toASCIIString(): replace non-ASCII char by '.'

Bytes with value lower than 32 (' ') or higher than 127 (DEL) are
replaced by '.' to get only printable characters.

smartcard/util/__init__.py

@@ -80,9 +80,18 @@ def toASCIIString(bytelist):
 
     >>> toASCIIString([0x4E,0x75,0x6D,0x62,0x65,0x72,0x20,0x31,0x30,0x31])
     'Number 101'
+    >>> toASCIIString([0x01, 0x20, 0x80, 0x7E, 0xF0])
+    ". .~."
     """
 
-    return ''.join(map(chr, bytelist))
+    res = list()
+    for b in bytelist:
+        if b < 32 or b > 127:
+            c = '.'
+        else:
+            c = chr(b)
+        res.append(c)
+    return ''.join(res)
 
 
 def toBytes(bytestring):

test/test_util.py

@@ -48,6 +48,10 @@ def test_toASCIIString(self):
         data_out = "Number 101"
         self.assertEqual(toASCIIString(data_in), data_out)
 
+        data_in = [0x01, 0x20, 0x80, 0x7E, 0xF0]
+        data_out = ". .~."
+        self.assertEqual(toASCIIString(data_in), data_out)
+
     def test_toGSM3_38Bytes(self):
         data_in = "@Pascal"
         data_out = [0x00, 0x50, 0x61, 0x73, 0x63, 0x61, 0x6C]