| Current File : /home/inlingua/miniconda3/lib/python3.1/site-packages/conda/gateways/disk/link.py |
# Copyright (C) 2012 Anaconda, Inc & Jason R. Coombs
# SPDX-License-Identifier: BSD-3-Clause, MIT
"""Disk utility functions for symlinking files and folders.
Portions of the code within this module are taken from https://github.com/jaraco/jaraco.windows
which is MIT licensed by Jason R. Coombs.
https://github.com/jaraco/skeleton/issues/1#issuecomment-285448440
"""
import sys
from logging import getLogger
from os import chmod as os_chmod
from os.path import abspath, isdir
from os.path import islink as os_islink
from os.path import lexists as os_lexists
from ...common.compat import on_win
from ...exceptions import CondaOSError, ParseError
__all__ = ("islink", "lchmod", "lexists", "link", "readlink", "symlink")
log = getLogger(__name__)
PYPY = sys.implementation.name == "pypy"
try:
from os import lchmod as os_lchmod
lchmod = os_lchmod
except ImportError: # pragma: no cover
def lchmod(path, mode):
# On systems that don't allow permissions on symbolic links, skip
# links entirely.
if not islink(path):
os_chmod(path, mode)
if not on_win: # pragma: win no cover
from os import link, symlink
link = link
symlink = symlink
else: # pragma: unix no cover
from ctypes import windll, wintypes
CreateHardLink = windll.kernel32.CreateHardLinkW
CreateHardLink.restype = wintypes.BOOL
CreateHardLink.argtypes = [wintypes.LPCWSTR, wintypes.LPCWSTR, wintypes.LPVOID]
try:
CreateSymbolicLink = windll.kernel32.CreateSymbolicLinkW
CreateSymbolicLink.restype = wintypes.BOOL
CreateSymbolicLink.argtypes = [
wintypes.LPCWSTR,
wintypes.LPCWSTR,
wintypes.DWORD,
]
except AttributeError:
CreateSymbolicLink = None
def win_hard_link(src, dst):
"""Equivalent to os.link, using the win32 CreateHardLink call."""
if not CreateHardLink(dst, src, None):
raise CondaOSError(f"win32 hard link failed\n src: {src}\n dst: {dst}")
def win_soft_link(src, dst):
"""Equivalent to os.symlink, using the win32 CreateSymbolicLink call."""
if CreateSymbolicLink is None:
raise CondaOSError("win32 soft link not supported")
if not CreateSymbolicLink(dst, src, isdir(src)):
raise CondaOSError(f"win32 soft link failed\n src: {src}\n dst: {dst}")
link = win_hard_link
symlink = win_soft_link
if not (on_win and PYPY):
from os import readlink
islink = os_islink
lexists = os_lexists
readlink = readlink
else: # pragma: no cover
import builtins
import inspect
import sys
from ctypes import POINTER, Structure, byref, c_uint64, cast, windll, wintypes
from os import getcwd
from os.path import isfile
def islink(path):
"""Determine if the given path is a symlink"""
return is_reparse_point(path) and is_symlink(path)
def lexists(path):
if islink(path):
return True
if isdir(path):
return True
if isfile(path):
return True
return False
MAX_PATH = 260
IO_REPARSE_TAG_SYMLINK = 0xA000000C
INVALID_FILE_ATTRIBUTES = 0xFFFFFFFF
FILE_ATTRIBUTE_REPARSE_POINT = 0x400
NULL = 0
ERROR_NO_MORE_FILES = 0x12
class WIN32_FIND_DATA(Structure):
_fields_ = [
("file_attributes", wintypes.DWORD),
("creation_time", wintypes.FILETIME),
("last_access_time", wintypes.FILETIME),
("last_write_time", wintypes.FILETIME),
("file_size_words", wintypes.DWORD * 2),
("reserved", wintypes.DWORD * 2),
("filename", wintypes.WCHAR * MAX_PATH),
("alternate_filename", wintypes.WCHAR * 14),
]
@property
def file_size(self):
return cast(self.file_size_words, POINTER(c_uint64)).contents
LPWIN32_FIND_DATA = POINTER(WIN32_FIND_DATA)
FindFirstFile = windll.kernel32.FindFirstFileW
FindFirstFile.argtypes = (wintypes.LPWSTR, LPWIN32_FIND_DATA)
FindFirstFile.restype = wintypes.HANDLE
FindNextFile = windll.kernel32.FindNextFileW
FindNextFile.argtypes = (wintypes.HANDLE, LPWIN32_FIND_DATA)
FindNextFile.restype = wintypes.BOOLEAN
INVALID_HANDLE_VALUE = wintypes.HANDLE(-1).value
GetFileAttributes = windll.kernel32.GetFileAttributesW
GetFileAttributes.restype = wintypes.DWORD
GetFileAttributes.argtypes = (wintypes.LPWSTR,)
def handle_nonzero_success(result):
if result == 0:
raise OSError()
def format_system_message(errno):
"""
Call FormatMessage with a system error number to retrieve
the descriptive error message.
