* fix to Real codec exponent encoding (should be in 2's complement form)

* some more test cases added

5 files changed, 41 insertions, 11 deletions

diff --git a/CHANGES b/CHANGES
index c2dabc0..6629118 100644
--- a/CHANGES
+++ b/CHANGES
@@ -18,6 +18,8 @@ Revision 0.1.4
 - Package classifiers updated.
 - The __init__.py's made non-empty (rumors are that they may be optimized 
   out by package managers).
+- Fix to Real codec exponent encoding (should be in 2's complement form),
+  some more test cases added.
 - Fix in Boolean truth testing built-in methods
 - Fix to substrate underrun error handling at ObjectIdentifier BER decoder
 - Fix to BER Boolean decoder that allows other pre-computed
diff --git a/pyasn1/codec/ber/decoder.py b/pyasn1/codec/ber/decoder.py
index 365faeb..f63ae8c 100644
--- a/pyasn1/codec/ber/decoder.py
+++ b/pyasn1/codec/ber/decoder.py
@@ -245,18 +245,13 @@ class RealDecoder(AbstractSimpleDecoder):
         if fo & 0x40:  # infinite value
             value = fo & 0x01 and '-inf' or 'inf'
         elif fo & 0x80:  # binary enoding
-            if fo & 0x11 == 0:
-                n = 1
-            elif fo & 0x01:
-                n = 2
-            elif fo & 0x02:
-                n = 3
-            else:
+            n = (fo & 0x03) + 1
+            if n == 4:
                 n = oct2int(head[0])
             eo, head = head[:n], head[n:]
             if not eo or not head:
                 raise error.PyAsn1Error('Real exponent screwed')
-            e = 0
+            e = oct2int(eo[0]) & 0x80 and -1 or 0
             while eo:         # exponent
                 e <<= 8
                 e |= oct2int(eo[0])
diff --git a/pyasn1/codec/ber/encoder.py b/pyasn1/codec/ber/encoder.py
index afcc567..181fbde 100644
--- a/pyasn1/codec/ber/encoder.py
+++ b/pyasn1/codec/ber/encoder.py
@@ -1,7 +1,7 @@
 # BER encoder
 from pyasn1.type import base, tag, univ, char, useful
 from pyasn1.codec.ber import eoo
-from pyasn1.compat.octets import int2oct, ints2octs, null, str2octs
+from pyasn1.compat.octets import int2oct, oct2int, ints2octs, null, str2octs
 from pyasn1 import debug, error
 
 class Error(Exception): pass
@@ -203,9 +203,11 @@ class RealEncoder(AbstractItemEncoder):
                 m >>= 1
                 e += 1
             eo = null
-            while e:
+            while e not in (0, -1):
                 eo = int2oct(e&0xff) + eo
                 e >>= 8
+            if e == 0 and eo and oct2int(eo[0]) & 0x80:
+                eo = int2oct(0) + eo
             n = len(eo)
             if n > 0xff:
                 raise error.PyAsn1Error('Real exponent overflow')
diff --git a/test/codec/ber/decoder.py b/test/codec/ber/decoder.py
index cfb5ee7..04d6526 100644
--- a/test/codec/ber/decoder.py
+++ b/test/codec/ber/decoder.py
@@ -188,6 +188,32 @@ class ObjectIdentifierDecoderTestCase(unittest.TestCase):
             pass
         else:
             assert 1, 'Leading 0x80 tolarated'
+
+class RealDecoderTestCase(unittest.TestCase):
+    def testChar(self):
+        assert decoder.decode(
+            ints2octs((9, 7, 3, 49, 50, 51, 69, 49, 49))
+        ) == (univ.Real((123, 10, 11)), null)
+
+    def testBin1(self):
+        assert decoder.decode(
+            ints2octs((9, 4, 128, 245, 4, 77))
+        ) == (univ.Real((1101, 2, -11)), null)
+
+    def testBin2(self):
+        assert decoder.decode(
+            ints2octs((9, 4, 128, 11, 4, 77))
+        ) == (univ.Real((1101, 2, 11)), null)
+
+    def testPlusInf(self):
+        assert decoder.decode(
+            ints2octs((9, 1, 64))
+        ) == (univ.Real('inf'), null)
+ 
+    def testMinusInf(self):
+        assert decoder.decode(
+            ints2octs((9, 1, 65))
+        ) == (univ.Real('-inf'), null)
  
 class SequenceDecoderTestCase(unittest.TestCase):
     def setUp(self):
diff --git a/test/codec/ber/encoder.py b/test/codec/ber/encoder.py
index 5755cf5..af08159 100644
--- a/test/codec/ber/encoder.py
+++ b/test/codec/ber/encoder.py
@@ -134,11 +134,16 @@ class RealEncoderTestCase(unittest.TestCase):
             univ.Real((123, 10, 11))
             ) == ints2octs((9, 7, 3, 49, 50, 51, 69, 49, 49))
 
-    def testBin(self):
+    def testBin1(self):
         assert encoder.encode(
             univ.Real((1101, 2, 11))
             ) == ints2octs((9, 4, 128, 11, 4, 77))
 
+    def testBin2(self):
+        assert encoder.encode(
+            univ.Real((1101, 2, -11))
+            ) == ints2octs((9, 4, 128, 245, 4, 77))
+
     def testPlusInf(self):
         assert encoder.encode(univ.Real('inf')) == ints2octs((9, 1, 64))