From 7f273ac6d0f05208b5b228da95205e20c0e8286c Mon Sep 17 00:00:00 2001
From: aycabta <aycabta@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Sat, 20 Apr 2019 08:51:20 +0000
Subject: IRB is improved with Reline and RDoc

Reline is a readline stdlib compatible library. It also supports
multiline input. IRB is improved with Reline and supports multiline.
Besides, supports showing documents when completed.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67645 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 lib/reline/kill_ring.rb | 113 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 113 insertions(+)
 create mode 100644 lib/reline/kill_ring.rb

(limited to 'lib/reline/kill_ring.rb')

diff --git a/lib/reline/kill_ring.rb b/lib/reline/kill_ring.rb
new file mode 100644
index 0000000000..842fd04697
--- /dev/null
+++ b/lib/reline/kill_ring.rb
@@ -0,0 +1,113 @@
+class Reline::KillRing
+  module State
+    FRESH = :fresh
+    CONTINUED = :continued
+    PROCESSED = :processed
+    YANK = :yank
+  end
+
+  RingPoint = Struct.new(:backward, :forward, :str) do
+    def initialize(str)
+      super(nil, nil, str)
+    end
+
+    def ==(other)
+      object_id == other.object_id
+    end
+  end
+
+  class RingBuffer
+    attr_reader :size
+    attr_reader :head
+
+    def initialize(max = 1024)
+      @max = max
+      @size = 0
+      @head = nil # reading head of ring-shaped tape
+    end
+
+    def <<(point)
+      if @size.zero?
+        @head = point
+        @head.backward = @head
+        @head.forward = @head
+        @size = 1
+      elsif @size >= @max
+        tail = @head.forward
+        new_tail = tail.forward
+        @head.forward = point
+        point.backward = @head
+        new_tail.backward = point
+        point.forward = new_tail
+        @head = point
+      else
+        tail = @head.forward
+        @head.forward = point
+        point.backward = @head
+        tail.backward = point
+        point.forward = tail
+        @head = point
+        @size += 1
+      end
+    end
+
+    def empty?
+      @size.zero?
+    end
+  end
+
+  def initialize(max = 1024)
+    @ring = RingBuffer.new(max)
+    @ring_pointer = nil
+    @buffer = nil
+    @state = State::FRESH
+  end
+
+  def append(string, before_p = false)
+    case @state
+    when State::FRESH, State::YANK
+      @ring << RingPoint.new(string)
+      @state = State::CONTINUED
+    when State::CONTINUED, State::PROCESSED
+      if before_p
+        @ring.head.str.prepend(string)
+      else
+        @ring.head.str.concat(string)
+      end
+      @state = State::CONTINUED
+    end
+  end
+
+  def process
+    case @state
+    when State::FRESH
+      # nothing to do
+    when State::CONTINUED
+      @state = State::PROCESSED
+    when State::PROCESSED
+      @state = State::FRESH
+    when State::YANK
+      # nothing to do
+    end
+  end
+
+  def yank
+    unless @ring.empty?
+      @state = State::YANK
+      @ring_pointer = @ring.head
+      @ring_pointer.str
+    else
+      nil
+    end
+  end
+
+  def yank_pop
+    if @state == State::YANK
+      prev_yank = @ring_pointer.str
+      @ring_pointer = @ring_pointer.backward
+      [@ring_pointer.str, prev_yank]
+    else
+      nil
+    end
+  end
+end
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