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| 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 counting 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 | |
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36 | no warnings; |
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37 | |
| 25 | use Coro (); |
38 | use Coro (); |
| 26 | |
39 | |
| 27 | $VERSION = 0.07; |
40 | $VERSION = 5.0; |
| 28 | |
41 | |
| 29 | =item new [inital count, default zero] |
42 | =item new [inital count] |
| 30 | |
43 | |
| 31 | Creates a new sempahore object with the given initial lock count. The |
44 | Creates a new sempahore object with the given initial lock count. The |
| 32 | default lock count is 1, which means it is unlocked by default. |
45 | default lock count is 1, which means it is unlocked by default. Zero (or |
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46 | negative values) are also allowed, in which case the semaphore is locked |
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47 | by default. |
| 33 | |
48 | |
| 34 | =cut |
49 | =item $sem->count |
| 35 | |
50 | |
| 36 | sub new { |
51 | Returns the current semaphore count. |
| 37 | bless [defined $_[1] ? $_[1] : 1], $_[0]; |
52 | |
| 38 | } |
53 | =item $sem->adjust ($diff) |
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54 | |
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55 | Atomically adds the amount given to the current semaphore count. If the |
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56 | count becomes positive, wakes up any waiters. Does not block if the count |
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57 | becomes negative, however. |
| 39 | |
58 | |
| 40 | =item $sem->down |
59 | =item $sem->down |
| 41 | |
60 | |
| 42 | Decrement the counter, therefore "locking" the semaphore. This method |
61 | Decrement the counter, therefore "locking" the semaphore. This method |
| 43 | waits until the semaphore is available if the counter is zero. |
62 | waits until the semaphore is available if the counter is zero. |
| 44 | |
63 | |
| 45 | =cut |
64 | =cut |
| 46 | |
65 | |
| 47 | sub down { |
66 | #=item $status = $sem->timed_down ($timeout) |
| 48 | my $self = shift; |
67 | # |
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68 | #Like C<down>, but returns false if semaphore couldn't be acquired within |
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69 | #$timeout seconds, otherwise true. |
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70 | |
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71 | #sub timed_down { |
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72 | # require Coro::Timer; |
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73 | # my $timeout = Coro::Timer::timeout ($_[1]); |
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74 | # |
| 49 | while ($self->[0] <= 0) { |
75 | # while ($_[0][0] <= 0) { |
| 50 | push @{$self->[1]}, $Coro::current; |
76 | # push @{$_[0][1]}, $Coro::current; |
| 51 | Coro::schedule; |
77 | # &Coro::schedule; |
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78 | # if ($timeout) { |
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79 | # # ugly as hell. slow, too, btw! |
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80 | # for (0..$#{$_[0][1]}) { |
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81 | # if ($_[0][1][$_] == $Coro::current) { |
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82 | # splice @{$_[0][1]}, $_, 1; |
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83 | # return; |
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84 | # } |
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85 | # } |
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86 | # die; |
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87 | # } |
| 52 | } |
88 | # } |
| 53 | --$self->[0]; |
89 | # |
| 54 | } |
90 | # --$_[0][0]; |
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91 | # return 1; |
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92 | #} |
| 55 | |
93 | |
| 56 | =item $sem->up |
94 | =item $sem->up |
| 57 | |
95 | |
| 58 | Unlock the semaphore again. |
96 | Unlock the semaphore again. |
| 59 | |
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| 60 | =cut |
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| 61 | |
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| 62 | sub up { |
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| 63 | my $self = shift; |
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| 64 | if (++$self->[0] > 0) { |
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| 65 | (shift @{$self->[1]})->ready if @{$self->[1]}; |
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| 66 | } |
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| 67 | } |
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| 68 | |
97 | |
| 69 | =item $sem->try |
98 | =item $sem->try |
| 70 | |
99 | |
| 71 | Try to C<down> the semaphore. Returns true when this was possible, |
100 | Try to C<down> the semaphore. Returns true when this was possible, |
| 72 | otherwise return false and leave the semaphore unchanged. |
101 | otherwise return false and leave the semaphore unchanged. |
| 73 | |
102 | |
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103 | =item $sem->waiters |
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104 | |
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105 | In scalar context, returns the number of coroutines waiting for this |
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106 | semaphore. |
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107 | |
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108 | =item $guard = $sem->guard |
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109 | |
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110 | This method calls C<down> and then creates a guard object. When the guard |
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111 | object is destroyed it automatically calls C<up>. |
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112 | |
| 74 | =cut |
113 | =cut |
| 75 | |
114 | |
| 76 | sub try { |
115 | sub guard { |
| 77 | my $self = shift; |
116 | &down; |
| 78 | if ($self->[0] > 0) { |
117 | # double indirection because bless works on the referenced |
| 79 | --$self->[0]; |
118 | # object, not (only) on the reference itself. |
| 80 | return 1; |
119 | bless \\$_[0], Coro::Semaphore::guard::; |
| 81 | } else { |
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| 82 | return 0; |
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| 83 | } |
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| 84 | } |
120 | } |
| 85 | |
121 | |
| 86 | 1; |
122 | #=item $guard = $sem->timed_guard ($timeout) |
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123 | # |
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124 | #Like C<guard>, but returns undef if semaphore couldn't be acquired within |
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125 | #$timeout seconds, otherwise the guard object. |
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126 | |
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127 | #sub timed_guard { |
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128 | # &timed_down |
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129 | # ? bless \\$_[0], Coro::Semaphore::guard:: |
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130 | # : (); |
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131 | #} |
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132 | |
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133 | sub Coro::Semaphore::guard::DESTROY { |
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134 | &up(${${$_[0]}}); |
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135 | } |
| 87 | |
136 | |
| 88 | =back |
137 | =back |
| 89 | |
138 | |
| 90 | =head1 AUTHOR |
139 | =head1 AUTHOR |
| 91 | |
140 | |
| 92 | Marc Lehmann <pcg@goof.com> |
141 | Marc Lehmann <schmorp@schmorp.de> |
| 93 | http://www.goof.com/pcg/marc/ |
142 | http://home.schmorp.de/ |
| 94 | |
143 | |
| 95 | =cut |
144 | =cut |
| 96 | |
145 | |
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146 | 1 |
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147 | |
