borg/attic/xattr.py

"""A basic extended attributes (xattr) implementation for Linux and MacOS X
"""
import errno
import os
import sys
import tempfile


def is_enabled():
    """Determine if xattr is enabled on the filesystem
    """
    with tempfile.NamedTemporaryFile() as fd:
        try:
            setxattr(fd.fileno(), 'user.name', b'value')
        except OSError:
            return False
        return getxattr(fd.fileno(), 'user.name') == b'value'


def get_all(path, follow_symlinks=True):
    return dict((name, getxattr(path, name, follow_symlinks=follow_symlinks))
                for name in listxattr(path, follow_symlinks=follow_symlinks))


try:
    # Currently only available on Python 3.3+ on Linux
    from os import getxattr, setxattr, listxattr2
except ImportError:
    from ctypes import CDLL, create_string_buffer, c_ssize_t, c_size_t, c_char_p, c_int, c_uint32, get_errno
    from ctypes.util import find_library
    libc = CDLL(find_library('c'), use_errno=True)

    def _check(rv, path=None):
        if rv < 0:
            raise OSError(get_errno(), path)
        return rv

    if sys.platform.startswith('linux'):
        libc.llistxattr.argtypes = (c_char_p, c_char_p, c_size_t)
        libc.llistxattr.restype = c_ssize_t
        libc.flistxattr.argtypes = (c_int, c_char_p, c_size_t)
        libc.flistxattr.restype = c_ssize_t
        libc.lsetxattr.argtypes = (c_char_p, c_char_p, c_char_p, c_size_t, c_int)
        libc.lsetxattr.restype = c_int
        libc.fsetxattr.argtypes = (c_int, c_char_p, c_char_p, c_size_t, c_int)
        libc.fsetxattr.restype = c_int
        libc.lgetxattr.argtypes = (c_char_p, c_char_p, c_char_p, c_size_t)
        libc.lgetxattr.restype = c_ssize_t
        libc.fgetxattr.argtypes = (c_int, c_char_p, c_char_p, c_size_t)
        libc.fgetxattr.restype = c_ssize_t

        def listxattr(path, *, follow_symlinks=True):
            if isinstance(path, str):
                path = os.fsencode(path)
            if isinstance(path, int):
                func = libc.flistxattr
            elif follow_symlinks:
                func = libc.listxattr
            else:
                func = libc.llistxattr
            n = _check(func(path, None, 0), path)
            if n == 0:
                return []
            namebuf = create_string_buffer(n)
            n2 = _check(func(path, namebuf, n), path)
            if n2 != n:
                raise Exception('listxattr failed')
            return [os.fsdecode(name) for name in namebuf.raw.split(b'\0')[:-1]]

        def getxattr(path, name, *, follow_symlinks=True):
            name = os.fsencode(name)
            if isinstance(path, str):
                path = os.fsencode(path)
            if isinstance(path, int):
                func = libc.fgetxattr
            elif follow_symlinks:
                func = libc.getxattr
            else:
                func = libc.lgetxattr
            n = _check(func(path, name, None, 0))
            if n == 0:
                return
            valuebuf = create_string_buffer(n)
            n2 = _check(func(path, name, valuebuf, n), path)
            if n2 != n:
                raise Exception('getxattr failed')
            return valuebuf.raw

        def setxattr(path, name, value, *, follow_symlinks=True):
            name = os.fsencode(name)
            value = os.fsencode(value)
            if isinstance(path, str):
                path = os.fsencode(path)
            if isinstance(path, int):
                func = libc.fsetxattr
            elif follow_symlinks:
                func = libc.setxattr
            else:
                func = libc.lsetxattr
            _check(func(path, name, value, len(value), 0), path)

    elif sys.platform == 'darwin':
        libc.listxattr.argtypes = (c_char_p, c_char_p, c_size_t, c_int)
        libc.listxattr.restype = c_ssize_t
        libc.flistxattr.argtypes = (c_int, c_char_p, c_size_t)
        libc.flistxattr.restype = c_ssize_t
        libc.setxattr.argtypes = (c_char_p, c_char_p, c_char_p, c_size_t, c_uint32, c_int)
        libc.setxattr.restype = c_int
        libc.fsetxattr.argtypes = (c_int, c_char_p, c_char_p, c_size_t, c_uint32, c_int)
        libc.fsetxattr.restype = c_int
        libc.getxattr.argtypes = (c_char_p, c_char_p, c_char_p, c_size_t, c_uint32, c_int)
        libc.getxattr.restype = c_ssize_t
        libc.fgetxattr.argtypes = (c_int, c_char_p, c_char_p, c_size_t, c_uint32, c_int)
        libc.fgetxattr.restype = c_ssize_t

