"""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

except ImportError:

    def _set_cloexec(fd):

        pass

else:

    def _set_cloexec(fd):

        try:

            flags = _fcntl.fcntl(fd, _fcntl.F_GETFD, 0)

        except IOError:

            pass

        else:

            # 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()

if hasattr(_os, "lstat"):

    _stat = _os.lstat

elif hasattr(_os, "stat"):

    _stat = _os.stat

else:

    # Fallback.  All we need is something that raises os.error if the

    # file doesn't exist.

    def _stat(fn):

        try:

            f = open(fn)

        except IOError:

            raise _os.error

        f.close()

def _exists(fn):

    try:

        _stat(fn)

    except _os.error:

        return False

    else:

        return True

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, _os.path.abspath(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 _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):

        # Attribute lookups are delegated to the underlying file

        # and cached for non-numeric results

        # (i.e. methods are cached, closed and friends are not)

        file = self.__dict__['file']

        a = getattr(file, name)

        if type(a) != type(0):

            setattr(self, name, a)

        return a

    # The underlying __enter__ method returns the wrong object

    # (self.file) so override it to return the wrapper

    def __enter__(self):

        self.file.__enter__()

        return self

    # 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()

        # Need to trap __exit__ as well to ensure the file gets

        # deleted when used in a with statement

        def __exit__(self, exc, value, tb):

            result = self.file.__exit__(exc, value, tb)

            self.close()

            return result

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 an object with a file-like interface; 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', '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 an object with a file-like interface.  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