(-)

diff --git a/simgear/environment/metar.cxx b/simgear/environment/metar.cxx
index ec4375ab..4e96839c 100644
--- a/simgear/environment/metar.cxx
+++ b/simgear/environment/metar.cxx
@@ -23,6 +23,16 @@
 /**
  * @file metar.cxx
  * Interface for encoded Meteorological Aerodrome Reports (METAR).
+ *
+ * @see WMO-49
+ * Technical Regulations, Basic Documents No. 2 (WMO No. 49)
+ * Volume II - Meteorological Service for International Air Navigation
+ * http://library.wmo.int/pmb_ged/wmo_49-v2_2013_en.pdf
+ *
+ * Refer to Table A3-2 (Template for METAR and SPECI) following page 78.
+ *
+ * For general information:
+ * World Meteorological Organization http://library.wmo.int
  */
 #ifdef HAVE_CONFIG_H
 #  include <simgear_config.h>
@@ -465,6 +475,7 @@ bool SGMetar::scanRwyVisRange()
 	char *m = _m;
 	int i;
 	SGMetarRunway r;
+
 	if (*m++ != 'R')
 		return false;
 	if (!scanNumber(&m, &i, 2))
@@ -582,6 +593,14 @@ bool SGMetar::scanWeather()
 	string weather;
 	const struct Token *a;
 
+	// @see WMO-49 Section 4.4.2.9
+	// Denotes a temporary failure of the sensor
+	if (!strncmp(m, "// ", 3)) {
+		_m += 3;
+		_grpcount++;
+		return false;
+	}
+
 	if ((a = scanToken(&m, special))) {
 		if (!scanBoundary(&m))
 			return false;
@@ -591,7 +610,7 @@ bool SGMetar::scanWeather()
 	}
 
 	string pre, post;
-    struct Weather w;
+	struct Weather w;
 	if (*m == '-')
 		m++, pre = "light ", w.intensity = LIGHT;
 	else if (*m == '+')
@@ -685,7 +704,7 @@ bool SGMetar::scanSkyCondition()
 			return false;
 
 		if (i == 3) {
-            cl._coverage = SGMetarCloud::COVERAGE_CLEAR;
+			cl._coverage = SGMetarCloud::COVERAGE_CLEAR;
 			_clouds.push_back(cl);
 		} else {
 			_cavok = true;
@@ -716,7 +735,7 @@ bool SGMetar::scanSkyCondition()
 	} else if (!scanNumber(&m, &i, 3))
 		i = -1;
 
-    if (cl._coverage == SGMetarCloud::COVERAGE_NIL) {
+	if (cl._coverage == SGMetarCloud::COVERAGE_NIL) {
 		if (!scanBoundary(&m))
 			return false;
 		if (i == -1)			// 'VV///'
@@ -735,9 +754,15 @@ bool SGMetar::scanSkyCondition()
 		cl._type = a->id;
 		cl._type_long = a->text;
 	}
+
+	// @see WMO-49 Section 4.5.4.5
+	// Denotes temporary failure of sensor and covers cases like FEW045///
+	if (!strncmp(m, "///", 3))
+		m += 3;
 	if (!scanBoundary(&m))
 		return false;
 	_clouds.push_back(cl);
+
 	_m = m;
 	_grpcount++;
 	return true;
diff --git a/simgear/environment/test_metar.cxx b/simgear/environment/test_metar.cxx
index 814094b2..41934188 100644
--- a/simgear/environment/test_metar.cxx
+++ b/simgear/environment/test_metar.cxx
@@ -58,6 +58,37 @@ void test_basic()
     COMPARE(m1.getWindDir(), 270);
     FUZZY_COMPARE(m1.getWindSpeed_kt(), 12, TEST_EPSILON);
     
+    COMPARE(m1.getWeather().size(), 1);
+    COMPARE(m1.getClouds().size(), 2);
+
+    FUZZY_COMPARE(m1.getTemperature_C(), 10, TEST_EPSILON);
+    FUZZY_COMPARE(m1.getDewpoint_C(), 5, TEST_EPSILON);
+    FUZZY_COMPARE(m1.getPressure_hPa(), 1025, TEST_EPSILON);
+}
+
+void test_sensor_failure_weather()
+{
+    SGMetar m1("2011/10/20 11:25 EHAM 201125Z 27012KT 240V300 9999 // FEW025CB SCT048 10/05 Q1025");
+    COMPARE(m1.getWindDir(), 270);
+    FUZZY_COMPARE(m1.getWindSpeed_kt(), 12, TEST_EPSILON);
+
+    COMPARE(m1.getWeather().size(), 0);
+    COMPARE(m1.getClouds().size(), 2);
+
+    FUZZY_COMPARE(m1.getTemperature_C(), 10, TEST_EPSILON);
+    FUZZY_COMPARE(m1.getDewpoint_C(), 5, TEST_EPSILON);
+    FUZZY_COMPARE(m1.getPressure_hPa(), 1025, TEST_EPSILON);
+}
+
+void test_sensor_failure_cloud()
+{
+    SGMetar m1("2011/10/20 11:25 EHAM 201125Z 27012KT 240V300 9999 FEW025CB/// SCT048/// 10/05 Q1025");
+    COMPARE(m1.getWindDir(), 270);
+    FUZZY_COMPARE(m1.getWindSpeed_kt(), 12, TEST_EPSILON);
+
+    COMPARE(m1.getWeather().size(), 0);
+    COMPARE(m1.getClouds().size(), 2);
+
     FUZZY_COMPARE(m1.getTemperature_C(), 10, TEST_EPSILON);
     FUZZY_COMPARE(m1.getDewpoint_C(), 5, TEST_EPSILON);
     FUZZY_COMPARE(m1.getPressure_hPa(), 1025, TEST_EPSILON);
@@ -66,7 +97,9 @@ void test_basic()
 int main(int argc, char* argv[])
 {
     try {
-    test_basic();
+        test_basic();
+        test_sensor_failure_weather();
+        test_sensor_failure_cloud();
     } catch (sg_exception& e) {
         cerr << "got exception:" << e.getMessage() << endl;
         return -1;
-- 
2.39.5