esphome/esphome/symlink_ops.py
Guillermo Ruffino d27b01f02c Better symlink support under Windows (#487)
* Better symlink support under Windows

* Conditional loading of ctypes wintypes module

* Shortening comment line for pylint

* Adding plint bypass for Python 3
2019-03-23 22:58:25 +01:00

165 lines
6.5 KiB
Python

import os
if hasattr(os, 'symlink'):
def symlink(src, dst):
return os.symlink(src, dst)
def islink(path):
return os.path.islink(path)
def readlink(path):
return os.readlink(path)
def unlink(path):
return os.unlink(path)
else:
import ctypes
from ctypes import wintypes
# Code taken from
# https://stackoverflow.com/questions/27972776/having-trouble-implementing-a-readlink-function
kernel32 = ctypes.WinDLL('kernel32', use_last_error=True)
FILE_READ_ATTRIBUTES = 0x0080
OPEN_EXISTING = 3
FILE_FLAG_OPEN_REPARSE_POINT = 0x00200000
FILE_FLAG_BACKUP_SEMANTICS = 0x02000000
FILE_ATTRIBUTE_REPARSE_POINT = 0x0400
IO_REPARSE_TAG_MOUNT_POINT = 0xA0000003
IO_REPARSE_TAG_SYMLINK = 0xA000000C
FSCTL_GET_REPARSE_POINT = 0x000900A8
MAXIMUM_REPARSE_DATA_BUFFER_SIZE = 0x4000
LPDWORD = ctypes.POINTER(wintypes.DWORD)
LPWIN32_FIND_DATA = ctypes.POINTER(wintypes.WIN32_FIND_DATAW)
INVALID_HANDLE_VALUE = wintypes.HANDLE(-1).value
def IsReparseTagNameSurrogate(tag):
return bool(tag & 0x20000000)
def _check_invalid_handle(result, func, args):
if result == INVALID_HANDLE_VALUE:
raise ctypes.WinError(ctypes.get_last_error())
return args
def _check_bool(result, func, args):
if not result:
raise ctypes.WinError(ctypes.get_last_error())
return args
kernel32.FindFirstFileW.errcheck = _check_invalid_handle
kernel32.FindFirstFileW.restype = wintypes.HANDLE
kernel32.FindFirstFileW.argtypes = (
wintypes.LPCWSTR, # _In_ lpFileName
LPWIN32_FIND_DATA) # _Out_ lpFindFileData
kernel32.FindClose.argtypes = (
wintypes.HANDLE,) # _Inout_ hFindFile
kernel32.CreateFileW.errcheck = _check_invalid_handle
kernel32.CreateFileW.restype = wintypes.HANDLE
kernel32.CreateFileW.argtypes = (
wintypes.LPCWSTR, # _In_ lpFileName
wintypes.DWORD, # _In_ dwDesiredAccess
wintypes.DWORD, # _In_ dwShareMode
wintypes.LPVOID, # _In_opt_ lpSecurityAttributes
wintypes.DWORD, # _In_ dwCreationDisposition
wintypes.DWORD, # _In_ dwFlagsAndAttributes
wintypes.HANDLE) # _In_opt_ hTemplateFile
kernel32.CloseHandle.argtypes = (
wintypes.HANDLE,) # _In_ hObject
kernel32.DeviceIoControl.errcheck = _check_bool
kernel32.DeviceIoControl.argtypes = (
wintypes.HANDLE, # _In_ hDevice
wintypes.DWORD, # _In_ dwIoControlCode
wintypes.LPVOID, # _In_opt_ lpInBuffer
wintypes.DWORD, # _In_ nInBufferSize
wintypes.LPVOID, # _Out_opt_ lpOutBuffer
wintypes.DWORD, # _In_ nOutBufferSize
LPDWORD, # _Out_opt_ lpBytesReturned
wintypes.LPVOID) # _Inout_opt_ lpOverlapped
class REPARSE_DATA_BUFFER(ctypes.Structure):
class ReparseData(ctypes.Union):
class LinkData(ctypes.Structure):
_fields_ = (('SubstituteNameOffset', wintypes.USHORT),
('SubstituteNameLength', wintypes.USHORT),
('PrintNameOffset', wintypes.USHORT),
('PrintNameLength', wintypes.USHORT))
@property
def PrintName(self):
dt = wintypes.WCHAR * (self.PrintNameLength // ctypes.sizeof(wintypes.WCHAR))
name = dt.from_address(ctypes.addressof(self.PathBuffer) +
self.PrintNameOffset).value
if name.startswith(r'\??'):
name = r'\\?' + name[3:] # NT => Windows
return name
class SymbolicLinkData(LinkData):
_fields_ = (('Flags', wintypes.ULONG), ('PathBuffer', wintypes.BYTE * 0))
class MountPointData(LinkData):
_fields_ = (('PathBuffer', wintypes.BYTE * 0),)
class GenericData(ctypes.Structure):
_fields_ = (('DataBuffer', wintypes.BYTE * 0),)
_fields_ = (('SymbolicLinkReparseBuffer', SymbolicLinkData),
('MountPointReparseBuffer', MountPointData),
('GenericReparseBuffer', GenericData))
_fields_ = (('ReparseTag', wintypes.ULONG),
('ReparseDataLength', wintypes.USHORT),
('Reserved', wintypes.USHORT),
('ReparseData', ReparseData))
_anonymous_ = ('ReparseData',)
def symlink(src, dst):
csl = ctypes.windll.kernel32.CreateSymbolicLinkW
csl.argtypes = (ctypes.c_wchar_p, ctypes.c_wchar_p, ctypes.c_uint32)
csl.restype = ctypes.c_ubyte
flags = 1 if os.path.isdir(src) else 0
if csl(dst, src, flags) == 0:
error = ctypes.WinError()
# pylint: disable=no-member
if error.winerror == 1314 and error.errno == 22:
from esphome.core import EsphomeError
raise EsphomeError("Cannot create symlink from '%s' to '%s'. Try running tool \
with elevated privileges" % (src, dst))
raise error
def islink(path):
if not os.path.isdir(path):
return False
data = wintypes.WIN32_FIND_DATAW()
kernel32.FindClose(kernel32.FindFirstFileW(path, ctypes.byref(data)))
if not data.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT:
return False
return IsReparseTagNameSurrogate(data.dwReserved0)
def readlink(path):
n = wintypes.DWORD()
buf = (wintypes.BYTE * MAXIMUM_REPARSE_DATA_BUFFER_SIZE)()
flags = FILE_FLAG_OPEN_REPARSE_POINT | FILE_FLAG_BACKUP_SEMANTICS
handle = kernel32.CreateFileW(path, FILE_READ_ATTRIBUTES, 0, None,
OPEN_EXISTING, flags, None)
try:
kernel32.DeviceIoControl(handle, FSCTL_GET_REPARSE_POINT, None, 0,
buf, ctypes.sizeof(buf), ctypes.byref(n), None)
finally:
kernel32.CloseHandle(handle)
rb = REPARSE_DATA_BUFFER.from_buffer(buf)
tag = rb.ReparseTag
if tag == IO_REPARSE_TAG_SYMLINK:
return rb.SymbolicLinkReparseBuffer.PrintName
if tag == IO_REPARSE_TAG_MOUNT_POINT:
return rb.MountPointReparseBuffer.PrintName
if not IsReparseTagNameSurrogate(tag):
raise ValueError("not a link")
raise ValueError("unsupported reparse tag: %d" % tag)
def unlink(path):
return os.rmdir(path)