simplify eof detection

mitmproxy/contrib/tnetstring.py

@@ -172,6 +172,8 @@ def load(file_handle):
     #  Read the length prefix one char at a time.
     #  Note that the netstring spec explicitly forbids padding zeros.
     c = file_handle.read(1)
+    if c == b"":  # we want to detect this special case.
+        raise ValueError("not a tnetstring: empty file")
     data_length = b""
     while c.isdigit():
         data_length += c

mitmproxy/flow/io.py

@@ -26,16 +26,6 @@ class FlowReader:
         """
             Yields Flow objects from the dump.
         """
-
-        # There is a weird mingw bug that breaks .tell() when reading from stdin.
-        try:
-            self.fo.tell()
-        except IOError:  # pragma: no cover
-            can_tell = False
-        else:
-            can_tell = True
-
-        off = 0
         try:
             while True:
                 data = tnetstring.load(self.fo)
@@ -43,15 +33,12 @@ class FlowReader:
                     data = io_compat.migrate_flow(data)
                 except ValueError as e:
                     raise exceptions.FlowReadException(str(e))
-                if can_tell:
-                    off = self.fo.tell()
                 if data["type"] not in models.FLOW_TYPES:
                     raise exceptions.FlowReadException("Unknown flow type: {}".format(data["type"]))
                 yield models.FLOW_TYPES[data["type"]].from_state(data)
-        except ValueError:
-            # Error is due to EOF
-            if can_tell and self.fo.tell() == off and self.fo.read() == b'':
-                return
+        except ValueError as e:
+            if str(e) == "not a tnetstring: empty file":
+                return  # Error is due to EOF
             raise exceptions.FlowReadException("Invalid data format.")