        XATTR_NOFOLLOW = 0x0001

        def listxattr(path, *, follow_symlinks=True):
            func = libc.listxattr
            flags = 0
            if isinstance(path, str):
                path = os.fsencode(path)
            if isinstance(path, int):
                func = libc.flistxattr
            elif not follow_symlinks:
                flags = XATTR_NOFOLLOW
            n = _check(func(path, None, 0, flags), path)
            if n == 0:
                return []
            namebuf = create_string_buffer(n)
            n2 = _check(func(path, namebuf, n, flags), path)
            if n2 != n:
                raise Exception('listxattr failed')
            return [os.fsdecode(name) for name in namebuf.raw.split(b'\0')[:-1]]

        def getxattr(path, name, *, follow_symlinks=True):
            name = os.fsencode(name)
            func = libc.getxattr
            flags = 0
            if isinstance(path, str):
                path = os.fsencode(path)
            if isinstance(path, int):
                func = libc.fgetxattr
            elif not follow_symlinks:
                flags = XATTR_NOFOLLOW
            n = _check(func(path, name, None, 0, 0, flags))
            if n == 0:
                return
            valuebuf = create_string_buffer(n)
            n2 = _check(func(path, name, valuebuf, n, 0, flags), path)
            if n2 != n:
                raise Exception('getxattr failed')
            return valuebuf.raw

        def setxattr(path, name, value, *, follow_symlinks=True):
            name = os.fsencode(name)
            value = os.fsencode(value)
            func = libc.setxattr
            flags = 0
            if isinstance(path, str):
                path = os.fsencode(path)
            if isinstance(path, int):
                func = libc.fsetxattr
            elif not follow_symlinks:
                flags = XATTR_NOFOLLOW
            _check(func(path, name, value, len(value), 0, flags), path)

    elif sys.platform.startswith('freebsd'):
        EXTATTR_NAMESPACE_USER = 0x0001
        libc.extattr_list_fd.argtypes = (c_int, c_int, c_char_p, c_size_t)
        libc.extattr_list_fd.restype = c_ssize_t
        libc.extattr_list_link.argtypes = (c_char_p, c_int, c_char_p, c_size_t)
        libc.extattr_list_link.restype = c_ssize_t
        libc.extattr_list_file.argtypes = (c_char_p, c_int, c_char_p, c_size_t)
        libc.extattr_list_file.restype = c_ssize_t
        libc.extattr_get_fd.argtypes = (c_int, c_int, c_char_p, c_char_p, c_size_t)
        libc.extattr_get_fd.restype = c_ssize_t
        libc.extattr_get_link.argtypes = (c_char_p, c_int, c_char_p, c_char_p, c_size_t)
        libc.extattr_get_link.restype = c_ssize_t
        libc.extattr_get_file.argtypes = (c_char_p, c_int, c_char_p, c_char_p, c_size_t)
        libc.extattr_get_file.restype = c_ssize_t
        libc.extattr_set_fd.argtypes = (c_int, c_int, c_char_p, c_char_p, c_size_t)
        libc.extattr_set_fd.restype = c_int
        libc.extattr_set_link.argtypes = (c_char_p, c_int, c_char_p, c_char_p, c_size_t)
        libc.extattr_set_link.restype = c_int
        libc.extattr_set_file.argtypes = (c_char_p, c_int, c_char_p, c_char_p, c_size_t)
        libc.extattr_set_file.restype = c_int

        def listxattr(path, *, follow_symlinks=True):
            ns = EXTATTR_NAMESPACE_USER
            if isinstance(path, str):
                path = os.fsencode(path)
            if isinstance(path, int):
                func = libc.extattr_list_fd
            elif follow_symlinks:
                func = libc.extattr_list_file
            else:
                func = libc.extattr_list_link
            try:
                n = _check(func(path, ns, None, 0), path)
            except OSError as e:
                if e.errno == errno.ENOTSUP:
                    return []
                raise
            if n == 0:
                return []
            namebuf = create_string_buffer(n)
            n2 = _check(func(path, ns, namebuf, n), path)
            if n2 != n:
                raise Exception('listxattr failed')
            names = []
            mv = memoryview(namebuf.raw)
            while mv:
                length = mv[0]
                # Python < 3.3 returns bytes instead of int
                if isinstance(length, bytes):
                    length = ord(length)
                names.append(os.fsdecode(bytes(mv[1:1+length])))
                mv = mv[1+length:]
            return names

        def getxattr(path, name, *, follow_symlinks=True):
            name = os.fsencode(name)
            if isinstance(path, str):
                path = os.fsencode(path)
            if isinstance(path, int):
                func = libc.extattr_get_fd
            elif follow_symlinks:
                func = libc.extattr_get_file
            else:
                func = libc.extattr_get_link
            n = _check(func(path, EXTATTR_NAMESPACE_USER, name, None, 0))
            if n == 0:
                return
            valuebuf = create_string_buffer(n)
            n2 = _check(func(path, EXTATTR_NAMESPACE_USER, name, valuebuf, n), path)
            if n2 != n:
                raise Exception('getxattr failed')
            return valuebuf.raw

        def setxattr(path, name, value, *, follow_symlinks=True):
            name = os.fsencode(name)
            value = os.fsencode(value)
            if isinstance(path, str):
                path = os.fsencode(path)
            if isinstance(path, int):
                func = libc.extattr_set_fd
            elif follow_symlinks:
                func = libc.extattr_set_file
            else:
                func = libc.extattr_set_link
            _check(func(path, EXTATTR_NAMESPACE_USER, name, value, len(value)), path)

    else:
        raise Exception('Unsupported platform: %s' % sys.platform)