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Revision 1.4 by root, Sun Jul 10 21:04:46 2005 UTC vs.
Revision 1.7 by root, Wed Jul 20 21:55:38 2005 UTC

1NAME 1NAME
2 IO::AIO - Asynchronous Input/Output 2 IO::AIO - Asynchronous Input/Output
3 3
4SYNOPSIS 4SYNOPSIS
5 use IO::AIO; 5 use IO::AIO;
6
7 aio_open "/etc/passwd", O_RDONLY, 0, sub {
8 my ($fh) = @_;
9 ...
10 };
11
12 aio_unlink "/tmp/file", sub { };
13
14 aio_read $fh, 30000, 1024, $buffer, 0, sub {
15 $_[0] > 0 or die "read error: $!";
16 };
17
18 # Event
19 Event->io (fd => IO::AIO::poll_fileno,
20 poll => 'r',
21 cb => \&IO::AIO::poll_cb);
22
23 # Glib/Gtk2
24 add_watch Glib::IO IO::AIO::poll_fileno,
25 in => sub { IO::AIO::poll_cb; 1 };
26
27 # Tk
28 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
29 readable => \&IO::AIO::poll_cb);
30
31 # Danga::Socket
32 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
33 \&IO::AIO::poll_cb);
6 34
7DESCRIPTION 35DESCRIPTION
8 This module implements asynchronous I/O using whatever means your 36 This module implements asynchronous I/O using whatever means your
9 operating system supports. 37 operating system supports.
10 38
… …
17 currently, for example), and they would only support aio_read and 45 currently, for example), and they would only support aio_read and
18 aio_write, so the remaining functionality would have to be implemented 46 aio_write, so the remaining functionality would have to be implemented
19 using threads anyway. 47 using threads anyway.
20 48
21 Although the module will work with in the presence of other threads, it 49 Although the module will work with in the presence of other threads, it
22 is currently not reentrant, so use appropriate locking yourself. 50 is currently not reentrant, so use appropriate locking yourself, always
51 call "poll_cb" from within the same thread, or never call "poll_cb" (or
52 other "aio_" functions) recursively.
23 53
24FUNCTIONS 54FUNCTIONS
25 AIO FUNCTIONS 55 AIO FUNCTIONS
26 All the "aio_*" calls are more or less thin wrappers around the syscall 56 All the "aio_*" calls are more or less thin wrappers around the syscall
27 with the same name (sans "aio_"). The arguments are similar or 57 with the same name (sans "aio_"). The arguments are similar or
28 identical, and they all accept an additional $callback argument which 58 identical, and they all accept an additional (and optional) $callback
29 must be a code reference. This code reference will get called with the 59 argument which must be a code reference. This code reference will get
30 syscall return code (e.g. most syscalls return -1 on error, unlike perl, 60 called with the syscall return code (e.g. most syscalls return -1 on
31 which usually delivers "false") as it's sole argument when the given 61 error, unlike perl, which usually delivers "false") as it's sole
32 syscall has been executed asynchronously. 62 argument when the given syscall has been executed asynchronously.
33 63
34 All functions that expect a filehandle will also accept a file 64 All functions that expect a filehandle will also accept a file
35 descriptor. 65 descriptor.
36 66
37 The filenames you pass to these routines *must* be absolute. The reason 67 The filenames you pass to these routines *must* be absolute. The reason
38 is that at the time the request is being executed, the current working 68 for this is that at the time the request is being executed, the current
39 directory could have changed. Alternatively, you can make sure that you 69 working directory could have changed. Alternatively, you can make sure
40 never change the current working directory. 70 that you never change the current working directory.
41 71
42 aio_open $pathname, $flags, $mode, $callback 72 aio_open $pathname, $flags, $mode, $callback
43 Asynchronously open or create a file and call the callback with a 73 Asynchronously open or create a file and call the callback with a
44 newly created filehandle for the file. 74 newly created filehandle for the file.
45 75
46 The pathname passed to "aio_open" must be absolute. See API NOTES, 76 The pathname passed to "aio_open" must be absolute. See API NOTES,
47 above, for an explanation. 77 above, for an explanation.
48 78
49 The $mode argument is a bitmask. See the "Fcntl" module for a list. 79 The $flags argument is a bitmask. See the "Fcntl" module for a list.
