Merge pull request #41 from vesuvisian/master

Map "error" and "out of range" values to None

klvdata/common.py

@@ -111,7 +111,6 @@ def linear_map(src_value, src_domain, dst_range):
     it should always fall within the src_domain. If not, that's a problem.
     """
     src_min, src_max, dst_min, dst_max = src_domain + dst_range
-    # assert(src_min <= src_value <= src_max)
 
     if not (src_min <= src_value <= src_max):
         raise ValueError
@@ -125,9 +124,13 @@ def linear_map(src_value, src_domain, dst_range):
     return dst_value
 
 
-def bytes_to_float(value, _domain, _range):
+def bytes_to_float(value, _domain, _range, _error=None):
     """Convert the fixed point value self.value to a floating point value."""
     src_value = int().from_bytes(value, byteorder='big', signed=(min(_domain) < 0))
+
+    if src_value == _error:
+        return None
+
     return linear_map(src_value, _domain, _range)
 
 
@@ -142,15 +145,18 @@ def ieee754_bytes_to_fp(value):
     else:
         raise ValueError
 
-def float_to_bytes(value, _domain, _range):
+def float_to_bytes(value, _domain, _range, _error=None):
     """Convert the fixed point value self.value to a floating point value."""
     # Some classes like MappedElement are calling float_to_bytes with arguments _domain
     # and _range in the incorrect order. The naming convention used is confusing and
     # needs addressed. Until that time, swap the order here as a workaround...
     src_domain, dst_range = _range, _domain
     src_min, src_max, dst_min, dst_max = src_domain + dst_range
     length = int((dst_max - dst_min - 1).bit_length() / 8)
-    dst_value = linear_map(value, src_domain=src_domain, dst_range=dst_range)
+    if value is None:
+        dst_value = _error
+    else:
+        dst_value = linear_map(value, src_domain=src_domain, dst_range=dst_range)
     return round(dst_value).to_bytes(length, byteorder='big', signed=(dst_min < 0))
 
 

klvdata/elementparser.py

@@ -133,7 +133,7 @@ def __str__(self):
 
 class MappedElementParser(ElementParser, metaclass=ABCMeta):
     def __init__(self, value):
-        super().__init__(MappedValue(value, self._domain, self._range))
+        super().__init__(MappedValue(value, self._domain, self._range, self._error))
 
     @property
     @classmethod
@@ -147,18 +147,25 @@ def _domain(cls):
     def _range(cls):
         pass
 
+    @property
+    @classmethod
+    @abstractmethod
+    def _error(cls):
+        pass
+
 class MappedValue(BaseValue):
-    def __init__(self, value, _domain, _range):
+    def __init__(self, value, _domain, _range, _error):
         self._domain = _domain
         self._range = _range
+        self._error = _error
 
         try:
-            self.value = bytes_to_float(value, self._domain, self._range)
+            self.value = bytes_to_float(value, self._domain, self._range, self._error)
         except TypeError:
             self.value = value
 
     def __bytes__(self):
-        return float_to_bytes(self.value, self._domain, self._range)
+        return float_to_bytes(self.value, self._domain, self._range, self._error)
 
     def __str__(self):
         if self.value is not None: