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On Wed, 03 Mar 1999 09:32:37 -0600, Ken Forbus wrote:

>This is a technical support list for a particular Lisp product.

Well then, I'd like to ask a technical question.

Does anyone ever implemented custom streams using the CLOSified
streams of ACL? Documentation on ACL's implementation of streams is
nowhere as clear as I'd like. A few examples would be *very* welcome.

I'm writing bindings for using the ZLib open-source compression
library from ACL for Windows. That works just fine. Now I'd like to
write a wrapper so the user could write:

(with-gzfile-stream (gzfile "d:/usr/test/test.gz"
                            :direction :output
		            :if-does-not-exist :create
		            :mode :text))
  (format gzfile "This is a ~A~%" "line of data")
  (write-string "This is another line of data" gzfile)
  (terpri gzfile))

etc.

Now I've reached the point where I can create a custom stream (with
excl::def-stream-class) and really write to/read from it. But the
interface through open seems clumsy. I don't know how to use open to
create the stream *without* it also creating the file. I don't want
that, as gz-open does it already. I can skip open altogether and use
(make-instance 'gzfile-stream) directly, but then I have to write my
own parsing of open keyword parameters, etc...

ZLib has a gzfdopen call that reuses a file descriptor, but
unfortunately that fd is a C RTL thingy and not a Windows filehandle,
so I cannot pass it the internal fd used by the file-stream
implementation...

So, why do you (the generic "you", I mean) think is the best approach?
Does anyone have code/examples of deriving the string-stream classes
or other streams that do *not* directly connect with a physical file?

Thanks for your input,

                                                       /L/e/k/t/u

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