Use helper function getIndexForValue in MulticastRoutingCoordinator.

The SparseArray.indexOfValue() uses == to compare values,
MulticastRoutingCoordinator uses SparseArray with String type values,
and the indexOfValue function would sometimes return -1 when looking for
a value in the SparseArray.

Added a helper function getIndexForValue in CollectionUtils to get index
by comparing values with equals, and used this function in MulticastRoutingCoordinator.

Updated
MulticastRoutingCoordinatorServiceTest#testMulticastRouting_applyConfigNone_removesMfc
test case to use copies of interface names when updating the multicast
configs, so the test would fail without this fix.

Test: atest NetworkStaticLibTests:com.android.net.moduletests.util.CollectionUtilsTest#testGetIndexForValue
atest android.net.connectivity.com.android.server.connectivity.MulticastRoutingCoordinatorServiceTest#testMulticastRouting_applyConfigNone_removesMfc

Change-Id: I862242d6be01b8552cdd6af6c9691948a9f0bfe0

staticlibs/framework/com/android/net/module/util/CollectionUtils.java

@@ -389,4 +389,28 @@ public final class CollectionUtils {
         }
         return dest;
     }
+
+    /**
+     * Returns an index of the given SparseArray that contains the given value, or -1
+     * number if no keys map to the given value.
+     *
+     * <p>Note this is a linear search, and if multiple keys can map to the same value
+     * then the smallest index is returned.
+     *
+     * <p>This function compares values with {@code equals} while the
+     * {@link SparseArray#indexOfValue} compares values using {@code ==}.
+     */
+    public static <T> int getIndexForValue(SparseArray<T> sparseArray, T value) {
+        for(int i = 0, nsize = sparseArray.size(); i < nsize; i++) {
+            T valueAt = sparseArray.valueAt(i);
+            if (valueAt == null) {
+                if (value == null) {
+                    return i;
+                };
+            } else if (valueAt.equals(value)) {
+                return i;
+            }
+        }
+        return -1;
+    }
 }

staticlibs/tests/unit/src/com/android/net/module/util/CollectionUtilsTest.kt

@@ -16,6 +16,7 @@
 
 package com.android.net.module.util
 
+import android.util.SparseArray
 import androidx.test.filters.SmallTest
 import androidx.test.runner.AndroidJUnit4
 import com.android.testutils.assertThrows
@@ -179,4 +180,20 @@ class CollectionUtilsTest {
             CollectionUtils.assoc(listOf(1, 2), list15)
         }
     }
+
+    @Test
+    fun testGetIndexForValue() {
+        val sparseArray = SparseArray<String>();
+        sparseArray.put(5, "hello");
+        sparseArray.put(10, "abcd");
+        sparseArray.put(20, null);
+
+        val value1 = "abcd";
+        val value1Copy = String(value1.toCharArray())
+        val value2 = null;
+
+        assertEquals(1, CollectionUtils.getIndexForValue(sparseArray, value1));
+        assertEquals(1, CollectionUtils.getIndexForValue(sparseArray, value1Copy));
+        assertEquals(2, CollectionUtils.getIndexForValue(sparseArray, value2));
+    }
 }