live: add parttypes.py

Adds parttypes.py module with utility functions to get partition types
(parttypes) from python-libfdisk.

Supports standard partition types, either DOS or GPT.
DOS labels use a hex code to define partition types, python-libfdisk
exposes get_parttype_from_code to look up for DOS partition types from a
given hexcode.
GPT label uses a string (UUID) for each supported partition type,
python-libfdisk exposes get_parttype_from_string to look up for GPT
partition types from a given string.

src/live/parttypes.py

@@ -0,0 +1,55 @@
+#
+# Copyright (C) 2023 Soleta Networks <info@soleta.eu>
+#
+# This program is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Affero General Public License as published by the
+# Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+
+import fdisk
+
+GPT_PARTTYPES = {
+    'LINUX':    '0FC63DAF-8483-4772-8E79-3D69D8477DE4',
+    'NTFS':     'EBD0A0A2-B9E5-4433-87C0-68B6B72699C7',
+    'EFI':      'C12A7328-F81F-11D2-BA4B-00A0C93EC93B',
+    'HFS':      '48465300-0000-11AA-AA11-00306543ECAC',
+}
+
+DOS_PARTTYPES = {
+    'EXTENDED': 0x0f,
+    'EMPTY':    0x00,
+    'LINUX':    0x83,
+    'CACHE':    0x83,
+    'NTFS':     0x07,
+    'HFS':      0xaf,
+}
+
+
+def get_dos_parttype(cxt, ptype_str):
+    l = cxt.label
+    code = DOS_PARTTYPES.get(ptype_str, 0x0)
+    parttype = l.get_parttype_from_code(code)
+    return parttype
+
+
+def get_gpt_parttype(cxt, ptype_str):
+    l = cxt.label
+    uuid = GPT_PARTTYPES.get(ptype_str, GPT_PARTTYPES['LINUX'])
+    parttype = l.get_parttype_from_string(uuid)
+    return parttype
+
+
+def get_parttype(cxt, ptype_str):
+    if not cxt:
+        raise RuntimeError('No libfdisk context')
+    if not cxt.label or cxt.label.name not in ['dos', 'gpt']:
+        raise RuntimeError('Unknown libfdisk label')
+    if type(ptype_str) != str:
+        raise RuntimeError('Invalid partition type')
+
+    if cxt.label.name == 'dos':
+        return get_dos_parttype(cxt, ptype_str)
+    elif cxt.label.name == 'gpt':
+        return get_gpt_parttype(cxt, ptype_str)
+    else:
+        raise RuntimeError('BUG: Invalid partition label')