Break circular dependencies for Python 3 compatibility.

diff --git a/doc/module_dependencies.txt b/doc/module_dependencies.txt
new file mode 100644 (file)
index 0000000..92b4f8d
--- /dev/null
+++ b/doc/module_dependencies.txt
@@ -0,0 +1,39 @@
+With Python 3, Cython is pickier about circular dependencies.  This is
+all well and good, but sometimes lower level objects (e.g. Subdevice
+instances) need pointers from higher level objects (e.g. Device
+instances).  How does that work?
+
+All of the C types used in the library are defined in library-specific
+``_*_h.pxd`` files at the bottom of the dependency tree.  The
+low-level objects don't really need the higher level objects (which
+would create a circular import), they need the *pointers* held by the
+higher level object.  The solution is to store higher-level objects as
+generic Python objects (e.g. Subdevice.device).  When you need the
+device ``comedi_t *`` for a subdevice method, use
+``Subdevice._device``, which assumes the ``Subdevice.device`` has been
+setup with a ``Device`` instance, and extracts the pointer with the
+appropriate casting.
+
+This deals with the circular imports, but is the casting safe?
+Kindof.  While it would be nice to do something like::
+
+  cdef class Subdevice (object):
+      cdef _comedilib_h.comedi_t * _device(self):
+          if not isinstance(self.device, _device.Device):
+              raise ValueError(self.device)
+          return <_comedilib_h.comedi_t *> self.device.device
+
+we can't perform the check without circularly importing
+``pycomedi.device``.  So the cast is blind, which could cause all
+sorts of problems.
+
+In practice, however, all ``Subdevice`` instances are likely to come
+from the ``Device.subdevice()`` method, which sets up the ``.device``
+attribute appropriately.  This means that while you *could* put
+something else in the ``.device`` attribute and blow things up, you
+probably won't do so accidentally.  This conforms to the Python style
+of assuming that we are all consenting adults.
+
+For clarity in the above, I discussed the ``Device`` / ``Subdevice``
+relationship, but the same logic holds for similar high- / low-level
+relationships (e.g. ``Subdevice`` / ``Channel``, etc.).

diff --git a/pycomedi/calibration.pxd b/pycomedi/calibration.pxd
index ca0b302d017a519a35c4d4a60721a1770126f90a..a0a687ae3e1bf2758689afbf224c073d709f0735 100644 (file)
--- a/pycomedi/calibration.pxd
+++ b/pycomedi/calibration.pxd
@@ -17,8 +17,6 @@
 "Expose `CalibratedConverter` internals at the C level for other Cython modules"
 
 cimport _comedilib_h
-from device cimport Device as _Device
-from subdevice cimport Subdevice as _Subdevice
 
 
 cdef class CalibratedConverter (object):
@@ -40,7 +38,7 @@ cdef class Caldac (object):
 
 cdef class CalibrationSetting (object):
     cdef _comedilib_h.comedi_calibration_setting_t *setting
-    cdef public _Subdevice subdevice
+    cdef public object subdevice  # pycomedi.subdevice.Subdevice
 
     cdef _caldacs_set_single(self, index, Caldac caldac)
     cpdef _soft_calibration_set(self, CalibratedConverter value)
@@ -48,6 +46,6 @@ cdef class CalibrationSetting (object):
 
 cdef class Calibration (object):
     cdef _comedilib_h.comedi_calibration_t *calibration
-    cdef public _Device device
+    cdef public object device  # pycomedi.device.Device
 
     cpdef from_file(self, path)

diff --git a/pycomedi/calibration.pyx b/pycomedi/calibration.pyx
index 248745befb20ce3b13f7126b4242b85c10761918..70388de1911cace970d719405eb0b323ba4020a4 100644 (file)
--- a/pycomedi/calibration.pyx
+++ b/pycomedi/calibration.pyx
@@ -451,6 +451,7 @@ cdef class CalibrationSetting (object):
     """
     def __cinit__(self):
         self.setting = NULL
+        self.subdevice = None
 
