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| 4 | |
4 | |
| 5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
| 6 | |
6 | |
| 7 | use Coro::Semaphore; |
7 | use Coro::Semaphore; |
| 8 | |
8 | |
| 9 | $sig = new Coro::Semaphore [init]; |
9 | $sig = new Coro::Semaphore [initial value]; |
| 10 | |
10 | |
| 11 | $sig->down; # wait for signal |
11 | $sig->down; # wait for signal |
| 12 | |
12 | |
| 13 | # ... some other "thread" |
13 | # ... some other "thread" |
| 14 | |
14 | |
| 15 | $sig->up; |
15 | $sig->up; |
| 16 | |
16 | |
| 17 | =head1 DESCRIPTION |
17 | =head1 DESCRIPTION |
| 18 | |
18 | |
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19 | This module implements counted semaphores. You can initialize a mutex |
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20 | with any level of parallel users, that is, you can intialize a sempahore |
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21 | that can be C<down>ed more than once until it blocks. There is no owner |
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22 | associated with semaphores, so one coroutine can C<down> it while another |
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23 | can C<up> it. |
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24 | |
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25 | Counting semaphores are typically used to coordinate access to |
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26 | resources, with the semaphore count initialized to the number of free |
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27 | resources. Coroutines then increment the count when resources are added |
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28 | and decrement the count when resources are removed. |
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29 | |
| 19 | =over 4 |
30 | =over 4 |
| 20 | |
31 | |
| 21 | =cut |
32 | =cut |
| 22 | |
33 | |
| 23 | package Coro::Semaphore; |
34 | package Coro::Semaphore; |
| 24 | |
35 | |
| 25 | use Coro::Process (); |
36 | use Coro (); |
| 26 | |
37 | |
| 27 | $VERSION = 0.01; |
38 | $VERSION = 0.12; |
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39 | |
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40 | =item new [inital count, default one] |
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41 | |
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42 | Creates a new sempahore object with the given initial lock count. The |
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43 | default lock count is 1, which means it is unlocked by default. Zero (or |
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44 | negative values) are also allowed, in which case the semaphore is locked |
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45 | by default. |
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46 | |
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47 | =cut |
| 28 | |
48 | |
| 29 | sub new { |
49 | sub new { |
| 30 | bless [$_[1]], $_[0]; |
50 | bless [defined $_[1] ? $_[1] : 1], $_[0]; |
| 31 | } |
51 | } |
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52 | |
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53 | =item $sem->down |
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54 | |
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55 | Decrement the counter, therefore "locking" the semaphore. This method |
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56 | waits until the semaphore is available if the counter is zero. |
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57 | |
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58 | =cut |
| 32 | |
59 | |
| 33 | sub down { |
60 | sub down { |
| 34 | my $self = shift; |
61 | my $self = shift; |
| 35 | while ($self->[0] <= 0) { |
62 | while ($self->[0] <= 0) { |
| 36 | push @{$self->[1]}, $Coro::current; |
63 | push @{$self->[1]}, $Coro::current; |
| 37 | Coro::Process::schedule; |
64 | Coro::schedule; |
| 38 | } |
65 | } |
| 39 | --$self->[0]; |
66 | --$self->[0]; |
| 40 | } |
67 | } |
| 41 | |
68 | |
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69 | =item $sem->up |
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70 | |
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71 | Unlock the semaphore again. |
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72 | |
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73 | =cut |
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74 | |
| 42 | sub up { |
75 | sub up { |
| 43 | my $self = shift; |
76 | my $self = shift; |
| 44 | if (++@{$self->[1]} == 0) { |
77 | if (++$self->[0] > 0) { |
| 45 | (shift @{$self->[1]})->ready if @{$self->[1]}; |
78 | (shift @{$self->[1]})->ready if @{$self->[1]}; |
| 46 | } |
79 | } |
| 47 | } |
80 | } |
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81 | |
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82 | =item $sem->try |
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83 | |
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84 | Try to C<down> the semaphore. Returns true when this was possible, |
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85 | otherwise return false and leave the semaphore unchanged. |
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86 | |
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87 | =cut |
| 48 | |
88 | |
| 49 | sub try { |
89 | sub try { |
| 50 | my $self = shift; |
90 | my $self = shift; |
| 51 | if ($self->[0] > 0) { |
91 | if ($self->[0] > 0) { |
| 52 | --$self->[0]; |
92 | --$self->[0]; |
