From f345ac1bdd5f23f95370b2db8fa42085fa13a0b5 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Mon, 17 Oct 2016 09:11:10 +0530
Subject: [PATCH] A function to efficiently check for the common case pure
 ascii strings

---
 kitty/utils.py           |  8 ++++++++
 kitty_tests/datatypes.py | 11 +++++++++++
 2 files changed, 19 insertions(+)

diff --git a/kitty/utils.py b/kitty/utils.py
index c2068cb06..4aaa3fea5 100644
--- a/kitty/utils.py
+++ b/kitty/utils.py
@@ -3,6 +3,7 @@
 # License: GPL v3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>
 
 import os
+import sys
 import termios
 import struct
 import shlex
@@ -82,3 +83,10 @@ def hangup():
         pgrp = os.getpgid(pid)
         os.killpg(pgrp, signal.SIGHUP)
         os.close(create_pty()[0])
+
+base_size = sys.getsizeof('')
+
+
+def is_simple_string(x):
+    ' We use the fact that python stores unicode strings with a 1-byte representation when possible '
+    return sys.getsizeof(x) == base_size + len(x)
diff --git a/kitty_tests/datatypes.py b/kitty_tests/datatypes.py
index 75cf16eda..a90abf3d7 100644
--- a/kitty_tests/datatypes.py
+++ b/kitty_tests/datatypes.py
@@ -2,9 +2,12 @@
 # vim:fileencoding=utf-8
 # License: GPL v3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>
 
+import codecs
+
 from . import BaseTest, set_text_in_line
 
 from kitty.data_types import Line, Cursor
+from kitty.utils import is_simple_string, wcwidth
 
 
 class TestDataTypes(BaseTest):
@@ -72,3 +75,11 @@ class TestDataTypes(BaseTest):
         l.set_decoration(0, q.decoration)
         c = l.cursor_from(0)
         self.ae(c, q)
+
+    def test_utils(self):
+        d = codecs.getincrementaldecoder('utf-8')('strict').decode
+        self.ae(tuple(map(wcwidth, 'a1\0コ')), (1, 1, 0, 2))
+        for s in ('abd38453*(+\n\t\f\r !\0~[]{}()"\':;<>/?ASD`',):
+            self.assertTrue(is_simple_string(s))
+            self.assertTrue(is_simple_string(d(s.encode('utf-8'))))
+        self.assertFalse(is_simple_string('a1コ'))