:POSITION/:BOUND broken on current Quicklisp version

[edicl]

:POSITION/:BOUND broken on current Quicklisp version

[mfiano]

Can reproduce. It seems position is always 0 and bound is interpreted as the relative offset from the supplied position. Seems a little strange, and doesn't align with the docstring.

[stassats]

I don't see where this behavior is documented anywhere.

[phoe]

https://edicl.github.io/flexi-streams/#make-flexi-stream

position is the initial octet position of the stream and must only be provided for input streams, the default is 0. bound should be NIL (the default) or an integer and must only be provided for input streams. If the octet position of the stream has gone beyond this bound, the stream will behave as if no more input is available.

[stassats]

It doesn't say that it moves the position of the underlying stream.

[phoe]

What does it do, then, and why does it interact with bound in the way it does?

[stassats]

It gets incremented.

[phoe]

OK, let me approach the problem from another way.

I have a file with contents #(0 1 2 3 4 5 6 7 8 9). I would like to get an open stream to that file that will only refer to the "slice" #(2 3 4 5) inside that file (e.g. when read-sequence is called on the stream). What is the canonical way of achieving that via flexi-streams? Does it involve the :bound and :position arguments?

[stassats]

Call FILE-POSITION beforehand.

[stassats]

Or even (setf flexi:stream-file-position)

[phoe]

So like the following, I assume:

CL-USER> (with-open-file (stream #p"/tmp/bytes" :element-type '(unsigned-byte 8)
                                                :direction :input)
           (let ((flexi-stream (flex:make-flexi-stream stream :position 4 :bound 8
                                                              :element-type '(unsigned-byte 8)))
                 (output (make-array 10 :initial-element 0)))
             (file-position stream 4)
             (read-sequence output flexi-stream)
             output))
#(4 5 6 7 0 0 0 0 0 0)

OK, this works. Thanks.

(flex:stream-file-position is unexported; file-position works just fine though.)

[stassats]

it's actually from gray streams. So file-position will dispatch to it keeping everything in sync.

[stassats]

Assuming you call it (file-position flexi-stream 4), no need to supply :position 4 then.