IfcOpenShell/src/ifcopenshell-python/ifcopenshell/guid.py

# IfcOpenShell - IFC toolkit and geometry engine
# Copyright (C) 2021 Thomas Krijnen <thomas@aecgeeks.com>
#
# This file is part of IfcOpenShell.
#
# IfcOpenShell is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# IfcOpenShell is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.

"""Reads and writes encoded GlobalIds

IFC entities may be identified using a unique ID (called a UUID or GUID). This
128-bit label is often represented in the form
xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. However, in IFC, it is also usually
stored as a 22 character base 64 encoded string. This module lets you convert
between these representations and generate new UUIDs.
"""

import uuid
import string

from functools import reduce

chars = string.digits + string.ascii_uppercase + string.ascii_lowercase + "_$"


def compress(g):
    bs = [int(g[i : i + 2], 16) for i in range(0, len(g), 2)]

    def b64(v, l=4):
        return "".join([chars[(v // (64**i)) % 64] for i in range(l)][::-1])

    return "".join([b64(bs[0], 2)] + [b64((bs[i] << 16) + (bs[i + 1] << 8) + bs[i + 2]) for i in range(1, 16, 3)])


def expand(g):
    def b64(v):
        return reduce(lambda a, b: a * 64 + b, map(lambda c: chars.index(c), v))

    bs = [b64(g[0:2])]
    for i in range(5):
        d = b64(g[2 + 4 * i : 6 + 4 * i])
        bs += [(d >> (8 * (2 - j))) % 256 for j in range(3)]
    return "".join(["%02x" % b for b in bs])


def split(g):
    return "{%s-%s-%s-%s-%s}" % (g[:8], g[8:12], g[12:16], g[16:20], g[20:])


def new():
    return compress(uuid.uuid4().hex)