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920dae64 AT |
1 | package FileCache; |
2 | ||
3 | our $VERSION = '1.06'; | |
4 | ||
5 | =head1 NAME | |
6 | ||
7 | FileCache - keep more files open than the system permits | |
8 | ||
9 | =head1 SYNOPSIS | |
10 | ||
11 | use FileCache; | |
12 | # or | |
13 | use FileCache maxopen => 16; | |
14 | ||
15 | cacheout $mode, $path; | |
16 | # or | |
17 | cacheout $path; | |
18 | print $path @data; | |
19 | ||
20 | $fh = cacheout $mode, $path; | |
21 | # or | |
22 | $fh = cacheout $path; | |
23 | print $fh @data; | |
24 | ||
25 | =head1 DESCRIPTION | |
26 | ||
27 | The C<cacheout> function will make sure that there's a filehandle open | |
28 | for reading or writing available as the pathname you give it. It | |
29 | automatically closes and re-opens files if you exceed your system's | |
30 | maximum number of file descriptors, or the suggested maximum I<maxopen>. | |
31 | ||
32 | =over | |
33 | ||
34 | =item cacheout EXPR | |
35 | ||
36 | The 1-argument form of cacheout will open a file for writing (C<< '>' >>) | |
37 | on it's first use, and appending (C<<< '>>' >>>) thereafter. | |
38 | ||
39 | Returns EXPR on success for convenience. You may neglect the | |
40 | return value and manipulate EXPR as the filehandle directly if you prefer. | |
41 | ||
42 | =item cacheout MODE, EXPR | |
43 | ||
44 | The 2-argument form of cacheout will use the supplied mode for the initial | |
45 | and subsequent openings. Most valid modes for 3-argument C<open> are supported | |
46 | namely; C<< '>' >>, C<< '+>' >>, C<< '<' >>, C<< '<+' >>, C<<< '>>' >>>, | |
47 | C< '|-' > and C< '-|' > | |
48 | ||
49 | To pass supplemental arguments to a program opened with C< '|-' > or C< '-|' > | |
50 | append them to the command string as you would system EXPR. | |
51 | ||
52 | Returns EXPR on success for convenience. You may neglect the | |
53 | return value and manipulate EXPR as the filehandle directly if you prefer. | |
54 | ||
55 | =back | |
56 | ||
57 | =head1 CAVEATS | |
58 | ||
59 | While it is permissible to C<close> a FileCache managed file, | |
60 | do not do so if you are calling C<FileCache::cacheout> from a package other | |
61 | than which it was imported, or with another module which overrides C<close>. | |
62 | If you must, use C<FileCache::cacheout_close>. | |
63 | ||
64 | Although FileCache can be used with piped opens ('-|' or '|-') doing so is | |
65 | strongly discouraged. If FileCache finds it necessary to close and then reopen | |
66 | a pipe, the command at the far end of the pipe will be reexecuted - the results | |
67 | of performing IO on FileCache'd pipes is unlikely to be what you expect. The | |
68 | ability to use FileCache on pipes may be removed in a future release. | |
69 | ||
70 | FileCache does not store the current file offset if it finds it necessary to | |
71 | close a file. When the file is reopened, the offset will be as specified by the | |
72 | original C<open> file mode. This could be construed to be a bug. | |
73 | ||
74 | =head1 BUGS | |
75 | ||
76 | F<sys/param.h> lies with its C<NOFILE> define on some systems, | |
77 | so you may have to set I<maxopen> yourself. | |
78 | ||
79 | =cut | |
80 | ||
81 | require 5.006; | |
82 | use Carp; | |
83 | use Config; | |
84 | use strict; | |
85 | no strict 'refs'; | |
86 | ||
87 | # These are not C<my> for legacy reasons. | |
