http_stream:stream_range

DataStream is a stream whose size is defined by the option size(ContentLength). Closing DataStream does not close RawStream. Options processed:

size(+Bytes): Number of bytes represented by the main stream.
onclose(:Closure): Calls call(Closure, RawStream, BytesLeft) when DataStream is closed. BytesLeft is the number of bytes of the range stream that have not been read, i.e., 0 (zero) if all data has been read from the stream when the range is closed. This was introduced for supporting Keep-alive in http_open/3 to reschedule the original stream for a new request if the data of the previous request was processed.