|
11 | 11 |
|
12 | 12 | fromgitdb.utilimport ( |
13 | 13 | stream_copy, |
14 | | -make_sha |
| 14 | +make_sha, |
| 15 | +FDStreamWrapper, |
| 16 | +LockedFD |
15 | 17 | ) |
16 | 18 |
|
17 | 19 |
|
@@ -271,146 +273,6 @@ def _obtain_lock(self): |
271 | 273 | break |
272 | 274 | # END endless loop |
273 | 275 |
|
274 | | - |
275 | | -classFDStreamWrapper(object): |
276 | | -"""A simple wrapper providing the most basic functions on a file descriptor |
277 | | -with the fileobject interface. Cannot use os.fdopen as the resulting stream |
278 | | -takes ownership""" |
279 | | -__slots__= ("_fd",'_pos') |
280 | | -def__init__(self,fd): |
281 | | -self._fd=fd |
282 | | -self._pos=0 |
283 | | - |
284 | | -defwrite(self,data): |
285 | | -self._pos+=len(data) |
286 | | -os.write(self._fd,data) |
287 | | - |
288 | | -defread(self,count=0): |
289 | | -ifcount==0: |
290 | | -count=os.path.getsize(self._filepath) |
291 | | -# END handle read everything |
292 | | - |
293 | | -bytes=os.read(self._fd,count) |
294 | | -self._pos+=len(bytes) |
295 | | -returnbytes |
296 | | - |
297 | | -deffileno(self): |
298 | | -returnself._fd |
299 | | - |
300 | | -deftell(self): |
301 | | -returnself._pos |
302 | | - |
303 | | - |
304 | | -classLockedFD(LockFile): |
305 | | -"""This class facilitates a safe read and write operation to a file on disk. |
306 | | -If we write to 'file', we obtain a lock file at 'file.lock' and write to |
307 | | -that instead. If we succeed, the lock file will be renamed to overwrite |
308 | | -the original file. |
309 | | -
|
310 | | -When reading, we obtain a lock file, but to prevent other writers from |
311 | | -succeeding while we are reading the file. |
312 | | -
|
313 | | -This type handles error correctly in that it will assure a consistent state |
314 | | -on destruction. |
315 | | -
|
316 | | -:note: with this setup, parallel reading is not possible""" |
317 | | -__slots__= ("_filepath",'_fd','_write') |
318 | | - |
319 | | -def__init__(self,filepath): |
320 | | -"""Initialize an instance with the givne filepath""" |
321 | | -self._filepath=filepath |
322 | | -self._fd=None |
323 | | -self._write=None# if True, we write a file |
324 | | - |
325 | | -def__del__(self): |
326 | | -# will do nothing if the file descriptor is already closed |
327 | | -ifself._fdisnotNone: |
328 | | -self.rollback() |
329 | | - |
330 | | -def_lockfilepath(self): |
331 | | -return"%s.lock"%self._filepath |
332 | | - |
333 | | -defopen(self,write=False,stream=False): |
334 | | -"""Open the file descriptor for reading or writing, both in binary mode. |
335 | | -:param write: if True, the file descriptor will be opened for writing. Other |
336 | | -wise it will be opened read-only. |
337 | | -:param stream: if True, the file descriptor will be wrapped into a simple stream |
338 | | -object which supports only reading or writing |
339 | | -:return: fd to read from or write to. It is still maintained by this instance |
340 | | -and must not be closed directly |
341 | | -:raise IOError: if the lock could not be retrieved |
342 | | -:raise OSError: If the actual file could not be opened for reading |
343 | | -:note: must only be called once""" |
344 | | -ifself._writeisnotNone: |
345 | | -raiseAssertionError("Called %s multiple times"%self.open) |
346 | | - |
347 | | -self._write=write |
348 | | - |
349 | | -# try to open the lock file |
350 | | -binary=getattr(os,'O_BINARY',0) |
351 | | -lockmode=os.O_WRONLY|os.O_CREAT|os.O_EXCL|binary |
352 | | -try: |
353 | | -fd=os.open(self._lockfilepath(),lockmode) |
354 | | -ifnotwrite: |
355 | | -os.close(fd) |
356 | | -else: |
357 | | -self._fd=fd |
358 | | -# END handle file descriptor |
359 | | -exceptOSError: |
360 | | -raiseIOError("Lock at %r could not be obtained"%self._lockfilepath()) |
361 | | -# END handle lock retrieval |
362 | | - |
363 | | -# open actual file if required |
364 | | -ifself._fdisNone: |
365 | | -# we could specify exlusive here, as we obtained the lock anyway |
366 | | -self._fd=os.open(self._filepath,os.O_RDONLY|binary) |
367 | | -# END open descriptor for reading |
368 | | - |
369 | | -ifstream: |
370 | | -returnFDStreamWrapper(self._fd) |
371 | | -else: |
372 | | -returnself._fd |
373 | | -# END handle stream |
374 | | - |
375 | | -defcommit(self): |
376 | | -"""When done writing, call this function to commit your changes into the |
377 | | -actual file. |
378 | | -The file descriptor will be closed, and the lockfile handled. |
379 | | -:note: can be called multiple times""" |
380 | | -self._end_writing(successful=True) |
381 | | - |
382 | | -defrollback(self): |
383 | | -"""Abort your operation without any changes. The file descriptor will be |
384 | | -closed, and the lock released. |
385 | | -:note: can be called multiple times""" |
386 | | -self._end_writing(successful=False) |
387 | | - |
388 | | -def_end_writing(self,successful=True): |
389 | | -"""Handle the lock according to the write mode """ |
390 | | -ifself._writeisNone: |
391 | | -raiseAssertionError("Cannot end operation if it wasn't started yet") |
392 | | - |
393 | | -ifself._fdisNone: |
394 | | -return |
395 | | - |
396 | | -os.close(self._fd) |
397 | | -self._fd=None |
398 | | - |
399 | | -lockfile=self._lockfilepath() |
400 | | -ifself._writeandsuccessful: |
401 | | -# on windows, rename does not silently overwrite the existing one |
402 | | -ifsys.platform=="win32": |
403 | | -ifos.path.isfile(self._filepath): |
404 | | -os.remove(self._filepath) |
405 | | -# END remove if exists |
406 | | -# END win32 special handling |
407 | | -os.rename(lockfile,self._filepath) |
408 | | -else: |
409 | | -# just delete the file so far, we failed |
410 | | -os.remove(lockfile) |
411 | | -# END successful handling |
412 | | - |
413 | | - |
414 | 276 |
|
415 | 277 | classLazyMixin(object): |
416 | 278 | """ |
|