Fix overflow/underflow problem in comparison

Here's overflow/underflow problem in comparators.
"when1 - when2" may suffer in overflow/underflow condition.
Comparing them directly can avoid this problem.

Change-Id: Id46af3db2adac90654210182d26ade1986ee0661

diff --git a/services/core/java/com/android/server/AlarmManagerService.java b/services/core/java/com/android/server/AlarmManagerService.java
index 8adfcc4..fa906f7 100644 (file)
--- a/services/core/java/com/android/server/AlarmManagerService.java
+++ b/services/core/java/com/android/server/AlarmManagerService.java
@@ -369,10 +369,10 @@ class AlarmManagerService extends SystemService {
         public int compare(Batch b1, Batch b2) {
             long when1 = b1.start;
             long when2 = b2.start;
-            if (when1 - when2 > 0) {
+            if (when1 > when2) {
                 return 1;
             }
-            if (when1 - when2 < 0) {
+            if (when1 < when2) {
                 return -1;
             }
             return 0;
@@ -1482,10 +1482,10 @@ class AlarmManagerService extends SystemService {
         public int compare(Alarm a1, Alarm a2) {
             long when1 = a1.whenElapsed;
             long when2 = a2.whenElapsed;
-            if (when1 - when2 > 0) {
+            if (when1 > when2) {
                 return 1;
             }
-            if (when1 - when2 < 0) {
+            if (when1 < when2) {
                 return -1;
             }
             return 0;