java 14 and JEP 370: Foreign-Memory Access API-- Array Of Bytes.

[Maurizio Cimadamore]

Hi,
your example is almost correct, the problem is in your cast:

byte value[] = (byte[]) byteHandle.get(address.addOffset(0));

This should be:

byte value = (byte) byteHandle.get(address.addOffset(0));

That is, you read one byte at a time.

Does this help?

Thanks
Maurizio

On 25/03/2020 15:02, Ahmed Hamdallah wrote:
> hello,
>
> Regarding java 14 new feature of new Foreign-Memory API. it is actually bit complicated for me regarding classes SequenceLayout & VarHandle.
>
> since it is a new feature, i could not find many example to access MemorySegment data.
>
> my question, using MemorySegment & VarHandle classes how to read/write array of bytes at one shot. not byte by byte.
>
> Yes, I am aware of asByteBuffer(). but as per documentation the main reason for this new Memory Segment access is to avoid ByteBuffer class.
>
> this is example
>
> byte[] bytesArrayString = "Hello MemorySegment".getBytes();
>
>      MemoryAddress address = MemorySegment.allocateNative(4096).baseAddress();
>
>      SequenceLayout bytes = MemoryLayout.ofSequence(bytesArrayString.length, MemoryLayouts.JAVA_BYTE);
>
>      VarHandle byteHandle = bytes.varHandle(byte.class, MemoryLayout.PathElement.sequenceElement());
>
>      byteHandle.set(address.addOffset(0), (byte[]) bytesArrayString);
>
>      byte value[] = (byte[]) byteHandle.get(address.addOffset(0));
>
>      System.out.println("Memory Value: " + value.length + new String(value));
>
> error
>
> java.lang.invoke.WrongMethodTypeException: cannot convert MethodHandle(VarHandle,MemoryAddressProxy,long,byte)void to (VarHandle,MemoryAddress,long,byte[])void
> java<https://stackoverflow.com/questions/tagged/java>