From c117674cfecf98b158e9ba82c7151fda6cfa422c Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby.or.jp>
Date: Fri, 20 Jun 2025 14:02:39 +0900
Subject: [PATCH] mruby-set: refactor Set#replace

The code is written by Atlassian Rovodev.
---
 mrbgems/mruby-set/mrblib/set.rb | 17 ++++++++++++++
 mrbgems/mruby-set/src/set.c     | 41 +++++++++++++++++++++++++--------
 2 files changed, 48 insertions(+), 10 deletions(-)

diff --git a/mrbgems/mruby-set/mrblib/set.rb b/mrbgems/mruby-set/mrblib/set.rb
index 6509af374..b36669fb0 100644
--- a/mrbgems/mruby-set/mrblib/set.rb
+++ b/mrbgems/mruby-set/mrblib/set.rb
@@ -30,6 +30,23 @@ class Set
     end
   end
 
+  # Replaces the contents of the set with the contents of the given enumerable
+  # object and returns self.
+  #
+  # @param [Enumerable] enum The enumerable object to replace with
+  # @return [Set] self
+  def replace(enum)
+    if enum.is_a?(Set)
+      # Fast path: Call C-implemented function for Set-to-Set replace
+      __set_replace(enum)
+    else
+      # General path: Clear and add each element from the enumerable
+      clear
+      __do_with_enum(enum) { |o| add(o) }
+      self
+    end
+  end
+
   # Deletes every element that appears in the given enumerable object and
   # returns self.
   #
diff --git a/mrbgems/mruby-set/src/set.c b/mrbgems/mruby-set/src/set.c
index cbedbe3a7..097d4cf38 100644
--- a/mrbgems/mruby-set/src/set.c
+++ b/mrbgems/mruby-set/src/set.c
@@ -310,20 +310,41 @@ set_delete_p(mrb_state *mrb, mrb_value self)
 }
 
 /*
- * call-seq:
- *   set.replace(enum) -> self
- *
- * Replaces the contents of the set with the contents of the given enumerable
- * object and returns self.
+ * Core implementation of Set-to-Set replace
+ * This is an internal method that will be called from Ruby
  */
 static mrb_value
-set_replace(mrb_state *mrb, mrb_value self)
+set_core_replace(mrb_state *mrb, mrb_value self)
 {
-  mrb_value enum_obj;
+  mrb_value other;
+  khash_t(set) *self_kh, *other_kh;
 
-  mrb_get_args(mrb, "o", &enum_obj);
+  mrb_get_args(mrb, "o", &other);
+
+  /* Clear the current set */
   set_clear(mrb, self);
-  return mrb_funcall_id(mrb, self, MRB_SYM(merge), 1, enum_obj);
+
+  self_kh = set_get_khash(mrb, self);
+  if (!self_kh) {
+    /* If self is empty after clearing, create a new hash */
+    self_kh = kh_init(set, mrb);
+    set_set_khash(mrb, self, self_kh);
+  }
+
+  /* Add all elements from other set */
+  other_kh = set_get_khash(mrb, other);
+  if (other_kh) {
+    khiter_t k;
+    int ai = mrb_gc_arena_save(mrb);
+    for (k = kh_begin(other_kh); k != kh_end(other_kh); k++) {
+      if (kh_exist(other_kh, k)) {
+        kh_put(set, mrb, self_kh, kh_key(other_kh, k));
+        mrb_gc_arena_restore(mrb, ai);
+      }
+    }
+  }
+
+  return self;
 }
 
 /*
@@ -944,7 +965,7 @@ mrb_mruby_set_gem_init(mrb_state *mrb)
   mrb_define_method(mrb, set, "delete", set_delete, MRB_ARGS_REQ(1));
   mrb_define_method(mrb, set, "delete?", set_delete_p, MRB_ARGS_REQ(1));
 
-  mrb_define_method(mrb, set, "replace", set_replace, MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, set, "__set_replace", set_core_replace, MRB_ARGS_REQ(1));
   mrb_define_method(mrb, set, "__set_merge", set_core_merge, MRB_ARGS_REQ(1));
   mrb_define_method(mrb, set, "__set_subtract", set_core_subtract, MRB_ARGS_REQ(1));