"""
Convert user-provided internal UFO names to spec-compliant filenames.
This module implements the algorithm for converting between a "user name" -
something that a user can choose arbitrarily inside a font editor - and a file
name suitable for use in a wide range of operating systems and filesystems.
The `UFO 3 specification <http://unifiedfontobject.org/versions/ufo3/conventions/>`_
provides an example of an algorithm for such conversion, which avoids illegal
characters, reserved file names, ambiguity between upper- and lower-case
characters, and clashes with existing files.
This code was originally copied from
`ufoLib <https://github.com/unified-font-object/ufoLib/blob/8747da7/Lib/ufoLib/filenames.py>`_
by Tal Leming and is copyright (c) 2005-2016, The RoboFab Developers:
- Erik van Blokland
- Tal Leming
- Just van Rossum
"""
# Restrictions are taken mostly from
# https://docs.microsoft.com/en-gb/windows/win32/fileio/naming-a-file#naming-conventions.
#
# 1. Integer value zero, sometimes referred to as the ASCII NUL character.
# 2. Characters whose integer representations are in the range 1 to 31,
# inclusive.
# 3. Various characters that (mostly) Windows and POSIX-y filesystems don't
# allow, plus "(" and ")", as per the specification.
illegalCharacters = {
"\x00",
"\x01",
"\x02",
"\x03",
"\x04",
"\x05",
"\x06",
"\x07",
"\x08",
"\t",
"\n",
"\x0b",
"\x0c",
"\r",
"\x0e",
"\x0f",
"\x10",
"\x11",
"\x12",
"\x13",
"\x14",
"\x15",
"\x16",
"\x17",
"\x18",
"\x19",
"\x1a",
"\x1b",
"\x1c",
"\x1d",
"\x1e",
"\x1f",
'"',
"*",
"+",
"/",
":",
"<",
">",
"?",
"[",
"\\",
"]",
"(",
")",
"|",
"\x7f",
}
reservedFileNames = {
"aux",
"clock$",
"com1",
"com2",
"com3",
"com4",
"com5",
"com6",
"com7",
"com8",
"com9",
"con",
"lpt1",
"lpt2",
"lpt3",
"lpt4",
"lpt5",
"lpt6",
"lpt7",
"lpt8",
"lpt9",
"nul",
"prn",
}
maxFileNameLength = 255
[docs]
class NameTranslationError(Exception):
pass
[docs]
def userNameToFileName(userName: str, existing=(), prefix="", suffix=""):
"""Converts from a user name to a file name.
Takes care to avoid illegal characters, reserved file names, ambiguity between
upper- and lower-case characters, and clashes with existing files.
Args:
userName (str): The input file name.
existing: A case-insensitive list of all existing file names.
prefix: Prefix to be prepended to the file name.
suffix: Suffix to be appended to the file name.
Returns:
A suitable filename.
Raises:
NameTranslationError: If no suitable name could be generated.
Examples::
>>> userNameToFileName("a") == "a"
True
>>> userNameToFileName("A") == "A_"
True
>>> userNameToFileName("AE") == "A_E_"
True
>>> userNameToFileName("Ae") == "A_e"
True
>>> userNameToFileName("ae") == "ae"
True
>>> userNameToFileName("aE") == "aE_"
True
>>> userNameToFileName("a.alt") == "a.alt"
True
>>> userNameToFileName("A.alt") == "A_.alt"
True
>>> userNameToFileName("A.Alt") == "A_.A_lt"
True
>>> userNameToFileName("A.aLt") == "A_.aL_t"
True
>>> userNameToFileName(u"A.alT") == "A_.alT_"
True
>>> userNameToFileName("T_H") == "T__H_"
True
>>> userNameToFileName("T_h") == "T__h"
True
>>> userNameToFileName("t_h") == "t_h"
True
>>> userNameToFileName("F_F_I") == "F__F__I_"
True
>>> userNameToFileName("f_f_i") == "f_f_i"
True
>>> userNameToFileName("Aacute_V.swash") == "A_acute_V_.swash"
True
>>> userNameToFileName(".notdef") == "_notdef"
True
>>> userNameToFileName("con") == "_con"
True
>>> userNameToFileName("CON") == "C_O_N_"
True
>>> userNameToFileName("con.alt") == "_con.alt"
True
>>> userNameToFileName("alt.con") == "alt._con"
True
"""
# the incoming name must be a string
if not isinstance(userName, str):
raise ValueError("The value for userName must be a string.")
