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_util.py
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_util.py
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# Copyright (C) 2006 Joe Wreschnig
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
"""Utility classes for Mutagen.
You should not rely on the interfaces here being stable. They are
intended for internal use in Mutagen only.
"""
import sys
import struct
import codecs
import errno
import decimal
from io import BytesIO
from collections import namedtuple
from contextlib import contextmanager
from functools import wraps
from fnmatch import fnmatchcase
_DEFAULT_BUFFER_SIZE = 2 ** 18
def endswith(text, end):
# usefull for paths which can be both, str and bytes
if isinstance(text, str):
if not isinstance(end, str):
end = end.decode("ascii")
else:
if not isinstance(end, bytes):
end = end.encode("ascii")
return text.endswith(end)
def reraise(tp, value, tb):
raise tp(value).with_traceback(tb)
def bchr(x):
return bytes([x])
def iterbytes(b):
return (bytes([v]) for v in b)
def intround(value):
"""Given a float returns a rounded int. Should give the same result on
both Py2/3
"""
return int(decimal.Decimal.from_float(
value).to_integral_value(decimal.ROUND_HALF_EVEN))
def is_fileobj(fileobj):
"""Returns:
bool: if an argument passed ot mutagen should be treated as a
file object
"""
return not (isinstance(fileobj, (str, bytes)) or
hasattr(fileobj, "__fspath__"))
def verify_fileobj(fileobj, writable=False):
"""Verifies that the passed fileobj is a file like object which
we can use.
Args:
writable (bool): verify that the file object is writable as well
Raises:
ValueError: In case the object is not a file object that is readable
(or writable if required) or is not opened in bytes mode.
"""
try:
data = fileobj.read(0)
except Exception:
if not hasattr(fileobj, "read"):
raise ValueError("%r not a valid file object" % fileobj)
raise ValueError("Can't read from file object %r" % fileobj)
if not isinstance(data, bytes):
raise ValueError(
"file object %r not opened in binary mode" % fileobj)
if writable:
try:
fileobj.write(b"")
except Exception:
if not hasattr(fileobj, "write"):
raise ValueError("%r not a valid file object" % fileobj)
raise ValueError("Can't write to file object %r" % fileobj)
def verify_filename(filename):
"""Checks of the passed in filename has the correct type.
Raises:
ValueError: if not a filename
"""
if is_fileobj(filename):
raise ValueError("%r not a filename" % filename)
def fileobj_name(fileobj):
"""
Returns:
text: A potential filename for a file object. Always a valid
path type, but might be empty or non-existent.
"""
value = getattr(fileobj, "name", u"")
if not isinstance(value, (str, bytes)):
value = str(value)
return value
def loadfile(method=True, writable=False, create=False):
"""A decorator for functions taking a `filething` as a first argument.
Passes a FileThing instance as the first argument to the wrapped function.
Args:
method (bool): If the wrapped functions is a method
writable (bool): If a filename is passed opens the file readwrite, if
passed a file object verifies that it is writable.
create (bool): If passed a filename that does not exist will create
a new empty file.
"""
def convert_file_args(args, kwargs):
filething = args[0] if args else None
filename = kwargs.pop("filename", None)
fileobj = kwargs.pop("fileobj", None)
return filething, filename, fileobj, args[1:], kwargs
def wrap(func):
@wraps(func)
def wrapper(self, *args, **kwargs):
filething, filename, fileobj, args, kwargs = \
convert_file_args(args, kwargs)
with _openfile(self, filething, filename, fileobj,
writable, create) as h:
return func(self, h, *args, **kwargs)
@wraps(func)
def wrapper_func(*args, **kwargs):
filething, filename, fileobj, args, kwargs = \
convert_file_args(args, kwargs)
with _openfile(None, filething, filename, fileobj,
writable, create) as h:
return func(h, *args, **kwargs)
return wrapper if method else wrapper_func
return wrap
def convert_error(exc_src, exc_dest):
"""A decorator for reraising exceptions with a different type.
