[phobos] UnbufferedFile, or, abstracting the File ranges

[Steve Schveighoffer]

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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