From e50607efab69c62d1a7b5ba9bb3dff47449483c9 Mon Sep 17 00:00:00 2001
From: Lifu Tang <lifu@google.com>
Date: Thu, 7 Apr 2016 19:25:24 -0700
Subject: [PATCH] Fixed the sign error in GnssClock

Bug: 28068514
Change-Id: I71b68acb70d4139f94f3829bd4a280d926e251de
---
 location/java/android/location/GnssClock.java | 10 ++++----
 ...d_server_location_GnssLocationProvider.cpp | 25 +++++++++++--------
 2 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/location/java/android/location/GnssClock.java b/location/java/android/location/GnssClock.java
index d1b1be9393743..25d247deff24d 100644
--- a/location/java/android/location/GnssClock.java
+++ b/location/java/android/location/GnssClock.java
@@ -97,7 +97,7 @@ public final class GnssClock implements Parcelable {
      *
      * <p>The sign of the value is defined by the following equation:
      * <pre>
-     *     UtcTimeNanos = TimeNanos + (FullBiasNanos + BiasNanos) - LeapSecond * 1,000,000,000</pre>
+     *     UtcTimeNanos = TimeNanos - (FullBiasNanos + BiasNanos) - LeapSecond * 1,000,000,000</pre>
      *
      * <p>The value is only available if {@link #hasLeapSecond()} is {@code true}.
      */
@@ -130,9 +130,9 @@ public final class GnssClock implements Parcelable {
      *
      * <p>This value is expected to be monotonically increasing while the hardware clock remains
      * powered on. For the case of a hardware clock that is not continuously on, see the
-     * {@link #getHardwareClockDiscontinuityCount} field. The GPS time can be derived by adding
-     * {@link #getFullBiasNanos()} and {@link #getBiasNanos()} (when they are available) to this
-     * value. Sub-nanosecond accuracy can be provided by means of {@link #getBiasNanos()}.
+     * {@link #getHardwareClockDiscontinuityCount} field. The GPS time can be derived by subtracting
+     * the sum of {@link #getFullBiasNanos()} and {@link #getBiasNanos()} (when they are available)
+     * from this value. Sub-nanosecond accuracy can be provided by means of {@link #getBiasNanos()}.
      *
      * <p>The error estimate for this value (if applicable) is {@link #getTimeUncertaintyNanos()}.
      */
@@ -213,7 +213,7 @@ public final class GnssClock implements Parcelable {
      * <p>The sign of the value is defined by the following equation:
      *
      * <pre>
-     *     local estimate of GPS time = TimeNanos + (FullBiasNanos + BiasNanos)</pre>
+     *     local estimate of GPS time = TimeNanos - (FullBiasNanos + BiasNanos)</pre>
      */
     public long getFullBiasNanos() {
         return mFullBiasNanos;
diff --git a/services/core/jni/com_android_server_location_GnssLocationProvider.cpp b/services/core/jni/com_android_server_location_GnssLocationProvider.cpp
index ae050429efed5..78b0844e8ed44 100644
--- a/services/core/jni/com_android_server_location_GnssLocationProvider.cpp
+++ b/services/core/jni/com_android_server_location_GnssLocationProvider.cpp
@@ -1112,7 +1112,7 @@ static jobject translate_gps_clock(JNIEnv* env, GpsClock* clock) {
     JavaObject object(env, "android/location/GnssClock");
     GpsClockFlags flags = clock->flags;
 
-    SET_IF(GNSS_CLOCK_HAS_LEAP_SECOND,
+    SET_IF(GPS_CLOCK_HAS_LEAP_SECOND,
            LeapSecond,
            static_cast<int32_t>(clock->leap_second));
 
@@ -1121,8 +1121,9 @@ static jobject translate_gps_clock(JNIEnv* env, GpsClock* clock) {
     // old GPS_CLOCK types (active only in a limited number of older devices),
     // the GPS time information is handled as an always discontinuous HW clock,
     // with the GPS time information put into the full_bias_ns instead - so that
-    // time_ns + full_bias_ns = local estimate of GPS time (as remains true, in
-    // the new GnssClock struct.)
+    // time_ns - full_bias_ns = local estimate of GPS time. Additionally, the
+    // sign of full_bias_ns and bias_ns has flipped between GpsClock &
+    // GnssClock, so that is also handled below.
     switch (clock->type) {
       case GPS_CLOCK_TYPE_UNKNOWN:
         // Clock type unsupported.
@@ -1133,7 +1134,7 @@ static jobject translate_gps_clock(JNIEnv* env, GpsClock* clock) {
         break;
       case GPS_CLOCK_TYPE_GPS_TIME:
         // GPS time, need to convert.
-        flags |= GNSS_CLOCK_HAS_FULL_BIAS;
+        flags |= GPS_CLOCK_HAS_FULL_BIAS;
         clock->full_bias_ns = clock->time_ns;
         clock->time_ns = 0;
         SET(HardwareClockDiscontinuityCount,
@@ -1142,16 +1143,20 @@ static jobject translate_gps_clock(JNIEnv* env, GpsClock* clock) {
     }
 
     SET(TimeNanos, clock->time_ns);
-    SET_IF(GNSS_CLOCK_HAS_TIME_UNCERTAINTY,
+    SET_IF(GPS_CLOCK_HAS_TIME_UNCERTAINTY,
            TimeUncertaintyNanos,
            clock->time_uncertainty_ns);
-    SET_IF(GNSS_CLOCK_HAS_FULL_BIAS, FullBiasNanos, clock->full_bias_ns);
-    SET_IF(GNSS_CLOCK_HAS_BIAS, BiasNanos, clock->bias_ns);
-    SET_IF(GNSS_CLOCK_HAS_BIAS_UNCERTAINTY,
+
+    // Definition of sign for full_bias_ns & bias_ns has been changed since N,
+    // so flip signs here.
+    SET_IF(GPS_CLOCK_HAS_FULL_BIAS, FullBiasNanos, -(clock->full_bias_ns));
+    SET_IF(GPS_CLOCK_HAS_BIAS, BiasNanos, -(clock->bias_ns));
+
+    SET_IF(GPS_CLOCK_HAS_BIAS_UNCERTAINTY,
            BiasUncertaintyNanos,
            clock->bias_uncertainty_ns);
-    SET_IF(GNSS_CLOCK_HAS_DRIFT, DriftNanosPerSecond, clock->drift_nsps);
-    SET_IF(GNSS_CLOCK_HAS_DRIFT_UNCERTAINTY,
+    SET_IF(GPS_CLOCK_HAS_DRIFT, DriftNanosPerSecond, clock->drift_nsps);
+    SET_IF(GPS_CLOCK_HAS_DRIFT_UNCERTAINTY,
            DriftUncertaintyNanosPerSecond,
            clock->drift_uncertainty_nsps);