Move duplicated union of HashSets logic into helper class

Bug: 36850431
Test: adb shell am instrument -w -e package com.android.server.backup com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner
Change-Id: I83a95919d7b85131cc7ad73575d7a89c7f2d78f9

3 files changed, 111 insertions, 18 deletions

diff --git a/services/backup/java/com/android/server/backup/RefactoredBackupManagerService.java b/services/backup/java/com/android/server/backup/RefactoredBackupManagerService.java
index 674e9725cc8a..3c28d87ee0cf 100644
--- a/services/backup/java/com/android/server/backup/RefactoredBackupManagerService.java
+++ b/services/backup/java/com/android/server/backup/RefactoredBackupManagerService.java
@@ -117,10 +117,14 @@ import com.android.server.backup.restore.PerformUnifiedRestoreTask;
 import com.android.server.backup.utils.AppBackupUtils;
 import com.android.server.backup.utils.BackupManagerMonitorUtils;
 import com.android.server.backup.utils.BackupObserverUtils;
+import com.android.server.backup.utils.PasswordUtils;
+import com.android.server.backup.utils.SparseArrayUtils;
 import com.android.server.power.BatterySaverPolicy.ServiceType;
 
 import libcore.io.IoUtils;
 
+import com.google.android.collect.Sets;
+
 import java.io.BufferedInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.DataInputStream;
@@ -2317,21 +2321,13 @@ public class RefactoredBackupManagerService implements BackupManagerServiceInter
         }
 
         // a caller with full permission can ask to back up any participating app
-        HashSet<String> targets = new HashSet<>();
         if (PACKAGE_MANAGER_SENTINEL.equals(packageName)) {
-            targets.add(PACKAGE_MANAGER_SENTINEL);
+            return Sets.newHashSet(PACKAGE_MANAGER_SENTINEL);
         } else {
             synchronized (mBackupParticipants) {
-                int N = mBackupParticipants.size();
-                for (int i = 0; i < N; i++) {
-                    HashSet<String> s = mBackupParticipants.valueAt(i);
-                    if (s != null) {
-                        targets.addAll(s);
-                    }
-                }
+                return SparseArrayUtils.union(mBackupParticipants);
             }
         }
-        return targets;
     }
 
     private void writeToJournalLocked(String str) {
@@ -2423,14 +2419,7 @@ public class RefactoredBackupManagerService implements BackupManagerServiceInter
             // a caller with full permission can ask to back up any participating app
             // !!! TODO: allow data-clear of ANY app?
             if (MORE_DEBUG) Slog.v(TAG, "Privileged caller, allowing clear of other apps");
-            apps = new HashSet<>();
-            int N = mBackupParticipants.size();
-            for (int i = 0; i < N; i++) {
-                HashSet<String> s = mBackupParticipants.valueAt(i);
-                if (s != null) {
-                    apps.addAll(s);
-                }
-            }
+            apps = SparseArrayUtils.union(mBackupParticipants);
         }
 
         // Is the given app an available participant?
diff --git a/services/backup/java/com/android/server/backup/utils/SparseArrayUtils.java b/services/backup/java/com/android/server/backup/utils/SparseArrayUtils.java
new file mode 100644
index 000000000000..954d714f6d60
--- /dev/null
+++ b/services/backup/java/com/android/server/backup/utils/SparseArrayUtils.java
@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License
+ */
+
+package com.android.server.backup.utils;
+
+import android.util.SparseArray;
+
+import java.util.HashSet;
+
+/**
+ * Helper functions for manipulating instances of {@link SparseArray}.
+ */
+public final class SparseArrayUtils {
+    // Statics only
+    private SparseArrayUtils() {}
+
+    /**
+     * Given a {@link SparseArray<HashSet>}, returns a new {@link HashSet} containing every element
+     * from every set in the array.
+     *
+     * @param sets The array of sets from which to take the union.
+     * @param <V> The type of element contained in the set.
+     * @return The complete set.
+     */
+    public static<V> HashSet<V> union(SparseArray<HashSet<V>> sets) {
+        HashSet<V> unionSet = new HashSet<>();
+        int n = sets.size();
+        for (int i = 0; i < n; i++) {
+            HashSet<V> ithSet = sets.valueAt(i);
+            if (ithSet != null) {
+                unionSet.addAll(ithSet);
+            }
+        }
+        return unionSet;
+    }
+}
diff --git a/services/tests/servicestests/src/com/android/server/backup/utils/SparseArrayUtilsTest.java b/services/tests/servicestests/src/com/android/server/backup/utils/SparseArrayUtilsTest.java
new file mode 100644
index 000000000000..db55120dc023
--- /dev/null
+++ b/services/tests/servicestests/src/com/android/server/backup/utils/SparseArrayUtilsTest.java
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License
+ */
+
+package com.android.server.backup.utils;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import android.platform.test.annotations.Presubmit;
+import android.support.test.filters.SmallTest;
+import android.support.test.runner.AndroidJUnit4;
+import android.util.SparseArray;
+
+import com.google.android.collect.Sets;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import java.util.HashSet;
+
+@SmallTest
+@Presubmit
+@RunWith(AndroidJUnit4.class)
+public class SparseArrayUtilsTest {
+    @Test
+    public void union_mergesSets() {
+        SparseArray<HashSet<String>> sparseArray = new SparseArray<>();
+        sparseArray.append(12, Sets.newHashSet("a", "b", "c"));
+        sparseArray.append(45, Sets.newHashSet("d", "e"));
+        sparseArray.append(46, Sets.newHashSet());
+        sparseArray.append(66, Sets.newHashSet("a", "e", "f"));
+
+        assertThat(SparseArrayUtils.union(sparseArray)).isEqualTo(
+                Sets.newHashSet("a", "b", "c", "d", "e", "f"));
+    }
+
+    @Test
+    public void union_returnsEmptySetForEmptyList() {
+        SparseArray<HashSet<String>> sparseArray = new SparseArray<>();
+
+        assertThat(SparseArrayUtils.union(sparseArray)).isEqualTo(Sets.newHashSet());
+    }
+}