* ext/psych/lib/psych/stream.rb: adding YAML streaming API for

  infinite length streams.
* ext/psych/lib/psych.rb: refactoring for streaming API
* ext/psych/lib/psych/{handler, stream, tree_builder}.rb: ditto

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@27912 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

2 files changed, 29 insertions, 8 deletions

diff --git a/ext/psych/lib/psych/visitors/visitor.rb b/ext/psych/lib/psych/visitors/visitor.rb
index ccd8c3bd55..3471c43dfa 100644
--- a/ext/psych/lib/psych/visitors/visitor.rb
+++ b/ext/psych/lib/psych/visitors/visitor.rb
@@ -1,6 +1,15 @@
 module Psych
   module Visitors
     class Visitor
+      attr_reader :started, :finished
+      alias :finished? :finished
+      alias :started? :started
+
+      def initialize
+        @started  = false
+        @finished = false
+      end
+
       def accept target
         case target
         when Psych::Nodes::Scalar   then visit_Psych_Nodes_Scalar target
diff --git a/ext/psych/lib/psych/visitors/yaml_tree.rb b/ext/psych/lib/psych/visitors/yaml_tree.rb
index 4adb8d4c66..93ccc5832b 100644
--- a/ext/psych/lib/psych/visitors/yaml_tree.rb
+++ b/ext/psych/lib/psych/visitors/yaml_tree.rb
@@ -10,11 +10,9 @@ module Psych
     class YAMLTree < Psych::Visitors::Visitor
       def initialize options = {}, emitter = Psych::TreeBuilder.new
         super()
-        @emitter = emitter
-        @st      = {}
-        @ss      = ScalarScanner.new
-
-        @emitter.start_stream Psych::Nodes::Stream::UTF8
+        @emitter  = emitter
+        @st       = {}
+        @ss       = ScalarScanner.new
 
         @dispatch_cache = Hash.new do |h,klass|
           method = "visit_#{(klass.name || '').split('::').join('_')}"
@@ -27,15 +25,29 @@ module Psych
         end
       end
 
+      def start encoding = Nodes::Stream::UTF8
+        @emitter.start_stream(encoding).tap do
+          @started = true
+        end
+      end
+
+      def finish
+        @emitter.end_stream.tap do
+          @finished = true
+        end
+      end
+
       def tree
-        @emitter.end_stream
+        finish unless finished?
       end
 
-      def << object
+      def push object
+        start unless started?
         @emitter.start_document [], [], false
         accept object
-        @emitter.end_document true
+        @emitter.end_document
       end
+      alias :<< :push
 
       def accept target
         # return any aliases we find