update to use frozen string literal

Author: Stephen von Takach

.gitignore

@@ -18,3 +18,5 @@ _yardoc
 doc/
 
 Gemfile.lock
+
+.DS_Store

lib/ruby-tls.rb

@@ -1,5 +1,6 @@
+# frozen_string_literal: true
 
-require "ruby-tls/ssl"    # Loads OpenSSL using FFI
+require 'ruby-tls/ssl'    # Loads OpenSSL using FFI
 
 module RubyTls
 end

lib/ruby-tls/ssl.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'ffi'
 require 'ffi-compiler/loader'
 require 'thread'
@@ -289,8 +291,8 @@ def self.SSL_CTX_sess_set_cache_size(ssl_ctx, op)
 
         class Context
             # Based on information from https://raymii.org/s/tutorials/Strong_SSL_Security_On_nginx.html
-            CIPHERS = 'EECDH+AESGCM:EDH+AESGCM:ECDHE-RSA-AES128-GCM-SHA256:AES256+EECDH:DHE-RSA-AES128-GCM-SHA256:AES256+EDH:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES256-GCM-SHA384:AES128-GCM-SHA256:AES256-SHA256:AES128-SHA256:AES256-SHA:AES128-SHA:DES-CBC3-SHA:HIGH:!aNULL:!eNULL:!EXPORT:!DES:!MD5:!PSK:!RC4'.freeze
-            SESSION = 'ruby-tls'.freeze
+            CIPHERS = 'EECDH+AESGCM:EDH+AESGCM:ECDHE-RSA-AES128-GCM-SHA256:AES256+EECDH:DHE-RSA-AES128-GCM-SHA256:AES256+EDH:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES256-GCM-SHA384:AES128-GCM-SHA256:AES256-SHA256:AES128-SHA256:AES256-SHA:AES128-SHA:DES-CBC3-SHA:HIGH:!aNULL:!eNULL:!EXPORT:!DES:!MD5:!PSK:!RC4'
+            SESSION = 'ruby-tls'
 
 
             ALPN_LOOKUP = ThreadSafe::Cache.new
@@ -368,7 +370,7 @@ def cleanup
 
 
             def self.build_alpn_string(protos)
-                protocols = ''.force_encoding('ASCII-8BIT')
+                protocols = String.new.force_encoding('ASCII-8BIT')
                 protos.each do |prot|
                     protocol = prot.to_s
                     protocols << protocol.length
@@ -677,7 +679,7 @@ def put_plain_text(data)
             end
 
 
-            CIPHER_DISPATCH_FAILED = 'Cipher text dispatch failed'.freeze
+            CIPHER_DISPATCH_FAILED = 'Cipher text dispatch failed'
             def dispatch_cipher_text
                 begin
                     did_work = false

lib/ruby-tls/version.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module RubyTls
-    VERSION = "2.1.2"
+    VERSION = '2.2.0'
 end

ruby-tls.gemspec

@@ -1,4 +1,6 @@
+# frozen_string_literal: true
 # -*- encoding: utf-8 -*-
+
 $:.push File.expand_path("../lib", __FILE__)
 require "ruby-tls/version"
 
@@ -11,15 +13,15 @@ Gem::Specification.new do |s|
     s.homepage    = "https://github.com/cotag/ruby-tls"
     s.summary     = "Abstract TLS for Ruby"
     s.description = <<-EOF
-        Allows transport layers outside Ruby TCP be secured.
+        Allows transport layers outside Ruby TCP to be secured.
     EOF
 
 
-    s.add_dependency 'ffi-compiler', '>= 0.0.2'
-    s.add_dependency 'thread_safe'
+    s.add_dependency 'ffi-compiler',    '>= 1.0', '< 2.0'
+    s.add_dependency 'concurrent-ruby', '~> 1.0'
 
-    s.add_development_dependency 'rspec'
-    s.add_development_dependency 'yard'
+    s.add_development_dependency 'rspec', '~> 3.5'
+    s.add_development_dependency 'yard',  '~> 0.9'
 
 
     s.files = Dir["{lib}/**/*"] + %w(ruby-tls.gemspec README.md)