50 They are the same as used in "sysopen". 80 They are the same as used by "sysopen".
81
82 Likewise, $mode specifies the mode of the newly created file, if it
83 didn't exist and "O_CREAT" has been given, just like perl's
84 "sysopen", except that it is mandatory (i.e. use 0 if you don't
85 create new files, and 0666 or 0777 if you do).
51 86
52 Example: 87 Example:
53 88
54 aio_open "/etc/passwd", O_RDONLY, 0, sub { 89 aio_open "/etc/passwd", O_RDONLY, 0, sub {
55 if ($_[0]) { 90 if ($_[0]) {
… …
62 97
63 aio_close $fh, $callback 98 aio_close $fh, $callback
64 Asynchronously close a file and call the callback with the result 99 Asynchronously close a file and call the callback with the result
65 code. *WARNING:* although accepted, you should not pass in a perl 100 code. *WARNING:* although accepted, you should not pass in a perl
66 filehandle here, as perl will likely close the file descriptor 101 filehandle here, as perl will likely close the file descriptor
67 itself when the filehandle is destroyed. Normally, you can safely 102 another time when the filehandle is destroyed. Normally, you can
68 call perls "close" or just let filehandles go out of scope. 103 safely call perls "close" or just let filehandles go out of scope.
104
105 This is supposed to be a bug in the API, so that might change. It's
106 therefore best to avoid this function.
69 107
70 aio_read $fh,$offset,$length, $data,$dataoffset,$callback 108 aio_read $fh,$offset,$length, $data,$dataoffset,$callback
71 aio_write $fh,$offset,$length, $data,$dataoffset,$callback 109 aio_write $fh,$offset,$length, $data,$dataoffset,$callback
72 Reads or writes "length" bytes from the specified "fh" and "offset" 110 Reads or writes "length" bytes from the specified "fh" and "offset"
73 into the scalar given by "data" and offset "dataoffset" and calls 111 into the scalar given by "data" and offset "dataoffset" and calls
74 the callback without the actual number of bytes read (or -1 on 112 the callback without the actual number of bytes read (or -1 on
75 error, just like the syscall). 113 error, just like the syscall).
76 114
77 Example: Read 15 bytes at offset 7 into scalar $buffer, strating at 115 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
78 offset 0 within the scalar: 116 offset 0 within the scalar:
79 117
80 aio_read $fh, 7, 15, $buffer, 0, sub { 118 aio_read $fh, 7, 15, $buffer, 0, sub {
81 $_[0] >= 0 or die "read error: $!"; 119 $_[0] > 0 or die "read error: $!";
82 print "read <$buffer>\n"; 120 print "read $_[0] bytes: <$buffer>\n";
83 }; 121 };
84 122
85 aio_readahead $fh,$offset,$length, $callback 123 aio_readahead $fh,$offset,$length, $callback
86 Asynchronously reads the specified byte range into the page cache, 124 Asynchronously reads the specified byte range into the page cache,
87 using the "readahead" syscall. If that syscall doesn't exist the 125 using the "readahead" syscall. If that syscall doesn't exist (likely
88 status will be -1 and $! is set to ENOSYS. 126 if your OS isn't Linux) the status will be -1 and $! is set to
127 "ENOSYS".
89 128
90 readahead() populates the page cache with data from a file so that 129 "aio_readahead" populates the page cache with data from a file so
91 subsequent reads from that file will not block on disk I/O. The 130 that subsequent reads from that file will not block on disk I/O. The
92 $offset argument specifies the starting point from which data is to 131 $offset argument specifies the starting point from which data is to
93 be read and $length specifies the number of bytes to be read. I/O is 132 be read and $length specifies the number of bytes to be read. I/O is
94 performed in whole pages, so that offset is effectively rounded down 133 performed in whole pages, so that offset is effectively rounded down
95 to a page boundary and bytes are read up to the next page boundary 134 to a page boundary and bytes are read up to the next page boundary
96 greater than or equal to (off-set+length). aio_readahead() does not 135 greater than or equal to (off-set+length). "aio_readahead" does not
97 read beyond the end of the file. The current file offset of the file 136 read beyond the end of the file. The current file offset of the file
98 is left unchanged. 137 is left unchanged.
