From 5fc904b099a7a65591465ee815d27c24cb1b0b52 Mon Sep 17 00:00:00 2001
From: Evan Phoenix <evan@fallingsnow.net>
Date: Tue, 6 Dec 2011 13:28:54 -0800
Subject: [PATCH] Use FFI on JRuby to perform fast restart

---
 lib/puma/cli.rb           |  9 +++++++--
 lib/puma/jruby_restart.rb | 22 ++++++++++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 lib/puma/jruby_restart.rb

diff --git a/lib/puma/cli.rb b/lib/puma/cli.rb
index ded837e5..20279c5e 100644
--- a/lib/puma/cli.rb
+++ b/lib/puma/cli.rb
@@ -81,8 +81,13 @@ module Puma
     end
 
     def restart!
-      Dir.chdir @restart_dir
-      Kernel.exec(*@restart_argv)
+      if IS_JRUBY
+        require 'puma/jruby_restart'
+        JRubyRestart.chdir_exec(@restart_dir, Gem.ruby, *@restart_argv)
+      else
+        Dir.chdir @restart_dir
+        Kernel.exec(*@restart_argv)
+      end
     end
 
     # Write +str+ to +@stdout+
diff --git a/lib/puma/jruby_restart.rb b/lib/puma/jruby_restart.rb
new file mode 100644
index 00000000..ddadc82c
--- /dev/null
+++ b/lib/puma/jruby_restart.rb
@@ -0,0 +1,22 @@
+require 'ffi'
+
+module Puma
+  module JRubyRestart
+    extend FFI::Library
+    ffi_lib 'c'
+
+    attach_function :execlp, [:string, :varargs], :int
+    attach_function :chdir, [:string], :int
+
+    def self.chdir_exec(dir, cmd, *argv)
+      chdir(dir)
+      argv.unshift(cmd)
+      argv = ([:string] * argv.size).zip(argv).flatten
+      argv <<:int
+      argv << 0
+      execlp(cmd, *argv)
+      raise SystemCallError.new(FFI.errno)
+    end
+  end
+end
+