Unsafe.{get,put}-X-Unaligned; Efficient array comparison intrinsics

[Andrew Haley]

On 03/04/2015 02:29 PM, Andrew Haley wrote:
>> My inclination is to remove the get*Unaligned(..., boolean
>> bigEndian) methods and thereby consistently use Bits.swap in the
>> heap buffer. A similar pattern applies for float/double conversion.
>
> I suggest that you and John argue that between yourselves!  I think
> there's a lot to be said for that approach on architectures which can
> do unaligned accesses and have big- and little-endian memory
> operators.

The new API gives us HeapByteBuffer methods

    public long getLong(int i) {
        return unsafe.getLongUnaligned(hb, byteOffset(checkIndex(i, 8)), bigEndian);
    }

If we get rid of the get*Unaligned(..., boolean bigEndian) methods
we'll end up with

    public long getLong(int i) {
        long x = unsafe.getLongUnaligned(hb, byteOffset(checkIndex(i, 8)));
        return nativeByteOrder ? x : Bits.swap(x));
    }

... which has the disadvantage that all of the Buffer methods have to
know about the native endianness.

One suggestion: if we exposed Unsafe.fromEndian we could do something
like

    public long getLong(int i) {
        long x = unsafe.getLongUnaligned(hb, byteOffset(checkIndex(i, 8)));
        return unsafe.fromEndian(bigEndian, x));
    }

Andrew.