Add trivial CLI tool for calculating identicons

main.py

@@ -0,0 +1,52 @@
+from sys import argv, stdin
+from sys import exit as sysexit
+from select import select
+from hashlib import blake2b
+from io import BytesIO
+
+from identicon import Identicon
+
+
+DIGEST_SIZE = 20
+BUF_SIZE = 4096
+
+
+def main():
+    if not (stream := get_input_stream()):
+        print_usage_and_exit()
+
+    i = Identicon(get_digest(stream))
+    i.calculate()
+    print(i)
+
+
+def get_input_stream():
+    io = None
+    if len(argv) == 2:
+        io = BytesIO(argv[1].encode())
+    elif stdin_has_data():
+        io = stdin.buffer
+    return io
+
+
+def stdin_has_data():
+    return bool(select([stdin], [], [], 0.0)[0])
+
+
+def print_usage_and_exit():
+    print('Usage: identicon [TEXT]')
+    print('Print OpenSSH style randomart identicon for arbitrary data.\n')
+    print('If TEXT is not supplied, data is read from STDIN.')
+    sysexit(1)
+
+
+def get_digest(stream):
+    hasher = blake2b(digest_size=DIGEST_SIZE)
+    while data := stream.read(BUF_SIZE):
+        hasher.update(data)
+    return hasher.digest()
+
+
+
+if __name__ == '__main__':
+    main()