88 | # Previous versions requested the user set $cacheout_maxopen by hand. | |
89 | # Some authors fiddled with %saw to overcome the clobber on initial open. | |
90 | use vars qw(%saw $cacheout_maxopen); | |
91 | $cacheout_maxopen = 16; | |
92 | ||
93 | use base 'Exporter'; | |
94 | our @EXPORT = qw[cacheout cacheout_close]; | |
95 | ||
96 | ||
97 | my %isopen; | |
98 | my $cacheout_seq = 0; | |
99 | ||
100 | sub import { | |
101 | my ($pkg,%args) = @_; | |
102 | ||
103 | # Use Exporter. %args are for us, not Exporter. | |
104 | # Make sure to up export_to_level, or we will import into ourselves, | |
105 | # rather than our calling package; | |
106 | ||
107 | __PACKAGE__->export_to_level(1); | |
108 | Exporter::import( $pkg ); | |
109 | ||
110 | # Truth is okay here because setting maxopen to 0 would be bad | |
111 | return $cacheout_maxopen = $args{maxopen} if $args{maxopen}; | |
112 | ||
113 | # XXX This code is crazy. Why is it a one element foreach loop? | |
114 | # Why is it using $param both as a filename and filehandle? | |
115 | foreach my $param ( '/usr/include/sys/param.h' ){ | |
116 | if (open($param, '<', $param)) { | |
117 | local ($_, $.); | |
118 | while (<$param>) { | |
119 | if( /^\s*#\s*define\s+NOFILE\s+(\d+)/ ){ | |
120 | $cacheout_maxopen = $1 - 4; | |
121 | close($param); | |
122 | last; | |
123 | } | |
124 | } | |
125 | close $param; | |
126 | } | |
127 | } | |
128 | $cacheout_maxopen ||= 16; | |
129 | } | |
130 | ||
131 | # Open in their package. | |
132 | sub cacheout_open { | |
133 | return open(*{caller(1) . '::' . $_[1]}, $_[0], $_[1]) && $_[1]; | |
134 | } | |
135 | ||
136 | # Close in their package. | |
137 | sub cacheout_close { | |
138 | # Short-circuit in case the filehandle disappeared | |
139 | my $pkg = caller($_[1]||0); | |
140 | fileno(*{$pkg . '::' . $_[0]}) && | |
141 | CORE::close(*{$pkg . '::' . $_[0]}); | |
142 | delete $isopen{$_[0]}; | |
143 | } | |
144 | ||
145 | # But only this sub name is visible to them. | |
146 | sub cacheout { | |
147 | my($mode, $file, $class, $ret, $ref, $narg); | |
148 | croak "Not enough arguments for cacheout" unless $narg = scalar @_; | |
149 | croak "Too many arguments for cacheout" if $narg > 2; | |
150 | ||
151 | ($mode, $file) = @_; | |
152 | ($file, $mode) = ($mode, $file) if $narg == 1; | |
153 | croak "Invalid mode for cacheout" if $mode && | |
154 | ( $mode !~ /^\s*(?:>>|\+?>|\+?<|\|\-|)|\-\|\s*$/ ); | |
155 | ||
156 | # Mode changed? | |
157 | if( $isopen{$file} && ($mode||'>') ne $isopen{$file}->[1] ){ | |
158 | &cacheout_close($file, 1); | |
159 | } | |
160 | ||
161 | if( $isopen{$file}) { | |
162 | $ret = $file; | |
163 | $isopen{$file}->[0]++; | |
164 | } | |
165 | else{ | |
166 | if( scalar keys(%isopen) > $cacheout_maxopen -1 ) { | |
167 | my @lru = sort{ $isopen{$a}->[0] <=> $isopen{$b}->[0] } keys(%isopen); | |
168 | $cacheout_seq = 0; | |
169 | $isopen{$_}->[0] = $cacheout_seq++ for | |
170 | splice(@lru, int($cacheout_maxopen / 3)||$cacheout_maxopen); | |
171 | &cacheout_close($_, 1) for @lru; | |
172 | } | |
173 | ||
174 | unless( $ref ){ | |
175 | $mode ||= $saw{$file} ? '>>' : ($saw{$file}=1, '>'); | |
176 | } | |
177 | #XXX should we just return the value from cacheout_open, no croak? | |
178 | $ret = cacheout_open($mode, $file) or croak("Can't create $file: $!"); | |
179 | ||
180 | $isopen{$file} = [++$cacheout_seq, $mode]; | |
181 | } | |
182 | return $ret; | |
183 | } | |
184 | 1; |