cache key generation using params, path, color, and style

1 files changed, 37 insertions, 0 deletions

diff --git a/lib/utils/cache.py b/lib/utils/cache.py
index 46d8ec59..767978ca 100644
--- a/lib/utils/cache.py
+++ b/lib/utils/cache.py
@@ -4,6 +4,8 @@
 # Licensed under the GNU GPL version 3.0 or later.  See the file LICENSE for details.
 import os
 import atexit
+import hashlib
+import pickle
 
 import appdirs
 import diskcache
@@ -31,3 +33,38 @@ def get_stitch_plan_cache():
         atexit.register(__stitch_plan_cache.close)
 
     return __stitch_plan_cache
+
+
+class CacheKeyGenerator(object):
+    """Generate cache keys given arbitrary data.
+
+    Given arbitrary data, generate short cache key that is extremely likely
+    to be unique.
+
+    Use example:
+
+        >>> generator = CacheKeyGenerator()
+        >>> generator.update(b'12345')
+        >>> generator.update([1, 2, 3, {4, 5, 6}])
+        >>> generator.get_cache_key()
+    """
+
+    def __init__(self):
+        # SHA1 is chosen for speed.  We don't need cryptography-grade hashing
+        # for this use case.
+        self._hasher = hashlib.sha1()
+
+    def update(self, data):
+        """Provide data to be hashed into a cache key.
+
+        Arguments:
+            data -- a bytes object or any object that can be pickled
+        """
+
+        if not isinstance(data, bytes):
+            data = pickle.dumps(data)
+
+        self._hasher.update(data)
+
+    def get_cache_key(self):
+        return self._hasher.hexdigest()