1 files changed, 45 insertions, 1 deletions
diff --git a/coverage/misc.py b/coverage/misc.py
index 4218536d..4f3748fe 100644
--- a/coverage/misc.py
+++ b/coverage/misc.py
@@ -1,5 +1,10 @@
 """Miscellaneous stuff for Coverage."""
 
+import inspect
+from coverage.backward import md5, sorted       # pylint: disable=W0622
+from coverage.backward import string_class, to_bytes
+
+
 def nice_pair(pair):
     """Make a nice string representation of a pair of numbers.
 
@@ -68,12 +73,51 @@ def bool_or_none(b):
         return bool(b)
 
 
+class Hasher(object):
+    """Hashes Python data into md5."""
+    def __init__(self):
+        self.md5 = md5()
+
+    def update(self, v):
+        """Add `v` to the hash, recursively if needed."""
+        self.md5.update(to_bytes(str(type(v))))
+        if isinstance(v, string_class):
+            self.md5.update(to_bytes(v))
+        elif isinstance(v, (int, float)):
+            self.update(str(v))
+        elif isinstance(v, (tuple, list)):
+            for e in v:
+                self.update(e)
+        elif isinstance(v, dict):
+            keys = v.keys()
+            for k in sorted(keys):
+                self.update(k)
+                self.update(v[k])
+        else:
+            for k in dir(v):
+                if k.startswith('__'):
+                    continue
+                a = getattr(v, k)
+                if inspect.isroutine(a):
+                    continue
+                self.update(k)
+                self.update(a)
+
+    def digest(self):
+        """Retrieve the digest of the hash."""
+        return self.md5.digest()
+
+
 class CoverageException(Exception):
     """An exception specific to Coverage."""
     pass
 
 class NoSource(CoverageException):
-    """Used to indicate we couldn't find the source for a module."""
+    """We couldn't find the source for a module."""
+    pass
+
+class NotPython(CoverageException):
+    """A source file turned out not to be parsable Python."""
     pass
 
 class ExceptionDuringRun(CoverageException):