From 77262cea760dd319c1d064615fe1f9354cd552f4 Mon Sep 17 00:00:00 2001
From: Lorenzo Colitti <lorenzo@google.com>
Date: Wed, 27 Jan 2021 00:48:41 +0900
Subject: [PATCH] Add an isEmpty convenience method to BpfMap.

Test: new unit test
Change-Id: Ibec09f328e24111aee4760af2f75ea5a80ba84c3
---
 .../com/android/networkstack/tethering/BpfMap.java  |  5 +++++
 .../android/networkstack/tethering/BpfMapTest.java  | 13 +++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/Tethering/src/com/android/networkstack/tethering/BpfMap.java b/Tethering/src/com/android/networkstack/tethering/BpfMap.java
index 78d212c027..89caa8a82d 100644
--- a/Tethering/src/com/android/networkstack/tethering/BpfMap.java
+++ b/Tethering/src/com/android/networkstack/tethering/BpfMap.java
@@ -134,6 +134,11 @@ public class BpfMap<K extends Struct, V extends Struct> implements AutoCloseable
         return deleteMapEntry(mMapFd, key.writeToBytes());
     }
 
+    /** Returns {@code true} if this map contains no elements. */
+    public boolean isEmpty() throws ErrnoException {
+        return getFirstKey() == null;
+    }
+
     private K getNextKeyInternal(@Nullable K key) throws ErrnoException {
         final byte[] rawKey = getNextRawKey(
                 key == null ? null : key.writeToBytes());
diff --git a/Tethering/tests/privileged/src/com/android/networkstack/tethering/BpfMapTest.java b/Tethering/tests/privileged/src/com/android/networkstack/tethering/BpfMapTest.java
index a0129b8ed5..cceaa8c82e 100644
--- a/Tethering/tests/privileged/src/com/android/networkstack/tethering/BpfMapTest.java
+++ b/Tethering/tests/privileged/src/com/android/networkstack/tethering/BpfMapTest.java
@@ -91,6 +91,7 @@ public final class BpfMapTest {
             }
         });
         assertNull(mTestMap.getFirstKey());
+        assertTrue(mTestMap.isEmpty());
     }
 
     private TetherDownstream6Key createTetherDownstream6Key(long iif, String address)
@@ -135,6 +136,18 @@ public final class BpfMapTest {
         }
     }
 
+    @Test
+    public void testIsEmpty() throws Exception {
+        assertNull(mTestMap.getFirstKey());
+        assertTrue(mTestMap.isEmpty());
+
+        mTestMap.insertEntry(mTestData.keyAt(0), mTestData.valueAt(0));
+        assertFalse(mTestMap.isEmpty());
+
+        mTestMap.deleteEntry((mTestData.keyAt(0)));
+        assertTrue(mTestMap.isEmpty());
+    }
+
     @Test
     public void testGetFirstKey() throws Exception {
         // getFirstKey on an empty map returns null.