Merge changes I099c8315,I21e958d3 am: 6317dae7fb

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/2429553

Change-Id: I156623158ed9b02dfb16cafbb877bb92d69c6e2b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

core/java/com/android/internal/util/ArrayUtils.java

@@ -39,8 +39,7 @@ import java.util.Set;
 import java.util.function.IntFunction;
 
 /**
- * ArrayUtils contains some methods that you can call to find out
+ * Static utility methods for arrays that aren't already included in {@link java.util.Arrays}.
- * the most efficient increments by which to grow arrays.
  */
 public class ArrayUtils {
     private static final int CACHE_SIZE = 73;
@@ -341,10 +340,11 @@ public class ArrayUtils {
     }
 
     /**
-     * Combine multiple arrays into a single array.
+     * Returns the concatenation of the given arrays.  Only works for object arrays, not for
+     * primitive arrays.  See {@link #concat(byte[]...)} for a variant that works on byte arrays.
      *
      * @param kind The class of the array elements
-     * @param arrays The arrays to combine
+     * @param arrays The arrays to concatenate.  Null arrays are treated as empty.
      * @param <T> The class of the array elements (inferred from kind).
      * @return A single array containing all the elements of the parameter arrays.
      */
@@ -390,6 +390,29 @@ public class ArrayUtils {
         return (T[]) Array.newInstance(kind, 0);
     }
 
+    /**
+     * Returns the concatenation of the given byte arrays.  Null arrays are treated as empty.
+     */
+    public static @NonNull byte[] concat(@Nullable byte[]... arrays) {
+        if (arrays == null) {
+            return new byte[0];
+        }
+        int totalLength = 0;
+        for (byte[] a : arrays) {
+            if (a != null) {
+                totalLength += a.length;
+            }
+        }
+        final byte[] result = new byte[totalLength];
+        int pos = 0;
+        for (byte[] a : arrays) {
+            if (a != null) {
+                System.arraycopy(a, 0, result, pos, a.length);
+                pos += a.length;
+            }
+        }
+        return result;
+    }
 
     /**
      * Adds value to given array if not already present, providing set-like

core/tests/utiltests/src/com/android/internal/util/ArrayUtilsTest.java

@@ -207,4 +207,54 @@ public class ArrayUtilsTest extends TestCase {
 
         assertArrayEquals(expectation, ArrayUtils.concat(String.class, array1, array2, array3));
     }
+
+    public void testConcat_zeroByteArrays() {
+        // empty varargs array
+        assertArrayEquals(new byte[] {}, ArrayUtils.concat());
+        // null varargs array
+        assertArrayEquals(new byte[] {}, ArrayUtils.concat((byte[][]) null));
+    }
+
+    public void testConcat_oneByteArray() {
+        assertArrayEquals(new byte[] { 1, 2 }, ArrayUtils.concat(new byte[] { 1, 2 }));
+    }
+
+    public void testConcat_oneEmptyByteArray() {
+        assertArrayEquals(new byte[] {}, ArrayUtils.concat((byte[]) null));
+        assertArrayEquals(new byte[] {}, ArrayUtils.concat(new byte[] {}));
+    }
+
+    public void testConcat_twoByteArrays() {
+        assertArrayEquals(new byte[] { 1 }, ArrayUtils.concat(new byte[] { 1 }, new byte[] {}));
+        assertArrayEquals(new byte[] { 1 }, ArrayUtils.concat(new byte[] {}, new byte[] { 1 }));
+        assertArrayEquals(new byte[] { 1, 2 },
+                ArrayUtils.concat(new byte[] { 1 }, new byte[] { 2 }));
+        assertArrayEquals(new byte[] { 1, 2, 3, 4 },
+                ArrayUtils.concat(new byte[] { 1, 2 }, new byte[] { 3, 4 }));
+    }
+
+    public void testConcat_twoEmptyByteArrays() {
+        assertArrayEquals(new byte[] {}, ArrayUtils.concat((byte[]) null, null));
+        assertArrayEquals(new byte[] {}, ArrayUtils.concat(new byte[] {}, null));
+        assertArrayEquals(new byte[] {}, ArrayUtils.concat((byte[]) null, new byte[] {}));
+        assertArrayEquals(new byte[] {}, ArrayUtils.concat(new byte[] {}, new byte[] {}));
+    }
+
+    public void testConcat_threeByteArrays() {
+        byte[] array1 = { 1, 2 };
+        byte[] array2 = { 3, 4 };
+        byte[] array3 = { 5, 6 };
+        byte[] expectation = { 1, 2, 3, 4, 5, 6 };
+
+        assertArrayEquals(expectation, ArrayUtils.concat(array1, array2, array3));
+    }
+
+    public void testConcat_threeByteArraysWithNull() {
+        byte[] array1 = { 1, 2 };
+        byte[] array2 = null;
+        byte[] array3 = { 5, 6 };
+        byte[] expectation = { 1, 2, 5, 6 };
+
+        assertArrayEquals(expectation, ArrayUtils.concat(array1, array2, array3));
+    }
 }