Decoder.try_next

implementations/python/preserves/preserves.py

@@ -179,11 +179,15 @@ class SymbolStream(BinaryStream):
     minor = 3
 
 class Decoder(Codec):
-    def __init__(self, packet):
+    def __init__(self, packet=b''):
         super(Decoder, self).__init__()
         self.packet = packet
         self.index = 0
 
+    def extend(self, data):
+        self.packet = self.packet[self.index:] + data
+        self.index = 0
+
     def nextbyte(self):
         if self.index >= len(self.packet):
             raise ShortPacket('Short packet')
@@ -299,6 +303,14 @@ class Decoder(Codec):
         else: # major == 3
             return self.decodecollection(minor, self.nextvalues(self.wirelength(arg)))
 
+    def try_next(self):
+        start = self.index
+        try:
+            return self.next()
+        except ShortPacket:
+            self.index = start
+            return None
+
 class Encoder(Codec):
     def __init__(self):
         super(Encoder, self).__init__()

implementations/python/setup.py

@@ -5,7 +5,7 @@ except ImportError:
 
 setup(
     name="preserves",
-    version="0.0.1",
+    version="0.0.2",
     author="Tony Garnock-Jones",
     author_email="tonyg@leastfixedpoint.com",
     license="GNU General Public License v3 or later (GPLv3+)",