An 1-bit increment of one should indicate missing compressed data

Fix a bug where an 1-bit increment of one is treated as normal
increment.

According to WMO spec 94.1.6
   The convention for representing missing data for compressed data
   within the binary Data section shall be to set the corresponding
   increments to fields of all ones.

There it should be processed as missing data.

Resolves: #33

pybufrkit/__init__.py

@@ -33,7 +33,7 @@
                               UnknownDescriptor,
                               PyBufrKitError)
 
-__version__ = '0.2.21'
+__version__ = '0.2.22'
 __author__ = '[email protected]'
 
 LOGGER = logging.getLogger('PyBufrKit')

pybufrkit/decoder.py

@@ -273,6 +273,9 @@ def process_numeric_compressed(self, state, bit_reader, descriptor, nbits_min_va
         else:
             for decoded_values in state.decoded_values_all_subsets:
                 diff = bit_reader.read_uint_or_none(nbits_diff)
+                # A one-bit increment of value one is considered as missing
+                if diff == 1 and nbits_diff == 1:
+                    diff = None
                 if diff is None:
                     value = None
                 else:
@@ -332,6 +335,9 @@ def process_codeflag_compressed(self, state, bit_reader, descriptor, nbits_min_v
         else:
             for decoded_values in state.decoded_values_all_subsets:
                 diff = bit_reader.read_uint_or_none(nbits_diff)
+                # A one-bit increment of value one is considered as missing
+                if diff == 1 and nbits_diff == 1:
+                    diff = None
                 if diff is None:
                     value = None
                 else:

tests/data/ISMD01_OKPR.values.cmp

@@ -132,8 +132,8 @@
 16 -80.0
 17 8
 18 None
-19 92510.0
-20 750
+19 None
+20 None
 21 2.0
 22 271.85
 23 271.75
@@ -156,7 +156,7 @@
 40 7
 41 120.0
 42 1
-43 12
+43 None
 44 None
 45 None
 46 None
@@ -248,8 +248,8 @@
 16 -110.0
 17 8
 18 None
-19 92510.0
-20 750
+19 None
+20 None
 21 2.0
 22 273.05
 23 271.15
@@ -272,7 +272,7 @@
 40 7
 41 240.0
 42 1
-43 12
+43 None
 44 None
 45 None
 46 None
@@ -364,8 +364,8 @@
 16 -70.0
 17 5
 18 None
-19 92510.0
-20 750
+19 None
+20 None
 21 1.98
 22 273.65
 23 271.95
@@ -388,7 +388,7 @@
 40 7
 41 240.0
 42 1
-43 12
+43 None
 44 None
 45 None
 46 None
@@ -480,8 +480,8 @@
 16 -130.0
 17 7
 18 None
-19 92510.0
-20 750
+19 None
+20 None
 21 2.01
 22 271.85
 23 270.85
@@ -504,7 +504,7 @@
 40 7
 41 120.0
 42 1
-43 12
+43 None
 44 None
 45 None
 46 None
@@ -596,8 +596,8 @@
 16 -120.0
 17 8
 18 None
-19 92510.0
-20 750
+19 None
+20 None
 21 2.0
 22 275.05
 23 272.45
@@ -620,7 +620,7 @@
 40 7
 41 450.0
 42 1
-43 12
+43 None
 44 None
 45 None
 46 None
@@ -712,8 +712,8 @@
 16 -170.0
 17 7
 18 None
-19 92510.0
-20 750
+19 None
+20 None
 21 2.0
 22 278.65
 23 273.05
@@ -736,7 +736,7 @@
 40 0
 41 6900.0
 42 1
-43 12
+43 None
 44 None
 45 None
 46 None