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[msysgit/historical-msysgit.git] / lib / perl5 / 5.6.1 / FileCache.pm
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1 package FileCache;
3 =head1 NAME
5 FileCache - keep more files open than the system permits
7 =head1 SYNOPSIS
9 cacheout $path;
10 print $path @data;
12 =head1 DESCRIPTION
14 The C<cacheout> function will make sure that there's a filehandle open
15 for writing available as the pathname you give it. It automatically
16 closes and re-opens files if you exceed your system file descriptor
17 maximum.
19 =head1 BUGS
21 F<sys/param.h> lies with its C<NOFILE> define on some systems,
22 so you may have to set $FileCache::cacheout_maxopen yourself.
24 =cut
26 require 5.000;
27 use Carp;
28 use Exporter;
30 @ISA = qw(Exporter);
31 @EXPORT = qw(
32 cacheout
35 # Open in their package.
37 sub cacheout_open {
38 my $pack = caller(1);
39 open(*{$pack . '::' . $_[0]}, $_[1]);
42 sub cacheout_close {
43 my $pack = caller(1);
44 close(*{$pack . '::' . $_[0]});
47 # But only this sub name is visible to them.
49 $cacheout_seq = 0;
50 $cacheout_numopen = 0;
52 sub cacheout {
53 ($file) = @_;
54 unless (defined $cacheout_maxopen) {
55 if (open(PARAM,'/usr/include/sys/param.h')) {
56 local ($_, $.);
57 while (<PARAM>) {
58 $cacheout_maxopen = $1 - 4
59 if /^\s*#\s*define\s+NOFILE\s+(\d+)/;
61 close PARAM;
63 $cacheout_maxopen = 16 unless $cacheout_maxopen;
65 if (!$isopen{$file}) {
66 if (++$cacheout_numopen > $cacheout_maxopen) {
67 my @lru = sort {$isopen{$a} <=> $isopen{$b};} keys(%isopen);
68 splice(@lru, $cacheout_maxopen / 3);
69 $cacheout_numopen -= @lru;
70 for (@lru) { &cacheout_close($_); delete $isopen{$_}; }
72 cacheout_open($file, ($saw{$file}++ ? '>>' : '>') . $file)
73 or croak("Can't create $file: $!");
75 $isopen{$file} = ++$cacheout_seq;