Mostly useful for IOError.
Args:
exc_src (type): The source exception type
exc_dest (type): The target exception type.
"""
def wrap(func):
@wraps(func)
def wrapper(*args, **kwargs):
try:
return func(*args, **kwargs)
except exc_dest:
raise
except exc_src as err:
reraise(exc_dest, err, sys.exc_info()[2])
return wrapper
return wrap
FileThing = namedtuple("FileThing", ["fileobj", "filename", "name"])
"""filename is None if the source is not a filename. name is a filename which
can be used for file type detection
"""
@contextmanager
def _openfile(instance, filething, filename, fileobj, writable, create):
"""yields a FileThing
Args:
filething: Either a file name, a file object or None
filename: Either a file name or None
fileobj: Either a file object or None
writable (bool): if the file should be opened
create (bool): if the file should be created if it doesn't exist.
implies writable
Raises:
MutagenError: In case opening the file failed
TypeError: in case neither a file name or a file object is passed
"""
assert not create or writable
# to allow stacked context managers, just pass the result through
if isinstance(filething, FileThing):
filename = filething.filename
fileobj = filething.fileobj
filething = None
if filething is not None:
if is_fileobj(filething):
fileobj = filething
elif hasattr(filething, "__fspath__"):
filename = filething.__fspath__()
if not isinstance(filename, (bytes, str)):
raise TypeError("expected __fspath__() to return a filename")
else:
filename = filething
if instance is not None:
# XXX: take "not writable" as loading the file..
if not writable:
instance.filename = filename
elif filename is None:
filename = getattr(instance, "filename", None)
if fileobj is not None:
verify_fileobj(fileobj, writable=writable)
yield FileThing(fileobj, filename, filename or fileobj_name(fileobj))
elif filename is not None:
verify_filename(filename)
inmemory_fileobj = False
try:
fileobj = open(filename, "rb+" if writable else "rb")
except IOError as e:
if writable and e.errno == errno.EOPNOTSUPP:
# Some file systems (gvfs over fuse) don't support opening
# files read/write. To make things still work read the whole
# file into an in-memory file like object and write it back
# later.
# https://github.com/quodlibet/mutagen/issues/300
try:
with open(filename, "rb") as fileobj:
fileobj = BytesIO(fileobj.read())
except IOError as e2:
raise MutagenError(e2)
inmemory_fileobj = True
elif create and e.errno == errno.ENOENT:
assert writable
try:
fileobj = open(filename, "wb+")
except IOError as e2:
raise MutagenError(e2)
else:
raise MutagenError(e)
with fileobj as fileobj:
yield FileThing(fileobj, filename, filename)
if inmemory_fileobj:
assert writable
data = fileobj.getvalue()
try:
with open(filename, "wb") as fileobj:
fileobj.write(data)
except IOError as e:
raise MutagenError(e)
else:
raise TypeError("Missing filename or fileobj argument")
class MutagenError(Exception):
"""Base class for all custom exceptions in mutagen
.. versionadded:: 1.25
"""
__module__ = "mutagen"
def total_ordering(cls):
"""Adds all possible ordering methods to a class.
Needs a working __eq__ and __lt__ and will supply the rest.
"""
assert "__eq__" in cls.__dict__
assert "__lt__" in cls.__dict__
cls.__le__ = lambda self, other: self == other or self < other
cls.__gt__ = lambda self, other: not (self == other or self < other)
cls.__ge__ = lambda self, other: not self < other
cls.__ne__ = lambda self, other: not self.__eq__(other)
return cls
def hashable(cls):
"""Makes sure the class is hashable.
Needs a working __eq__ and __hash__ and will add a __ne__.
"""
assert cls.__dict__["__hash__"] is not None
assert "__eq__" in cls.__dict__
cls.__ne__ = lambda self, other: not self.__eq__(other)
return cls
def enum(cls):
"""A decorator for creating an int enum class.
Makes the values a subclass of the type and implements repr/str.
The new class will be a subclass of int.
