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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 = $maker->(); |
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17 | |
18 | # make sure the method slot has not changed since deferral time |
19 | if (defined($target) && $deferred eq *{_getglob($target)}{CODE}||'') { |
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20 | no warnings 'redefine'; |
21 | *{_getglob($target)} = $made; |
22 | } |
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23 | push @{$DEFERRED{$made} = $DEFERRED{$deferred}}, $made; |
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24 | |
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25 | return $made; |
26 | } |
27 | |
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28 | sub defer_info { |
29 | my ($deferred) = @_; |
30 | $DEFERRED{$deferred||''}; |
31 | } |
32 | |
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33 | sub defer_sub { |
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34 | my ($target, $maker) = @_; |
35 | my $undeferred; |
36 | my $deferred_string; |
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37 | my $deferred = sub { |
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38 | goto &{$undeferred ||= undefer_sub($deferred_string)}; |
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39 | }; |
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40 | $deferred_string = "$deferred"; |
41 | $DEFERRED{$deferred} = [ $target, $maker, \$undeferred ]; |
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42 | *{_getglob $target} = $deferred if defined($target); |
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43 | return $deferred; |
44 | } |
45 | |
46 | 1; |
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47 | |
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48 | =head1 NAME |
49 | |
50 | Sub::Defer - defer generation of subroutines until they are first called |
51 | |
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52 | =head1 SYNOPSIS |
53 | |
54 | use Sub::Defer; |
55 | |
56 | my $deferred = defer_sub 'Logger::time_since_first_log' => sub { |
57 | my $t = time; |
58 | sub { time - $t }; |
59 | }; |
60 | |
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61 | Logger->time_since_first_log; # returns 0 and replaces itself |
62 | Logger->time_since_first_log; # returns time - $t |
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63 | |
64 | =head1 DESCRIPTION |
65 | |
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66 | These subroutines provide the user with a convenient way to defer creation of |
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67 | subroutines and methods until they are first called. |
68 | |
69 | =head1 SUBROUTINES |
70 | |
71 | =head2 defer_sub |
72 | |
73 | my $coderef = defer_sub $name => sub { ... }; |
74 | |
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75 | This subroutine returns a coderef that encapsulates the provided sub - when |
76 | it is first called, the provided sub is called and is -itself- expected to |
77 | return a subroutine which will be goto'ed to on subsequent calls. |
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78 | |
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79 | If a name is provided, this also installs the sub as that name - and when |
80 | the subroutine is undeferred will re-install the final version for speed. |
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81 | |
82 | =head2 undefer_sub |
83 | |
84 | my $coderef = undefer_sub \&Foo::name; |
85 | |
86 | If the passed coderef has been L<deferred|/defer_sub> this will "undefer" it. |
87 | If the passed coderef has not been deferred, this will just return it. |
88 | |
89 | If this is confusing, take a look at the example in the L</SYNOPSIS>. |