"""
# first some flags used by FormatMessageW
ALLOCATE_BUFFER = 0x100
FROM_SYSTEM = 0x1000
# Let FormatMessageW allocate the buffer (we'll free it below)
# Also, let it know we want a system error message.
flags = ALLOCATE_BUFFER | FROM_SYSTEM
source = None
message_id = errno
language_id = 0
result_buffer = wintypes.LPWSTR()
buffer_size = 0
arguments = None
bytes = windll.kernel32.FormatMessageW(
flags,
source,
message_id,
language_id,
byref(result_buffer),
buffer_size,
arguments,
)
# note the following will cause an infinite loop if GetLastError
# repeatedly returns an error that cannot be formatted, although
# this should not happen.
handle_nonzero_success(bytes)
message = result_buffer.value
windll.kernel32.LocalFree(result_buffer)
return message
class WindowsError(builtins.WindowsError):
# more info about errors at http://msdn.microsoft.com/en-us/library/ms681381(VS.85).aspx
def __init__(self, value=None):
if value is None:
value = windll.kernel32.GetLastError()
strerror = format_system_message(value)
args = 0, strerror, None, value
super().__init__(*args)
@property
def message(self):
return self.strerror
@property
def code(self):
return self.winerror
def __str__(self):
return self.message
def __repr__(self):
return "{self.__class__.__name__}({self.winerror})".format(**vars())
def _is_symlink(find_data):
return find_data.reserved[0] == IO_REPARSE_TAG_SYMLINK
def _patch_path(path):
r"""
Paths have a max length of api.MAX_PATH characters (260). If a target path
is longer than that, it needs to be made absolute and prepended with
\\?\ in order to work with API calls.
See http://msdn.microsoft.com/en-us/library/aa365247%28v=vs.85%29.aspx for
details.
"""
if path.startswith("\\\\?\\"):
return path
path = abspath(path)
if not path[1] == ":":
# python doesn't include the drive letter, but \\?\ requires it
path = getcwd()[:2] + path
return "\\\\?\\" + path
def local_format(string):
"""Format the string using variables in the caller's local namespace.
.. code-block:: pycon
>>> a = 3
>>> local_format("{a:5}")
' 3'
"""
context = inspect.currentframe().f_back.f_locals
return string.format_map(context)
def is_symlink(path):
"""Assuming path is a reparse point, determine if it's a symlink."""
path = _patch_path(path)
try:
return _is_symlink(next(find_files(path)))
except OSError as orig_error: # NOQA
tmpl = "Error accessing {path}: {orig_error.message}"
raise OSError(local_format(tmpl))
def find_files(spec):
r"""
A pythonic wrapper around the FindFirstFile/FindNextFile win32 api.
>>> root_files = tuple(find_files(r'c:\*'))
>>> len(root_files) > 1
True
>>> root_files[0].filename == root_files[1].filename
False
>>> # This test might fail on a non-standard installation
>>> 'Windows' in (fd.filename for fd in root_files)
True
"""
fd = WIN32_FIND_DATA()
handle = FindFirstFile(spec, byref(fd))
while True:
if handle == INVALID_HANDLE_VALUE:
raise OSError()
yield fd
fd = WIN32_FIND_DATA()
res = FindNextFile(handle, byref(fd))
if res == 0: # error
error = WindowsError()
if error.code == ERROR_NO_MORE_FILES:
break
else:
raise error
# todo: how to close handle when generator is destroyed?
# hint: catch GeneratorExit
windll.kernel32.FindClose(handle)
def is_reparse_point(path):
"""
Determine if the given path is a reparse point.
Return False if the file does not exist or the file attributes cannot
be determined.
