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# Copyright 2024 Helmut Grohne <helmut@subdivi.de>
# SPDX-License-Identifier: GPL-3
"""Communicate with a systemd instance to create e.g. delegated croups."""
import os
import sys
import typing
_DBUS_INTEGER_BOUNDS = (
("q", 0, 1 << 16),
("n", -(1 << 15), 1 << 15),
("u", 0, 1 << 32),
("i", -(1 << 31), 1 << 31),
("t", 0, 1 << 64),
("x", -(1 << 63), 1 << 63),
)
def _guess_dbus_type(value: typing.Any) -> typing.Iterator[str]:
"""Guess the type of a Python value in dbus. May yield multiple candidates.
"""
if isinstance(value, bool):
yield "b"
elif isinstance(value, str):
yield "s"
elif isinstance(value, int):
found = False
for guess, low, high in _DBUS_INTEGER_BOUNDS:
if low <= value < high:
found = True
yield guess
if not found:
raise ValueError("integer out of bounds for dbus")
elif isinstance(value, float):
yield "d"
elif isinstance(value, list):
if not value:
raise ValueError("cannot guess dbus type for empty list")
types = [list(_guess_dbus_type(v)) for v in value]
found = False
for guess in types[0]:
if all(guess in guesses for guesses in types):
found = True
yield "a" + guess
if not found:
raise ValueError("could not determine homogeneous type of list")
else:
raise ValueError("failed to guess dbus type")
async def start_transient_unit(
unitname: str,
pids: list[int] | None = None,
properties: dict[str, typing.Any] | None = None,
dbusdriver: typing.Literal["auto", "jeepney", "dbussy"] = "auto",
) -> None:
"""Call the StartTransientUnit dbus method on the user manager."""
dbus_properties: list[tuple[str, tuple[str, typing.Any]]] = []
if pids is None:
pids = [os.getpid()]
dbus_properties.append(("PIDs", ("au", pids)))
for key, value in ({} if properties is None else properties).items():
try:
guess = next(_guess_dbus_type(value))
except ValueError as err:
raise ValueError(
f"cannot infer dbus type for property {key} value"
) from err
dbus_properties.append((key, (guess, value)))
if dbusdriver in ("auto", "jeepney"):
try:
from .jeepney import start_transient_unit as jeepney_impl
except ImportError:
pass
else:
return await jeepney_impl(unitname, dbus_properties)
if dbusdriver in ("auto", "dbussy"):
try:
from .dbussy import start_transient_unit as dbussy_impl
except ImportError:
pass
else:
return await dbussy_impl(unitname, dbus_properties)
raise NotImplementedError("requested dbusdriver not available")
def reexec_as_transient_unit(
unitname: str | None = None,
properties: dict[str, typing.Any] | None = None,
argv: list[str] | None = None,
) -> typing.NoReturn:
"""Reexecute the current process via systemd-run thus placing it into a new
.scope unit. If no argv is given, sys.argv is used.
"""
execargs = ["systemd-run", "--user", "--scope"]
if unitname is not None:
execargs.append("--unit=" + unitname)
if properties:
for key, value in properties.items():
if isinstance(value, int):
value = str(value)
elif not isinstance(value, str):
raise ValueError(f"cannot format property {key} value")
execargs.append(f"--property={key}={value}")
execargs.append("--")
execargs.extend(sys.argv if argv is None else argv)
os.execvp("systemd-run", execargs)
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