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=head1 NAME |
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Async::Interrupt - allow C/XS libraries to interrupt perl asynchronously |
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=head1 SYNOPSIS |
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use Async::Interrupt; |
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=head1 DESCRIPTION |
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This module implements a single feature only of interest to advanced perl |
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modules, namely asynchronous interruptions (think "unix signals", which |
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are very similar). |
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Sometimes, modules wish to run code asynchronously (in another thread), |
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and then signal the perl interpreter on certain events. One common way is |
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to write some data to a pipe and use an event handling toolkit to watch |
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for I/O events. Another way is to send a signal. Those methods are slow, |
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and in the case of a pipe, also not asynchronous - it won't interrupt a |
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running perl interpreter. |
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This module implements asynchronous notifications that enable you to |
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signal running perl code form another thread, asynchronously, without |
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issuing syscalls. |
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=over 4 |
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=cut |
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package Async::Interrupt; |
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BEGIN { |
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$VERSION = '0.02'; |
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require XSLoader; |
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XSLoader::load Async::Interrupt::, $VERSION; |
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} |
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=item $async = new Async::Interrupt key => value... |
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Creates a new Async::Interrupt object. You may only use async |
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notifications on this object while it exists, so you need to keep a |
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reference to it at all times while it is used. |
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Optional constructor arguments include (normally you would specify at |
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least one of C<cb> or C<c_cb>). |
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=over 4 |
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=item cb => $coderef->($value) |
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Registers a perl callback to be invoked whenever the async interrupt is |
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signalled. |
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Note that, since this callback can be invoked at basically any time, it |
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must not modify any well-known global variables such as C<$/>, C<$@> or |
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C<$!>, without restoring them again before returning. |
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=item c_cb => [$c_func, $c_data] |
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Registers a C callback the be invoked whenever the async interrupt is |
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signalled. |
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The C callback must have the following prototype: |
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void c_func (pTHX_ void *c_data, int value); |
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Both C<$c_func> and C<$c_data> must be specified as integers/IVs. |
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Note that, because the callback can be invoked at almost any time, you |
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have to be careful at saving and restoring global variables that Perl |
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might use, most notably C<errno>. The callback itself runs as part of the |
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perl context, so you can call any perl functions and modify any perl data |
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structures. |
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=item fh => $fileno_or_fh |
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Specifies a file descriptor (or file handle) that should be signalled |
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whenever the async interrupt is signalled. This means a single octet will |
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be written to it, and before the callback is being invoked, it will be |
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read again. Due to races, it is unlikely but possible that multiple octets |
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are written, therefore, it is recommended that the file handle is in |
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nonblocking mode. |
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(You can get a portable pipe and set non-blocking mode portably by using |
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e.g. L<AnyEvent::Util> from the L<AnyEvent> distro). |
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The object will keep a reference to the file handle. |
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This can be used to ensure that async notifications will interrupt event |
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frameworks as well. |
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=back |
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=cut |
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sub new { |
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my ($class, %arg) = @_; |
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my $self = _alloc $arg{cb}, @{$arg{c_cb}}[0,1], $arg{fh}; |
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bless \$self, $class |
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} |
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=item ($signal_func, $signal_arg) = $async->signal_cb |
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Returns the address of a function to call asynchronously. The function has |
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the following prototype and needs to be passed the specified C<$c_arg>, |
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which is a C<void *> cast to C<IV>: |
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void (*signal_func) (void *signal_arg, int value) |
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An example call would look like: |
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signal_func (signal_arg, 0); |
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The function is safe toc all from within signal and thread contexts, at |
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any time. The specified C<value> is passed to both C and Perl callback. |
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If the function is called while the Async::Interrupt object is already |
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signaled but before the callbacks are being executed, then the stored |
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C<value> is being overwritten. Due to the asynchronous nature of the code, |
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the C<value> can even be passed to two consecutive invocations of the |
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callback. |
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=item $async->signal ($value=0) |
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This signals the given async object from Perl code. Semi-obviously, this |
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will instantly trigger the callback invocation. |
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=cut |
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1; |
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=back |
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=head1 AUTHOR |
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Marc Lehmann <schmorp@schmorp.de> |
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http://home.schmorp.de/ |
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=cut |
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