     def __init__(self, subdevice):
         super(CalibrationSetting, self).__init__()
@@ -633,6 +634,7 @@ cdef class Calibration (object):
     """
     def __cinit__(self):
         self.calibration = NULL
+        self.device = None
 
     def __init__(self, device):
         super(Calibration, self).__init__()

diff --git a/pycomedi/channel.pyx b/pycomedi/channel.pyx
index 853448519e6eeb1894cc1720b451ddef56710caa..81f6df075fc22a47a7844a02cb72c215f8650cba 100644 (file)
--- a/pycomedi/channel.pyx
+++ b/pycomedi/channel.pyx
@@ -27,7 +27,6 @@ cimport _comedilib_h
 from calibration cimport CalibratedConverter as _CalibratedConverter
 from calibration cimport Calibration as _Calibration
 from range cimport Range as _Range
-from subdevice cimport Subdevice as _Subdevice
 
 from pycomedi import LOG as _LOG
 from chanspec import ChanSpec as _ChanSpec
@@ -58,10 +57,11 @@ cdef class Channel (object):
 
     >>> d.close()
     """
-    cdef public _Subdevice subdevice
+    cdef public object subdevice  # pycomedi.subdevice.Subdevice
     cdef public int index
 
     def __cinit__(self):
+        self.subdevice = None
         self.index = -1
 
     def __init__(self, subdevice, index):
@@ -69,18 +69,19 @@ cdef class Channel (object):
         self.subdevice = subdevice
         self.index = index
 
+    cdef _comedilib_h.comedi_t * _device(self):
+        return <_comedilib_h.comedi_t *> self.subdevice.device.device
+
     def get_maxdata(self):
         ret = _comedilib_h.comedi_get_maxdata(
-            self.subdevice.device.device,
-            self.subdevice.index, self.index)
+            self._device(), self.subdevice.index, self.index)
         if ret < 0:
             _error.raise_error(function_name='comedi_get_maxdata', ret=ret)
         return ret
 
     def get_n_ranges(self):
         ret = _comedilib_h.comedi_get_n_ranges(
-            self.subdevice.device.device,
-            self.subdevice.index, self.index)
+            self._device(), self.subdevice.index, self.index)
         if ret < 0:
             _error.raise_error(function_name='comedi_get_n_ranges', ret=ret)
         return ret
@@ -90,8 +91,7 @@ cdef class Channel (object):
         cdef _Range ret
         # Memory pointed to by the return value is freed on Device.close().
         rng = _comedilib_h.comedi_get_range(
-            self.subdevice.device.device,
-            self.subdevice.index, self.index, index)
+            self._device(), self.subdevice.index, self.index, index)
         if rng is NULL:
             _error.raise_error(function_name='comedi_get_range')
         ret = _Range(value=index)
@@ -108,8 +108,7 @@ cdef class Channel (object):
     def _find_range(self, unit, min, max):
         "Search for range"
         ret = _comedilib_h.comedi_find_range(
-            self.subdevice.device.device,
-            self.subdevice.index, self.index,
+            self._device(), self.subdevice.index, self.index,
             _constant.bitwise_value(unit), min, max)
         if ret < 0:
             _error.raise_error(function_name='comedi_find_range', ret=ret)
@@ -172,8 +171,7 @@ cdef class DigitalChannel (Channel):
         `dir` should be an item from `constants.IO_DIRECTION`.
         """
         ret = _comedilib_h.comedi_dio_config(
-            self.subdevice.device.device,
-            self.subdevice.index, self.index,
+            self._device(), self.subdevice.index, self.index,
             _constant.bitwise_value(dir))
         if ret < 0:
             _error.raise_error(function_name='comedi_dio_config', ret=ret)
@@ -185,8 +183,7 @@ cdef class DigitalChannel (Channel):
         """
         cpdef unsigned int dir
         ret = _comedilib_h.comedi_dio_get_config(
-            self.subdevice.device.device,
-           self.subdevice.index, self.index, &dir)
+            self._device(), self.subdevice.index, self.index, &dir)
         if ret < 0:
             _error.raise_error(function_name='comedi_dio_get_config', ret=ret)
         return _constant.IO_DIRECTION.index_by_value(dir)
@@ -195,8 +192,7 @@ cdef class DigitalChannel (Channel):
         "Read a single bit"
         cpdef unsigned int bit
         ret = _comedilib_h.comedi_dio_read(
-            self.subdevice.device.device,
-            self.subdevice.index, self.index, &bit)
+            self._device(), self.subdevice.index, self.index, &bit)
         if ret < 0:
             _error.raise_error(function_name='comedi_dio_read', ret=ret)
         return int(bit)
@@ -204,8 +200,7 @@ cdef class DigitalChannel (Channel):
     def dio_write(self, bit):
         "Write a single bit"
         ret = _comedilib_h.comedi_dio_write(
-            self.subdevice.device.device,
-            self.subdevice.index, self.index, bit)
+            self._device(), self.subdevice.index, self.index, bit)
         if ret < 0:
             _error.raise_error(function_name='comedi_dio_write', ret=ret)
 
