rewrite parse_digest_response for escapes

The previous version did not handle escapes at all. Now I added two test
cases for escaping and rewrote the function to meet all test cases.

1 files changed, 42 insertions, 20 deletions

diff --git a/wsgitools/digest.py b/wsgitools/digest.py
index 53b7dea..964fa0a 100644
--- a/wsgitools/digest.py
+++ b/wsgitools/digest.py
@@ -60,28 +60,50 @@ def parse_digest_response(data, ret=None):
     ... except ValueError:
     ...     print("ValueError")
     ValueError
+    >>> # backslashes: doc string, eval => two backslashes
+    >>> parse_digest_response('backslash="\\\\\\\\"')
+    {'backslash': '\\\\'}
+    >>> parse_digest_response('foo="quo\\\\"te"')
+    {'foo': 'quo"te'}
     """
     assert isinstance(data, str)
-    if ret is None:
-        ret = {}
-    data = data.strip()
-    key, rest = data.split('=', 1) # raises ValueError
-    if rest.startswith('"'):
-        rest = rest[1:]
-        value, rest = rest.split('"', 1) # raises ValueError
-        if not rest:
-            ret[key] = value
-            return ret
-        if rest[0] != ',':
-            raise ValueError("invalid digest response")
-        rest = rest[1:]
-    else:
-        if ',' not in rest:
-            ret[key] = rest
-            return ret
-        value, rest = rest.split(',' , 1)
-    ret[key] = value
-    return parse_digest_response(rest, ret)
+    result = dict()
+    while True:
+        data = data.strip()
+        key, data = data.split('=', 1) # raises ValueError
+        if data.startswith('"'):
+            data = data[1:]
+            value = ""
+            while True:
+                part, data = data.split('"', 1) # raises ValueError
+                # how many consecutive backslashes did we see?
+                escape = -1 # the first iteration does not indicate a backslash
+                for part in part.split('\\'):
+                    escape += 1 # backslash before part
+                    if escape > 2:
+                        value += "\\"
+                        escape -= 2
+                    if part:
+                        escape = 0
+                        value += part
+                if escape == 2:
+                    value += "\\"
+                elif escape == 1:
+                    value += '"'
+                    continue
+                break
+            result[key] = value
+            if not data:
+                return result
+            if data[0] != ",":
+                raise ValueError("invalid digest response")
+            data = data[1:]
+        else:
+            if ',' not in data:
+                result[key] = data
+                return result
+            value, data = data.split(',', 1)
+            result[key] = value
 
 class AuthenticationRequired(Exception):
     """