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272 lines
9.2 KiB
Python
272 lines
9.2 KiB
Python
"""Temporary files and filenames."""
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# XXX This tries to be not UNIX specific, but I don't know beans about
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# how to choose a temp directory or filename on MS-DOS or other
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# systems so it may have to be changed...
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import os
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__all__ = ["mktemp", "TemporaryFile", "tempdir", "gettempprefix"]
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# Parameters that the caller may set to override the defaults
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tempdir = None
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template = None
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def gettempdir():
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"""Function to calculate the directory to use."""
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global tempdir
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if tempdir is not None:
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return tempdir
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# _gettempdir_inner deduces whether a candidate temp dir is usable by
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# trying to create a file in it, and write to it. If that succeeds,
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# great, it closes the file and unlinks it. There's a race, though:
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# the *name* of the test file it tries is the same across all threads
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# under most OSes (Linux is an exception), and letting multiple threads
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# all try to open, write to, close, and unlink a single file can cause
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# a variety of bogus errors (e.g., you cannot unlink a file under
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# Windows if anyone has it open, and two threads cannot create the
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# same file in O_EXCL mode under Unix). The simplest cure is to serialize
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# calls to _gettempdir_inner. This isn't a real expense, because the
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# first thread to succeed sets the global tempdir, and all subsequent
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# calls to gettempdir() reuse that without trying _gettempdir_inner.
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_tempdir_lock.acquire()
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try:
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return _gettempdir_inner()
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finally:
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_tempdir_lock.release()
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def _gettempdir_inner():
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"""Function to calculate the directory to use."""
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global tempdir
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if tempdir is not None:
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return tempdir
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try:
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pwd = os.getcwd()
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except (AttributeError, os.error):
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pwd = os.curdir
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attempdirs = ['/tmp', '/var/tmp', '/usr/tmp', pwd]
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if os.name == 'nt':
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attempdirs.insert(0, 'C:\\TEMP')
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attempdirs.insert(0, '\\TEMP')
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elif os.name == 'mac':
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import macfs, MACFS
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try:
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refnum, dirid = macfs.FindFolder(MACFS.kOnSystemDisk,
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MACFS.kTemporaryFolderType, 1)
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dirname = macfs.FSSpec((refnum, dirid, '')).as_pathname()
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attempdirs.insert(0, dirname)
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except macfs.error:
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pass
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elif os.name == 'riscos':
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scrapdir = os.getenv('Wimp$ScrapDir')
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if scrapdir:
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attempdirs.insert(0, scrapdir)
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for envname in 'TMPDIR', 'TEMP', 'TMP':
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if os.environ.has_key(envname):
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attempdirs.insert(0, os.environ[envname])
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testfile = gettempprefix() + 'test'
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for dir in attempdirs:
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try:
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filename = os.path.join(dir, testfile)
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if os.name == 'posix':
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try:
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fd = os.open(filename,
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os.O_RDWR | os.O_CREAT | os.O_EXCL, 0700)
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except OSError:
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pass
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else:
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fp = os.fdopen(fd, 'w')
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fp.write('blat')
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fp.close()
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os.unlink(filename)
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del fp, fd
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tempdir = dir
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break
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else:
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fp = open(filename, 'w')
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fp.write('blat')
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fp.close()
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os.unlink(filename)
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tempdir = dir
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break
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except IOError:
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pass
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if tempdir is None:
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msg = "Can't find a usable temporary directory amongst " + `attempdirs`
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raise IOError, msg
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return tempdir
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# template caches the result of gettempprefix, for speed, when possible.
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# XXX unclear why this isn't "_template"; left it "template" for backward
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# compatibility.
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if os.name == "posix":
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# We don't try to cache the template on posix: the pid may change on us
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# between calls due to a fork, and on Linux the pid changes even for
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# another thread in the same process. Since any attempt to keep the
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# cache in synch would have to call os.getpid() anyway in order to make
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# sure the pid hasn't changed between calls, a cache wouldn't save any
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# time. In addition, a cache is difficult to keep correct with the pid
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# changing willy-nilly, and earlier attempts proved buggy (races).
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template = None
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# Else the pid never changes, so gettempprefix always returns the same
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# string.
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elif os.name == "nt":
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template = '~' + `os.getpid()` + '-'
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elif os.name in ('mac', 'riscos'):
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template = 'Python-Tmp-'
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else:
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template = 'tmp' # XXX might choose a better one
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def gettempprefix():
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"""Function to calculate a prefix of the filename to use.