# establish the prefix and suffix lengths
prefixLength = len(prefix)
suffixLength = len(suffix)
# replace an initial period with an _
# if no prefix is to be added
if not prefix and userName[0] == ".":
userName = "_" + userName[1:]
# filter the user name
filteredUserName = []
for character in userName:
# replace illegal characters with _
if character in illegalCharacters:
character = "_"
# add _ to all non-lower characters
elif character != character.lower():
character += "_"
filteredUserName.append(character)
userName = "".join(filteredUserName)
# clip to 255
sliceLength = maxFileNameLength - prefixLength - suffixLength
userName = userName[:sliceLength]
# test for illegal files names
parts = []
for part in userName.split("."):
if part.lower() in reservedFileNames:
part = "_" + part
parts.append(part)
userName = ".".join(parts)
# test for clash
fullName = prefix + userName + suffix
if fullName.lower() in existing:
fullName = handleClash1(userName, existing, prefix, suffix)
# finished
return fullName
[docs]
def handleClash1(userName, existing=[], prefix="", suffix=""):
"""A helper function that resolves collisions with existing names when choosing a filename.
This function attempts to append an unused integer counter to the filename.
Args:
userName (str): The input file name.
existing: A case-insensitive list of all existing file names.
prefix: Prefix to be prepended to the file name.
suffix: Suffix to be appended to the file name.
Returns:
A suitable filename.
>>> prefix = ("0" * 5) + "."
>>> suffix = "." + ("0" * 10)
>>> existing = ["a" * 5]
>>> e = list(existing)
>>> handleClash1(userName="A" * 5, existing=e,
... prefix=prefix, suffix=suffix) == (
... '00000.AAAAA000000000000001.0000000000')
True
>>> e = list(existing)
>>> e.append(prefix + "aaaaa" + "1".zfill(15) + suffix)
>>> handleClash1(userName="A" * 5, existing=e,
... prefix=prefix, suffix=suffix) == (
... '00000.AAAAA000000000000002.0000000000')
True
>>> e = list(existing)
>>> e.append(prefix + "AAAAA" + "2".zfill(15) + suffix)
>>> handleClash1(userName="A" * 5, existing=e,
... prefix=prefix, suffix=suffix) == (
... '00000.AAAAA000000000000001.0000000000')
True
"""
# if the prefix length + user name length + suffix length + 15 is at
# or past the maximum length, silce 15 characters off of the user name
prefixLength = len(prefix)
suffixLength = len(suffix)
if prefixLength + len(userName) + suffixLength + 15 > maxFileNameLength:
l = prefixLength + len(userName) + suffixLength + 15
sliceLength = maxFileNameLength - l
userName = userName[:sliceLength]
finalName = None
# try to add numbers to create a unique name
counter = 1
while finalName is None:
name = userName + str(counter).zfill(15)
fullName = prefix + name + suffix
if fullName.lower() not in existing:
finalName = fullName
break
else:
counter += 1
if counter >= 999999999999999:
break
# if there is a clash, go to the next fallback
if finalName is None:
finalName = handleClash2(existing, prefix, suffix)
# finished
return finalName
[docs]
def handleClash2(existing=[], prefix="", suffix=""):
"""A helper function that resolves collisions with existing names when choosing a filename.
This function is a fallback to :func:`handleClash1`. It attempts to append an unused integer counter to the filename.
Args:
userName (str): The input file name.
existing: A case-insensitive list of all existing file names.
prefix: Prefix to be prepended to the file name.
suffix: Suffix to be appended to the file name.
Returns:
A suitable filename.
Raises:
NameTranslationError: If no suitable name could be generated.
Examples::
>>> prefix = ("0" * 5) + "."
>>> suffix = "." + ("0" * 10)
>>> existing = [prefix + str(i) + suffix for i in range(100)]
>>> e = list(existing)
>>> handleClash2(existing=e, prefix=prefix, suffix=suffix) == (
... '00000.100.0000000000')
True
>>> e = list(existing)
>>> e.remove(prefix + "1" + suffix)
>>> handleClash2(existing=e, prefix=prefix, suffix=suffix) == (
... '00000.1.0000000000')
True
>>> e = list(existing)
>>> e.remove(prefix + "2" + suffix)
>>> handleClash2(existing=e, prefix=prefix, suffix=suffix) == (
... '00000.2.0000000000')
True
"""
# calculate the longest possible string
maxLength = maxFileNameLength - len(prefix) - len(suffix)
maxValue = int("9" * maxLength)
# try to find a number
finalName = None
counter = 1
while finalName is None:
fullName = prefix + str(counter) + suffix
if fullName.lower() not in existing:
finalName = fullName
break
else:
counter += 1
if counter >= maxValue:
break
# raise an error if nothing has been found
if finalName is None:
raise NameTranslationError("No unique name could be found.")
# finished
return finalName
if __name__ == "__main__":
import doctest
doctest.testmod()