1 files changed, 78 insertions, 0 deletions
diff --git a/lib/FileCache.pm b/lib/FileCache.pm
new file mode 100644
index 0000000000..3d01371b3b
--- /dev/null
+++ b/lib/FileCache.pm
@@ -0,0 +1,78 @@
+package FileCache;
+
+=head1 NAME
+
+FileCache - keep more files open than the system permits
+
+=head1 SYNOPSIS
+
+    cacheout $path;
+    print $path @data;
+
+=head1 DESCRIPTION
+
+The C<cacheout> function will make sure that there's a filehandle open
+for writing available as the pathname you give it.  It automatically
+closes and re-opens files if you exceed your system file descriptor
+maximum.
+
+=head1 BUGS
+
+F<sys/param.h> lies with its C<NOFILE> define on some systems,
+so you may have to set $cacheout::maxopen yourself.
+
+=cut
+
+require 5.000;
+use Carp;
+use Exporter;
+
+@ISA = qw(Exporter);
+@EXPORT = qw(
+    cacheout
+);
+
+# Open in their package.
+
+sub cacheout_open {
+    my $pack = caller(1);
+    open(*{$pack . '::' . $_[0]}, $_[1]);
+}
+
+sub cacheout_close {
+    my $pack = caller(1);
+    close(*{$pack . '::' . $_[0]});
+}
+
+# But only this sub name is visible to them.
+
+$cacheout_seq = 0;
+$cacheout_numopen = 0;
+
+sub cacheout {
+    ($file) = @_;
+    unless (defined $cacheout_maxopen) {
+	if (open(PARAM,'/usr/include/sys/param.h')) {
+	    local $.;
+	    while (<PARAM>) {
+		$cacheout_maxopen = $1 - 4
+		    if /^\s*#\s*define\s+NOFILE\s+(\d+)/;
+	    }
+	    close PARAM;
+	}
+	$cacheout_maxopen = 16 unless $cacheout_maxopen;
+    }
+    if (!$isopen{$file}) {
+	if (++$cacheout_numopen > $cacheout_maxopen) {
+	    my @lru = sort {$isopen{$a} <=> $isopen{$b};} keys(%isopen);
+	    splice(@lru, $cacheout_maxopen / 3);
+	    $cacheout_numopen -= @lru;
+	    for (@lru) { &cacheout_close($_); delete $isopen{$_}; }
+	}
+	cacheout_open($file, ($saw{$file}++ ? '>>' : '>') . $file)
+	    or croak("Can't create $file: $!");
+    }
+    $isopen{$file} = ++$cacheout_seq;
+}
+
+1;