added tests for sha256

* added tests and docstring for sha256

Author: pvprajwal

docs/source/pydatastructs/strings/algorithms.rst

@@ -1,4 +1,6 @@
 Algorithms
 ==========
 
-.. autofunction:: pydatastructs.find
+.. autofunction:: pydatastructs.find
+
+.. autoclass:: pydatastructs.Crypto

pydatastructs/strings/__init__.py

@@ -12,7 +12,8 @@
 __all__.extend(trie.__all__)
 
 from .algorithms import (
-    find
+    find,
+    Crypto
 )
 
 __all__.extend(algorithms.__all__)

pydatastructs/strings/algorithms.py

@@ -5,7 +5,7 @@
 import struct
 
 __all__ = [
-    'find'
+    'find',
     'Crypto'
 ]
 
@@ -249,12 +249,44 @@ def _z_function(text, query):
     return positions
 
 class Crypto:
+
     @staticmethod
     def _right_rotate(value, shift, size=32):
         return (value >> shift) | (value << (size - shift)) & (2**size - 1)
 
     @staticmethod
-    def sha256_encrypt(text):
+    def sha256_encrypt(text) -> str:
+        """
+        Finds the SHA256 ciphertext of the given plaintext
+
+        Parameters
+        ==========
+
+        text: str
+            The string on which SHA256 encryption is to be performed.
+
+        Returns
+        =======
+
+        text: str
+            The SHA256 encoded ciphertext
+
+        Examples
+        ========
+
+        >>> from pydatastructs.strings.algorithms import Crypto
+        >>> text = "PyDataStructs"
+        >>> ciphertext = Crypto.sha256_encrypt(text)
+        >>> print(ciphertext)
+        "777a305fe4f1cfc7ce270891ec50651331e2ab6d09312b906740a5ea413bd057"
+
+        References
+        ==========
+
+        .. [1] https://en.wikipedia.org/wiki/SHA-2
+        .. [2] https://github.com/TheAlgorithms/Python/blob/master/hashes/sha256.py
+
+        """
         # SHA-256 Constants
         k = [
             0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,

pydatastructs/strings/tests/test_algorithms.py

@@ -1,4 +1,4 @@
-from pydatastructs.strings import find
+from pydatastructs.strings import find, Crypto
 
 import random, string
 
@@ -74,3 +74,26 @@ def gen_random_string(length):
         if text != query:
             positions = find(text, query, algorithm)
             assert positions.size == 0
+
+def _test_sha256_encrypt():
+    
+    test_cases = [
+        "HelloWorld",
+        "1234567890",
+        "abcdefABCDEF",
+        "",
+        "The quick brown fox jumps over the lazy dog",
+        "Pydatastructs"
+    ]
+    
+    expected_hashes = [
+        "872e4e50ce9990d8b041330c47c9ddd11bec6b503ae9386a99da8584e9bb12c4",
+        "c775e7b757ede630cd0aa1113bd102661ab38829ca52a6422ab782862f268646",
+        "4a098074bfa74c04454ebbc7d286d085c420934c27ab11e9c00cc53247d9959e",
+        "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+        "d7a8fbb307d7809469ca9abcb0082e4f8d5651e46d3cdb762d02d0bf37c9e592",
+        "1b5b22944c188c3e90d126ebd27e10d7497fbf5924f23c05775fa2dd9e1d8c86"
+    ]
+    
+    for text, expected in zip(test_cases, expected_hashes):
+        assert Crypto.sha256_encrypt(text) == expected