Unpooled.buffer() backing array on Oracle JDK 8 and openjdk-11.0.3

[Priyanka Perera]

Hi,

It appears that with openjdk-11.0.3 the Unpooled.buffer() may return a ByteBuf with a backing array elements initialized to non zero values.

In Oracle JDK 8 however, the elements of the backing array are initialized to zero.

Using netty-4.1.41.Final.

Appreciate if this can be explained.

Is there an API to get a ByteBuf with backing array elements initialized to zero ?.

@Test(invocationCount = 10000)
public void testInitialization() {
    final int SIZE = 10000;
    ByteBuf byteBuf = Unpooled.buffer(SIZE);

    int arrayLength = byteBuf.array().length;
    for (int arrayIndex = 0; arrayIndex < arrayLength; arrayIndex++) {
        Assert.assertEquals(byteBuf.array()[arrayIndex], 0);
    }
}

[Priyanka Perera]

Any insight on this much appreciated.

[Frederic]

Hi,

I checked on my side.

- Using JDK (Oracle) 8 1.8.0_221 (Linux)

- Using OpenJDK 8 1.8.0_232 (Linux)

- Using both Netty 4.1.50

Both versions gives 0 bytes initialized ByteBufs.

However, in general, assuming an allocation gives a zero values array is a wrong assertion (at least in many languages).

If you want to ensure your ByteBuf is set to 0, allocate as you do and then:

  byteBuf.setZero(byteBuf.readerIndex(), SIZE);

Cheers,

Frederic