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|
# -*- coding: utf-8 -*-
"""Simulated VISA Library.
:copyright: 2014 by PyVISA-sim Authors, see AUTHORS for more details.
:license: MIT, see LICENSE for more details.
"""
import random
from collections import OrderedDict
from traceback import format_exc
from typing import Any, Dict, SupportsInt, Tuple, Union, overload
import pyvisa.errors as errors
from pyvisa import constants, highlevel, rname
from pyvisa.typing import VISAEventContext, VISARMSession, VISASession
from pyvisa.util import LibraryPath
# This import is required to register subclasses
from . import parser
from .sessions import gpib, serial, tcpip, usb # noqa
from .sessions.session import Session
class SimVisaLibrary(highlevel.VisaLibraryBase):
"""A pure Python backend for PyVISA.
The object is basically a dispatcher with some common functions implemented.
When a new resource object is requested to pyvisa, the library creates a Session
object (that knows how to perform low-level communication operations) associated
with a session handle (a number, usually referred just as session).
A call to a library function is handled by PyVisaLibrary if it involves a resource
agnostic function or dispatched to the correct session object (obtained from the
session id).
Importantly, the user is unaware of this. PyVisaLibrary behaves for the user
just as an IVIVisaLibrary.
"""
#: Maps session handle to session objects.
sessions: Dict[VISASession, Session]
@staticmethod
def get_library_paths() -> Tuple[LibraryPath]:
"""List a dummy library path to allow to create the library."""
return (LibraryPath("unset"),)
@staticmethod
def get_debug_info() -> Dict[str, str]:
"""Return a list of lines with backend info."""
from . import __version__
from .parser import SPEC_VERSION
d = OrderedDict()
d["Version"] = "%s" % __version__
d["Spec version"] = SPEC_VERSION
return d
def _init(self) -> None:
self.sessions: Dict[int, Session] = {}
try:
if self.library_path == "unset":
self.devices = parser.get_devices("default.yaml", True)
else:
self.devices = parser.get_devices(self.library_path, False)
except Exception as e:
msg = "Could not parse definitions file. %r"
raise type(e)(msg % format_exc())
@overload
def _register(self, obj: "SimVisaLibrary") -> VISARMSession:
...
@overload
def _register(self, obj: Session) -> VISASession:
...
def _register(self, obj):
"""Creates a random but unique session handle for a session object.
The handle is registered it in the sessions dictionary and returned.
"""
session = None
while session is None or session in self.sessions:
session = random.randint(1000000, 9999999)
self.sessions[session] = obj
return session
def open(
self,
session: VISARMSession,
resource_name: str,
access_mode: constants.AccessModes = constants.AccessModes.no_lock,
open_timeout: SupportsInt = constants.VI_TMO_IMMEDIATE,
) -> Tuple[VISASession, constants.StatusCode]:
"""Opens a session to the specified resource.
Corresponds to viOpen function of the VISA library.
Parameters
----------
sessions : VISARMSession
Resource Manager session (should always be a session returned
from open_default_resource_manager()).
resource_name : str
Unique symbolic name of a resource.
access_mode : constants.AccessModes
Specifies the mode by which the resource is to be accessed.
open_timeout : int
Specifies the maximum time period (in milliseconds) that this operation
waits before returning an error.
Returns
-------
VISASession
Unique logical identifier reference to a session, return value of the
library call.
constants.StatusCode
Status code describing the operation execution.
"""
try:
open_timeout = int(open_timeout)
except ValueError:
raise ValueError(
"open_timeout (%r) must be an integer (or compatible type)"
% open_timeout
)
try:
parsed = rname.parse_resource_name(resource_name)
except rname.InvalidResourceName:
return VISASession(0), constants.StatusCode.error_invalid_resource_name
# Loops through all session types, tries to parse the resource name and if ok, open it.
cls = Session.get_session_class(
parsed.interface_type_const, parsed.resource_class
)
sess = cls(session, resource_name, parsed)
try:
r_name = sess.attrs[constants.ResourceAttribute.resource_name]
assert isinstance(r_name, str)
sess.device = self.devices[r_name]
except KeyError:
return VISASession(0), constants.StatusCode.error_resource_not_found
return self._register(sess), constants.StatusCode.success
def close(
self, session: Union[VISASession, VISARMSession, VISAEventContext]
) -> constants.StatusCode:
"""Closes the specified session, event, or find list.
Corresponds to viClose function of the VISA library.
Parameters
----------
session : Union[VISASession, VISARMSession, VISAEventContext]
Unique logical identifier to a session, event, or find list.
Returns
-------
constants.StatusCode
Return value of the library call.
