From 169654ad9b205d296e7e85dc46ad884179990cd3 Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby.or.jp>
Date: Fri, 20 Jun 2025 13:49:07 +0900
Subject: [PATCH] mruby-set: refactor Set#subtract

The code is written by Atlassian Rovodev.
---
 mrbgems/mruby-set/mrblib/set.rb | 18 +++++++++---
 mrbgems/mruby-set/src/set.c     | 52 ++++++++++++++-------------------
 2 files changed, 36 insertions(+), 34 deletions(-)

diff --git a/mrbgems/mruby-set/mrblib/set.rb b/mrbgems/mruby-set/mrblib/set.rb
index 31d4c12dc..16e35428b 100644
--- a/mrbgems/mruby-set/mrblib/set.rb
+++ b/mrbgems/mruby-set/mrblib/set.rb
@@ -20,10 +20,20 @@ class Set
     self
   end
 
-  # Helper method for subtract with enumerable
-  def __subtract_enum(enum)
-    __do_with_enum(enum) { |o| delete(o) }
-    self
+  # Deletes every element that appears in the given enumerable object and
+  # returns self.
+  #
+  # @param [Enumerable] enum The enumerable object containing elements to remove
+  # @return [Set] self
+  def subtract(enum)
+    if enum.is_a?(Set)
+      # Fast path: Call C-implemented function for Set-to-Set subtraction
+      __set_subtract(enum)
+    else
+      # General path: Remove each element from the enumerable
+      __do_with_enum(enum) { |o| delete(o) }
+      self
+    end
   end
 
   # Returns a new set containing elements common to the set and the given
diff --git a/mrbgems/mruby-set/src/set.c b/mrbgems/mruby-set/src/set.c
index b148f58a2..ad08139dd 100644
--- a/mrbgems/mruby-set/src/set.c
+++ b/mrbgems/mruby-set/src/set.c
@@ -368,43 +368,35 @@ set_merge(mrb_state *mrb, mrb_value self)
 }
 
 /*
- * call-seq:
- *   set.subtract(enum) -> self
- *
- * Deletes every element that appears in the given enumerable object and
- * returns self.
+ * Core implementation of Set-to-Set subtraction (mutating version)
+ * This is an internal method that will be called from Ruby
  */
 static mrb_value
-set_subtract(mrb_state *mrb, mrb_value self)
+set_core_subtract(mrb_state *mrb, mrb_value self)
 {
-  mrb_value enum_obj;
-  khash_t(set) *kh;
+  mrb_value other;
+  khash_t(set) *self_kh, *other_kh;
 
-  mrb_get_args(mrb, "o", &enum_obj);
-  kh = set_get_khash(mrb, self);
-  if (!kh) return self;
+  mrb_get_args(mrb, "o", &other);
 
-  if (mrb_obj_class(mrb, enum_obj) == mrb_obj_class(mrb, self)) {
-    /* Optimized path for Set objects */
-    khash_t(set) *other_kh = set_get_khash(mrb, enum_obj);
-    if (other_kh) {
-      khiter_t k, del_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)) {
-          del_k = kh_get(set, mrb, kh, kh_key(other_kh, k));
-          if (del_k != kh_end(kh)) {
-            kh_del(set, mrb, kh, del_k);
-          }
-          mrb_gc_arena_restore(mrb, ai);
-        }
+  self_kh = set_get_khash(mrb, self);
+  if (!self_kh) return self;
+
+  other_kh = set_get_khash(mrb, other);
+  if (!other_kh) return self;
+
+  /* Remove all elements that are in other set */
+  khiter_t k, del_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)) {
+      del_k = kh_get(set, mrb, self_kh, kh_key(other_kh, k));
+      if (del_k != kh_end(self_kh)) {
+        kh_del(set, mrb, self_kh, del_k);
       }
+      mrb_gc_arena_restore(mrb, ai);
     }
   }
-  else {
-    /* General enumerable path - delegate to Ruby */
-    return mrb_funcall_with_block(mrb, self, MRB_SYM(__subtract_enum), 1, &enum_obj, mrb_nil_value());
-  }
 
   return self;
 }
@@ -962,7 +954,7 @@ mrb_mruby_set_gem_init(mrb_state *mrb)
 
   mrb_define_method(mrb, set, "replace", set_replace, MRB_ARGS_REQ(1));
   mrb_define_method(mrb, set, "merge", set_merge, MRB_ARGS_REQ(1));
-  mrb_define_method(mrb, set, "subtract", set_subtract, MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, set, "__set_subtract", set_core_subtract, MRB_ARGS_REQ(1));
 
   mrb_define_method(mrb, set, "__set_union", set_core_union, MRB_ARGS_REQ(1));