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Revision 1.107 by root, Fri Jun 1 05:52:59 2007 UTC vs.
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62etc.), but can also be used to easily do operations in parallel that are 62etc.), but can also be used to easily do operations in parallel that are
63normally done sequentially, e.g. stat'ing many files, which is much faster 63normally done sequentially, e.g. stat'ing many files, which is much faster
64on a RAID volume or over NFS when you do a number of stat operations 64on a RAID volume or over NFS when you do a number of stat operations
65concurrently. 65concurrently.
66 66
67While most of this works on all types of file descriptors (for example 67While most of this works on all types of file descriptors (for
68sockets), using these functions on file descriptors that support 68example sockets), using these functions on file descriptors that
69nonblocking operation (again, sockets, pipes etc.) is very inefficient or 69support nonblocking operation (again, sockets, pipes etc.) is very
70might not work (aio_read fails on sockets/pipes/fifos). Use an event loop 70inefficient. Use an event loop for that (such as the L<Event|Event>
71for that (such as the L<Event|Event> module): IO::AIO will naturally fit 71module): IO::AIO will naturally fit into such an event loop itself.
72into such an event loop itself.
73 72
74In this version, a number of threads are started that execute your 73In this version, a number of threads are started that execute your
75requests and signal their completion. You don't need thread support 74requests and signal their completion. You don't need thread support
76in perl, and the threads created by this module will not be visible 75in perl, and the threads created by this module will not be visible
77to perl. In the future, this module might make use of the native aio 76to perl. In the future, this module might make use of the native aio
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79not well-supported or restricted (GNU/Linux doesn't allow them on normal 78not well-supported or restricted (GNU/Linux doesn't allow them on normal
80files currently, for example), and they would only support aio_read and 79files currently, for example), and they would only support aio_read and
81aio_write, so the remaining functionality would have to be implemented 80aio_write, so the remaining functionality would have to be implemented
82using threads anyway. 81using threads anyway.
83 82
84Although the module will work with in the presence of other (Perl-) 83Although the module will work in the presence of other (Perl-) threads,
85threads, it is currently not reentrant in any way, so use appropriate 84it is currently not reentrant in any way, so use appropriate locking
86locking yourself, always call C<poll_cb> from within the same thread, or 85yourself, always call C<poll_cb> from within the same thread, or never
87never call C<poll_cb> (or other C<aio_> functions) recursively. 86call C<poll_cb> (or other C<aio_> functions) recursively.
88 87
89=head2 EXAMPLE 88=head2 EXAMPLE
90 89
91This is a simple example that uses the Event module and loads 90This is a simple example that uses the Event module and loads
92F</etc/passwd> asynchronously: 91F</etc/passwd> asynchronously:
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328=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 327=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
329 328
330Reads or writes C<length> bytes from the specified C<fh> and C<offset> 329Reads or writes C<length> bytes from the specified C<fh> and C<offset>
331into the scalar given by C<data> and offset C<dataoffset> and calls the 330into the scalar given by C<data> and offset C<dataoffset> and calls the
332callback without the actual number of bytes read (or -1 on error, just 331callback without the actual number of bytes read (or -1 on error, just
333like the syscall). 332like the syscall). If C<offset> is undefined, then the current file offset
333will be used (and updated), otherwise the file offset will not be changed
334by these calls.
334 335
335The C<$data> scalar I<MUST NOT> be modified in any way while the request 336The C<$data> scalar I<MUST NOT> be modified in any way while the request
336is outstanding. Modifying it can result in segfaults or WW3 (if the 337is outstanding. Modifying it can result in segfaults or World War III (if
337necessary/optional hardware is installed). 338the necessary/optional hardware is installed).
338 339
339Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at 340Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
340offset C<0> within the scalar: 341offset C<0> within the scalar:
341 342
342 aio_read $fh, 7, 15, $buffer, 0, sub { 343 aio_read $fh, 7, 15, $buffer, 0, sub {

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