"""
try:
del self.sessions[session] # type: ignore
return constants.StatusCode.success
except KeyError:
return constants.StatusCode.error_invalid_object
def open_default_resource_manager(
self,
) -> Tuple[VISARMSession, constants.StatusCode]:
"""This function returns a session to the Default Resource Manager resource.
Corresponds to viOpenDefaultRM function of the VISA library.
Returns
-------
VISARMSession
Unique logical identifier to a Default Resource Manager session, return
value of the library call.
constants.StatusCode
Return value of the library call.
"""
return self._register(self), constants.StatusCode.success
def list_resources(
self, session: VISARMSession, query: str = "?*::INSTR"
) -> Tuple[str, ...]:
"""Returns a tuple of all connected devices matching query.
Parameters
----------
session : VISARMSession
Resource manager session
query : str
VISA regular expression used to match devices.
"""
# For each session type, ask for the list of connected resources and merge
# them into a single list.
resources = self.devices.list_resources()
resources = rname.filter(resources, query)
if resources:
return resources
raise errors.VisaIOError(errors.StatusCode.error_resource_not_found.value)
def read(
self, session: VISASession, count: int
) -> Tuple[bytes, constants.StatusCode]:
"""Reads data from device or interface synchronously.
Corresponds to viRead function of the VISA library.
Parameters
----------
session : VISASession
Unique logical identifier to a session.
count : int
Number of bytes to be read.
Returns
-------
bytes
Date read
constants.StatusCode
Return value of the library call.
"""
try:
sess = self.sessions[session]
except KeyError:
return b"", constants.StatusCode.error_invalid_object
try:
# We have an explicit except AttributeError
chunk, status = sess.read(count) # type: ignore
if status == constants.StatusCode.error_timeout:
raise errors.VisaIOError(constants.VI_ERROR_TMO)
return chunk, status
except AttributeError:
return b"", constants.StatusCode.error_nonsupported_operation
def write(
self, session: VISASession, data: bytes
) -> Tuple[int, constants.StatusCode]:
"""Writes data to device or interface synchronously.
Corresponds to viWrite function of the VISA library.
Parameters
----------
session : VISASession
Unique logical identifier to a session.
data : bytes
Data to be written.
Returns
-------
int
Number of bytes actually transferred
constants.StatusCode
Return value of the library call.
"""
try:
sess = self.sessions[session]
except KeyError:
return 0, constants.StatusCode.error_invalid_object
try:
# We have an explicit except AttributeError
return sess.write(data) # type: ignore
except AttributeError:
return 0, constants.StatusCode.error_nonsupported_operation
def get_attribute(
self,
session: Union[VISASession, VISARMSession, VISAEventContext],
attribute: Union[constants.ResourceAttribute, constants.EventAttribute],
) -> Tuple[Any, constants.StatusCode]:
"""Retrieves the state of an attribute.
Corresponds to viGetAttribute function of the VISA library.
Parameters
----------
session : Union[VISASession, VISARMSession, VISAEventContext]
Unique logical identifier to a session, event, or find list.
attribute : Union[constants.ResourceAttribute, constants.EventAttribute]
Resource attribute for which the state query is made (see Attributes.*)
Returns
-------
Any
State of the queried attribute for a specified resource
constants.StatusCode
Return value of the library call.
"""
try:
sess = self.sessions[session] # type: ignore
except KeyError:
return 0, constants.StatusCode.error_invalid_object
# Not sure how to handle events yet and I do not want to error if people keep
# using the bare attribute values.
return sess.get_attribute(attribute) # type: ignore
def set_attribute(
self,
session: Union[VISASession, VISARMSession, VISAEventContext],
attribute: Union[constants.ResourceAttribute, constants.EventAttribute],
attribute_state: Any,
) -> constants.StatusCode:
"""Sets the state of an attribute.
Corresponds to viSetAttribute function of the VISA library.
Parameters
----------
session : Union[VISASession, VISARMSession, VISAEventContext]
Unique logical identifier to a session.
attribute : Union[constants.ResourceAttribute, constants.EventAttribute]
Attribute for which the state is to be modified. (Attributes.*)
attribute_state : Any
The state of the attribute to be set for the specified object.
Returns
-------
constants.StatusCode
Return value of the library call.
"""
try:
sess = self.sessions[session] # type: ignore
except KeyError:
return constants.StatusCode.error_invalid_object
# Not sure how to handle events yet and I do not want to error if people keep
# using the bare attribute values.
return sess.set_attribute(attribute, attribute_state) # type: ignore
def disable_event(self, session, event_type, mechanism):
# TODO: implement this for GPIB finalization
pass
def discard_events(self, session, event_type, mechanism):
# TODO: implement this for GPIB finalization
pass
|