@@ -311,8 +306,7 @@ cdef class AnalogChannel (Channel):
         "Read one sample"
         cdef _comedi_h.lsampl_t data
         ret = _comedilib_h.comedi_data_read(
-            self.subdevice.device.device,
-            self.subdevice.index, self.index,
+            self._device(), self.subdevice.index, self.index,
             _constant.bitwise_value(self.range),
             _constant.bitwise_value(self.aref),
             &data)
@@ -324,8 +318,7 @@ cdef class AnalogChannel (Channel):
         "Read `n` samples (timing between samples is undefined)."
         data = _numpy.ndarray(shape=(n,), dtype=_numpy.uint32)
         ret = _comedilib_h.comedi_data_read_n(
-            self.subdevice.device.device,
-            self.subdevice.index, self.index,
+            self._device(), self.subdevice.index, self.index,
             _constant.bitwise_value(self.range),
             _constant.bitwise_value(self.aref),
             <_comedilib_h.lsampl_t *>_numpy.PyArray_DATA(data), n)
@@ -349,8 +342,7 @@ cdef class AnalogChannel (Channel):
         performs a conversion.
         """
         ret = _comedilib_h.comedi_data_read_hint(
-            self.subdevice.device.device,
-            self.subdevice.index, self.index,
+            self._device(), self.subdevice.index, self.index,
             _constant.bitwise_value(self.range),
             _constant.bitwise_value(self.aref))
         if ret < 0:
@@ -365,8 +357,7 @@ cdef class AnalogChannel (Channel):
         """
         cdef _comedi_h.lsampl_t data
         ret = _comedilib_h.comedi_data_read_delayed(
-            self.subdevice.device.device,
-            self.subdevice.index, self.index,
+            self._device(), self.subdevice.index, self.index,
             _constant.bitwise_value(self.range),
             _constant.bitwise_value(self.aref),
             &data, int(nano_sec))
@@ -381,8 +372,7 @@ cdef class AnalogChannel (Channel):
         Returns 1 (the number of data samples written).
         """
         ret = _comedilib_h.comedi_data_write(
-            self.subdevice.device.device,
-            self.subdevice.index, self.index,
+            self._device(), self.subdevice.index, self.index,
             _constant.bitwise_value(self.range),
             _constant.bitwise_value(self.aref),
             int(data))
@@ -418,8 +408,7 @@ cdef class AnalogChannel (Channel):
         """
         cdef _comedilib_h.comedi_polynomial_t poly
         rc = _comedilib_h.comedi_get_hardcal_converter(
-            self.subdevice.device.device,
-            self.subdevice.index, self.index,
+            self._device(), self.subdevice.index, self.index,
             _constant.bitwise_value(self.range),
             _constant.bitwise_value(direction), &poly)
         if rc < 0:
@@ -459,8 +448,7 @@ cdef class AnalogChannel (Channel):
             # automatically get a char * refernce into the Python string p
             path = p
         ret = _comedilib_h.comedi_apply_calibration(
-            self.subdevice.device.device,
-            self.subdevice.index, self.index,
+            self._device(), self.subdevice.index, self.index,
             _constant.bitwise_value(self.range),
             _constant.bitwise_value(self.aref),
             path)
@@ -471,8 +459,7 @@ cdef class AnalogChannel (Channel):
 
