text: ##############################################################################
  # Copyright (c) 2013-2017, Lawrence Livermore National Security, LLC.
  # Produced at the Lawrence Livermore National Laboratory.
  #
  # This file is part of Spack.
  # Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
  # LLNL-CODE-647188
  #
  # For details, see https://github.com/spack/spack
  # Please also see the NOTICE and LICENSE files for our notice and the LGPL.
  #
  # This program is free software; you can redistribute it and/or modify
  # it under the terms of the GNU Lesser General Public License (as
  # published by the Free Software Foundation) version 2.1, February 1999.
  #
  # This program is distributed in the hope that it will be useful, but
  # WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
  # conditions of the GNU Lesser General Public License for more details.
  #
  # You should have received a copy of the GNU Lesser General Public
  # License along with this program; if not, write to the Free Software
  # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  ##############################################################################
  from spack import *
  
  
  class Libevent(AutotoolsPackage):
      """The libevent API provides a mechanism to execute a callback function
         when a specific event occurs on a file descriptor or after a
         timeout has been reached. Furthermore, libevent also support
         callbacks due to signals or regular timeouts.
  
      """
  
      homepage = "http://libevent.org"
      url      = "https://github.com/downloads/libevent/libevent/libevent-2.0.21-stable.tar.gz"
      list_url = "http://libevent.org/old-releases.html"
  
      version('2.0.21', 'b2405cc9ebf264aa47ff615d9de527a2')
      version('2.0.20', '94270cdee32c0cd0aa9f4ee6ede27e8e')
      version('2.0.19', '91111579769f46055b0a438f5cc59572')
      version('2.0.18', 'aa1ce9bc0dee7b8084f6855765f2c86a')
      version('2.0.17', 'dad64aaaaff16b5fbec25160c06fee9a')
      version('2.0.16', '899efcffccdb3d5111419df76e7dc8df')
      version('2.0.15', '2643abe7ba242df15c08b2cc14ec8759')
      version('2.0.14', 'cac0f379da35d3b98f83ac16fcfe1df4')
      version('2.0.13', 'af786b4b3f790c9d3279792edf7867fc')
      version('2.0.12', '42986228baf95e325778ed328a93e070')
  
      # Does not build with OpenSSL 1.1.0
      variant('openssl', default=True,
              description="Build with encryption enabled at the libevent level.")
      depends_on('openssl @:1.0', when='+openssl')
  
      def configure_args(self):
          spec = self.spec
          configure_args = []
          if '+openssl' in spec:
              configure_args.append('--enable-openssl')
          else:
              configure_args.append('--disable-openssl')
  
          return configure_args
  