Normalize longitude without looping (#460)

* Normalize longitude without looping Change normalizeLongitude to remove loops. Returned value is a normalized longitude in range [-180;+180)
google · Nov 15, 2021 · 6707912 · 6707912
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commit 6707912
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diff --git a/java/src/main/java/com/google/openlocationcode/OpenLocationCode.java b/java/src/main/java/com/google/openlocationcode/OpenLocationCode.java
@@ -665,13 +665,16 @@ private static double clipLatitude(double latitude) {
   }
 
   private static double normalizeLongitude(double longitude) {
-    while (longitude < -LONGITUDE_MAX) {
-      longitude = longitude + LONGITUDE_MAX * 2;
+    if (longitude >= -LONGITUDE_MAX && longitude < LONGITUDE_MAX) {
+      // longitude is within proper range, no normalization necessary
+      return longitude;
     }
-    while (longitude >= LONGITUDE_MAX) {
-      longitude = longitude - LONGITUDE_MAX * 2;
-    }
-    return longitude;
+
+    // % in Java uses truncated division with the remainder having the same sign as
+    // the dividend. For any input longitude < -360, the result of longitude%CIRCLE_DEG
+    // will still be negative but > -360, so we need to add 360 and apply % a second time.
+    final long CIRCLE_DEG = 2 * LONGITUDE_MAX; // 360 degrees
+    return (longitude % CIRCLE_DEG + CIRCLE_DEG + LONGITUDE_MAX) % CIRCLE_DEG - LONGITUDE_MAX;
   }
 
   /**

diff --git a/test_data/encoding.csv b/test_data/encoding.csv
@@ -18,14 +18,25 @@
 1,1,11,6FH32222+222
 ################################################################################
 #
-# Special cases over 90 latitude and 180 longitude
+# Special cases over 90 latitude
 #
 ################################################################################
 90,1,4,CFX30000+
 92,1,4,CFX30000+
+90,1,10,CFX3X2X2+X2
+################################################################################
+#
+# Special cases with longitude needing normalization (<< -180 or >> +180)
+#
+################################################################################
 1,180,4,62H20000+
 1,181,4,62H30000+
-90,1,10,CFX3X2X2+X2
+20.3701135,362.78223535156,13,7FG49QCJ+2VXGJ
+47.0000625,728.0000625,10,8FVC2222+22
+-41.2730625,1254.7859375,10,4VCPPQGP+Q9
+20.3701135,-357.217764648,13,7FG49QCJ+2VXGJ
+47.0000625,-711.9999375,10,8FVC2222+22
+-41.2730625,-905.2140625,10,4VCPPQGP+Q9
 ################################################################################
 #
 # Test non-precise latitude/longitude value