Args:
cls (type): The class to convert to an enum
Returns:
type: A new class
::
@enum
class Foo(object):
FOO = 1
BAR = 2
"""
assert cls.__bases__ == (object,)
d = dict(cls.__dict__)
new_type = type(cls.__name__, (int,), d)
new_type.__module__ = cls.__module__
map_ = {}
for key, value in d.items():
if key.upper() == key and isinstance(value, int):
value_instance = new_type(value)
setattr(new_type, key, value_instance)
map_[value] = key
def str_(self):
if self in map_:
return "%s.%s" % (type(self).__name__, map_[self])
return "%d" % int(self)
def repr_(self):
if self in map_:
return "<%s.%s: %d>" % (type(self).__name__, map_[self], int(self))
return "%d" % int(self)
setattr(new_type, "__repr__", repr_)
setattr(new_type, "__str__", str_)
return new_type
def flags(cls):
"""A decorator for creating an int flags class.
Makes the values a subclass of the type and implements repr/str.
The new class will be a subclass of int.
Args:
cls (type): The class to convert to an flags
Returns:
type: A new class
::
@flags
class Foo(object):
FOO = 1
BAR = 2
"""
assert cls.__bases__ == (object,)
d = dict(cls.__dict__)
new_type = type(cls.__name__, (int,), d)
new_type.__module__ = cls.__module__
map_ = {}
for key, value in d.items():
if key.upper() == key and isinstance(value, int):
value_instance = new_type(value)
setattr(new_type, key, value_instance)
map_[value] = key
def str_(self):
value = int(self)
matches = []
for k, v in map_.items():
if value & k:
matches.append("%s.%s" % (type(self).__name__, v))
value &= ~k
if value != 0 or not matches:
matches.append(str(value))
return " | ".join(matches)
def repr_(self):
return "<%s: %d>" % (str(self), int(self))
setattr(new_type, "__repr__", repr_)
setattr(new_type, "__str__", str_)
return new_type
@total_ordering
class DictMixin(object):
"""Implement the dict API using keys() and __*item__ methods.
Similar to UserDict.DictMixin, this takes a class that defines
__getitem__, __setitem__, __delitem__, and keys(), and turns it
into a full dict-like object.
UserDict.DictMixin is not suitable for this purpose because it's
an old-style class.
This class is not optimized for very large dictionaries; many
functions have linear memory requirements. I recommend you
override some of these functions if speed is required.
"""
def __iter__(self):
return iter(self.keys())
def __has_key(self, key):
try:
self[key]
except KeyError:
return False
else:
return True
__contains__ = __has_key
def values(self):
return [self[k] for k in self.keys()]
def items(self):
return list(zip(self.keys(), self.values()))
def clear(self):
for key in list(self.keys()):
self.__delitem__(key)
def pop(self, key, *args):
if len(args) > 1:
raise TypeError("pop takes at most two arguments")
try:
value = self[key]
except KeyError:
if args:
return args[0]
else:
raise
del(self[key])
return value
def popitem(self):
for key in self.keys():
break
else:
raise KeyError("dictionary is empty")
return key, self.pop(key)
def update(self, other=None, **kwargs):
if other is None:
self.update(kwargs)
other = {}
try:
for key, value in other.items():
self.__setitem__(key, value)
except AttributeError:
for key, value in other:
self[key] = value
def setdefault(self, key, default=None):
try:
return self[key]
except KeyError:
self[key] = default
return default
def get(self, key, default=None):
try:
return self[key]
except KeyError:
return default
def __repr__(self):
return repr(dict(self.items()))
def __eq__(self, other):
return dict(self.items()) == other
def __lt__(self, other):
return dict(self.items()) < other
__hash__ = object.__hash__
def __len__(self):
