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| 265 | Asynchronously close a file and call the callback with the result |
265 | Asynchronously close a file and call the callback with the result |
| 266 | code. |
266 | code. |
| 267 | |
267 | |
| 268 | Unfortunately, you can't do this to perl. Perl *insists* very |
268 | Unfortunately, you can't do this to perl. Perl *insists* very |
| 269 | strongly on closing the file descriptor associated with the |
269 | strongly on closing the file descriptor associated with the |
| 270 | filehandle itself. Here is what aio_close will try: |
270 | filehandle itself. |
| 271 | |
271 | |
| 272 | 1. dup()licate the fd |
272 | Therefore, "aio_close" will not close the filehandle - instead it |
| 273 | 2. asynchronously close() the duplicated fd |
273 | will use dup2 to overwrite the file descriptor with the write-end of |
| 274 | 3. dup()licate the fd once more |
274 | a pipe (the pipe fd will be created on demand and will be cached). |
| 275 | 4. let perl close() the filehandle |
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| 276 | 5. asynchronously close the duplicated fd |
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| 277 | |
275 | |
| 278 | The idea is that the first close() flushes stuff to disk that |
276 | Or in other words: the file descriptor will be closed, but it will |
| 279 | closing an fd will flush, so when perl closes the fd, nothing much |
277 | not be free for reuse until the perl filehandle is closed. |
| 280 | will need to be flushed. The second async. close() will then flush |
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| 281 | stuff to disk that closing the last fd to the file will flush. |
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| 282 | |
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| 283 | Just FYI, SuSv3 has this to say on close: |
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| 284 | |
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| 285 | All outstanding record locks owned by the process on the file |
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| 286 | associated with the file descriptor shall be removed. |
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| 287 | |
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| 288 | If fildes refers to a socket, close() shall cause the socket to be |
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| 289 | destroyed. ... close() shall block for up to the current linger |
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| 290 | interval until all data is transmitted. |
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| 291 | [this actually sounds like a specification bug, but who knows] |
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| 292 | |
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| 293 | And at least Linux additionally actually flushes stuff on every |
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| 294 | close, even when the file itself is still open. |
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| 295 | |
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| 296 | Sounds enourmously inefficient and complicated? Yes... please show |
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| 297 | me how to nuke perl's fd out of existence... |
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| 298 | |
278 | |
| 299 | aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
279 | aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
| 300 | aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
280 | aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) |
| 301 | Reads or writes $length bytes from the specified $fh and $offset |
281 | Reads or writes $length bytes from the specified $fh and $offset |
| 302 | into the scalar given by $data and offset $dataoffset and calls the |
282 | into the scalar given by $data and offset $dataoffset and calls the |
