From 37e9a307e6e16ce12b7ad06af2b6a0c1cdb972a4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Diego=20Elio=20Petten=C3=B2?= <flameeyes@flameeyes.com>
Date: Tue, 30 Jul 2019 17:45:38 +0100
Subject: FreeStyle devices: don't error out for non-ASCII patient names.

This was brought up in issue #60. While the devices don't appear to care
much for patient names, and can't be expected to support UTF-8 (the Windows
software don't appear to allow that), it's worth protecting against this
and just replacing the non-ASCII characters.

To make this easier, the decoding is pushed down to the end of the
processing of the multi-packet response, rather than being done per-packet.
---
 glucometerutils/support/freestyle.py | 42 +++++++++++++++++++++++-------------
 1 file changed, 27 insertions(+), 15 deletions(-)

diff --git a/glucometerutils/support/freestyle.py b/glucometerutils/support/freestyle.py
index 13674df..b2d58d1 100644
--- a/glucometerutils/support/freestyle.py
+++ b/glucometerutils/support/freestyle.py
@@ -14,7 +14,7 @@ import logging
 import re
 
 try:
-    from typing import Iterator, List, Optional, Text, Tuple
+    from typing import AnyStr, Iterator, List, Optional, Text, Tuple
 except ImportError:
     pass
 
@@ -35,10 +35,10 @@ _FREESTYLE_MESSAGE = construct.Struct(
         construct.Prefixed(construct.Byte, construct.GreedyBytes)),
 )
 
-_TEXT_COMPLETION_RE = re.compile('CMD (?:OK|Fail!)')
+_TEXT_COMPLETION_RE = re.compile(b'CMD (?:OK|Fail!)')
 _TEXT_REPLY_FORMAT = re.compile(
-    '^(?P<message>.*)CKSM:(?P<checksum>[0-9A-F]{8})\r\n'
-    'CMD (?P<status>OK|Fail!)\r\n$', re.DOTALL)
+    b'^(?P<message>.*)CKSM:(?P<checksum>[0-9A-F]{8})\r\n'
+    b'CMD (?P<status>OK|Fail!)\r\n$', re.DOTALL)
 
 _MULTIRECORDS_FORMAT = re.compile(
     '^(?P<message>.+\r\n)(?P<count>[0-9]+),(?P<checksum>[0-9A-F]{8})\r\n$',
@@ -46,12 +46,12 @@ _MULTIRECORDS_FORMAT = re.compile(
 
 
 def _verify_checksum(message, expected_checksum_hex):
-    # type: (Text, Text) -> None
+    # type: (AnyStr, AnyStr) -> None
     """Calculate the simple checksum of the message and compare with expected.
 
     Args:
       message: (str) message to calculate the checksum of.
-      expected_checksum_hex: (str) hexadecimal string representing the checksum
+      expected_checksum_hex: hexadecimal string representing the checksum
         expected to match the message.
 
     Raises:
@@ -59,7 +59,12 @@ def _verify_checksum(message, expected_checksum_hex):
         received.
     """
     expected_checksum = int(expected_checksum_hex, 16)
-    calculated_checksum = sum(ord(c) for c in message)
+    if isinstance(message, bytes):
+        all_bytes = (c for c in message)
+    else:
+        all_bytes = (ord(c) for c in message)
+
+    calculated_checksum = sum(all_bytes)
 
     if expected_checksum != calculated_checksum:
         raise exceptions.InvalidChecksum(expected_checksum, calculated_checksum)
@@ -147,16 +152,19 @@ class FreeStyleHidDevice(hiddevice.HidDevice):
         self._send_command(self.TEXT_CMD, command)
 
         # Reply can stretch multiple buffers
-        full_content = ''
+        full_content = b''
         while True:
             message_type, content = self._read_response()
 
+            logging.debug(
+                'Received message: type %02x content %r', message_type, content)
+
             if message_type != self.TEXT_REPLY_CMD:
                 raise exceptions.InvalidResponse(
-                    'Message type %02x does not match expectations: %s' %
-                    (message_type, content.decode('ascii')))
+                    'Message type %02x does not match expectations: %r' %
+                    (message_type, content))
 
-            full_content += content.decode('ascii')
+            full_content += content
 
             if _TEXT_COMPLETION_RE.search(full_content):
                 break
@@ -168,10 +176,14 @@ class FreeStyleHidDevice(hiddevice.HidDevice):
         message = match.group('message')
         _verify_checksum(message, match.group('checksum'))
 
-        if match.group('status') != 'OK':
+        if match.group('status') != b'OK':
             raise exceptions.InvalidResponse(message or "Command failed")
 
-        return message
+        # If there is anything in the response that is not ASCII-safe, this is
+        # probably in the patient name. The Windows utility does not seem to
+        # validate those, so just replace anything non-ASCII with the correct
+        # unknown codepoint.
+        return message.decode('ascii', 'replace')
 
     # Some of the commands are also shared across devices that use this HID
     # protocol, but not many. Only provide here those that do seep to change
@@ -196,11 +208,11 @@ class FreeStyleHidDevice(hiddevice.HidDevice):
     def set_patient_name(self, name):
         # type: (Text) -> None
         try:
-            name = name.encode('ascii')
+            encoded_name = name.encode('ascii')
         except UnicodeDecodeError:
             raise ValueError('Only ASCII-safe names are tested working')
 
-        result = self._send_text_command(b'$ptname,' + name)
+        result = self._send_text_command(b'$ptname,' + encoded_name)
 
     def get_datetime(self):
         # type: () -> datetime.datetime
-- 
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