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comparison mercurial/util.py @ 34295:3bb2a9f25fe9

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util: add an mmapread method This is useful for large files that are only partly touched. Test Plan: Will be used and tested in a later patch. Differential Revision: https://phab.mercurial-scm.org/D476
author Mark Thomas <mbthomas@fb.com>
date Thu, 21 Sep 2017 05:54:34 -0700
parents be00af4a1ac5
children c41444a39de2
comparison
equal deleted inserted replaced
34294:05131c963767 34295:3bb2a9f25fe9
24 import datetime 24 import datetime
25 import errno 25 import errno
26 import gc 26 import gc
27 import hashlib 27 import hashlib
28 import imp 28 import imp
29 import mmap
29 import os 30 import os
30 import platform as pyplatform 31 import platform as pyplatform
31 import re as remod 32 import re as remod
32 import shutil 33 import shutil
33 import signal 34 import signal
404 if not data: 405 if not data:
405 self._eof = True 406 self._eof = True
406 else: 407 else:
407 self._lenbuf += len(data) 408 self._lenbuf += len(data)
408 self._buffer.append(data) 409 self._buffer.append(data)
410
411 def mmapread(fp):
412 try:
413 fd = getattr(fp, 'fileno', lambda: fp)()
414 return mmap.mmap(fd, 0, access=mmap.ACCESS_READ)
415 except ValueError:
416 # Empty files cannot be mmapped, but mmapread should still work. Check
417 # if the file is empty, and if so, return an empty buffer.
418 if os.fstat(fd).st_size == 0:
419 return ''
420 raise
409 421
410 def popen2(cmd, env=None, newlines=False): 422 def popen2(cmd, env=None, newlines=False):
411 # Setting bufsize to -1 lets the system decide the buffer size. 423 # Setting bufsize to -1 lets the system decide the buffer size.
412 # The default for bufsize is 0, meaning unbuffered. This leads to 424 # The default for bufsize is 0, meaning unbuffered. This leads to
413 # poor performance on Mac OS X: http://bugs.python.org/issue4194 425 # poor performance on Mac OS X: http://bugs.python.org/issue4194