     cdef _apply_parsed_calibration(self, _Calibration calibration):
         ret = _comedilib_h.comedi_apply_parsed_calibration(
-            self.subdevice.device.device,
-            self.subdevice.index, self.index,
+            self._device(), self.subdevice.index, self.index,
             _constant.bitwise_value(self.range),
             _constant.bitwise_value(self.aref),
             calibration.calibration)

diff --git a/pycomedi/subdevice.pxd b/pycomedi/subdevice.pxd
index 7aa3e83f8ac7d3db79dd816198016606eaf11853..a67790c628c0d14e9b2a0617ca1f094e315d296d 100644 (file)
--- a/pycomedi/subdevice.pxd
+++ b/pycomedi/subdevice.pxd
@@ -16,14 +16,15 @@
 
 "Expose `Subdevice` internals at the C level for other Cython modules"
 
-from device cimport Device as _Device
+cimport _comedilib_h
 from command cimport Command as _Command
 
 
 cdef class Subdevice (object):
-    cdef public _Device device
+    cdef public object device  # pycomedi.device.Device
     cdef public int index
 
+    cdef _comedilib_h.comedi_t * _device(self)
     cpdef dio_bitfield(self, unsigned int bits=*, write_mask=*, base_channel=*)
 
 cdef class StreamingSubdevice (Subdevice):

diff --git a/pycomedi/subdevice.pyx b/pycomedi/subdevice.pyx
index 82febcb2a4ed503a547f5b65cf038691486de225..2e4ef0cf0517fb484434581823ec727464f912b8 100644 (file)
--- a/pycomedi/subdevice.pyx
+++ b/pycomedi/subdevice.pyx
@@ -18,7 +18,6 @@
 
 cimport _comedi_h
 cimport _comedilib_h
-cimport device as _device
 cimport command as _command
 from pycomedi import LOG as _LOG
 import _error
@@ -68,16 +67,20 @@ cdef class Subdevice (object):
     """
     def __cinit__(self):
         self.index = -1
+        self.device = None
 
     def __init__(self, device, index):
         super(Subdevice, self).__init__()
         self.device = device
         self.index = index
 
+    cdef _comedilib_h.comedi_t * _device(self):
+        return <_comedilib_h.comedi_t *> self.device.device
+
     def get_type(self):
         "Type of subdevice (from `SUBDEVICE_TYPE`)"
         ret = _comedilib_h.comedi_get_subdevice_type(
-            self.device.device, self.index)
+            self._device(), self.index)
         if ret < 0:
             _error.raise_error(function_name='comedi_get_subdevice_type',
                                ret=ret)
@@ -86,7 +89,7 @@ cdef class Subdevice (object):
     def _get_flags(self):
         "Subdevice flags"
         ret = _comedilib_h.comedi_get_subdevice_flags(
-            self.device.device, self.index)
+            self._device(), self.index)
         if ret < 0:
             _error.raise_error(function_name='comedi_get_subdevice_flags',
                                ret=ret)
@@ -100,7 +103,7 @@ cdef class Subdevice (object):
     def get_n_channels(self):
         "Number of subdevice channels"
         ret = _comedilib_h.comedi_get_n_channels(
-            self.device.device, self.index)
+            self._device(), self.index)
         if ret < 0:
             _error.raise_error(function_name='comedi_get_n_channels',
                                ret=ret)
@@ -108,7 +111,7 @@ cdef class Subdevice (object):
 
