Changed Longs.concat() to throw IllegalArgumentException if the input arrays contain too many elements.

See #3303

Fixes #3304

RELNOTES=n/a
PiperOrigin-RevId: 543451555

Author: Istvan Neuwirth

android/guava-tests/test/com/google/common/primitives/LongsTest.java

@@ -198,6 +198,37 @@ public void testConcat() {
         .isEqualTo(new long[] {(long) 1, (long) 2, (long) 3, (long) 4});
   }
 
+  @GwtIncompatible // different overflow behavior; could probably be made to work by using ~~
+  public void testConcat_overflow_negative() {
+    int dim1 = 1 << 16;
+    int dim2 = 1 << 15;
+    assertThat(dim1 * dim2).isLessThan(0);
+    testConcat_overflow(dim1, dim2);
+  }
+
+  @GwtIncompatible // different overflow behavior; could probably be made to work by using ~~
+  public void testConcat_overflow_nonNegative() {
+    int dim1 = 1 << 16;
+    int dim2 = 1 << 16;
+    assertThat(dim1 * dim2).isAtLeast(0);
+    testConcat_overflow(dim1, dim2);
+  }
+
+  private static void testConcat_overflow(int arraysDim1, int arraysDim2) {
+    assertThat((long) arraysDim1 * arraysDim2).isNotEqualTo((long) (arraysDim1 * arraysDim2));
+
+    long[][] arrays = new long[arraysDim1][];
+    // it's shared to avoid using too much memory in tests
+    long[] sharedArray = new long[arraysDim2];
+    Arrays.fill(arrays, sharedArray);
+
+    try {
+      Longs.concat(arrays);
+      fail();
+    } catch (IllegalArgumentException expected) {
+    }
+  }
+
   private static void assertByteArrayEquals(byte[] expected, byte[] actual) {
     assertWithMessage(
             "Expected: " + Arrays.toString(expected) + ", but got: " + Arrays.toString(actual))

android/guava/src/com/google/common/primitives/Longs.java

@@ -244,13 +244,15 @@ public static long constrainToRange(long value, long min, long max) {
    *
    * @param arrays zero or more {@code long} arrays
    * @return a single array containing all the values from the source arrays, in order
+   * @throws IllegalArgumentException if the total number of elements in {@code arrays} does not fit
+   *     in an {@code int}
    */
   public static long[] concat(long[]... arrays) {
-    int length = 0;
+    long length = 0;
     for (long[] array : arrays) {
       length += array.length;
     }
-    long[] result = new long[length];
+    long[] result = new long[checkNoOverflow(length)];
     int pos = 0;
     for (long[] array : arrays) {
       System.arraycopy(array, 0, result, pos, array.length);
@@ -259,6 +261,14 @@ public static long[] concat(long[]... arrays) {
     return result;
   }
 
+  private static int checkNoOverflow(long result) {
+    checkArgument(
+        result == (int) result,
+        "the total number of elements (%s) in the arrays must fit in an int",
+        result);
+    return (int) result;
+  }
+
   /**
    * Returns a big-endian representation of {@code value} in an 8-element byte array; equivalent to
    * {@code ByteBuffer.allocate(8).putLong(value).array()}. For example, the input value {@code

guava-tests/test/com/google/common/primitives/LongsTest.java

@@ -198,6 +198,37 @@ public void testConcat() {
         .isEqualTo(new long[] {(long) 1, (long) 2, (long) 3, (long) 4});
   }
 
+  @GwtIncompatible // different overflow behavior; could probably be made to work by using ~~
+  public void testConcat_overflow_negative() {
+    int dim1 = 1 << 16;
+    int dim2 = 1 << 15;
+    assertThat(dim1 * dim2).isLessThan(0);
+    testConcat_overflow(dim1, dim2);
+  }
+
+  @GwtIncompatible // different overflow behavior; could probably be made to work by using ~~
+  public void testConcat_overflow_nonNegative() {
+    int dim1 = 1 << 16;
+    int dim2 = 1 << 16;
+    assertThat(dim1 * dim2).isAtLeast(0);
+    testConcat_overflow(dim1, dim2);
+  }
+
+  private static void testConcat_overflow(int arraysDim1, int arraysDim2) {
+    assertThat((long) arraysDim1 * arraysDim2).isNotEqualTo((long) (arraysDim1 * arraysDim2));
+
+    long[][] arrays = new long[arraysDim1][];
+    // it's shared to avoid using too much memory in tests
+    long[] sharedArray = new long[arraysDim2];
+    Arrays.fill(arrays, sharedArray);
+
+    try {
+      Longs.concat(arrays);
+      fail();
+    } catch (IllegalArgumentException expected) {
+    }
+  }
+
   private static void assertByteArrayEquals(byte[] expected, byte[] actual) {
     assertWithMessage(
             "Expected: " + Arrays.toString(expected) + ", but got: " + Arrays.toString(actual))

guava/src/com/google/common/primitives/Longs.java

@@ -246,13 +246,15 @@ public static long constrainToRange(long value, long min, long max) {
    *
    * @param arrays zero or more {@code long} arrays
    * @return a single array containing all the values from the source arrays, in order
+   * @throws IllegalArgumentException if the total number of elements in {@code arrays} does not fit
+   *     in an {@code int}
    */
   public static long[] concat(long[]... arrays) {
-    int length = 0;
+    long length = 0;
     for (long[] array : arrays) {
       length += array.length;
     }
-    long[] result = new long[length];
+    long[] result = new long[checkNoOverflow(length)];
     int pos = 0;
     for (long[] array : arrays) {
       System.arraycopy(array, 0, result, pos, array.length);
@@ -261,6 +263,14 @@ public static long[] concat(long[]... arrays) {
     return result;
   }
 
+  private static int checkNoOverflow(long result) {
+    checkArgument(
+        result == (int) result,
+        "the total number of elements (%s) in the arrays must fit in an int",
+        result);
+    return (int) result;
+  }
+
   /**
    * Returns a big-endian representation of {@code value} in an 8-element byte array; equivalent to
    * {@code ByteBuffer.allocate(8).putLong(value).array()}. For example, the input value {@code