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Diffstat (limited to 'tools/python/xen/util/tempfile.py')
| -rw-r--r-- | tools/python/xen/util/tempfile.py | 451 |
1 files changed, 451 insertions, 0 deletions
diff --git a/tools/python/xen/util/tempfile.py b/tools/python/xen/util/tempfile.py new file mode 100644 index 0000000000..756d8c8727 --- /dev/null +++ b/tools/python/xen/util/tempfile.py @@ -0,0 +1,451 @@ +"""Temporary files. + +This module provides generic, low- and high-level interfaces for +creating temporary files and directories. The interfaces listed +as "safe" just below can be used without fear of race conditions. +Those listed as "unsafe" cannot, and are provided for backward +compatibility only. + +This module also provides some data items to the user: + + TMP_MAX - maximum number of names that will be tried before + giving up. + template - the default prefix for all temporary names. + You may change this to control the default prefix. + tempdir - If this is set to a string before the first use of + any routine from this module, it will be considered as + another candidate location to store temporary files. +""" + +__all__ = [ + "NamedTemporaryFile", "TemporaryFile", # high level safe interfaces + "mkstemp", "mkdtemp", # low level safe interfaces + "mktemp", # deprecated unsafe interface + "TMP_MAX", "gettempprefix", # constants + "tempdir", "gettempdir" + ] + + +# Imports. + +import os as _os +import errno as _errno +from random import Random as _Random + +if _os.name == 'mac': + import Carbon.Folder as _Folder + import Carbon.Folders as _Folders + +try: + import fcntl as _fcntl + # If PYTHONCASEOK is set on Windows, stinking FCNTL.py gets + # imported, and we don't get an ImportError then. Provoke + # an AttributeError instead in that case. + _fcntl.fcntl +except (ImportError, AttributeError): + def _set_cloexec(fd): + pass +else: + def _set_cloexec(fd): + flags = _fcntl.fcntl(fd, _fcntl.F_GETFD, 0) + if flags >= 0: + # flags read successfully, modify + flags |= _fcntl.FD_CLOEXEC + _fcntl.fcntl(fd, _fcntl.F_SETFD, flags) + + +try: + import thread as _thread +except ImportError: + import dummy_thread as _thread +_allocate_lock = _thread.allocate_lock + +_text_openflags = _os.O_RDWR | _os.O_CREAT | _os.O_EXCL +if hasattr(_os, 'O_NOINHERIT'): + _text_openflags |= _os.O_NOINHERIT +if hasattr(_os, 'O_NOFOLLOW'): + _text_openflags |= _os.O_NOFOLLOW + +_bin_openflags = _text_openflags +if hasattr(_os, 'O_BINARY'): + _bin_openflags |= _os.O_BINARY + +if hasattr(_os, 'TMP_MAX'): + TMP_MAX = _os.TMP_MAX +else: + TMP_MAX = 10000 + +template = "tmp" + +tempdir = None + +# Internal routines. + +_once_lock = _allocate_lock() + +class _RandomNameSequence: + """An instance of _RandomNameSequence generates an endless + sequence of unpredictable strings which can safely be incorporated + into file names. Each string is six characters long. Multiple + threads can safely use the same instance at the same time. + + _RandomNameSequence is an iterator.""" + + characters = ("abcdefghijklmnopqrstuvwxyz" + + "ABCDEFGHIJKLMNOPQRSTUVWXYZ" + + "0123456789-_") + + def __init__(self): + self.mutex = _allocate_lock() + self.rng = _Random() + self.normcase = _os.path.normcase + + def __iter__(self): + return self + + def next(self): + m = self.mutex + c = self.characters + choose = self.rng.choice + + m.acquire() + try: + letters = [choose(c) for dummy in "123456"] + finally: + m.release() + + return self.normcase(''.join(letters)) + +def _candidate_tempdir_list(): + """Generate a list of candidate temporary directories which + _get_default_tempdir will try.""" + + dirlist = [] + + # First, try the environment. + for envname in 'TMPDIR', 'TEMP', 'TMP': + dirname = _os.getenv(envname) + if dirname: dirlist.append(dirname) + + # Failing that, try OS-specific locations. + if _os.name == 'mac': + try: + fsr = _Folder.FSFindFolder(_Folders.kOnSystemDisk, + _Folders.kTemporaryFolderType, 1) + dirname = fsr.as_pathname() + dirlist.append(dirname) + except _Folder.error: + pass + elif _os.name == 'riscos': + dirname = _os.getenv('Wimp$ScrapDir') + if dirname: dirlist.append(dirname) + elif _os.name == 'nt': + dirlist.extend([ r'c:\temp', r'c:\tmp', r'\temp', r'\tmp' ]) + else: + dirlist.extend([ '/tmp', '/var/tmp', '/usr/tmp' ]) + + # As a