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- Subject: Re: Some 4.0 portability problems.
- From: "Michael T. Richter" <mtr@...>
- Date: Thu, 28 Dec 2000 10:34:59 -0500
----- Original Message -----
> ZIO is just a uniform interface for reading bytes transparently from
> strings and byte arrays.
> However, in the case of files, it ZIO them to be opened first and we left
> this to the user. Moreover, in the case of Lua, we have to look into the
> to see whether they contain Lua source or Lua precompiled chunks. That's
> why we need freopen and why parse_file in ldo.c is complicated.
> How would you change parse_file?
I would make ZIO a beefier abstraction of stream handling which dealt with
opening files, etc. as well as its current duties. This way all the work
for handling non-ANSI file I/O can be done in one location instead of
searching around throughout the code. For example, in Win32 in general
calling the native APIs for file I/O is more efficient than calling the ANSI
ones. I could, for example, make file I/O much more efficient by, say,
using overlapped I/O calls. I can't do this with the ANSI APIs. If all of
the stream I/O (file or otherwise) was localized within a single
subcomponent, I could -- no matter what the platform -- optimize stream I/O
handling using whatever special tools the underlying platform provides. And
in cases where the underlying platform doesn't supply particular
functionality (freopen being a case in point), I can fake it using whatever
facilities are actually available.
> I agree that stdin, stdout, stderr only make sense for environment that
> have consoles. but not about freopen. Am I missing something?
Freopen is typically used to redirect stdin, et al in my experience and I
made the unwarranted leap that this is what you were doing here. Later
inspection proved that wrong and I replaced the call to freopen with an
fclose followed by an fopen.
> Anyway, the bottom line is: does Windows CE implement stdio from ANSI C?
Only partially. This is why I'm always an advocate of abstraction layers
when writing code.
Michael T. Richter
"Be seeing you."