- use a different bitwise approach here that doesn't require iterating

through all possible set values

2 files changed, 10 insertions, 1 deletions

diff --git a/lib/sqlalchemy/util/__init__.py b/lib/sqlalchemy/util/__init__.py
index dfed5b90a..7c85ef94b 100644
--- a/lib/sqlalchemy/util/__init__.py
+++ b/lib/sqlalchemy/util/__init__.py
@@ -36,7 +36,7 @@ from .langhelpers import iterate_attributes, class_hierarchy, \
     generic_repr, counter, PluginLoader, hybridproperty, hybridmethod, \
     safe_reraise,\
     get_callable_argspec, only_once, attrsetter, ellipses_string, \
-    warn_limited
+    warn_limited, map_bits
 
 from .deprecations import warn_deprecated, warn_pending_deprecation, \
     deprecated, pending_deprecation, inject_docstring_text
diff --git a/lib/sqlalchemy/util/langhelpers.py b/lib/sqlalchemy/util/langhelpers.py
index 7f57e501a..b708665f9 100644
--- a/lib/sqlalchemy/util/langhelpers.py
+++ b/lib/sqlalchemy/util/langhelpers.py
@@ -92,6 +92,15 @@ def _unique_symbols(used, *bases):
             raise NameError("exhausted namespace for symbol base %s" % base)
 
 
+def map_bits(fn, n):
+    """Call the given function given each nonzero bit from n."""
+
+    while n:
+        b = n & (~n + 1)
+        yield fn(b)
+        n ^= b
+
+
 def decorator(target):
     """A signature-matching decorator factory."""