from __future__ import annotations
import asyncio
import functools
from typing import AsyncGenerator, Callable, Dict, Generic, Optional, Union
from bluesky.protocols import (
Descriptor,
Locatable,
Location,
Movable,
Readable,
Reading,
Stageable,
Subscribable,
)
from .async_status import AsyncStatus
from .device import Device
from .signal_backend import SignalBackend
from .sim_signal_backend import SimSignalBackend
from .utils import DEFAULT_TIMEOUT, Callback, ReadingValueCallback, T
_sim_backends: Dict[Signal, SimSignalBackend] = {}
def _add_timeout(func):
@functools.wraps(func)
async def wrapper(self: Signal, *args, **kwargs):
return await asyncio.wait_for(func(self, *args, **kwargs), self._timeout)
return wrapper
def _fail(self, other, *args, **kwargs):
if isinstance(other, Signal):
raise TypeError(
"Can't compare two Signals, did you mean await signal.get_value() instead?"
)
else:
return NotImplemented
[docs]
class Signal(Device, Generic[T]):
"""A Device with the concept of a value, with R, RW, W and X flavours"""
def __init__(
self, backend: SignalBackend[T], timeout: Optional[float] = DEFAULT_TIMEOUT
) -> None:
self._name = ""
self._timeout = timeout
self._init_backend = self._backend = backend
@property
def name(self) -> str:
return self._name
def set_name(self, name: str = ""):
self._name = name
async def connect(self, sim=False, timeout=DEFAULT_TIMEOUT):
if sim:
self._backend = SimSignalBackend(
datatype=self._init_backend.datatype, source=self._init_backend.source
)
_sim_backends[self] = self._backend
else:
self._backend = self._init_backend
_sim_backends.pop(self, None)
await self._backend.connect(timeout=timeout)
@property
def source(self) -> str:
"""Like ca://PV_PREFIX:SIGNAL, or "" if not set"""
return self._backend.source
__lt__ = __le__ = __eq__ = __ge__ = __gt__ = __ne__ = _fail
def __hash__(self):
# Restore the default implementation so we can use in a set or dict
return hash(id(self))
class _SignalCache(Generic[T]):
def __init__(self, backend: SignalBackend[T], signal: Signal):
self._signal = signal
self._staged = False
self._listeners: Dict[Callback, bool] = {}
self._valid = asyncio.Event()
self._reading: Optional[Reading] = None
self._value: Optional[T] = None
self.backend = backend
backend.set_callback(self._callback)
def close(self):
self.backend.set_callback(None)
async def get_reading(self) -> Reading:
await self._valid.wait()
assert self._reading is not None, "Monitor not working"
return self._reading
async def get_value(self) -> T:
await self._valid.wait()
assert self._value is not None, "Monitor not working"
return self._value
def _callback(self, reading: Reading, value: T):
self._reading = reading
self._value = value
self._valid.set()
for function, want_value in self._listeners.items():
self._notify(function, want_value)
def _notify(self, function: Callback, want_value: bool):
if want_value:
function(self._value)
else:
function({self._signal.name: self._reading})
def subscribe(self, function: Callback, want_value: bool) -> None:
self._listeners[function] = want_value
if self._valid.is_set():
self._notify(function, want_value)
def unsubscribe(self, function: Callback) -> bool:
self._listeners.pop(function)
return self._staged or bool(self._listeners)
def set_staged(self, staged: bool):
self._staged = staged
return self._staged or bool(self._listeners)
[docs]
class SignalR(Signal[T], Readable, Stageable, Subscribable):
"""Signal that can be read from and monitored"""
_cache: Optional[_SignalCache] = None
def _backend_or_cache(
self, cached: Optional[bool]
) -> Union[_SignalCache, SignalBackend]:
# If cached is None then calculate it based on whether we already have a cache
if cached is None:
cached = self._cache is not None
if cached:
assert self._cache, f"{self.source} not being monitored"
return self._cache
else:
return self._backend
def _get_cache(self) -> _SignalCache:
if not self._cache:
self._cache = _SignalCache(self._backend, self)
return self._cache
def _del_cache(self, needed: bool):
if self._cache and not needed:
self._cache.close()
self._cache = None
[docs]
@_add_timeout
async def read(self, cached: Optional[bool] = None) -> Dict[str, Reading]:
"""Return a single item dict with the reading in it"""
return {self.name: await self._backend_or_cache(cached).get_reading()}
[docs]
@_add_timeout
async def describe(self) -> Dict[str, Descriptor]:
"""Return a single item dict with the descriptor in it"""
return {self.name: await self._backend.get_descriptor()}
[docs]
@_add_timeout
async def get_value(self, cached: Optional[bool] = None) -> T:
"""The current value"""
return await self._backend_or_cache(cached).get_value()
[docs]
def subscribe_value(self, function: Callback[T]):
"""Subscribe to updates in value of a device"""
self._get_cache().subscribe(function, want_value=True)
[docs]
def subscribe(self, function: Callback[Dict[str, Reading]]) -> None:
"""Subscribe to updates in the reading"""
self._get_cache().subscribe(function, want_value=False)
[docs]
def clear_sub(self, function: Callback) -> None:
"""Remove a subscription."""
self._del_cache(self._get_cache().unsubscribe(function))
[docs]
@AsyncStatus.wrap
async def stage(self) -> None:
"""Start caching this signal"""
self._get_cache().set_staged(True)
[docs]
@AsyncStatus.wrap
async def unstage(self) -> None:
"""Stop caching this signal"""
self._del_cache(self._get_cache().set_staged(False))
USE_DEFAULT_TIMEOUT = "USE_DEFAULT_TIMEOUT"
[docs]
class SignalW(Signal[T], Movable):
"""Signal that can be set"""
[docs]
def set(self, value: T, wait=True, timeout=USE_DEFAULT_TIMEOUT) -> AsyncStatus:
"""Set the value and return a status saying when it's done"""
if timeout is USE_DEFAULT_TIMEOUT:
timeout = self._timeout
coro = self._backend.put(value, wait=wait, timeout=timeout)
return AsyncStatus(coro)
[docs]
class SignalRW(SignalR[T], SignalW[T], Locatable):
"""Signal that can be both read and set"""
async def locate(self) -> Location:
location: Location = {
"setpoint": await self._backend.get_setpoint(),
"readback": await self.get_value(),
}
return location
[docs]
class SignalX(Signal):
"""Signal that puts the default value"""
[docs]
def trigger(self, wait=True, timeout=USE_DEFAULT_TIMEOUT) -> AsyncStatus:
"""Trigger the action and return a status saying when it's done"""
if timeout is USE_DEFAULT_TIMEOUT:
timeout = self._timeout
coro = self._backend.put(None, wait=wait, timeout=timeout)
return AsyncStatus(coro)
[docs]
def set_sim_value(signal: Signal[T], value: T):
"""Set the value of a signal that is in sim mode."""
_sim_backends[signal]._set_value(value)
[docs]
def set_sim_put_proceeds(signal: Signal[T], proceeds: bool):
"""Allow or block a put with wait=True from proceeding"""
event = _sim_backends[signal].put_proceeds
if proceeds:
event.set()
else:
event.clear()
[docs]
def set_sim_callback(signal: Signal[T], callback: ReadingValueCallback[T]) -> None:
"""Monitor the value of a signal that is in sim mode"""
return _sim_backends[signal].set_callback(callback)
[docs]
async def observe_value(signal: SignalR[T]) -> AsyncGenerator[T, None]:
"""Subscribe to the value of a signal so it can be iterated from.
Parameters
----------
signal:
Call subscribe_value on this at the start, and clear_sub on it at the
end
Notes
-----
Example usage::
async for value in observe_value(sig):
do_something_with(value)
"""
q: asyncio.Queue[T] = asyncio.Queue()
signal.subscribe_value(q.put_nowait)
try:
while True:
yield await q.get()
finally:
signal.clear_sub(q.put_nowait)
class _ValueChecker(Generic[T]):
def __init__(self, matcher: Callable[[T], bool], matcher_name: str):
self._last_value: Optional[T] = None
self._matcher = matcher
self._matcher_name = matcher_name
async def _wait_for_value(self, signal: SignalR[T]):
async for value in observe_value(signal):
self._last_value = value
if self._matcher(value):
return
async def wait_for_value(self, signal: SignalR[T], timeout: Optional[float]):
try:
await asyncio.wait_for(self._wait_for_value(signal), timeout)
except asyncio.TimeoutError as e:
raise TimeoutError(
f"{signal.name} didn't match {self._matcher_name} in {timeout}s, "
f"last value {self._last_value!r}"
) from e
[docs]
async def wait_for_value(
signal: SignalR[T], match: Union[T, Callable[[T], bool]], timeout: Optional[float]
):
"""Wait for a signal to have a matching value.
Parameters
----------
signal:
Call subscribe_value on this at the start, and clear_sub on it at the
end
match:
If a callable, it should return True if the value matches. If not
callable then value will be checked for equality with match.
timeout:
How long to wait for the value to match
Notes
-----
Example usage::
wait_for_value(device.acquiring, 1, timeout=1)
Or::
wait_for_value(device.num_captured, lambda v: v > 45, timeout=1)
"""
if callable(match):
checker = _ValueChecker(match, match.__name__)
else:
checker = _ValueChecker(lambda v: v == match, repr(match))
await checker.wait_for_value(signal, timeout)
[docs]
async def set_and_wait_for_value(
signal: SignalRW[T],
value: T,
timeout: float = DEFAULT_TIMEOUT,
status_timeout: Optional[float] = None,
) -> AsyncStatus:
"""Set a signal and monitor it until it has that value.
Useful for busy record, or other Signals with pattern:
- Set Signal with wait=True and stash the Status
- Read the same Signal to check the operation has started
- Return the Status so calling code can wait for operation to complete
This function sets a signal to a specified value, optionally with or without a
ca/pv put callback, and waits for the readback value of the signal to match the
value it was set to.
Parameters
----------
signal:
The signal to set and monitor
value:
The value to set it to
timeout:
How long to wait for the signal to have the value
status_timeout:
How long the returned Status will wait for the set to complete
Notes
-----
Example usage::
set_and_wait_for_value(device.acquire, 1)
"""
status = signal.set(value, timeout=status_timeout)
await wait_for_value(signal, value, timeout=timeout)
return status
