7 FileCache - keep more files open than the system permits
13 use FileCache maxopen => 16;
18 cacheout $mode, $path;
23 The C<cacheout> function will make sure that there's a filehandle open
24 for reading or writing available as the pathname you give it. It
25 automatically closes and re-opens files if you exceed your system's
26 maximum number of file descriptors, or the suggested maximum.
32 The 1-argument form of cacheout will open a file for writing (C<< '>' >>)
33 on it's first use, and appending (C<<< '>>' >>>) thereafter.
35 =item cacheout MODE, EXPR
37 The 2-argument form of cacheout will use the supplied mode for the initial
38 and subsequent openings. Most valid modes for 3-argument C<open> are supported
39 namely; C<< '>' >>, C<< '+>' >>, C<< '<' >>, C<< '<+' >>, C<<< '>>' >>>,
40 C< '|-' > and C< '-|' >
44 If you use cacheout with C<'|-'> or C<'-|'> you should catch SIGPIPE
45 and explicitly close the filehandle., when it is closed from the
46 other end some cleanup needs to be done.
50 F<sys/param.h> lies with its C<NOFILE> define on some systems,
51 so you may have to set maxopen (I<$FileCache::cacheout_maxopen>) yourself.
59 use vars qw(%saw $cacheout_maxopen);
60 # These are not C<my> for legacy reasons.
61 # Previous versions requested the user set $cacheout_maxopen by hand.
62 # Some authors fiddled with %saw to overcome the clobber on initial open.
68 *{caller(1).'::cacheout'} = \&cacheout;
69 *{caller(1).'::close'} = \&cacheout_close;
71 # Truth is okay here because setting maxopen to 0 would be bad
72 return $cacheout_maxopen = $args{maxopen} if $args{maxopen} ;
73 if (open(PARAM,'/usr/include/sys/param.h')) {
76 $cacheout_maxopen = $1 - 4
77 if /^\s*#\s*define\s+NOFILE\s+(\d+)/;
81 $cacheout_maxopen ||= 16;
84 # Open in their package.
87 open(*{caller(1) . '::' . $_[1]}, $_[0], $_[1]);
90 # Close in their package.
93 fileno(*{caller(1) . '::' . $_[0]}) &&
94 CORE::close(*{caller(1) . '::' . $_[0]});
95 delete $isopen{$_[0]};
98 # But only this sub name is visible to them.
101 croak "Not enough arguments for cacheout" unless @_;
102 croak "Too many arguments for cacheout" if scalar @_ > 2;
104 ($file, $mode) = ($mode, $file) if scalar @_ == 1;
105 # We don't want children
106 croak "Invalid file for cacheout" if $file =~ /^\s*(?:\|\-)|(?:\-\|)\s*$/;
107 croak "Invalid mode for cacheout" if $mode &&
108 ( $mode !~ /^\s*(?:>>)|(?:\+?>)|(?:\+?<)|(?:\|\-)|(?:\-\|)\s*$/ );
110 unless( $isopen{$file}) {
111 if( scalar keys(%isopen) > $cacheout_maxopen -1 ) {
112 my @lru = sort {$isopen{$a} <=> $isopen{$b};} keys(%isopen);
113 &cacheout_close($_) for splice(@lru, $cacheout_maxopen / 3);
115 $mode ||= ( $saw{$file} = ! $saw{$file} ) ? '>': '>>';
116 cacheout_open($mode, $file) or croak("Can't create $file: $!");
118 $isopen{$file} = ++$cacheout_seq;