Re: with-open-file/FSRead

[slh@digitool.com (Steve Hain)]

At 9:12 PM 4/5/95, Rick Dukes wrote:
>Is there a way to use FSRead (ccl:examples;mac-file-io) on a file stream
>created using with-open-file?  I'm attempting to speed up copying data from
>a file stream to a tcp stream.  There is a stream-copy-until-eof function
>which gets an INPUT-FILE-STREAM object and a tcp stream object.  I have
>access to the tcp data buffer via a mac-ptr, but there seems to be no way
>to get the INPUT-FILE-STREAM object to use it.
>
>I have a working method using with-FSOpen-file/FSRead.  I'm just wondering
>if with-open-file and FSRead can be used together.

The with-FSOpen-file macro uses FSOpen, which creates a parameter block to
be passed to FSRead and its friends. The with-open-file macro uses open,
which creates a stream instance to be passed to higher-level I/O functions.
Internally, the stream uses a structure called an FBLOCK, which contains
a parameter block. You can get the parameter block from the stream using
(ccl::%fblock.pb (slot-value stream 'ccl::fblock)). If you do this, note
two things: (1) directly manipulating the parameter block will leave the
fblock in an inconsistent state, so don't mix low-level and high-level
I/O calls; (2) these are internal details and may change in the future
(although they haven't yet for MCL 3.0).

- Steve Hain

Digitool, Inc.
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