     def range_is_chan_specific(self):
         ret = _comedilib_h.comedi_range_is_chan_specific(
-            self.device.device, self.index)
+            self._device(), self.index)
         if ret < 0:
             _error.raise_error(
                 function_name='comedi_range_is_chan_specific', ret=ret)
@@ -116,7 +119,7 @@ cdef class Subdevice (object):
 
     def maxdata_is_chan_specific(self):
         ret = _comedilib_h.comedi_maxdata_is_chan_specific(
-            self.device.device, self.index)
+            self._device(), self.index)
         if ret < 0:
             _error.raise_error(
                 function_name='comedi_maxdata_is_chan_specific', ret=ret)
@@ -124,13 +127,13 @@ cdef class Subdevice (object):
 
     def lock(self):
         "Reserve the subdevice"
-        ret = _comedilib_h.comedi_lock(self.device.device, self.index)
+        ret = _comedilib_h.comedi_lock(self._device(), self.index)
         if ret < 0:
             _error.raise_error(function_name='comedi_lock', ret=ret)
 
     def unlock(self):
         "Release the subdevice"
-        ret = _comedilib_h.comedi_unlock(self.device.device, self.index)
+        ret = _comedilib_h.comedi_unlock(self._device(), self.index)
         if ret < 0:
             _error.raise_error(function_name='comedi_unlock', ret=ret)
 
@@ -144,7 +147,7 @@ cdef class Subdevice (object):
         channels and the last written value of all output channels.
         """
         ret = _comedilib_h.comedi_dio_bitfield2(
-            self.device.device, self.index, write_mask, &bits, base_channel)
+            self._device(), self.index, write_mask, &bits, base_channel)
         if ret < 0:
             _error.raise_error(function_name='comedi_dio_bitfield2', ret=ret)
         return bits
@@ -262,7 +265,7 @@ cdef class StreamingSubdevice (Subdevice):
         cdef _command.Command cmd
         cmd = _command.Command()
         ret = _comedilib_h.comedi_get_cmd_src_mask(
-            self.device.device, self.index, cmd.get_comedi_cmd_pointer())
+            self._device(), self.index, cmd.get_comedi_cmd_pointer())
         if ret < 0:
             _error.raise_error(function_name='comedi_get_cmd_src_mask', ret=ret)
         return cmd
@@ -287,7 +290,7 @@ cdef class StreamingSubdevice (Subdevice):
         cdef _command.Command cmd
         cmd = _command.Command()
         ret = _comedilib_h.comedi_get_cmd_generic_timed(
-            self.device.device, self.index, cmd.get_comedi_cmd_pointer(),
+            self._device(), self.index, cmd.get_comedi_cmd_pointer(),
             chanlist_len, int(scan_period_ns))
         cmd.chanlist = [0 for i in range(chanlist_len)]
         if ret < 0:
@@ -297,21 +300,21 @@ cdef class StreamingSubdevice (Subdevice):
 
     def cancel(self):
         "Stop streaming input/output in progress."
-        ret = _comedilib_h.comedi_cancel(self.device.device, self.index)
+        ret = _comedilib_h.comedi_cancel(self._device(), self.index)
         if ret < 0:
             _error.raise_error(function_name='comedi_cancel', ret=ret)
 
     def command(self):
         "Start streaming input/output"
         ret = _comedilib_h.comedi_command(
-            self.device.device, self.cmd.get_comedi_cmd_pointer())
+            self._device(), self.cmd.get_comedi_cmd_pointer())
         if ret < 0:
             _error.raise_error(function_name='comedi_command', ret=ret)
 
