[phobos] UnbufferedFile, or, abstracting the File ranges

[Lars Tandle Kyllingstad]

Yeah, the ubyte functions were just examples.  My intention was to use
templates:

  size_t read(T)(ref T[] b);
  size_t write(T)(T[] b);

Then you get a sensible error message if the number of raw bytes read
isn't a multiple of the size of your target type.  Also, the returned
number is the length of the resulting array, and not the number of raw
bytes read.

Thanks for the tips! :)

-Lars



On Mon, 2010-05-10 at 05:24 -0700, Steve Schveighoffer wrote:
> I would define only 2 i/o functions:
> 
> size_t read(void[] b);
> size_t write(const(void)[] b);
> 
> And then the various paraphernalia around it (close, open, etc).
> 
> The reason to use void[] is because any array data type can be passed
> to it without casting (imagine you wanted to read an array of ints).
> 
> Reading and writing a single byte should be discouraged with
> unbuffered streams.  This is how it is in most I/O libs.  You build
> your unbuffered I/O to abstract the OS functions, then build your
> buffered I/O and fancy functionality on top of it.
> 
> -Steve
> 
> 
> 
> ______________________________________________________________________
> From: Lars Tandle Kyllingstad <lars at kyllingen.net>
> To: Discuss the phobos library for D <phobos at puremagic.com>
> Sent: Mon, May 10, 2010 8:14:26 AM
> Subject: Re: [phobos] UnbufferedFile, or, abstracting the File ranges
> 
> Well, that would at least mean less work for me. :)
> 
> Which I/O methods should it contain, then, in your opinion?  Would
> 
>         bool read(ref ubyte b);
>         size_t read(ref ubyte[] b);
>         void write(ubyte b);
>         void write(ubyte[] b);
> 
> suffice?
> 
> -Lars
> 
> 
> 
> On Mon, 2010-05-10 at 05:02 -0700, Steve Schveighoffer wrote:
> > Re: byLine and byChunk, I don't think these are a good idea on
> > unbuffered files.
> > 
> > For example, your current implementation will be extremely slow.
> > Reading one char at a time is OK on a buffered file, because most
> > times its just a simple fetch of a char from a buffer.  But your
> > implementation reads a single character at a time from the actual
> file
> > on disk, a very slow operation.
> > 
> > I think unbuffered files are good for when you want to handle the
> > buffering yourself, or when you want to pass them to child
> processes.
> > 
> > -Steve
> > 
> > 
> > 
> > 
> >
> ______________________________________________________________________
> > From: Lars Tandle Kyllingstad <lars at kyllingen.net>
> > To: Phobos mailing list <phobos at puremagic.com>
> > Sent: Mon, May 10, 2010 7:40:15 AM
> > Subject: [phobos] UnbufferedFile, or, abstracting the File ranges
> > 
> > In the process of designing std.process it has become obvious, as
> > pointed out by Steve, that Phobos needs facilities for unbuffered
> I/O.
> > To that end, I've started writing an UnbufferedFile type, the
> current
> > status of which can be seen here:
> > 
> >        Code:
> > http://github.com/kyllingstad/ltk/blob/master/ltk/stdio.d
> >        Docs: http://kyllingen.net/code/ltk/doc/stdio.html
> > 
> > (Disclaimer: This is very much a work-in-progress, there's lots of
> > stuff
> > that needs to be added yet, and I'd be surprised if there wasn't
> lots
> > of
> > room for improvement, performance-wise.)
> > 
> > 
> > Now, while writing this it has kind of annoyed me that I have to
> write
> > new implementations of the byLine and byChunk ranges.  I've
> personally
> > found them incredibly useful, so I want them in UnbufferedFile, but
> > the
> > ones in std.stdio are tailored for File.
> > 
> > I therefore suggest we try to abstract these ranges, so they can
> > operate
> > on general types that define a set of primitives such as read(),
> > readc()
> > and readln().
> > 
> > Are there problems with this?  Any comments?
> > 
> > -Lars
> > 
> > _______________________________________________
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> > phobos at puremagic.com
> > http://lists.puremagic.com/mailman/listinfo/phobos
> > 
> > 
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> 
> 
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