[Pharo-project] ExternalAddress and block copy?

Are there any well-worn ways to move data into and out of external memory? The best I have been able to uncover are recommendations to either do it one byte at a time (yuk!) or to (ab)use bitblt. There must be better ways, right? If not, what tools are present in the image that need to be brought to the surface? How/where should that be done so that it works on all three platforms? To what extent, if any, can String and ByteArray be used as buffers for external calls? Dolphin made that robust, but there were hints that the gc was slightly tamed to allow it. The little reading I have done in squeak-dev archives suggests that squeak/pharo is not so forgiving. Is that true? Bill