Decimal representation of scale, offset, minimum and maximum.

Gussy · Nov 24, 2018 · 93525d2 · 93525d2
1 parent 68d4a4d
commit 93525d2
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Showing 7 changed files with 189 additions and 15 deletions.
diff --git a/cantools/database/can/formats/dbc.py b/cantools/database/can/formats/dbc.py
@@ -22,6 +22,7 @@
 from ..attribute_definition import AttributeDefinition
 from ..attribute import Attribute
 from ..signal import Signal
+from ..signal import Decimal as SignalDecimal
 from ..message import Message
 from ..node import Node
 from ..internal_database import InternalDatabase
@@ -962,16 +963,28 @@ def get_receivers(receivers):
         return [_get_node_name(attributes, receiver) for receiver in receivers]
 
     def get_minimum(minimum, maximum):
-        if minimum == maximum == 0:
+        if minimum == maximum == '0':
             return None
         else:
-            return minimum
+            return num(minimum)
 
     def get_maximum(minimum, maximum):
-        if minimum == maximum == 0:
+        if minimum == maximum == '0':
             return None
         else:
-            return maximum
+            return num(maximum)
+
+    def get_minimum_decimal(minimum, maximum):
+        if minimum == maximum == '0':
+            return None
+        else:
+            return Decimal(minimum)
+
+    def get_maximum_decimal(minimum, maximum):
+        if minimum == maximum == '0':
+            return None
+        else:
+            return Decimal(maximum)
 
     def get_protocol(frame_id_dbc):
         """Get protocol for a given message.
@@ -1063,10 +1076,14 @@ def get_signal_name(frame_id_dbc, name):
                             is_signed=(signal[8] == '-'),
                             scale=num(signal[10]),
                             offset=num(signal[12]),
-                            minimum=get_minimum(num(signal[15]),
-                                                num(signal[17])),
-                            maximum=get_maximum(num(signal[15]),
-                                                num(signal[17])),
+                            minimum=get_minimum(signal[15], signal[17]),
+                            maximum=get_maximum(signal[15], signal[17]),
+                            decimal=SignalDecimal(Decimal(signal[10]),
+                                                  Decimal(signal[12]),
+                                                  get_minimum_decimal(signal[15],
+                                                                      signal[17]),
+                                                  get_maximum_decimal(signal[15],
+                                                                      signal[17])),
                             unit=None if signal[19] == '' else signal[19],
                             choices=get_choices(frame_id_dbc,
                                                 signal[1][0]),

diff --git a/cantools/database/can/formats/kcd.py b/cantools/database/can/formats/kcd.py
@@ -3,12 +3,14 @@
 import sys
 import logging
 from collections import defaultdict
+from decimal import Decimal
 
 from xml.etree import ElementTree
 from xml.etree.ElementTree import Element
 from xml.etree.ElementTree import SubElement
 
 from ..signal import Signal
+from ..signal import Decimal as SignalDecimal
 from ..message import Message
 from ..node import Node
 from ..bus import Bus
@@ -59,7 +61,8 @@ def _load_signal_element(signal, nodes):
     labels = None
     notes = None
     receivers = []
-
+    decimal = SignalDecimal(Decimal(slope), Decimal(intercept))
+
     # Signal XML attributes.
     for key, value in signal.attrib.items():
         if key == 'name':
@@ -80,12 +83,16 @@ def _load_signal_element(signal, nodes):
         for key, value in value.attrib.items():
             if key == 'min':
                 minimum = num(value)
+                decimal.minimum = Decimal(value)
             elif key == 'max':
                 maximum = num(value)
+                decimal.maximum = Decimal(value)
             elif key == 'slope':
                 slope = num(value)
+                decimal.scale = Decimal(value)
             elif key == 'intercept':
                 intercept = num(value)
+                decimal.offset = Decimal(value)
             elif key == 'unit':
                 unit = value
             elif key == 'type':
@@ -135,7 +142,8 @@ def _load_signal_element(signal, nodes):
                   unit=unit,
                   choices=labels,
                   comment=notes,
-                  is_float=is_float)
+                  is_float=is_float,
+                  decimal=decimal)
 
 
 def _load_multiplex_element(mux, nodes):

diff --git a/cantools/database/can/formats/sym.py b/cantools/database/can/formats/sym.py
@@ -2,6 +2,8 @@
 
 import logging
 from collections import OrderedDict as odict
+from decimal import Decimal
+
 from pyparsing import Word
 from pyparsing import Literal
 from pyparsing import Keyword
@@ -21,6 +23,7 @@
 from pyparsing import ParseSyntaxException
 
 from ..signal import Signal
+from ..signal import Decimal as SignalDecimal
 from ..message import Message
 from ..internal_database import InternalDatabase
 
@@ -176,7 +179,8 @@ def _load_signal(tokens, enums):
     maximum = None
     enum = None
     length = 0
-
+    decimal = SignalDecimal(Decimal(factor), Decimal(offset))
+
     # Type and length.
     type_ = tokens[1]
 
