1 files changed, 31 insertions, 0 deletions
diff --git a/django/utils/datastructures.py b/django/utils/datastructures.py
index 4c278c0d8e..21a72f2d1e 100644
--- a/django/utils/datastructures.py
+++ b/django/utils/datastructures.py
@@ -343,3 +343,34 @@ class FileDict(dict):
             d = dict(self, content='<omitted>')
             return dict.__repr__(d)
         return dict.__repr__(self)
+
+class DictWrapper(dict):
+    """
+    Wraps accesses to a dictionary so that certain values (those starting with
+    the specified prefix) are passed through a function before being returned.
+    The prefix is removed before looking up the real value.
+
+    Used by the SQL construction code to ensure that values are correctly
+    quoted before being used.
+    """
+    def __init__(self, data, func, prefix):
+        super(DictWrapper, self).__init__(data)
+        self.func = func
+        self.prefix = prefix
+
+    def __getitem__(self, key):
+        """
+        Retrieves the real value after stripping the prefix string (if
+        present). If the prefix is present, pass the value through self.func
+        before returning, otherwise return the raw value.
+        """
+        if key.startswith(self.prefix):
+            use_func = True
+            key = key[len(self.prefix):]
+        else:
+            use_func = False
+        value = super(DictWrapper, self).__getitem__(key)
+        if use_func:
+            return self.func(value)
+        return value
+