filename.writeln() across network

[Jonathan M Davis]

On Thursday, June 21, 2012 18:14:26 Regan Heath wrote:
> On Thu, 21 Jun 2012 14:56:37 +0100, Paul <phshaffer at gmail.com> wrote:
> > I wrote a program that parses a text file and writes results as it is
> > processing the file (i.e. many writeln()'s). On my local harddrive it
> > works fine. When I later used it on a file located on a file server, it
> > went from 500ms to 1 minute processing time.
> > 
> > It there a more efficient way to write out the results that would say
> > maybe only access the harddrive as it closes the connection...or
> > somesuch?
> > 
> > Thanks for your assistance.
> 
> I imagine writeln is synchronous/non-overlapped IO. Meaning, the call to
> writeln doesn't return until the write has "completed". So, on every call
> you're basically waiting for the network IO to complete before you process
> something else locally.
> 
> What you want is asynchronous or overlapped IO where the write starts, and
> the function returns, and then you later get notified that the write has
> completed. This lets you continue processing locally while the write
> happens in the background.
> 
> That's the theory, in practice I'm not sure what options you have in
> phobos for overlapped IO. If you're on windows you can pull in the win32
> functions CreateFile, WriteFile etc and define the data structures
> required for overlapped IO.

If he's pulling in data from the network and then writing it to disk, he could 
use std.concurrency to have the network stuff on one thread and the writing on 
another. It would probably mean copying the data to be able to pass it across 
threads (unless he's using different buffers every time he's reading the data 
from the network, in which case casting to immutable could do the trick), but 
it would disconnect the reading from the writing. IIRC, there's an example in 
TDPL's concurrency chapter on how to use std.concurrency to read and write 
files concurrently, which could be used as a starting point.

http://www.informit.com/articles/article.aspx?p=1609144

- Jonathan M Davis