feat(hashes): add Jenkins-One-At-A-Time function

hashes/joaat.py

@@ -0,0 +1,39 @@
+"""
+The Bob Jenkins hash is a fast, non-cryptographic hash function
+designed for general-purpose use, such as hash table lookups.
+
+source: https://en.wikipedia.org/wiki/Jenkins_hash_function
+"""
+
+
+def joaat(key: str) -> int:
+    """
+    Calculate Jenkins One-at-a-Time hash for a key.
+
+    >>> joaat("apple")
+    2297466611
+    >>> joaat("test")
+    1064684737
+    >>> joaat("")
+    0
+    """
+    hash_value = 0
+    mask = 0xFFFFFFFF
+    key_bytes = key.encode("utf-8")
+
+    for byte in key_bytes:
+        hash_value = (hash_value + byte) & mask
+        hash_value = (hash_value + (hash_value << 10)) & mask
+        hash_value = (hash_value ^ (hash_value >> 6)) & mask
+
+    hash_value = (hash_value + (hash_value << 3)) & mask
+    hash_value = (hash_value ^ (hash_value >> 11)) & mask
+    hash_value = (hash_value + (hash_value << 15)) & mask
+
+    return hash_value
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()