@@ -207,12 +211,16 @@ def _load_signal(tokens, enums):
             unit = value
         elif key == '/f:':
             factor = num(value)
+            decimal.scale = Decimal(value)
         elif key == '/o:':
             offset = num(value)
+            decimal.offset = Decimal(value)
         elif key == '/min:':
             minimum = num(value)
+            decimal.minimum = Decimal(value)
         elif key == '/max:':
             maximum = num(value)
+            decimal.maximum = Decimal(value)
         elif key == '/e:':
             enum = enums[value]
         else:
@@ -231,7 +239,8 @@ def _load_signal(tokens, enums):
                   unit=unit,
                   choices=enum,
                   is_multiplexer=False,
-                  is_float=is_float)
+                  is_float=is_float,
+                  decimal=decimal)
 
 
 def _load_signals(tokens, enums):
@@ -271,7 +280,8 @@ def _load_message_signal(tokens,
                   is_multiplexer=signal.is_multiplexer,
                   multiplexer_ids=multiplexer_ids,
                   multiplexer_signal=multiplexer_signal,
-                  is_float=signal.is_float)
+                  is_float=signal.is_float,
+                  decimal=signal.decimal)
 
 
 def _load_message_signals_inner(message_tokens,

diff --git a/cantools/database/can/formats/utils.py b/cantools/database/can/formats/utils.py
@@ -1,4 +1,3 @@
-
 def num(number_as_string):
     """Convert given string to an integer or a float.
 

diff --git a/cantools/database/can/signal.py b/cantools/database/can/signal.py
@@ -1,5 +1,73 @@
 # A CAN signal.
 
+class Decimal(object):
+    """Holds the same values as
+    :attr:`~cantools.database.can.Signal.scale`,
+    :attr:`~cantools.database.can.Signal.offset`,
+    :attr:`~cantools.database.can.Signal.minimum` and
+    :attr:`~cantools.database.can.Signal.maximum`, but as
+    ``decimal.Decimal`` instead of ``int`` and ``float`` for higher
+    precision (no rounding errors).
+
+    """
+
+    def __init__(self, scale=None, offset=None, minimum=None, maximum=None):
+        self._scale = scale
+        self._offset = offset
+        self._minimum = minimum
+        self._maximum = maximum
+
+    @property
+    def scale(self):
+        """The scale factor of the signal value as ``decimal.Decimal``.
+
+        """
+
+        return self._scale
+
+    @scale.setter
+    def scale(self, value):
+        self._scale = value
+
+    @property
+    def offset(self):
+        """The offset of the signal value as ``decimal.Decimal``.
+
+        """
+
+        return self._offset
+
+    @offset.setter
+    def offset(self, value):
+        self._offset = value
+
+    @property
+    def minimum(self):
+        """The minimum value of the signal as ``decimal.Decimal``, or ``None``
+        if unavailable.
+
+        """
+
+        return self._minimum
+
+    @minimum.setter
+    def minimum(self, value):
+        self._minimum = value
+
+    @property
+    def maximum(self):
+        """The maximum value of the signal as ``decimal.Decimal``, or ``None``
+        if unavailable.
+
+        """
+
+        return self._maximum
+
+    @maximum.setter
+    def maximum(self, value):
+        self._maximum = value
+
+
 class Signal(object):
     """A CAN signal with position, size, unit and other information. A
     signal is part of a message.
@@ -54,7 +122,8 @@ def __init__(self,
                  is_multiplexer=False,
                  multiplexer_ids=None,
                  multiplexer_signal=None,
-                 is_float=False):
+                 is_float=False,
+                 decimal=None):
         self._name = name
         self._start = start
         self._length = length
@@ -64,6 +133,7 @@ def __init__(self,
         self._offset = offset
         self._minimum = minimum
         self._maximum = maximum
+        self._decimal = Decimal() if decimal is None else decimal
         self._unit = unit
         self._choices = choices
         self._dbc = dbc_specifics
@@ -196,6 +266,21 @@ def maximum(self):
     def maximum(self, value):
         self._maximum = value
 
+    @property
+    def decimal(self):
+        """The high precision values of
+        :attr:`~cantools.database.can.Signal.scale`,
+        :attr:`~cantools.database.can.Signal.offset`,
+        :attr:`~cantools.database.can.Signal.minimum` and
+        :attr:`~cantools.database.can.Signal.maximum`.
+
+        See :class:`~cantools.database.can.signal.Decimal` for more
+        details.
+
+        """
+
+        return self._decimal
+
     @property
     def unit(self):
         """The unit of the signal as a string, or ``None`` if unavailable.

diff --git a/docs/index.rst b/docs/index.rst
@@ -29,6 +29,9 @@ Functions and classes
 .. autoclass:: cantools.database.can.Signal
     :members:
 
+.. autoclass:: cantools.database.can.signal.Decimal
+    :members:                      
+
 .. autoclass:: cantools.database.diagnostics.Database
     :members: