From a98359faa7927a0443e25a7787546ddf93c06ba9 Mon Sep 17 00:00:00 2001
From: dearblue <dearblue@users.noreply.github.com>
Date: Tue, 1 Jan 2019 13:21:12 +0900
Subject: Add enumerator chain feature (CRuby-2.6 compatible)

  - Enumerator::Chain
  - Enumerable#chain
  - Enumerable#+
---
 mrbgems/mruby-enum-chain/mrbgem.rake     |  6 ++++
 mrbgems/mruby-enum-chain/mrblib/chain.rb | 60 ++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+)
 create mode 100644 mrbgems/mruby-enum-chain/mrbgem.rake
 create mode 100644 mrbgems/mruby-enum-chain/mrblib/chain.rb

diff --git a/mrbgems/mruby-enum-chain/mrbgem.rake b/mrbgems/mruby-enum-chain/mrbgem.rake
new file mode 100644
index 000000000..7294f2644
--- /dev/null
+++ b/mrbgems/mruby-enum-chain/mrbgem.rake
@@ -0,0 +1,6 @@
+MRuby::Gem::Specification.new('mruby-enum-chain') do |spec|
+  spec.license = 'MIT'
+  spec.author  = 'mruby developers'
+  spec.summary = 'Enumerator::Chain class'
+  spec.add_dependency('mruby-enumerator', :core => 'mruby-enumerator')
+end
diff --git a/mrbgems/mruby-enum-chain/mrblib/chain.rb b/mrbgems/mruby-enum-chain/mrblib/chain.rb
new file mode 100644
index 000000000..98515ea14
--- /dev/null
+++ b/mrbgems/mruby-enum-chain/mrblib/chain.rb
@@ -0,0 +1,60 @@
+##
+# chain.rb Enumerator::Chain class
+# See Copyright Notice in mruby.h
+
+module Enumerable
+  def chain(*args)
+    Enumerator::Chain.new(self, *args)
+  end
+
+  def +(other)
+    Enumerator::Chain.new(self, other)
+  end
+end
+
+class Enumerator
+  class Chain
+    include Enumerable
+
+    def initialize(*args)
+      @enums = args
+    end
+
+    def initialize_copy(orig)
+      @enums = orig.__copy_enums
+    end
+
+    def each(&block)
+      return to_enum unless block_given?
+
+      @enums.each { |e| e.each(&block) }
+
+      self
+    end
+
+    def size
+      @enums.reduce(0) do |a, e|
+        return nil unless e.respond_to?(:size)
+        a + e.size
+      end
+    end
+
+    def rewind
+      @enums.reverse_each do |e|
+        e.rewind if e.respond_to?(:rewind)
+      end
+
+      self
+    end
+
+    def inspect
+      "#<#{self.class}: #{@enums.inspect}>"
+    end
+
+    def __copy_enums
+      @enums.each_with_object([]) do |e, a|
+        a << e.clone
+      end
+    end
+  end
+end
-- 
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