last resort, the current directory. + try: + dirlist.append(_os.getcwd()) + except (AttributeError, _os.error): + dirlist.append(_os.curdir) + + return dirlist + +def _get_default_tempdir(): + """Calculate the default directory to use for temporary files. + This routine should be called exactly once. + + We determine whether or not a candidate temp dir is usable by + trying to create and write to a file in that directory. If this + is successful, the test file is deleted. To prevent denial of + service, the name of the test file must be randomized.""" + + namer = _RandomNameSequence() + dirlist = _candidate_tempdir_list() + flags = _text_openflags + + for dir in dirlist: + if dir != _os.curdir: + dir = _os.path.normcase(_os.path.abspath(dir)) + # Try only a few names per directory. + for seq in xrange(100): + name = namer.next() + filename = _os.path.join(dir, name) + try: + fd = _os.open(filename, flags, 0600) + fp = _os.fdopen(fd, 'w') + fp.write('blat') + fp.close() + _os.unlink(filename) + del fp, fd + return dir + except (OSError, IOError), e: + if e[0] != _errno.EEXIST: + break # no point trying more names in this directory + pass + raise IOError, (_errno.ENOENT, + ("No usable temporary directory found in %s" % dirlist)) + +_name_sequence = None + +def _get_candidate_names(): + """Common setup sequence for all user-callable interfaces.""" + + global _name_sequence + if _name_sequence is None: + _once_lock.acquire() + try: + if _name_sequence is None: + _name_sequence = _RandomNameSequence() + finally: + _once_lock.release() + return _name_sequence + + +def _mkstemp_inner(dir, pre, suf, flags): + """Code common to mkstemp, TemporaryFile, and NamedTemporaryFile.""" + + names = _get_candidate_names() + + for seq in xrange(TMP_MAX): + name = names.next() + file = _os.path.join(dir, pre + name + suf) + try: + fd = _os.open(file, flags, 0600) + _set_cloexec(fd) + return (fd, file) + except OSError, e: + if e.errno == _errno.EEXIST: + continue # try again + raise + + raise IOError, (_errno.EEXIST, "No usable temporary file name found") + + +# User visible interfaces. + +def gettempprefix(): + """Accessor for tempdir.template.""" + return template + +tempdir = None + +def gettempdir(): + """Accessor for tempdir.tempdir.""" + global tempdir + if tempdir is None: + _once_lock.acquire() + try: + if tempdir is None: + tempdir = _get_default_tempdir() + finally: + _once_lock.release() + return tempdir + +def mkstemp(suffix="", prefix=template, dir=None, text=False): + """mkstemp([suffix, [prefix, [dir, [text]]]]) + User-callable function to create and return a unique temporary + file. The return value is a pair (fd, name) where fd is the + file descriptor returned by os.open, and name is the filename. + + If 'suffix' is specified, the file name will end with that suffix, + otherwise there will be no suffix. + + If 'prefix' is specified, the file name will begin with that prefix, + otherwise a default prefix is used. + + If 'dir' is specified, the file will be created in that directory, + otherwise a default directory is used. + + If 'text' is specified and true, the file is opened in text + mode. Else (the default) the file is opened in binary mode. On + some operating systems, this makes no difference. + + The file is readable and writable only by the creating user ID. + If the operating system uses permission bits to indicate whether a + file is executable, the file is executable by no one. The file + descriptor is not inherited by children of this process. + + Caller is responsible for deleting the file when done with it. + """ + + if dir is None: + dir = gettempdir() + + if text: + flags = _text_openflags + else: + flags = _bin_openflags + + return _mkstemp_inner(dir, prefix, suffix, flags) + + +def mkdtemp(suffix="", prefix=template, dir=None): + """mkdtemp([suffix, [prefix, [dir]]]) + User-callable function to create and return a unique temporary + directory. The return value is the pathname of the directory. + + Arguments are as for mkstemp, except that the 'text' argument is + not accepted. + + The directory is readable, writable, and searchable only by the + creating user. + + Caller is responsible for deleting the directory when done with it. + """ + + if dir is None: + dir = gettempdir() + + names = _get_candidate_names() + + for