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import os
from ctypes import *
from ctypes.util import find_library
class Xattr(object):
"""singleton that wraps the extended attribues system
interface for python using ctypes
Just implement it to the degree we need it, in particular
- we need just the l*xattr variants, ie. we never want symlinks to be
followed
- don't need size discovery for getxattr, as we always know the exact
sizes we expect
"""
libc = CDLL(find_library("libc"))
@classmethod
def geterrno(cls):
return c_int.in_dll(cls.libc, 'errno').value
@classmethod
def raise_oserr(cls):
errn = cls.geterrno()
raise OSError(errn, os.strerror(errn))
@classmethod
def _query_xattr(cls, path, siz, syscall, *a):
if siz:
buf = create_string_buffer('\0' * siz)
else:
buf = None
ret = getattr(cls.libc, syscall)(*((path,) + a + (buf, siz)))
if ret == -1:
cls.raise_oserr()
if siz:
return buf.raw[:ret]
else:
return ret
@classmethod
def lgetxattr(cls, path, attr, siz=0):
return cls._query_xattr( path, siz, 'lgetxattr', attr)
@classmethod
def lgetxattr_buf(cls, path, attr):
"""lgetxattr variant with size discovery"""
size = cls.lgetxattr(path, attr)
if size == -1:
cls.raise_oserr()
if size == 0:
return ''
return cls.lgetxattr(path, attr, size)
@classmethod
def llistxattr(cls, path, siz=0):
ret = cls._query_xattr(path, siz, 'llistxattr')
if isinstance(ret, str):
ret = ret.split('\0')
return ret
@classmethod
def lsetxattr(cls, path, attr, val):
ret = cls.libc.lsetxattr(path, attr, val, len(val), 0)
if ret == -1:
cls.raise_oserr()
@classmethod
def lsetxattr_l(cls, path, attr, val):
""" lazy lsetxattr(): caller handles errno """
cls.libc.lsetxattr(path, attr, val, len(val), 0)
@classmethod
def lremovexattr(cls, path, attr):
ret = cls.libc.lremovexattr(path, attr)
if ret == -1:
cls.raise_oserr()
@classmethod
def llistxattr_buf(cls, path):
"""listxattr variant with size discovery"""
size = cls.llistxattr(path)
if size == -1:
cls.raise_oserr()
if size == 0:
return []
return cls.llistxattr(path, size)
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