return len(self.keys())
class DictProxy(DictMixin):
def __init__(self, *args, **kwargs):
self.__dict = {}
super(DictProxy, self).__init__(*args, **kwargs)
def __getitem__(self, key):
return self.__dict[key]
def __setitem__(self, key, value):
self.__dict[key] = value
def __delitem__(self, key):
del(self.__dict[key])
def keys(self):
return self.__dict.keys()
def _fill_cdata(cls):
"""Add struct pack/unpack functions"""
funcs = {}
for key, name in [("b", "char"), ("h", "short"),
("i", "int"), ("q", "longlong")]:
for echar, esuffix in [("<", "le"), (">", "be")]:
esuffix = "_" + esuffix
for unsigned in [True, False]:
s = struct.Struct(echar + (key.upper() if unsigned else key))
get_wrapper = lambda f: lambda *a, **k: f(*a, **k)[0]
unpack = get_wrapper(s.unpack)
unpack_from = get_wrapper(s.unpack_from)
def get_unpack_from(s):
def unpack_from(data, offset=0):
return s.unpack_from(data, offset)[0], offset + s.size
return unpack_from
unpack_from = get_unpack_from(s)
pack = s.pack
prefix = "u" if unsigned else ""
if s.size == 1:
esuffix = ""
bits = str(s.size * 8)
if unsigned:
max_ = 2 ** (s.size * 8) - 1
min_ = 0
else:
max_ = 2 ** (s.size * 8 - 1) - 1
min_ = - 2 ** (s.size * 8 - 1)
funcs["%s%s_min" % (prefix, name)] = min_
funcs["%s%s_max" % (prefix, name)] = max_
funcs["%sint%s_min" % (prefix, bits)] = min_
funcs["%sint%s_max" % (prefix, bits)] = max_
funcs["%s%s%s" % (prefix, name, esuffix)] = unpack
funcs["%sint%s%s" % (prefix, bits, esuffix)] = unpack
funcs["%s%s%s_from" % (prefix, name, esuffix)] = unpack_from
funcs["%sint%s%s_from" % (prefix, bits, esuffix)] = unpack_from
funcs["to_%s%s%s" % (prefix, name, esuffix)] = pack
funcs["to_%sint%s%s" % (prefix, bits, esuffix)] = pack
for key, func in funcs.items():
setattr(cls, key, staticmethod(func))
class cdata(object):
"""C character buffer to Python numeric type conversions.
For each size/sign/endianness:
uint32_le(data)/to_uint32_le(num)/uint32_le_from(data, offset=0)
"""
error = struct.error
bitswap = b''.join(
bchr(sum(((val >> i) & 1) << (7 - i) for i in range(8)))
for val in range(256))
test_bit = staticmethod(lambda value, n: bool((value >> n) & 1))
_fill_cdata(cdata)
def get_size(fileobj):
"""Returns the size of the file.
The position when passed in will be preserved if no error occurs.
Args:
fileobj (fileobj)
Returns:
int: The size of the file
Raises:
IOError
"""
old_pos = fileobj.tell()
try:
fileobj.seek(0, 2)
return fileobj.tell()
finally:
fileobj.seek(old_pos, 0)
def read_full(fileobj, size):
"""Like fileobj.read but raises IOError if not all requested data is
returned.
If you want to distinguish IOError and the EOS case, better handle
the error yourself instead of using this.
Args:
fileobj (fileobj)
size (int): amount of bytes to read
Raises:
IOError: In case read fails or not enough data is read
"""
if size < 0:
raise ValueError("size must not be negative")
data = fileobj.read(size)
if len(data) != size:
raise IOError
return data
def seek_end(fileobj, offset):
"""Like fileobj.seek(-offset, 2), but will not try to go beyond the start
Needed since file objects from BytesIO will not raise IOError and
file objects from open() will raise IOError if going to a negative offset.
To make things easier for custom implementations, instead of allowing
both behaviors, we just don't do it.
Args:
fileobj (fileobj)
offset (int): how many bytes away from the end backwards to seek to
Raises:
IOError
"""
if offset < 0:
raise ValueError
if get_size(fileobj) < offset:
fileobj.seek(0, 0)
else:
fileobj.seek(-offset, 2)
def resize_file(fobj, diff, BUFFER_SIZE=_DEFAULT_BUFFER_SIZE):
"""Resize a file by `diff`.
New space will be filled with zeros.
Args:
fobj (fileobj)
diff (int): amount of size to change
Raises:
IOError
"""
fobj.seek(0, 2)
filesize = fobj.tell()
if diff < 0:
if filesize + diff < 0:
raise ValueError
# truncate flushes internally
fobj.truncate(filesize + diff)
elif diff > 0:
try:
while diff:
addsize = min(BUFFER_SIZE, diff)
fobj.write(b"\x00" * addsize)
diff -= addsize
fobj.flush()
except IOError as e:
if e.errno == errno.ENOSPC:
# To reduce the chance of corrupt files in case of missing
# space try to revert the file expansion back. Of course
# in reality every in-file-write can also fail due to COW etc.
# Note: IOError gets also raised in flush() due to buffering
fobj.truncate(filesize)
raise
def move_bytes(fobj, dest, src, count, BUFFER_SIZE=_DEFAULT_BUFFER_SIZE):
"""Moves data around using read()/write().
Args:
fileobj (fileobj)
dest (int): The destination offset
src (int): The source offset
count (int) The amount of data to move
Raises:
IOError: In case an operation on the fileobj fails
ValueError: In case invalid parameters were given
"""
if dest < 0 or src < 0 or count < 0:
raise ValueError
fobj.seek(0, 2)
filesize = fobj.tell()
if max(dest, src) + count > filesize:
raise ValueError("area outside of file")
if src > dest:
moved = 0
while count - moved:
this_move = min(BUFFER_SIZE, count - moved)
fobj.seek(src + moved)
buf = fobj.read(this_move)
fobj.seek(dest + moved)
fobj.write(buf)
moved += this_move
fobj.flush()
else:
while count:
this_move = min(BUFFER_SIZE, count)
fobj.seek(src + count - this_move)
buf = fobj.read(this_move)
fobj.seek(count + dest - this_move)
fobj.write(buf)
count -= this_move
fobj.flush()
def insert_bytes(fobj, size, offset, BUFFER_SIZE=_DEFAULT_BUFFER_SIZE):
"""Insert size bytes of empty space starting at offset.
fobj must be an open file object, open rb+ or
equivalent.
Args:
fobj (fileobj)
size (int): The amount of space to insert
offset (int): The offset at which to insert the space
Raises:
IOError
"""
if size < 0 or offset < 0:
raise ValueError
fobj.seek(0, 2)
filesize = fobj.tell()
movesize = filesize - offset
if movesize < 0:
raise ValueError
resize_file(fobj, size, BUFFER_SIZE)
move_bytes(fobj, offset + size, offset, movesize, BUFFER_SIZE)
def delete_bytes(fobj, size, offset, BUFFER_SIZE=_DEFAULT_BUFFER_SIZE):
"""Delete size bytes of empty space starting at offset.
fobj must be an open file object, open rb+ or
equivalent.
Args:
fobj (fileobj)
size (int): The amount of space to delete
offset (int): The start of the space to delete
Raises:
IOError
"""
if size < 0 or offset < 0:
raise ValueError
fobj.seek(0, 2)
filesize = fobj.tell()
movesize = filesize - offset - size
if movesize < 0:
raise ValueError
move_bytes(fobj, offset, offset + size, movesize, BUFFER_SIZE)
resize_file(fobj, -size, BUFFER_SIZE)
def resize_bytes(fobj, old_size, new_size, offset):
"""Resize an area in a file adding and deleting at the end of it.
Does nothing if no resizing is needed.
Args:
fobj (fileobj)
old_size (int): The area starting at offset
new_size (int): The new size of the area
offset (int): The start of the area
Raises:
IOError
"""
if new_size < old_size:
delete_size = old_size - new_size
delete_at = offset + new_size
delete_bytes(fobj, delete_size, delete_at)
elif new_size > old_size:
insert_size = new_size - old_size
insert_at = offset + old_size
insert_bytes(fobj, insert_size, insert_at)
def dict_match(d, key, default=None):
"""Like __getitem__ but works as if the keys() are all filename patterns.