seq in xrange(TMP_MAX): + name = names.next() + file = _os.path.join(dir, prefix + name + suffix) + try: + _os.mkdir(file, 0700) + return file + except OSError, e: + if e.errno == _errno.EEXIST: + continue # try again + raise + + raise IOError, (_errno.EEXIST, "No usable temporary directory name found") + +def mktemp(suffix="", prefix=template, dir=None): + """mktemp([suffix, [prefix, [dir]]]) + User-callable function to return a unique temporary file name. The + file is not created. + + Arguments are as for mkstemp, except that the 'text' argument is + not accepted. + + This function is unsafe and should not be used. The file name + refers to a file that did not exist at some point, but by the time + you get around to creating it, someone else may have beaten you to + the punch. + """ + +## from warnings import warn as _warn +## _warn("mktemp is a potential security risk to your program", +## RuntimeWarning, stacklevel=2) + + if dir is None: + dir = gettempdir() + + names = _get_candidate_names() + for seq in xrange(TMP_MAX): + name = names.next() + file = _os.path.join(dir, prefix + name + suffix) + if not _os.path.exists(file): + return file + + raise IOError, (_errno.EEXIST, "No usable temporary filename found") + +class _TemporaryFileWrapper: + """Temporary file wrapper + + This class provides a wrapper around files opened for + temporary use. In particular, it seeks to automatically + remove the file when it is no longer needed. + """ + + def __init__(self, file, name): + self.file = file + self.name = name + self.close_called = False + + def __getattr__(self, name): + file = self.__dict__['file'] + a = getattr(file, name) + if type(a) != type(0): + setattr(self, name, a) + return a + + # NT provides delete-on-close as a primitive, so we don't need + # the wrapper to do anything special. We still use it so that + # file.name is useful (i.e. not "(fdopen)") with NamedTemporaryFile. + if _os.name != 'nt': + + # Cache the unlinker so we don't get spurious errors at + # shutdown when the module-level "os" is None'd out. Note + # that this must be referenced as self.unlink, because the + # name TemporaryFileWrapper may also get None'd out before + # __del__ is called. + unlink = _os.unlink + + def close(self): + if not self.close_called: + self.close_called = True + self.file.close() + self.unlink(self.name) + + def __del__(self): + self.close() + +def NamedTemporaryFile(mode='w+b', bufsize=-1, suffix="", + prefix=template, dir=None): + """Create and return a temporary file. + Arguments: + 'prefix', 'suffix', 'dir' -- as for mkstemp. + 'mode' -- the mode argument to os.fdopen (default "w+b"). + 'bufsize' -- the buffer size argument to os.fdopen (default -1). + The file is created as mkstemp() would do it. + + Returns a file object; the name of the file is accessible as + file.name. The file will be automatically deleted when it is + closed. + """ + + if dir is None: + dir = gettempdir() + + if 'b' in mode: + flags = _bin_openflags + else: + flags = _text_openflags + + # Setting O_TEMPORARY in the flags causes the OS to delete + # the file when it is closed. This is only supported by Windows. + if _os.name == 'nt': + flags |= _os.O_TEMPORARY + + (fd, name) = _mkstemp_inner(dir, prefix, suffix, flags) + file = _os.fdopen(fd, mode, bufsize) + return _TemporaryFileWrapper(file, name) + +if _os.name != 'posix' or _os.sys.platform == 'cygwin': + # On non-POSIX and Cygwin systems, assume that we cannot unlink a file + # while it is open. + TemporaryFile = NamedTemporaryFile + +else: + def TemporaryFile(mode='w+b', bufsize=-1, suffix="", + prefix=template, dir=None): + """Create and return a temporary file. + Arguments: + 'prefix', 'suffix', 'directory' -- as for mkstemp. + 'mode' -- the mode argument to os.fdopen (default "w+b"). + 'bufsize' -- the buffer size argument to os.fdopen (default -1). + The file is created as mkstemp() would do it. + + Returns a file object. The file has no name, and will cease to + exist when it is closed. + """ + + if dir is None: + dir = gettempdir() + + if 'b' in mode: + flags = _bin_openflags + else: + flags = _text_openflags + + (fd, name) = _mkstemp_inner(dir, prefix, suffix, flags) + try: + _os.unlink(name) + return _os.fdopen(fd, mode, bufsize) + except: + _os.close(fd) + raise |