gh-102511: Speed up os.path.splitroot() with native helpers (GH-118089)

Lib/posixpath.py

@@ -134,33 +134,53 @@ def splitdrive(p):
     return p[:0], p
 
 
-def splitroot(p):
-    """Split a pathname into drive, root and tail. On Posix, drive is always
-    empty; the root may be empty, a single slash, or two slashes. The tail
-    contains anything after the root. For example:
+try:
+    from posix import _path_splitroot_ex
+except ImportError:
+    def splitroot(p):
+        """Split a pathname into drive, root and tail. On Posix, drive is always
+        empty; the root may be empty, a single slash, or two slashes. The tail
+        contains anything after the root. For example:
 
-        splitroot('foo/bar') == ('', '', 'foo/bar')
-        splitroot('/foo/bar') == ('', '/', 'foo/bar')
-        splitroot('//foo/bar') == ('', '//', 'foo/bar')
-        splitroot('///foo/bar') == ('', '/', '//foo/bar')
-    """
-    p = os.fspath(p)
-    if isinstance(p, bytes):
-        sep = b'/'
-        empty = b''
-    else:
-        sep = '/'
-        empty = ''
-    if p[:1] != sep:
-        # Relative path, e.g.: 'foo'
-        return empty, empty, p
-    elif p[1:2] != sep or p[2:3] == sep:
-        # Absolute path, e.g.: '/foo', '///foo', '////foo', etc.
-        return empty, sep, p[1:]
-    else:
-        # Precisely two leading slashes, e.g.: '//foo'. Implementation defined per POSIX, see
-        # https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13
-        return empty, p[:2], p[2:]
+            splitroot('foo/bar') == ('', '', 'foo/bar')
+            splitroot('/foo/bar') == ('', '/', 'foo/bar')
+            splitroot('//foo/bar') == ('', '//', 'foo/bar')
+            splitroot('///foo/bar') == ('', '/', '//foo/bar')
+        """
+        p = os.fspath(p)
+        if isinstance(p, bytes):
+            sep = b'/'
+            empty = b''
+        else:
+            sep = '/'
+            empty = ''
+        if p[:1] != sep:
+            # Relative path, e.g.: 'foo'
+            return empty, empty, p
+        elif p[1:2] != sep or p[2:3] == sep:
+            # Absolute path, e.g.: '/foo', '///foo', '////foo', etc.
+            return empty, sep, p[1:]
+        else:
+            # Precisely two leading slashes, e.g.: '//foo'. Implementation defined per POSIX, see
+            # https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13
+            return empty, p[:2], p[2:]
+else:
+    def splitroot(p):
+        """Split a pathname into drive, root and tail. On Posix, drive is always
+        empty; the root may be empty, a single slash, or two slashes. The tail
+        contains anything after the root. For example:
+
+            splitroot('foo/bar') == ('', '', 'foo/bar')
+            splitroot('/foo/bar') == ('', '/', 'foo/bar')
+            splitroot('//foo/bar') == ('', '//', 'foo/bar')
+            splitroot('///foo/bar') == ('', '/', '//foo/bar')
+        """
+        p = os.fspath(p)
+        if isinstance(p, bytes):
+            # Optimisation: the drive is always empty
+            _, root, tail = _path_splitroot_ex(os.fsdecode(p))
+            return b'', os.fsencode(root), os.fsencode(tail)
+        return _path_splitroot_ex(p)
 
 
 # Return the tail (basename) part of a path, same as split(path)[1].