bpo-30285: Optimize case-insensitive matching and searching (#1482)

of regular expressions.

Doc/whatsnew/3.7.rst

@@ -208,6 +208,10 @@ Optimizations
   using the :func:`os.scandir` function.
   (Contributed by Serhiy Storchaka in :issue:`25996`.)
 
+* Optimized case-insensitive matching and searching of :mod:`regular
+  expressions <re>`.  Searching some patterns can now be up to 20 times faster.
+  (Contributed by Serhiy Storchaka in :issue:`30285`.)
+
 
 Build and C API Changes
 =======================

Lib/test/test_re.py

@@ -891,15 +891,24 @@ class ReTests(unittest.TestCase):
             lo = ord(c.lower())
             self.assertEqual(_sre.ascii_tolower(i), lo)
             self.assertEqual(_sre.unicode_tolower(i), lo)
+            iscased = c in string.ascii_letters
+            self.assertEqual(_sre.ascii_iscased(i), iscased)
+            self.assertEqual(_sre.unicode_iscased(i), iscased)
 
         for i in list(range(128, 0x1000)) + [0x10400, 0x10428]:
             c = chr(i)
             self.assertEqual(_sre.ascii_tolower(i), i)
             if i != 0x0130:
                 self.assertEqual(_sre.unicode_tolower(i), ord(c.lower()))
+            iscased = c != c.lower() or c != c.upper()
+            self.assertFalse(_sre.ascii_iscased(i))
+            self.assertEqual(_sre.unicode_iscased(i),
+                             c != c.lower() or c != c.upper())
 
         self.assertEqual(_sre.ascii_tolower(0x0130), 0x0130)
         self.assertEqual(_sre.unicode_tolower(0x0130), ord('i'))
+        self.assertFalse(_sre.ascii_iscased(0x0130))
+        self.assertTrue(_sre.unicode_iscased(0x0130))
 
     def test_not_literal(self):
         self.assertEqual(re.search(r"\s([^a])", " b").group(1), "b")

Misc/NEWS

@@ -320,6 +320,9 @@ Extension Modules
 Library
 -------
 
+- bpo-30285: Optimized case-insensitive matching and searching of regular
+  expressions.
+
 - bpo-29990: Fix range checking in GB18030 decoder.  Original patch by Ma Lin.
 
 - bpo-29979: rewrite cgi.parse_multipart, reusing the FieldStorage class and

Modules/_sre.c

@@ -273,6 +273,38 @@ _sre_getcodesize_impl(PyObject *module)
     return sizeof(SRE_CODE);
 }
 
+/*[clinic input]
+_sre.ascii_iscased -> bool
+
+    character: int
+    /
+
+[clinic start generated code]*/
+
+static int
+_sre_ascii_iscased_impl(PyObject *module, int character)
+/*[clinic end generated code: output=4f454b630fbd19a2 input=9f0bd952812c7ed3]*/
+{
+    unsigned int ch = (unsigned int)character;
+    return ch != sre_lower(ch) || ch != sre_upper(ch);
+}
+
+/*[clinic input]
+_sre.unicode_iscased -> bool
+
+    character: int
+    /
+
+[clinic start generated code]*/
+
+static int
+_sre_unicode_iscased_impl(PyObject *module, int character)
+/*[clinic end generated code: output=9c5ddee0dc2bc258 input=51e42c3b8dddb78e]*/
+{
+    unsigned int ch = (unsigned int)character;
+    return ch != sre_lower_unicode(ch) || ch != sre_upper_unicode(ch);
+}
+
 /*[clinic input]
 _sre.ascii_tolower -> int
 
@@ -2750,6 +2782,8 @@ static PyTypeObject Scanner_Type = {
 static PyMethodDef _functions[] = {
     _SRE_COMPILE_METHODDEF
     _SRE_GETCODESIZE_METHODDEF
+    _SRE_ASCII_ISCASED_METHODDEF
+    _SRE_UNICODE_ISCASED_METHODDEF
     _SRE_ASCII_TOLOWER_METHODDEF
     _SRE_UNICODE_TOLOWER_METHODDEF
     {NULL, NULL}

Modules/clinic/_sre.c.h

@@ -29,6 +29,68 @@ exit:
     return return_value;
 }
 
+PyDoc_STRVAR(_sre_ascii_iscased__doc__,
+"ascii_iscased($module, character, /)\n"
+"--\n"
+"\n");
+
+#define _SRE_ASCII_ISCASED_METHODDEF    \
+    {"ascii_iscased", (PyCFunction)_sre_ascii_iscased, METH_O, _sre_ascii_iscased__doc__},
+
+static int
+_sre_ascii_iscased_impl(PyObject *module, int character);
+
+static PyObject *
+_sre_ascii_iscased(PyObject *module, PyObject *arg)
+{
+    PyObject *return_value = NULL;
+    int character;
+    int _return_value;
+
+    if (!PyArg_Parse(arg, "i:ascii_iscased", &character)) {
+        goto exit;
+    }
+    _return_value = _sre_ascii_iscased_impl(module, character);
+    if ((_return_value == -1) && PyErr_Occurred()) {
+        goto exit;
+    }
+    return_value = PyBool_FromLong((long)_return_value);
+
+exit:
+    return return_value;
+}
+
+PyDoc_STRVAR(_sre_unicode_iscased__doc__,
+"unicode_iscased($module, character, /)\n"
+"--\n"
+"\n");
+
+#define _SRE_UNICODE_ISCASED_METHODDEF    \
+    {"unicode_iscased", (PyCFunction)_sre_unicode_iscased, METH_O, _sre_unicode_iscased__doc__},
+
+static int
+_sre_unicode_iscased_impl(PyObject *module, int character);
+
+static PyObject *
+_sre_unicode_iscased(PyObject *module, PyObject *arg)
+{
+    PyObject *return_value = NULL;
+    int character;
+    int _return_value;
+
+    if (!PyArg_Parse(arg, "i:unicode_iscased", &character)) {
+        goto exit;
+    }
+    _return_value = _sre_unicode_iscased_impl(module, character);
+    if ((_return_value == -1) && PyErr_Occurred()) {
+        goto exit;
+    }
+    return_value = PyBool_FromLong((long)_return_value);
+
+exit:
+    return return_value;
+}
+
 PyDoc_STRVAR(_sre_ascii_tolower__doc__,
 "ascii_tolower($module, character, /)\n"
 "--\n"
@@ -715,4 +777,4 @@ _sre_SRE_Scanner_search(ScannerObject *self, PyObject *Py_UNUSED(ignored))
 {
     return _sre_SRE_Scanner_search_impl(self);
 }
-/*[clinic end generated code: output=811e67d7f8f5052e input=a9049054013a1b77]*/
+/*[clinic end generated code: output=5fe47c49e475cccb input=a9049054013a1b77]*/