From ec2d900b03dbc511504819caf353310b0a997fa6 Mon Sep 17 00:00:00 2001
From: bnMikheili <39998190+bnMikheili@users.noreply.github.com>
Date: Fri, 12 Jun 2020 00:22:16 +0400
Subject: [PATCH] implement sdbm hash algorithm (#2094)

* implement sdbm hash algorithm

* fix bug: styling

* fix styling for decimal_to_any
---
 conversions/decimal_to_any.py |  8 +++++---
 hashes/sdbm.py                | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 3 deletions(-)
 create mode 100644 hashes/sdbm.py

diff --git a/conversions/decimal_to_any.py b/conversions/decimal_to_any.py
index b91d84b9d..e3fb4e5d3 100644
--- a/conversions/decimal_to_any.py
+++ b/conversions/decimal_to_any.py
@@ -99,6 +99,8 @@ if __name__ == "__main__":
     for base in range(2, 37):
         for num in range(1000):
             assert int(decimal_to_any(num, base), base) == num, (
-                num, base, decimal_to_any(num, base),
-                int(decimal_to_any(num, base), base)
-                )
+                num,
+                base,
+                decimal_to_any(num, base),
+                int(decimal_to_any(num, base), base),
+            )
diff --git a/hashes/sdbm.py b/hashes/sdbm.py
new file mode 100644
index 000000000..f80941306
--- /dev/null
+++ b/hashes/sdbm.py
@@ -0,0 +1,32 @@
+"""
+    This algorithm was created for sdbm (a public-domain reimplementation of ndbm) database library.
+    It was found to do well in scrambling bits, causing better distribution of the keys and fewer splits.
+    It also happens to be a good general hashing function with good distribution.
+    The actual function (pseudo code) is:
+        for i in i..len(str):
+            hash(i) = hash(i - 1) * 65599 + str[i];
+
+    What is included below is the faster version used in gawk. [there is even a faster, duff-device version]
+    The magic constant 65599 was picked out of thin air while experimenting with different constants.
+    It turns out to be a prime.
+    This is one of the algorithms used in berkeley db (see sleepycat) and elsewhere.
+
+    source: http://www.cse.yorku.ca/~oz/hash.html
+"""
+
+
+def sdbm(plain_text: str) -> str:
+    """
+    Function implements sdbm hash, easy to use, great for bits scrambling.
+    iterates over each character in the given string and applies function to each of them.
+
+    >>> sdbm('Algorithms')
+    1462174910723540325254304520539387479031000036
+
+    >>> sdbm('scramble bits')
+    730247649148944819640658295400555317318720608290373040936089
+    """
+    hash = 0
+    for plain_chr in plain_text:
+        hash = ord(plain_chr) + (hash << 6) + (hash << 16) - hash
+    return hash