Source code for nidaqmx.system._collections.persisted_channel_collection

import ctypes
import six
from import Sequence

from nidaqmx._lib import lib_importer, ctypes_byte_str
from nidaqmx.errors import (
    check_for_error, is_string_buffer_too_small, DaqError)
from nidaqmx.error_codes import DAQmxErrors
from import PersistedChannel
from nidaqmx.utils import unflatten_channel_string

[docs]class PersistedChannelCollection(Sequence): """ Contains the collection of global channels for a DAQmx system. This class defines methods that implements a container object. """ def __contains__(self, item): channel_names = self.global_channel_names if isinstance(item, six.string_types): items = unflatten_channel_string(item) return all([i in channel_names for i in items]) elif isinstance(item, PersistedChannel): return item._name in channel_names def __eq__(self, other): if isinstance(other, self.__class__): return True return False def __getitem__(self, index): """ Indexes a subset of global channels on this global channel collection. Args: index: The value of the index. The following index types are supported: - str: Name of the global channel. You also can specify a string that contains a list or range of names to this input. If you have a list of names, use the DAQmx Flatten Channel String function to convert the list to a string. - int: Index/position of the global channel in the collection. - slice: Range of the indexes/positions of global channels in the collection. Returns: List[]: Indicates the of global channels indexed. """ if isinstance(index, six.integer_types): return PersistedChannel(self.global_channel_names[index]) elif isinstance(index, slice): return [PersistedChannel(name) for name in self.global_channel_names[index]] elif isinstance(index, six.string_types): names = unflatten_channel_string(index) if len(names) == 1: return PersistedChannel(names[0]) return [PersistedChannel(name) for name in names] else: raise DaqError( 'Invalid index type "{0}" used to access collection.' .format(type(index)), DAQmxErrors.UNKNOWN) def __iter__(self): for channel_name in self.global_channel_names: yield PersistedChannel(channel_name) def __len__(self): return len(self.global_channel_names) def __ne__(self, other): return not self.__eq__(other) def __reversed__(self): channel_names = self.global_channel_names channel_names.reverse() for channel_name in channel_names: yield PersistedChannel(channel_name) @property def global_channel_names(self): """ List[str]: The names of all the global channels on this collection. """ cfunc = lib_importer.windll.DAQmxGetSysGlobalChans if cfunc.argtypes is None: with cfunc.arglock: if cfunc.argtypes is None: cfunc.argtypes = [ ctypes.c_char_p, ctypes.c_uint] temp_size = 0 while True: val = ctypes.create_string_buffer(temp_size) size_or_code = cfunc( val, temp_size) if is_string_buffer_too_small(size_or_code): # Buffer size must have changed between calls; check again. temp_size = 0 elif size_or_code > 0 and temp_size == 0: # Buffer size obtained, use to retrieve data. temp_size = size_or_code else: break check_for_error(size_or_code) return unflatten_channel_string(val.value.decode('ascii'))