
Win32::SharedFileOpen Version 3.00
==================================

NAME

Win32::SharedFileOpen - Open a file for shared reading and/or writing

SYNOPSIS

	# Read and write files a la open(), but with mandatory file locking:
	# ------------------------------------------------------------------

	use Win32::SharedFileOpen;

	fsopen(FH1, 'readme', 'r', SH_DENYWR) or
		die "Can't read 'readme' and take write-lock: $^E\n";

	fsopen(FH2, 'writeme', 'w', SH_DENYRW) or
		die "Can't write 'writeme' and take read/write-lock: $^E\n";

	# Read and write files a la sysopen(), but with mandatory file locking:
	# ---------------------------------------------------------------------

	use Win32::SharedFileOpen;

	sopen(FH1, 'readme', O_RDONLY, SH_DENYWR) or
		die "Can't read 'readme' and take write-lock: $^E\n";

	sopen(FH2, 'writeme', O_WRONLY | O_CREAT | O_TRUNC, SH_DENYRW, S_IWRITE) or
		die "Can't write 'writeme' and take read/write-lock: $^E\n";

	# Retry opening the file if it fails due to a sharing violation:
	# --------------------------------------------------------------

	use Win32::SharedFileOpen qw(:DEFAULT :retry);

	$Max_Time      = 10;	# Try opening the file for up to 10 seconds
	$Retry_Timeout = 500;	# Wait 500 milliseconds between each try

	fsopen(FH, 'readme', 'r', SH_DENYNO) or
		die "Can't read 'readme' after retrying for $Max_Time seconds: $^E\n";

	# Use a lexical indirect filehandle that closes itself when destroyed:
	# --------------------------------------------------------------------

	use Win32::SharedFileOpen qw(:DEFAULT new_fh);

	{
		my $fh = new_fh();

		fsopen($fh, 'readme', 'r', SH_DENYNO) or
			die "Can't read 'readme': $^E\n";

		while (<$fh>) {
			# ... Do some stuff ...
		}

	}	# ... $fh is automatically closed here

DESCRIPTION

This module provides a Perl interface to the Microsoft Visual C functions
_fsopen() and _sopen(). These functions are counterparts to the standard C
library functions fopen(3) and open(2) respectively (which are already
effectively available in Perl as open() and sysopen() respectively), but are
intended for use when opening a file for subsequent shared reading and/or
writing.

INSTALLATION

To install this module type the following:

	perl Makefile.PL
	nmake
	nmake test
	nmake install

DEPENDENCIES

The only non-standard module required by this module is Win32::WinError. This is
part of the "libwin32" bundle, which is almost invariably present in Perl
installations on Microsoft Windows platforms anyway, and is available from CPAN
(http://www.perl.com/CPAN/).

Obviously this module only works on Microsoft Windows platforms, and requires
Microsoft Visual C to build it since other C build environments (e.g.
Cygwin/GCC) do not implement the Microsoft-specific functions which this module
provides wrappers to.

COMPATIBILITY

Prior to version 2.00 of this module, fsopen() and sopen() both created a
filehandle and returned it to the caller. (undef was returned instead on
failure.)

As of version 2.00 of this module, the arguments and return values of these two
functions now more closely resemble those of the Perl built-in functions open()
and sysopen(). Specifically, they now both expect a filehandle as their first
argument and they both return a boolean value to indicate success or failure.

THIS IS AN INCOMPATIBLE CHANGE. EXISTING SOFTWARE THAT USES THESE FUNCTIONS WILL
NEED TO BE MODIFIED.

COPYRIGHT AND LICENCE

Copyright (c) 2001-2002, Steve Hay. All rights reserved.

This program is free software; you can redistribute it and/or modify it under
the same terms as Perl itself.
