Respect decimal precision of HANA

pyhdb/protocol/types.py

@@ -180,8 +180,13 @@ def prepare(cls, value):
         if value is None:
             return struct.pack('b', 0)
 
+        if isinstance(value, float):
+            value = decimal.Decimal(value)
+
         sign, digits, exponent = value.as_tuple()
-        mantissa = int(''.join(map(str, value.as_tuple().digits)))
+        if len(digits) > 34:
+            exponent += len(digits) - 34
+        mantissa = int(''.join(map(str, digits[:34])))
         exponent += 6176
 
         packed = bytearray(16)
@@ -192,8 +197,8 @@ def prepare(cls, value):
         for i in iter_range(2, 16):
             packed[i] = (mantissa >> shift) & 0xFF
             shift -= 8
-        packed.reverse()
 
+        packed.reverse()
         return struct.pack('b', cls.type_code) + packed
 
 

tests/types/test_int.py

@@ -185,7 +185,9 @@ def test_pack_double(input, expected):
     (Decimal('-312313212312321.1245678910111213142'),
      b"\x05\x56\xe6\x47\x6f\x0e\xde\xd6\x93\x68\xb0\x26\x78\xfb\x99\x1a\xb0"),
     (Decimal('3.14159265359'),
-     b"\x05\x4f\xf6\x59\x25\x49\x00\x00\x00\x00\x00\x00\x00\x00\x00\x2a\x30")
+     b"\x05\x4f\xf6\x59\x25\x49\x00\x00\x00\x00\x00\x00\x00\x00\x00\x2a\x30"),
+    (Decimal("-15.756299999999999528199623455293476581573486328125"),
+     b"\x05\x03\xa0\x1d\x27\x14\xb4\xd7\xc3\x92\x8e\x1c\x3f\xaf\x4d\x00\xb0")
 ])
 def test_pack_decimal(input, expected):
     assert types.Decimal.prepare(input) == expected