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# -*- coding: utf-8 -*-
# Picard, the next-generation MusicBrainz tagger
# 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.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
import math
import os
import re
import struct
import sys
import unicodedata
from picard.util import _io_encoding, decode_filename, encode_filename
def _get_utf16_length(text):
"""Returns the number of code points used by a unicode object in its
UTF-16 representation.
if isinstance(text, bytes):
return len(text)
# if this is a narrow Python build, len will in fact return exactly
# what we're looking for
if sys.maxunicode == 0xFFFF:
return len(text)
# otherwise, encode the string in UTF-16 using the system's endianness,
# and divide the resulting length by 2
return len(text.encode("utf-16%ce" % sys.byteorder[0])) // 2
def _shorten_to_utf16_length(text, length):
"""Truncates a str object to the given number of UTF-16 code points.
assert isinstance(text, str), "This function only works on unicode"
# if this is a narrow Python build, regular slicing will do exactly
# what we're looking for
if sys.maxunicode == 0xFFFF:
shortened = text[:length]
# before returning, we need to check if we didn't cut in the middle
# of a surrogate pair
last = shortened[-1:]
if last and 0xD800 <= ord(last) <= 0xDBFF:
# it's a leading surrogate alright
return shortened[:-1]
# else...
return shortened
# otherwise, encode the string in UTF-16 using the system's endianness,
# and shorten by twice the length
enc = "utf-16%ce" % sys.byteorder[0]
shortened = text.encode(enc)[:length * 2]
# if we hit a surrogate pair, get rid of the last codepoint
last = shortened[-2:]
if last and 0xD800 <= struct.unpack("=H", last)[0] <= 0xDBFF:
shortened = shortened[:-2]
return shortened.decode(enc)
def _shorten_to_utf16_nfd_length(text, length):
text = unicodedata.normalize('NFD', text)
newtext = _shorten_to_utf16_length(text, length)
# if the first cut-off character was a combining one, remove our last
if unicodedata.combining(text[len(newtext)]):
newtext = newtext[:-1]
except IndexError:
return unicodedata.normalize('NFC', newtext)
_re_utf8 = re.compile(r'^utf([-_]?8)$', re.IGNORECASE)
def _shorten_to_bytes_length(text, length):
"""Truncates a unicode object to the given number of bytes it would take
when encoded in the "filesystem encoding".
assert isinstance(text, str), "This function only works on unicode"
raw = encode_filename(text)
# maybe there's no need to truncate anything
if len(raw) <= length:
return text
# or maybe there's nothing multi-byte here
if len(raw) == len(text):
return text[:length]
# if we're dealing with utf-8, we can use an efficient algorithm
# to deal with character boundaries
if _re_utf8.match(_io_encoding):
i = length
# a UTF-8 intermediate byte starts with the bits 10xxxxxx,
# so ord(char) & 0b11000000 = 0b10000000
while i > 0 and (raw[i] & 0xC0) == 0x80:
i -= 1
return decode_filename(raw[:i])
# finally, a brute force approach
i = length
while i > 0:
return decode_filename(raw[:i])
except UnicodeDecodeError:
i -= 1
# hmm. we got here?
return ""
def shorten_filename(filename, length, mode):
"""Truncates a filename to the given number of thingies,
as implied by `mode`.
if isinstance(filename, bytes):
return filename[:length]
if mode == SHORTEN_BYTES:
return _shorten_to_bytes_length(filename, length)
if mode == SHORTEN_UTF16:
return _shorten_to_utf16_length(filename, length)
if mode == SHORTEN_UTF16_NFD:
return _shorten_to_utf16_nfd_length(filename, length)
def shorten_path(path, length, mode):
"""Reduce path nodes' length to given limit(s).
path: Absolute or relative path to shorten.
length: Maximum number of code points / bytes allowed in a node.
shorten = lambda n, l: n and shorten_filename(n, l, mode).strip() or ""
dirpath, filename = os.path.split(path)
fileroot, ext = os.path.splitext(filename)
return os.path.join(
os.path.join(*[shorten(node, length)
for node in dirpath.split(os.path.sep)]),
shorten(fileroot, length - len(ext)) + ext
def _shorten_to_utf16_ratio(text, ratio):
"""Shortens the string to the given ratio (and strips it)."""
length = _get_utf16_length(text)
limit = max(1, int(math.floor(length / ratio)))
if isinstance(text, bytes):
return text[:limit].strip()
return _shorten_to_utf16_length(text, limit).strip()
def _make_win_short_filename(relpath, reserved=0):
r"""Shorten a relative file path according to WinAPI quirks.
relpath: The file's path.
reserved: Number of characters reserved for the parent path to be joined with,
e.g. 3 if it will be joined with "X:\", respectively 5 for "X:\y\".
(note the inclusion of the final backslash)
# See:
# The MAX_PATH is 260 characters, with this possible format for a file:
# "X:\<244-char dir path>\<11-char filename><NUL>".
# Our constraints:
# the entire path's length
# the entire parent directory path's length, *excluding* the final separator
# a single node's length (this seems to be the case for older NTFS)
# to make predictable directory paths we need to fit the directories in
# MAX_DIRPATH_LEN, and truncate the filename to whatever's left
remaining = MAX_DIRPATH_LEN - reserved
# to make things more readable...
shorten = lambda p, l: shorten_path(p, l, mode=SHORTEN_UTF16)
xlength = _get_utf16_length
# shorten to MAX_NODE_LEN from the beginning
relpath = shorten(relpath, MAX_NODE_LEN)
dirpath, filename = os.path.split(relpath)
# what if dirpath is already the right size?
dplen = xlength(dirpath)
if dplen <= remaining:
filename_max = MAX_FILEPATH_LEN - (reserved + dplen + 1) # the final separator
filename = shorten(filename, filename_max)
return os.path.join(dirpath, filename)
# compute the directory path and the maximum number of characters
# in a filename, and cache them
computed = _make_win_short_filename._computed
except AttributeError:
computed = _make_win_short_filename._computed = {}
finaldirpath, filename_max = computed[(dirpath, reserved)]
except KeyError:
dirnames = dirpath.split(os.path.sep)
# allocate space for the separators,
# but don't include the final one
remaining -= len(dirnames) - 1
# make sure we can have at least single-character dirnames
average = float(remaining) / len(dirnames)
if average < 1:
# TODO: a nice exception
raise IOError("Path too long. You need to move renamed files \
to a different directory.")
# try to reduce directories exceeding average with a ratio proportional
# to how much they exceed with; if not possible, reduce all dirs
# proportionally to their initial length
shortdirnames = [dn for dn in dirnames if len(dn) <= average]
totalchars = sum(map(xlength, dirnames))
shortdirchars = sum(map(xlength, shortdirnames))
# do we have at least 1 char for longdirs?
if remaining > shortdirchars + len(dirnames) - len(shortdirnames):
ratio = float(totalchars - shortdirchars) / (remaining - shortdirchars)
for i, dn in enumerate(dirnames):
if len(dn) > average:
dirnames[i] = _shorten_to_utf16_ratio(dn, ratio)
ratio = float(totalchars) / remaining
dirnames = [_shorten_to_utf16_ratio(dn, ratio) for dn in dirnames]
# here it is:
finaldirpath = os.path.join(*dirnames)
# did we win back some chars from .floor()s and .strip()s?
recovered = remaining - sum(map(xlength, dirnames))
# so how much do we have left for the filename?
filename_max = MAX_FILEPATH_LEN - MAX_DIRPATH_LEN - 1 + recovered
# ^ the final separator
# and don't forget to cache
computed[(dirpath, reserved)] = (finaldirpath, filename_max)
# finally...
filename = shorten(filename, filename_max)
return os.path.join(finaldirpath, filename)
def _get_mount_point(target):
"""Finds the target's mountpoint."""
# and caches it for future lookups
mounts = _get_mount_point._mounts
except AttributeError:
mounts = _get_mount_point._mounts = {}
mount = mounts[target]
except KeyError:
mount = target
while mount and not os.path.ismount(mount):
mount = os.path.dirname(mount)
mounts[target] = mount
return mount
# NOTE: this could be merged with the function above, and get all needed info
# in a single call, returning the filesystem type as well. (but python's
# posix.statvfs_result doesn't implement f_fsid)
def _get_filename_limit(target):
"""Finds the maximum filename length under the given directory."""
# and caches it
limits = _get_filename_limit._limits
except AttributeError:
limits = _get_filename_limit._limits = {}
limit = limits[target]
except KeyError:
# we need to call statvfs on an existing target
d = target
while not os.path.exists(d):
d = os.path.dirname(d)
limit = os.statvfs(d).f_namemax
except UnicodeEncodeError:
limit = os.statvfs(d.encode(_io_encoding)).f_namemax
limits[target] = limit
return limit
def make_short_filename(basedir, relpath, win_compat=False, relative_to=""):
"""Shorten a filename's path to proper limits.
basedir: Absolute path of the base directory where files will be moved.
relpath: File path, relative from the base directory.
win_compat: Windows is quirky.
relative_to: An ancestor directory of basedir, against which win_compat
will be applied.
# only deal with absolute paths. it saves a lot of grief,
# and is the right thing to do, even for renames.
basedir = os.path.abspath(basedir)
# also, make sure the relative path is clean
relpath = os.path.normpath(relpath)
if win_compat and relative_to:
relative_to = os.path.abspath(relative_to)
assert basedir.startswith(relative_to) and \
basedir.split(relative_to)[1][:1] in (os.path.sep, ''), \
"`relative_to` must be an ancestor of `basedir`"
# always strip the relpath parts
relpath = os.path.join(*[part.strip() for part in relpath.split(os.path.sep)])
# if we're on windows, delegate the work to a windows-specific function
if sys.platform == "win32":
reserved = len(basedir)
if not basedir.endswith(os.path.sep):
reserved += 1
return _make_win_short_filename(relpath, reserved)
# if we're being windows compatible, figure out how much
# needs to be reserved for the basedir part
if win_compat:
# if a relative ancestor wasn't provided,
# use the basedir's mount point
if not relative_to:
relative_to = _get_mount_point(basedir)
# if it's root, presume the parent will be copied over
# to windows, and hope for the best
if relative_to == os.path.sep:
relative_to = os.path.dirname(basedir)
reserved = len(basedir) - len(relative_to) + 3 + 1
# the drive name ^ + ^ the final separator
relpath = _make_win_short_filename(relpath, reserved)
# on *nix we can consider there is no path limit, but there is
# a filename length limit.
if sys.platform == "darwin":
# on OS X (i.e. HFS+), this is expressed in UTF-16 code points,
# in NFD normalization form
relpath = shorten_path(relpath, 255, mode=SHORTEN_UTF16_NFD)
# on everything else the limit is expressed in bytes,
# and filesystem-dependent
limit = _get_filename_limit(basedir)
relpath = shorten_path(relpath, limit, mode=SHORTEN_BYTES)
return relpath