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1 | package Sub::Defer; |
2 | |
3 | use strictures 1; |
4 | use base qw(Exporter); |
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5 | use Moo::_Utils; |
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6 | |
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7 | our $VERSION = '1.003000'; |
8 | $VERSION = eval $VERSION; |
9 | |
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10 | our @EXPORT = qw(defer_sub undefer_sub); |
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11 | |
12 | our %DEFERRED; |
13 | |
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14 | sub undefer_sub { |
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15 | my ($deferred) = @_; |
16 | my ($target, $maker, $undeferred_ref) = @{ |
17 | $DEFERRED{$deferred}||return $deferred |
18 | }; |
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19 | return ${$undeferred_ref} |
20 | if ${$undeferred_ref}; |
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21 | ${$undeferred_ref} = my $made = $maker->(); |
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22 | |
23 | # make sure the method slot has not changed since deferral time |
24 | if (defined($target) && $deferred eq *{_getglob($target)}{CODE}||'') { |
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25 | no warnings 'redefine'; |
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26 | |
27 | # I believe $maker already evals with the right package/name, so that |
28 | # _install_coderef calls are not necessary --ribasushi |
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29 | *{_getglob($target)} = $made; |
30 | } |
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31 | $DEFERRED{$made} = $DEFERRED{$deferred}; |
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32 | |
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33 | return $made; |
34 | } |
35 | |
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36 | sub defer_info { |
37 | my ($deferred) = @_; |
38 | $DEFERRED{$deferred||''}; |
39 | } |
40 | |
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41 | sub defer_sub { |
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42 | my ($target, $maker) = @_; |
43 | my $undeferred; |
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44 | my $deferred; |
45 | $deferred = sub { |
46 | $undeferred ||= undefer_sub($deferred); |
47 | goto &$undeferred; |
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48 | }; |
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49 | $DEFERRED{$deferred} = [ $target, $maker, \$undeferred, $deferred ]; |
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50 | _install_coderef($target => $deferred) if defined $target; |
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51 | return $deferred; |
52 | } |
53 | |
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54 | sub CLONE { |
55 | %DEFERRED = map { $_->[3] => $_ } values %DEFERRED; |
56 | } |
57 | |
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58 | 1; |
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59 | |
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60 | =head1 NAME |
61 | |
62 | Sub::Defer - defer generation of subroutines until they are first called |
63 | |
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64 | =head1 SYNOPSIS |
65 | |
66 | use Sub::Defer; |
67 | |
68 | my $deferred = defer_sub 'Logger::time_since_first_log' => sub { |
69 | my $t = time; |
70 | sub { time - $t }; |
71 | }; |
72 | |
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73 | Logger->time_since_first_log; # returns 0 and replaces itself |
74 | Logger->time_since_first_log; # returns time - $t |
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75 | |
76 | =head1 DESCRIPTION |
77 | |
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78 | These subroutines provide the user with a convenient way to defer creation of |
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79 | subroutines and methods until they are first called. |
80 | |
81 | =head1 SUBROUTINES |
82 | |
83 | =head2 defer_sub |
84 | |
85 | my $coderef = defer_sub $name => sub { ... }; |
86 | |
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87 | This subroutine returns a coderef that encapsulates the provided sub - when |
88 | it is first called, the provided sub is called and is -itself- expected to |
89 | return a subroutine which will be goto'ed to on subsequent calls. |
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90 | |
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91 | If a name is provided, this also installs the sub as that name - and when |
92 | the subroutine is undeferred will re-install the final version for speed. |
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93 | |
94 | =head2 undefer_sub |
95 | |
96 | my $coderef = undefer_sub \&Foo::name; |
97 | |
98 | If the passed coderef has been L<deferred|/defer_sub> this will "undefer" it. |
99 | If the passed coderef has not been deferred, this will just return it. |
100 | |
101 | If this is confusing, take a look at the example in the L</SYNOPSIS>. |
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102 | |
103 | =head1 SUPPORT |
104 | |
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105 | See L<Moo> for support and contact information. |
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106 | |
107 | =head1 AUTHORS |
108 | |
109 | See L<Moo> for authors. |
110 | |
111 | =head1 COPYRIGHT AND LICENSE |
112 | |
113 | See L<Moo> for the copyright and license. |