How to share a file in memory instead of hard disk

[juo]

Hello,

I would like to know if anybody has any idea on how I can share a file into memory of Windows and how I can read this file using Perl instead of writing a file to the hard disk. Often I create some file with some parameters which then later on or read and processed but I heared that in Visual C++ you can write files to memory and don't need to write them to hard disk. Does anybody know if this is also possible in Perl and how this can be done.

[davido]

If you're talking about sharing data in memory between processes (including forked processes), you might look at Win32::MMF::Shareable. It ought to do the trick. Note however, that Roger identified an issue that prevents this module from doing its job unless you require it in each process post-forking. For that discussion, look at Perl forking and shared memory strangeness under Windows.

[BrowserUk]

Yes, this is possible. The basis of the mechanism is the CreateFileMapping API. I don't think that there is any existing module publically available to do this.

You could use Win32::API::Prototype or related module to access the api's to do this from Perl. Perhaps the best way would be to model this behind a Tie::Handle tied interface.

[Crian]

Perhaps you could create a ram disk and then use that drive to write and read files normaly?

[zentara]

I don't know if this works on Windows, but how about using the often discussed "using a variable as a filehandle".

#!/usr/bin/perl
#Do you want to use a perl variable as if it were a file?  
#Previous versions of perl had IO::Stringy and IO::Scalar for that.  
#Perl 5.8 with PerlIO has it natively. Just use a reference to  
#the scalar in the filename slot of open. 

my $foo = '';
open FILEHANDLE, '+>', \$foo or die $!;
print FILEHANDLE "Contents of File";
seek(FILEHANDLE,0,0);
my @contents = <FILEHANDLE>;
close FILEHANDLE or die $!;
print 'From $foo: ', $foo, $/;
print 'From file read: ', @contents, $/;

[davido]

How do you then share that memory with other processes? I don't think that's possible with the "in-memory filehandle" trick you're using.