| … | |
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| 2 | |
2 | |
| 3 | Guard - safe cleanup blocks |
3 | Guard - safe cleanup blocks |
| 4 | |
4 | |
| 5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
| 6 | |
6 | |
| 7 | use Guard; |
7 | use Guard; |
| 8 | |
8 | |
| 9 | # temporarily chdir to "/etc" directory, but make sure |
9 | # temporarily chdir to "/etc" directory, but make sure |
| 10 | # to go back to "/" no matter how myfun exits: |
10 | # to go back to "/" no matter how myfun exits: |
| 11 | sub myfun { |
11 | sub myfun { |
| 12 | scope_guard { chdir "/" }; |
12 | scope_guard { chdir "/" }; |
| 13 | chdir "/etc"; |
13 | chdir "/etc"; |
| 14 | |
14 | |
| 15 | call_function_that_might_die_or_other_fun_stuff; |
15 | call_function_that_might_die_or_other_fun_stuff; |
| 16 | } |
16 | } |
| 17 | |
17 | |
| 18 | =head1 DESCRIPTION |
18 | =head1 DESCRIPTION |
| 19 | |
19 | |
| 20 | This module implements so-called "guards". A guard is something (usually |
20 | This module implements so-called "guards". A guard is something (usually |
| 21 | an object) that "guards" a resource, ensuring that it is cleaned up when |
21 | an object) that "guards" a resource, ensuring that it is cleaned up when |
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| 107 | |
107 | |
| 108 | See the EXCEPTIONS section for an explanation of how exceptions |
108 | See the EXCEPTIONS section for an explanation of how exceptions |
| 109 | (i.e. C<die>) are handled inside guard blocks. |
109 | (i.e. C<die>) are handled inside guard blocks. |
| 110 | |
110 | |
| 111 | Example: acquire a Coro::Semaphore for a second by registering a |
111 | Example: acquire a Coro::Semaphore for a second by registering a |
| 112 | timer. The timer callback references the guard used to unlock it again. |
112 | timer. The timer callback references the guard used to unlock it |
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113 | again. (Please ignore the fact that C<Coro::Semaphore> has a C<guard> |
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114 | method that does this already): |
| 113 | |
115 | |
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|
116 | use Guard; |
| 114 | use AnyEvent; |
117 | use AnyEvent; |
| 115 | use Coro::Semaphore; |
118 | use Coro::Semaphore; |
| 116 | |
119 | |
| 117 | my $sem = new Coro::Semaphore; |
120 | my $sem = new Coro::Semaphore; |
| 118 | |
121 | |
| 119 | sub lock_1s { |
122 | sub lock_for_a_second { |
| 120 | $sem->down; |
123 | $sem->down; |
| 121 | my $guard = guard { $sem->up }; |
124 | my $guard = guard { $sem->up }; |
| 122 | |
125 | |
| 123 | my $timer; |
126 | my $timer; |
| 124 | $timer = AnyEvent->timer (after => 1, sub { |
127 | $timer = AnyEvent->timer (after => 1, sub { |
