fix transfer of large data

Data larger than the max integer value would fail to transfer. changed
size of message read from the IPC protocol from an int to an unsigned
int. Also changed to load large data in chunks since stream.read() does
not support values larger than max int.

qpython/qreader.py

@@ -167,7 +167,7 @@ def read_header(self, source = None):
         # skip 1 byte
         self._buffer.skip()
 
-        message_size = self._buffer.get_int()
+        message_size = self._buffer.get_uint()
         return QMessage(None, message_type, message_size, message_compressed)
 
 
@@ -384,8 +384,28 @@ def _read_bytes(self, length):
 
         if length == 0:
             return b''
-        else:
+        if length <= sys.maxint:
             data = self._stream.read(length)
+        else:
+            try:
+                from cStringIO import StringIO
+            except:
+                from StringIO import StringIO
+
+            # for large messages, read from the stream in chunks
+            remaining = length
+            buff = StringIO()
+
+            while remaining > 0:
+                chunk = self._stream.read(min(remaining, 2048))
+
+                if chunk:
+                    remaining = remaining - len(chunk)
+                    buff.write(chunk)
+                else:
+                    break
+
+            data = buff.getvalue()
 
         if len(data) == 0:
             raise QReaderException('Error while reading data')
@@ -491,6 +511,15 @@ def get_byte(self):
             return self.get('b')
 
 
+        def get_uint(self):
+            '''
+            Gets a single unsigned 32-bit integer from the buffer.
+
+            :returns: single unsigned integer
+            '''
+            return self.get('I')
+
+
         def get_int(self):
             '''
             Gets a single 32-bit integer from the buffer.