Best effort zerocopy from Protobuf's ByteString to Netty's ByteBuf

[tisonkun]

I'm building a service with gRPC and using Netty's ByteBuf as a better byte buffer implementation.

So far, when I receive messages from the gRPC channel, bytes field is converted into Protobuf's ByteString. My internal service uses ByteBuf so there is a necessary conversion:

    public static ByteBuf byteStringToByteBuf(ByteString bytes) {
        final ByteBuffer byteBuffer = bytes.asReadOnlyByteBuffer();
        return Unpooled.buffer(byteBuffer.position()).writeBytes(byteBuffer);
    }

I implemented it as above, but this seems always to cause a bytes copy. Are there utilities or libraries to help in doing best-effort zerocopy between these two interfaces? Or is there a better way to write a service instance?

FWIW in my situation the returned bytebuf is always readonly.

[normanmaurer]

public static ByteBuf byteStringToByteBuf(ByteString bytes) {
    final ByteBuffer byteBuffer = bytes.asReadOnlyByteBuffer();
    return Unpooled.wrappedBuffer(byteBuffer);
}

[tisonkun]

Thank you! Although, the method name should be wrappedBuffer:

    public static ByteBuf byteStringToByteBuf(ByteString bytes) {
        final ByteBuffer byteBuffer = bytes.asReadOnlyByteBuffer();
        return Unpooled.wrappedBuffer(byteBuffer);
    }

[He-Pin]

Ha, yes, I missunderstand the issue, i was using something like this too.

  override def write(payload: ByteString): Boolean =
    if (channel.isWritable && channel.isOpen) {
      channel.writeAndFlush(Unpooled.wrappedBuffer(payload.asByteBuffer))
      true
    } else false