From 4b0c1b2c207b1c49732410653774981f754b976c Mon Sep 17 00:00:00 2001
From: Maple Ong <maple.ong@shopify.com>
Date: Tue, 4 May 2021 09:11:38 -0400
Subject: [PATCH] Use new TruffleRuby::ConcurrentMap backend for
 Concurrent::Map

---
 .../collection/map/truffleruby_map_backend.rb      | 14 ++++++++++++++
 lib/concurrent-ruby/concurrent/map.rb              |  9 +++++++--
 2 files changed, 21 insertions(+), 2 deletions(-)
 create mode 100644 lib/concurrent-ruby/concurrent/collection/map/truffleruby_map_backend.rb

diff --git a/lib/concurrent-ruby/concurrent/collection/map/truffleruby_map_backend.rb b/lib/concurrent-ruby/concurrent/collection/map/truffleruby_map_backend.rb
new file mode 100644
index 000000000..68a1b3884
--- /dev/null
+++ b/lib/concurrent-ruby/concurrent/collection/map/truffleruby_map_backend.rb
@@ -0,0 +1,14 @@
+module Concurrent
+
+  # @!visibility private
+  module Collection
+
+    # @!visibility private
+    class TruffleRubyMapBackend < TruffleRuby::ConcurrentMap
+      def initialize(options = nil)
+        options ||= {}
+        super(initial_capacity: options[:initial_capacity], load_factor: options[:load_factor])
+      end
+    end
+  end
+end
diff --git a/lib/concurrent-ruby/concurrent/map.rb b/lib/concurrent-ruby/concurrent/map.rb
index c83ae7808..a2010ad69 100644
--- a/lib/concurrent-ruby/concurrent/map.rb
+++ b/lib/concurrent-ruby/concurrent/map.rb
@@ -16,8 +16,13 @@ module Collection
                           require 'concurrent/collection/map/mri_map_backend'
                           MriMapBackend
                         when Concurrent.on_rbx? || Concurrent.on_truffleruby?
-                          require 'concurrent/collection/map/atomic_reference_map_backend'
-                          AtomicReferenceMapBackend
+                          if defined?(::TruffleRuby::ConcurrentMap)
+                            require 'concurrent/collection/map/truffleruby_map_backend'
+                            TruffleRubyMapBackend
+                          else
+                            require 'concurrent/collection/map/atomic_reference_map_backend'
+                            AtomicReferenceMapBackend
+                          end
                         else
                           warn 'Concurrent::Map: unsupported Ruby engine, using a fully synchronized Concurrent::Map implementation'
                           require 'concurrent/collection/map/synchronized_map_backend'