"""
res = GetFileAttributes(path)
return res != INVALID_FILE_ATTRIBUTES and bool(
res & FILE_ATTRIBUTE_REPARSE_POINT
)
OPEN_EXISTING = 3
FILE_FLAG_OPEN_REPARSE_POINT = 0x00200000
FILE_FLAG_BACKUP_SEMANTICS = 0x2000000
FSCTL_GET_REPARSE_POINT = 0x900A8
LPDWORD = POINTER(wintypes.DWORD)
LPOVERLAPPED = wintypes.LPVOID
# VOLUME_NAME_DOS = 0
class SECURITY_ATTRIBUTES(Structure):
_fields_ = (
("length", wintypes.DWORD),
("p_security_descriptor", wintypes.LPVOID),
("inherit_handle", wintypes.BOOLEAN),
)
LPSECURITY_ATTRIBUTES = POINTER(SECURITY_ATTRIBUTES)
CreateFile = windll.kernel32.CreateFileW
CreateFile.argtypes = (
wintypes.LPWSTR,
wintypes.DWORD,
wintypes.DWORD,
LPSECURITY_ATTRIBUTES,
wintypes.DWORD,
wintypes.DWORD,
wintypes.HANDLE,
)
CreateFile.restype = wintypes.HANDLE
CloseHandle = windll.kernel32.CloseHandle
CloseHandle.argtypes = (wintypes.HANDLE,)
CloseHandle.restype = wintypes.BOOLEAN
from ctypes import Array, c_byte, c_ulong, c_ushort, create_string_buffer, sizeof
class REPARSE_DATA_BUFFER(Structure):
_fields_ = [
("tag", c_ulong),
("data_length", c_ushort),
("reserved", c_ushort),
("substitute_name_offset", c_ushort),
("substitute_name_length", c_ushort),
("print_name_offset", c_ushort),
("print_name_length", c_ushort),
("flags", c_ulong),
("path_buffer", c_byte * 1),
]
def get_print_name(self):
wchar_size = sizeof(wintypes.WCHAR)
arr_typ = wintypes.WCHAR * (self.print_name_length // wchar_size)
data = byref(self.path_buffer, self.print_name_offset)
return cast(data, POINTER(arr_typ)).contents.value
def get_substitute_name(self):
wchar_size = sizeof(wintypes.WCHAR)
arr_typ = wintypes.WCHAR * (self.substitute_name_length // wchar_size)
data = byref(self.path_buffer, self.substitute_name_offset)
return cast(data, POINTER(arr_typ)).contents.value
def readlink(link):
"""Return a string representing the path to which the symbolic link points.
readlink(link) -> target
"""
handle = CreateFile(
link,
0,
0,
None,
OPEN_EXISTING,
FILE_FLAG_OPEN_REPARSE_POINT | FILE_FLAG_BACKUP_SEMANTICS,
None,
)
if handle == INVALID_HANDLE_VALUE:
raise OSError()
res = reparse_DeviceIoControl(handle, FSCTL_GET_REPARSE_POINT, None, 10240)
bytes = create_string_buffer(res)
p_rdb = cast(bytes, POINTER(REPARSE_DATA_BUFFER))
rdb = p_rdb.contents
if not rdb.tag == IO_REPARSE_TAG_SYMLINK:
raise ParseError("Expected IO_REPARSE_TAG_SYMLINK, but got %d" % rdb.tag)
handle_nonzero_success(CloseHandle(handle))
return rdb.get_substitute_name()
DeviceIoControl = windll.kernel32.DeviceIoControl
DeviceIoControl.argtypes = [
wintypes.HANDLE,
wintypes.DWORD,
wintypes.LPVOID,
wintypes.DWORD,
wintypes.LPVOID,
wintypes.DWORD,
LPDWORD,
LPOVERLAPPED,
]
DeviceIoControl.restype = wintypes.BOOL
def reparse_DeviceIoControl(
device, io_control_code, in_buffer, out_buffer, overlapped=None
):
if overlapped is not None:
raise NotImplementedError("overlapped handles not yet supported")
if isinstance(out_buffer, int):
out_buffer = create_string_buffer(out_buffer)
in_buffer_size = len(in_buffer) if in_buffer is not None else 0
out_buffer_size = len(out_buffer)
assert isinstance(out_buffer, Array)
returned_bytes = wintypes.DWORD()
res = DeviceIoControl(
device,
io_control_code,
in_buffer,
in_buffer_size,
out_buffer,
out_buffer_size,
returned_bytes,
overlapped,
)
handle_nonzero_success(res)
handle_nonzero_success(returned_bytes)
return out_buffer[: returned_bytes.value]