99 138
100 aio_stat $fh_or_path, $callback 139 aio_stat $fh_or_path, $callback
101 aio_lstat $fh, $callback 140 aio_lstat $fh, $callback
… …
126 Asynchronously call fsync on the given filehandle and call the 165 Asynchronously call fsync on the given filehandle and call the
127 callback with the fsync result code. 166 callback with the fsync result code.
128 167
129 aio_fdatasync $fh, $callback 168 aio_fdatasync $fh, $callback
130 Asynchronously call fdatasync on the given filehandle and call the 169 Asynchronously call fdatasync on the given filehandle and call the
131 callback with the fdatasync result code. 170 callback with the fdatasync result code. Might set $! to "ENOSYS" if
171 "fdatasync" is not available.
132 172
133 SUPPORT FUNCTIONS 173 SUPPORT FUNCTIONS
134 $fileno = IO::AIO::poll_fileno 174 $fileno = IO::AIO::poll_fileno
135 Return the *request result pipe filehandle*. This filehandle must be 175 Return the *request result pipe file descriptor*. This filehandle
136 polled for reading by some mechanism outside this module (e.g. Event 176 must be polled for reading by some mechanism outside this module
137 or select, see below). If the pipe becomes readable you have to call 177 (e.g. Event or select, see below or the SYNOPSIS). If the pipe
138 "poll_cb" to check the results. 178 becomes readable you have to call "poll_cb" to check the results.
139 179
140 See "poll_cb" for an example. 180 See "poll_cb" for an example.
141 181
142 IO::AIO::poll_cb 182 IO::AIO::poll_cb
143 Process all outstanding events on the result pipe. You have to call 183 Process all outstanding events on the result pipe. You have to call
144 this regularly. Returns the number of events processed. Returns 184 this regularly. Returns the number of events processed. Returns
145 immediately when no events are outstanding. 185 immediately when no events are outstanding.
146 186
147 You can use Event to multiplex, e.g.: 187 Example: Install an Event watcher that automatically calls
188 IO::AIO::poll_cb with high priority:
148 189
149 Event->io (fd => IO::AIO::poll_fileno, 190 Event->io (fd => IO::AIO::poll_fileno,
150 poll => 'r', async => 1, 191 poll => 'r', async => 1,
151 cb => \&IO::AIO::poll_cb); 192 cb => \&IO::AIO::poll_cb);
152 193
153 IO::AIO::poll_wait 194 IO::AIO::poll_wait
154 Wait till the result filehandle becomes ready for reading (simply 195 Wait till the result filehandle becomes ready for reading (simply
155 does a select on the filehandle. This is useful if you want to 196 does a "select" on the filehandle. This is useful if you want to
156 synchronously wait for some requests to finish). 197 synchronously wait for some requests to finish).
157 198
158 See "nreqs" for an example. 199 See "nreqs" for an example.
159 200
160 IO::AIO::nreqs 201 IO::AIO::nreqs
161 Returns the number of requests currently outstanding. 202 Returns the number of requests currently outstanding (i.e. for which
203 their callback has not been invoked yet).
162 204
163 Example: wait till there are no outstanding requests anymore: 205 Example: wait till there are no outstanding requests anymore:
164 206
165 IO::AIO::poll_wait, IO::AIO::poll_cb 207 IO::AIO::poll_wait, IO::AIO::poll_cb
166 while IO::AIO::nreqs; 208 while IO::AIO::nreqs;
209
210 IO::AIO::flush
211 Wait till all outstanding AIO requests have been handled.
212
213 Strictly equivalent to:
214
215 IO::AIO::poll_wait, IO::AIO::poll_cb
216 while IO::AIO::nreqs;
217
218 IO::AIO::poll
219 Waits until some requests have been handled.
220
221 Strictly equivalent to:
222
223 IO::AIO::poll_wait, IO::AIO::poll_cb
224 if IO::AIO::nreqs;
167 225
168 IO::AIO::min_parallel $nthreads 226 IO::AIO::min_parallel $nthreads
169 Set the minimum number of AIO threads to $nthreads. The default is 227 Set the minimum number of AIO threads to $nthreads. The default is
170 1, which means a single asynchronous operation can be done at one 228 1, which means a single asynchronous operation can be done at one
171 time (the number of outstanding operations, however, is unlimited). 229 time (the number of outstanding operations, however, is unlimited).

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