From 488b8e58bc90b29655bd9f85611abcebc58bb11f Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Wed, 6 May 2026 20:08:02 +0900
Subject: pathname: Move root? to pathname.c

---
 file.c              |  5 +++++
 internal/file.h     |  1 +
 pathname.c          | 19 +++++++++++++++++++
 pathname_builtin.rb | 11 -----------
 4 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/file.c b/file.c
index db29642ac2..b045e8e899 100644
--- a/file.c
+++ b/file.c
@@ -3767,6 +3767,11 @@ skipprefixroot(const char *path, const char *end, rb_encoding *enc)
 #endif
 }
 
+char *
+rb_enc_path_skip_prefix_root(const char *path, const char *end, rb_encoding *enc)
+{
+    return skipprefixroot(path, end, enc);
+}
 
 static char *
 enc_path_last_separator(const char *path, const char *end, bool mb_enc, rb_encoding *enc)
diff --git a/internal/file.h b/internal/file.h
index 29e9cdf4b9..1aa4c67043 100644
--- a/internal/file.h
+++ b/internal/file.h
@@ -25,6 +25,7 @@ VALUE rb_get_path_check_to_string(VALUE);
 VALUE rb_get_path_check_convert(VALUE);
 VALUE rb_get_path_check_no_convert(VALUE);
 int ruby_is_fd_loadable(int fd);
+char *rb_enc_path_skip_prefix_root(const char *path, const char *end, rb_encoding *enc);
 
 RUBY_SYMBOL_EXPORT_BEGIN
 /* file.c (export) */
diff --git a/pathname.c b/pathname.c
index 87382dd804..e8959bb976 100644
--- a/pathname.c
+++ b/pathname.c
@@ -111,6 +111,24 @@ path_sub(int argc, VALUE *argv, VALUE self)
     return rb_class_new_instance(1, &str, rb_obj_class(self));
 }
 
+/*
+ * Predicate method for root directories.  Returns +true+ if the
+ * pathname consists of consecutive slashes.
+ *
+ * It doesn't access the filesystem.  So it may return +false+ for some
+ * pathnames which points to roots such as <tt>/usr/..</tt>.
+ */
+static VALUE
+path_root_p(VALUE self)
+{
+    VALUE path = get_strpath(self);
+    if (RSTRING_LEN(path) == 0) return Qfalse;
+    const char *ptr = RSTRING_PTR(path), *end = RSTRING_END(path);
+    rb_encoding *enc = rb_enc_get(path);
+    const char *base = rb_enc_path_skip_prefix_root(ptr, end, enc);
+    return RBOOL(base == end);
+}
+
 /*
  * call-seq:
  *   absolute? -> true or false
@@ -159,6 +177,7 @@ InitVM_pathname(void)
     rb_cPathname = rb_define_class("Pathname", rb_cObject);
     rb_define_method(rb_cPathname, "<=>", path_cmp, 1);
     rb_define_method(rb_cPathname, "sub", path_sub, -1);
+    rb_define_method(rb_cPathname, "root?", path_root_p, 0);
     rb_define_method(rb_cPathname, "absolute?", path_absolute_p, 0);
 
     rb_provide("pathname.so");
diff --git a/pathname_builtin.rb b/pathname_builtin.rb
index b9cba0260f..cab20678db 100644
--- a/pathname_builtin.rb
+++ b/pathname_builtin.rb
@@ -621,17 +621,6 @@ class Pathname
     end
   end
 
-  #
-  # Predicate method for root directories.  Returns +true+ if the
-  # pathname consists of consecutive slashes.
-  #
-  # It doesn't access the filesystem.  So it may return +false+ for some
-  # pathnames which points to roots such as <tt>/usr/..</tt>.
-  #
-  def root?
-    chop_basename(@path) == nil && SEPARATOR_PAT.match?(@path)
-  end
-
   # The opposite of Pathname#absolute?
   #
   # It returns +false+ if the pathname begins with a slash.
-- 
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