1 files changed, 57 insertions, 0 deletions
diff --git a/gitlint/cache.py b/gitlint/cache.py
new file mode 100644
index 0000000..b7f9e6c
--- /dev/null
+++ b/gitlint/cache.py
@@ -0,0 +1,57 @@
+class PropertyCache(object):
+    """ Mixin class providing a simple cache. """
+
+    def __init__(self):
+        self._cache = {}
+
+    def _try_cache(self, cache_key, cache_populate_func):
+        """ Tries to get a value from the cache identified by `cache_key`.
+            If no value is found in the cache, do a function call to `cache_populate_func` to populate the cache
+            and then return the value from the cache. """
+        if cache_key not in self._cache:
+            cache_populate_func()
+        return self._cache[cache_key]
+
+
+def cache(original_func=None, cachekey=None):
+    """ Cache decorator. Caches function return values.
+        Requires the parent class to extend and initialize PropertyCache.
+        Usage:
+            # Use function name as cache key
+            @cache
+            def myfunc(args):
+                ...
+
+            # Specify cache key
+            @cache(cachekey="foobar")
+            def myfunc(args):
+                ...
+    """
+
+    # Decorators with optional arguments are a bit convoluted in python, especially if you want to support both
+    # Python 2 and 3. See some of the links below for details.
+
+    def cache_decorator(func):
+
+        # If no specific cache key is given, use the function name as cache key
+        if not cache_decorator.cachekey:
+            cache_decorator.cachekey = func.__name__
+
+        def wrapped(*args):
+            def cache_func_result():
+                # Call decorated function and store its result in the cache
+                args[0]._cache[cache_decorator.cachekey] = func(*args)
+            return args[0]._try_cache(cache_decorator.cachekey, cache_func_result)
+
+        return wrapped
+
+    # Passing parent function variables to child functions requires special voodoo in python2:
+    # https://stackoverflow.com/a/14678445/381010
+    cache_decorator.cachekey = cachekey  # attribute on the function
+
+    # To support optional kwargs for decorators, we need to check if a function is passed as first argument or not.
+    # https://stackoverflow.com/a/24617244/381010
+    if original_func:
+        return cache_decorator(original_func)
+
+    return cache_decorator