update

Task/SHA-256/00DESCRIPTION

@@ -1,3 +1,3 @@
-'''SHA-256''' is the recommended stronger alternative to [[SHA-1]].
+'''[[wp:SHA-256|SHA-256]]''' is the recommended stronger alternative to [[SHA-1]].
 
 Either by using a dedicated library or implementing the algorithm in your language, show that the SHA-256 digest of the string "Rosetta code" is: 764faf5c61ac315f1497f9dfa542713965b785e5cc2f707d6468d7d1124cdfcf

Task/SHA-256/Python/sha-256.py

@@ -1,4 +1,4 @@
 >>> import hashlib
->>> hashlib.sha256( "Rosetta code" ).hexdigest()
+>>> hashlib.sha256( "Rosetta code".encode() ).hexdigest()
 '764faf5c61ac315f1497f9dfa542713965b785e5cc2f707d6468d7d1124cdfcf'
 >>>

Task/SHA-256/Racket/sha-256.rkt

@@ -0,0 +1,20 @@
+#lang racket/base
+
+;; define a quick SH256 FFI interface, similar to the Racket's default
+;; SHA1 interface
+(require ffi/unsafe ffi/unsafe/define openssl/libcrypto
+         (only-in openssl/sha1 bytes->hex-string))
+(define-ffi-definer defcrypto libcrypto)
+(defcrypto SHA256_Init   (_fun _pointer -> _int))
+(defcrypto SHA256_Update (_fun _pointer _pointer _long -> _int))
+(defcrypto SHA256_Final  (_fun _pointer _pointer -> _int))
+(define (sha256 bytes)
+  (define ctx (malloc 128))
+  (define result (make-bytes 32))
+  (SHA256_Init ctx)
+  (SHA256_Update ctx bytes (bytes-length bytes))
+  (SHA256_Final result ctx)
+  (bytes->hex-string result))
+
+;; use the defined wrapper to solve the task
+(displayln (sha256 #"Rosetta code"))