     def command_test(self):
         "Test streaming input/output configuration"
         ret = _comedilib_h.comedi_command_test(
-            self.device.device, self.cmd.get_comedi_cmd_pointer())
+            self._device(), self.cmd.get_comedi_cmd_pointer())
         return self._command_test_errors[ret]
 
     def poll(self):
@@ -322,7 +325,7 @@ cdef class StreamingSubdevice (Subdevice):
         buffers or device FIFOs. If successful, the number of
         additional bytes available is returned.
         """
-        ret = _comedilib_h.comedi_poll(self.device.device, self.index)
+        ret = _comedilib_h.comedi_poll(self._device(), self.index)
         if ret < 0:
             _error.raise_error(function_name='comedi_poll', ret=ret)
         return ret
@@ -330,7 +333,7 @@ cdef class StreamingSubdevice (Subdevice):
     def get_buffer_size(self):
         "Streaming buffer size of subdevice"
         ret = _comedilib_h.comedi_get_buffer_size(
-            self.device.device, self.index)
+            self._device(), self.index)
         if ret < 0:
             _error.raise_error(function_name='comedi_get_buffer_size', ret=ret)
         return ret
@@ -351,7 +354,7 @@ cdef class StreamingSubdevice (Subdevice):
         `comedi_config`.
         """
         ret = _comedilib_h.comedi_set_buffer_size(
-            self.device.device, self.index, int(size))
+            self._device(), self.index, int(size))
         if ret < 0:
             _error.raise_error(function_name='comedi_set_buffer_size', ret=ret)
         return ret
@@ -359,7 +362,7 @@ cdef class StreamingSubdevice (Subdevice):
     def get_max_buffer_size(self):
         "Maximum streaming buffer size of subdevice"
         ret = _comedilib_h.comedi_get_max_buffer_size(
-            self.device.device, self.index)
+            self._device(), self.index)
         if ret < 0:
             _error.raise_error(function_name='comedi_get_max_buffer_size',
                                ret=ret)
@@ -371,7 +374,7 @@ cdef class StreamingSubdevice (Subdevice):
         Returns the old (max?) buffer size on success.
         """
         ret = _comedilib_h.comedi_set_max_buffer_size(
-            self.device.device, self.index, int(max_size))
+            self._device(), self.index, int(max_size))
         if ret < 0:
             _error.raise_error(function_name='comedi_set_max_buffer_size',
                                ret=ret)
@@ -380,7 +383,7 @@ cdef class StreamingSubdevice (Subdevice):
     def get_buffer_contents(self):
         "Number of bytes available on an in-progress command"
         ret = _comedilib_h.comedi_get_buffer_contents(
-            self.device.device, self.index)
+            self._device(), self.index)
         if ret < 0:
             _error.raise_error(function_name='comedi_get_buffer_contents',
                                ret=ret)
@@ -398,7 +401,7 @@ cdef class StreamingSubdevice (Subdevice):
         calls.
         """
         ret = _comedilib_h.comedi_mark_buffer_read(
-            self.device.device, self.index, num_bytes)
+            self._device(), self.index, num_bytes)
         if ret < 0:
             _error.raise_error(function_name='comedi_mark_buffer_read',
                                ret=ret)
@@ -416,7 +419,7 @@ cdef class StreamingSubdevice (Subdevice):
         `write()` calls.
         """
         ret = _comedilib_h.comedi_mark_buffer_written(
-            self.device.device, self.index, num_bytes)
+            self._device(), self.index, num_bytes)
         if ret < 0:
             _error.raise_error(function_name='comedi_mark_buffer_written',
                                ret=ret)
@@ -428,7 +431,7 @@ cdef class StreamingSubdevice (Subdevice):
         This offset is only useful for memory mapped buffers.
         """
         ret = _comedilib_h.comedi_get_buffer_offset(
-            self.device.device, self.index)
+            self._device(), self.index)
         if ret < 0:
             _error.raise_error(function_name='comedi_get_buffer_offset', ret=ret)
         return ret