Returns the value of any dict key that matches the passed key.
Args:
d (dict): A dict with filename patterns as keys
key (str): A key potentially matching any of the keys
default (object): The object to return if no pattern matched the
passed in key
Returns:
object: The dict value where the dict key matched the passed in key.
Or default if there was no match.
"""
if key in d and "[" not in key:
return d[key]
else:
for pattern, value in d.items():
if fnmatchcase(key, pattern):
return value
return default
def encode_endian(text, encoding, errors="strict", le=True):
"""Like text.encode(encoding) but always returns little endian/big endian
BOMs instead of the system one.
Args:
text (text)
encoding (str)
errors (str)
le (boolean): if little endian
Returns:
bytes
Raises:
UnicodeEncodeError
LookupError
"""
encoding = codecs.lookup(encoding).name
if encoding == "utf-16":
if le:
return codecs.BOM_UTF16_LE + text.encode("utf-16-le", errors)
else:
return codecs.BOM_UTF16_BE + text.encode("utf-16-be", errors)
elif encoding == "utf-32":
if le:
return codecs.BOM_UTF32_LE + text.encode("utf-32-le", errors)
else:
return codecs.BOM_UTF32_BE + text.encode("utf-32-be", errors)
else:
return text.encode(encoding, errors)
def decode_terminated(data, encoding, strict=True):
"""Returns the decoded data until the first NULL terminator
and all data after it.
Args:
data (bytes): data to decode
encoding (str): The codec to use
strict (bool): If True will raise ValueError in case no NULL is found
but the available data decoded successfully.
Returns:
Tuple[`text`, `bytes`]: A tuple containing the decoded text and the
remaining data after the found NULL termination.
Raises:
UnicodeError: In case the data can't be decoded.
LookupError:In case the encoding is not found.
ValueError: In case the data isn't null terminated (even if it is
encoded correctly) except if strict is False, then the decoded
string will be returned anyway.
"""
codec_info = codecs.lookup(encoding)
# normalize encoding name so we can compare by name
encoding = codec_info.name
# fast path
if encoding in ("utf-8", "iso8859-1"):
index = data.find(b"\x00")
if index == -1:
# make sure we raise UnicodeError first, like in the slow path
res = data.decode(encoding), b""
if strict:
raise ValueError("not null terminated")
else:
return res
return data[:index].decode(encoding), data[index + 1:]
# slow path
decoder = codec_info.incrementaldecoder()
r = []
for i, b in enumerate(iterbytes(data)):
c = decoder.decode(b)
if c == u"\x00":
return u"".join(r), data[i + 1:]
r.append(c)
else:
# make sure the decoder is finished
r.append(decoder.decode(b"", True))
if strict:
raise ValueError("not null terminated")
return u"".join(r), b""
class BitReaderError(Exception):
pass
class BitReader(object):
def __init__(self, fileobj):
self._fileobj = fileobj
self._buffer = 0
self._bits = 0
self._pos = fileobj.tell()
def bits(self, count):
"""Reads `count` bits and returns an uint, MSB read first.
May raise BitReaderError if not enough data could be read or
IOError by the underlying file object.
"""
if count < 0:
raise ValueError
if count > self._bits:
n_bytes = (count - self._bits + 7) // 8
data = self._fileobj.read(n_bytes)
if len(data) != n_bytes:
raise BitReaderError("not enough data")
for b in bytearray(data):
self._buffer = (self._buffer << 8) | b
self._bits += n_bytes * 8
self._bits -= count
value = self._buffer >> self._bits
self._buffer &= (1 << self._bits) - 1
assert self._bits < 8
return value
def bytes(self, count):
"""Returns a bytearray of length `count`. Works unaligned."""
if count < 0:
raise ValueError
# fast path
if self._bits == 0:
data = self._fileobj.read(count)
if len(data) != count:
raise BitReaderError("not enough data")