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以下摘录来自内部库(U2A_ERRWrapper用于__getattr__应用包装器函数、该函数检查 API 调用中的负状态代码并提高可读错误)：
class USB2ANY:
u2adll = U2A_ERRWrapper(ctypes.WinDLL(_DLL_PATH))
@classmethod
def _FindControllers(cls) -> int:
'''
Scan the USB, and return the total number of USB2ANY found.
'''
return cls.u2adll.u2aFindControllers()
@classmethod
def _GetSerialNumber(cls, index: int) -> ctypes.c_buffer:
'''
Returns a ctypes.c_buffer containing the ascii bytes corresponding to
the serial number of a USB2ANY at the given index, with respect to
the ordering determined by _FindControllers function.
'''
buf = ctypes.c_buffer(40) # `40` is from SERNUM_LEN in USB2ANY_SDK.h
status = cls.u2adll.u2aGetSerialNumber(index, buf)
return buf
@classmethod
def Controllers(cls) -> List[ctypes.c_buffer]:
'''
Returns a list of ctypes.c_buffers containing the serial numbers of
all detected USB2ANY.
'''
return [cls._GetSerialNumber(i)
for i in range(cls._FindControllers())]
def Open(self, controller: Optional[ctypes.c_buffer] = None) -> None:
'''
Acquires a handle to the controller specified by the serial number.
If controller argument is omitted, the handle will be acquired for
the first USB2ANY enumerated.
On failure, the handle is not assigned, and an exception is raised.
'''
if controller is None: # use an empty buffer to select first U2A
controller = ctypes.c_buffer(0)
self._handle = self.u2adll.u2aOpen(controller)