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This incorporates the current process id on systems that support such a
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notion, so that concurrent processes don't generate the same prefix.
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"""
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global template
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if template is None:
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return '@' + `os.getpid()` + '.'
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else:
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return template
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def mktemp(suffix=""):
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"""User-callable function to return a unique temporary file name."""
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dir = gettempdir()
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pre = gettempprefix()
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while 1:
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i = _counter.get_next()
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file = os.path.join(dir, pre + str(i) + suffix)
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if not os.path.exists(file):
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return file
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class TemporaryFileWrapper:
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"""Temporary file wrapper
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This class provides a wrapper around files opened for temporary use.
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In particular, it seeks to automatically remove the file when it is
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no longer needed.
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"""
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# Cache the unlinker so we don't get spurious errors at shutdown
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# when the module-level "os" is None'd out. Note that this must
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# be referenced as self.unlink, because the name TemporaryFileWrapper
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# may also get None'd out before __del__ is called.
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unlink = os.unlink
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def __init__(self, file, path):
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self.file = file
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self.path = path
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self.close_called = 0
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def close(self):
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if not self.close_called:
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self.close_called = 1
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self.file.close()
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self.unlink(self.path)
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def __del__(self):
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self.close()
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def __getattr__(self, name):
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file = self.__dict__['file']
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a = getattr(file, name)
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if type(a) != type(0):
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setattr(self, name, a)
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return a
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try:
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import fcntl as _fcntl
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def _set_cloexec(fd, flag=_fcntl.FD_CLOEXEC):
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flags = _fcntl.fcntl(fd, _fcntl.F_GETFD, 0)
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if flags >= 0:
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# flags read successfully, modify
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flags |= flag
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_fcntl.fcntl(fd, _fcntl.F_SETFD, flags)
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except (ImportError, AttributeError):
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def _set_cloexec(fd):
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pass
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def TemporaryFile(mode='w+b', bufsize=-1, suffix=""):
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"""Create and return a temporary file (opened read-write by default)."""
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name = mktemp(suffix)
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if os.name == 'posix':
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# Unix -- be very careful
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fd = os.open(name, os.O_RDWR|os.O_CREAT|os.O_EXCL, 0700)
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_set_cloexec(fd)
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try:
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os.unlink(name)
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return os.fdopen(fd, mode, bufsize)
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except:
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os.close(fd)
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raise
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elif os.name == 'nt':
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# Windows -- can't unlink an open file, but O_TEMPORARY creates a
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# file that "deletes itself" when the last handle is closed.
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# O_NOINHERIT ensures processes created via spawn() don't get a
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# handle to this too. That would be a security hole, and, on my
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# Win98SE box, when an O_TEMPORARY file is inherited by a spawned
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# process, the fd in the spawned process seems to lack the
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# O_TEMPORARY flag, so the file doesn't go away by magic then if the
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# spawning process closes it first.
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flags = (os.O_RDWR | os.O_CREAT | os.O_EXCL |
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os.O_TEMPORARY | os.O_NOINHERIT)
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if 'b' in mode:
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flags |= os.O_BINARY
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fd = os.open(name, flags, 0700)
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return os.fdopen(fd, mode, bufsize)
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else:
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# Assume we can't unlink a file that's still open, or arrange for
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# an automagically self-deleting file -- use wrapper.
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file = open(name, mode, bufsize)
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return TemporaryFileWrapper(file, name)
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# In order to generate unique names, mktemp() uses _counter.get_next().
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# This returns a unique integer on each call, in a threadsafe way (i.e.,
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# multiple threads will never see the same integer). The integer will
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# usually be a Python int, but if _counter.get_next() is called often
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# enough, it will become a Python long.
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# Note that the only names that survive this next block of code
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# are "_counter" and "_tempdir_lock".
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class _ThreadSafeCounter:
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def __init__(self, mutex, initialvalue=0):
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self.mutex = mutex
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self.i = initialvalue
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def get_next(self):
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self.mutex.acquire()
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result = self.i
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try:
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newi = result + 1
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except OverflowError:
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newi = long(result) + 1
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self.i = newi
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self.mutex.release()
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return result
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try:
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import thread
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except ImportError:
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class _DummyMutex:
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def acquire(self):
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pass
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release = acquire
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_counter = _ThreadSafeCounter(_DummyMutex())
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_tempdir_lock = _DummyMutex()
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del _DummyMutex
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else:
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_counter = _ThreadSafeCounter(thread.allocate_lock())
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_tempdir_lock = thread.allocate_lock()
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del thread
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del _ThreadSafeCounter
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