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1 | package FileCache; |
2 | |
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3 | our $VERSION = '1.04_01'; |
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4 | |
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5 | =head1 NAME |
6 | |
7 | FileCache - keep more files open than the system permits |
8 | |
9 | =head1 SYNOPSIS |
10 | |
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11 | use FileCache; |
12 | # or |
13 | use FileCache maxopen => 16; |
14 | |
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15 | cacheout $mode, $path; |
16 | # or |
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17 | cacheout $path; |
18 | print $path @data; |
19 | |
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20 | $fh = cacheout $mode, $path; |
21 | # or |
22 | $fh = cacheout $path; |
23 | print $fh @data; |
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24 | |
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25 | =head1 DESCRIPTION |
26 | |
27 | The C<cacheout> function will make sure that there's a filehandle open |
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28 | for reading or writing available as the pathname you give it. It |
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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>. |
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31 | |
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32 | =over |
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33 | |
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34 | =item cacheout EXPR |
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35 | |
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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 | |
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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 | |
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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 | |
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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 | |
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52 | Returns EXPR on success for convenience. You may neglect the |
53 | return value and manipulate EXPR as the filehandle directly if you prefer. |
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54 | |
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55 | =head1 CAVEATS |
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56 | |
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57 | While it is permissible to C<close> a FileCache managed file, |
58 | do not do so if you are calling C<FileCache::cacheout> from a package other |
59 | than which it was imported, or with another module which overrides C<close>. |
60 | If you must, use C<FileCache::cacheout_close>. |
61 | |
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62 | Although FileCache can be used with piped opens ('-|' or '|-') doing so is |
63 | strongly discouraged. If FileCache finds it necessary to close and then reopen |
64 | a pipe, the command at the far end of the pipe will be reexecuted - the results |
65 | of performing IO on FileCache'd pipes is unlikely to be what you expect. The |
66 | ability to use FileCache on pipes may be removed in a future release. |
67 | |
68 | FileCache does not store the current file offset if it finds it necessary to |
69 | close a file. When the file is reopened, the offset will be as specified by the |
70 | original C<open> file mode. This could be construed to be a bug. |
71 | |
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72 | =head1 BUGS |
73 | |
74 | F<sys/param.h> lies with its C<NOFILE> define on some systems, |
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75 | so you may have to set I<maxopen> yourself. |
76 | |
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77 | =cut |
78 | |
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79 | require 5.006; |
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80 | use Carp; |
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81 | use Config; |
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82 | use strict; |
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83 | no strict 'refs'; |
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84 | |
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85 | # These are not C<my> for legacy reasons. |
86 | # Previous versions requested the user set $cacheout_maxopen by hand. |
87 | # Some authors fiddled with %saw to overcome the clobber on initial open. |
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88 | use vars qw(%saw $cacheout_maxopen); |
89 | $cacheout_maxopen = 16; |
90 | |
91 | use base 'Exporter'; |
92 | our @EXPORT = qw[cacheout cacheout_close]; |
93 | |
94 | |
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95 | my %isopen; |
96 | my $cacheout_seq = 0; |
97 | |
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98 | sub import { |
99 | my ($pkg,%args) = @_; |
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100 | |
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101 | # Use Exporter. %args are for us, not Exporter. |
102 | # Make sure to up export_to_level, or we will import into ourselves, |
103 | # rather than our calling package; |
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104 | |
105 | __PACKAGE__->export_to_level(1); |
106 | Exporter::import( $pkg ); |
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107 | |
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108 | # Truth is okay here because setting maxopen to 0 would be bad |
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109 | return $cacheout_maxopen = $args{maxopen} if $args{maxopen}; |
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110 | |
111 | # XXX This code is crazy. Why is it a one element foreach loop? |
112 | # Why is it using $param both as a filename and filehandle? |
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113 | foreach my $param ( '/usr/include/sys/param.h' ){ |
114 | if (open($param, '<', $param)) { |
115 | local ($_, $.); |
116 | while (<$param>) { |
117 | if( /^\s*#\s*define\s+NOFILE\s+(\d+)/ ){ |
118 | $cacheout_maxopen = $1 - 4; |
119 | close($param); |
120 | last; |
121 | } |
122 | } |
123 | close $param; |
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124 | } |
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125 | } |
126 | $cacheout_maxopen ||= 16; |
127 | } |
128 | |
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129 | # Open in their package. |
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130 | sub cacheout_open { |
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131 | return open(*{caller(1) . '::' . $_[1]}, $_[0], $_[1]) && $_[1]; |
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132 | } |
133 | |
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134 | # Close in their package. |
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135 | sub cacheout_close { |
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136 | # Short-circuit in case the filehandle disappeared |
137 | my $pkg = caller($_[1]||0); |
138 | fileno(*{$pkg . '::' . $_[0]}) && |
139 | CORE::close(*{$pkg . '::' . $_[0]}); |
140 | delete $isopen{$_[0]}; |
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141 | } |
142 | |
143 | # But only this sub name is visible to them. |
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144 | sub cacheout { |
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145 | my($mode, $file, $class, $ret, $ref, $narg); |
146 | croak "Not enough arguments for cacheout" unless $narg = scalar @_; |
147 | croak "Too many arguments for cacheout" if $narg > 2; |
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148 | |
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149 | ($mode, $file) = @_; |
150 | ($file, $mode) = ($mode, $file) if $narg == 1; |
151 | croak "Invalid mode for cacheout" if $mode && |
152 | ( $mode !~ /^\s*(?:>>|\+?>|\+?<|\|\-|)|\-\|\s*$/ ); |
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153 | |
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154 | # Mode changed? |
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155 | if( $isopen{$file} && ($mode||'>') ne $isopen{$file}->[1] ){ |
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156 | &cacheout_close($file, 1); |
157 | } |
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158 | |
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159 | if( $isopen{$file}) { |
160 | $ret = $file; |
161 | $isopen{$file}->[0]++; |
162 | } |
163 | else{ |
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164 | if( scalar keys(%isopen) > $cacheout_maxopen -1 ) { |
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165 | my @lru = sort{ $isopen{$a}->[0] <=> $isopen{$b}->[0] } keys(%isopen); |
166 | $cacheout_seq = 0; |
167 | $isopen{$_}->[0] = $cacheout_seq++ for |
168 | splice(@lru, int($cacheout_maxopen / 3)||$cacheout_maxopen); |
169 | &cacheout_close($_, 1) for @lru; |
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170 | } |
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171 | |
172 | unless( $ref ){ |
173 | $mode ||= $saw{$file} ? '>>' : ($saw{$file}=1, '>'); |
174 | } |
175 | #XXX should we just return the value from cacheout_open, no croak? |
176 | $ret = cacheout_open($mode, $file) or croak("Can't create $file: $!"); |
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177 | |
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178 | $isopen{$file} = [++$cacheout_seq, $mode]; |
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179 | } |
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180 | return $ret; |
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181 | } |
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182 | 1; |