[Java][Memory] Murmur hash implementation failing to hash less than 4 bytes.

[manolama]

Describe the bug, including details regarding any error messages, version, and platform.

When attempting to use the MurmurHasher for values like foo and bar, the same hash was produced.

Reproduction:

@Test
  public void testHasherLessThanInt() {
    try (ArrowBuf buf1 = allocator.buffer(4);
         ArrowBuf buf2 = allocator.buffer(4)) {
      buf1.writeBytes("foo1".getBytes(StandardCharsets.UTF_8));
      buf2.writeBytes("bar2".getBytes(StandardCharsets.UTF_8));

      for (int i = 1; i <= 4; i ++) {
        verifyHashCodeNotEqual(buf1, 0, i, buf2, 0, i);
      }
    }
  }

  private void verifyHashCodeNotEqual(ArrowBuf buf1, int offset1, int length1,
                                      ArrowBuf buf2, int offset2, int length2) {
    int hashCode1 = hasher.hashCode(buf1, 0, length1);
    int hashCode2 = hasher.hashCode(buf2, 0, length2);
    System.out.println(hashCode1 + " != " + hashCode2);
    //assertNotEquals(hashCode1, hashCode2);
  }

produces

-1684229222 != -1684229222
-26109336 != -26109336
-235476567 != -235476567
779730367 != 296486961

Component(s)

Java