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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 @EXPORT = qw(defer_sub undefer_sub); |
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8 | |
9 | our %DEFERRED; |
10 | |
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11 | sub undefer_sub { |
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12 | my ($deferred) = @_; |
13 | my ($target, $maker, $undeferred_ref) = @{ |
14 | $DEFERRED{$deferred}||return $deferred |
15 | }; |
16 | ${$undeferred_ref} = my $made = $maker->(); |
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17 | if (defined($target)) { |
18 | no warnings 'redefine'; |
19 | *{_getglob($target)} = $made; |
20 | } |
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21 | push @{$DEFERRED{$made} = $DEFERRED{$deferred}}, $made; |
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22 | return $made; |
23 | } |
24 | |
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25 | sub defer_info { |
26 | my ($deferred) = @_; |
27 | $DEFERRED{$deferred||''}; |
28 | } |
29 | |
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30 | sub defer_sub { |
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31 | my ($target, $maker) = @_; |
32 | my $undeferred; |
33 | my $deferred_string; |
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34 | my $deferred = sub { |
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35 | goto &{$undeferred ||= undefer_sub($deferred_string)}; |
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36 | }; |
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37 | $deferred_string = "$deferred"; |
38 | $DEFERRED{$deferred} = [ $target, $maker, \$undeferred ]; |
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39 | *{_getglob $target} = $deferred if defined($target); |
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40 | return $deferred; |
41 | } |
42 | |
43 | 1; |
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44 | |
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45 | =head1 NAME |
46 | |
47 | Sub::Defer - defer generation of subroutines until they are first called |
48 | |
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49 | =head1 SYNOPSIS |
50 | |
51 | use Sub::Defer; |
52 | |
53 | my $deferred = defer_sub 'Logger::time_since_first_log' => sub { |
54 | my $t = time; |
55 | sub { time - $t }; |
56 | }; |
57 | |
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58 | Logger->time_since_first_log; # returns 0 and replaces itself |
59 | Logger->time_since_first_log; # returns time - $t |
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60 | |
61 | =head1 DESCRIPTION |
62 | |
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63 | These subroutines provide the user with a convenient way to defer creation of |
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64 | subroutines and methods until they are first called. |
65 | |
66 | =head1 SUBROUTINES |
67 | |
68 | =head2 defer_sub |
69 | |
70 | my $coderef = defer_sub $name => sub { ... }; |
71 | |
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72 | This subroutine returns a coderef that encapsulates the provided sub - when |
73 | it is first called, the provided sub is called and is -itself- expected to |
74 | return a subroutine which will be goto'ed to on subsequent calls. |
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75 | |
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76 | If a name is provided, this also installs the sub as that name - and when |
77 | the subroutine is undeferred will re-install the final version for speed. |
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78 | |
79 | =head2 undefer_sub |
80 | |
81 | my $coderef = undefer_sub \&Foo::name; |
82 | |
83 | If the passed coderef has been L<deferred|/defer_sub> this will "undefer" it. |
84 | If the passed coderef has not been deferred, this will just return it. |
85 | |
86 | If this is confusing, take a look at the example in the L</SYNOPSIS>. |