* ext/psych/lib: moved external library dependent files from lib.

  [ruby-core:29129]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@27112 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 44 insertions, 0 deletions

diff --git a/ext/psych/lib/psych/parser.rb b/ext/psych/lib/psych/parser.rb
new file mode 100644
index 0000000000..0e38a4ae7d
--- /dev/null
+++ b/ext/psych/lib/psych/parser.rb
@@ -0,0 +1,44 @@
+module Psych
+  ###
+  # YAML event parser class.  This class parses a YAML document and calls
+  # events on the handler that is passed to the constructor.  The events can
+  # be used for things such as constructing a YAML AST or deserializing YAML
+  # documents.  It can even be fed back to Psych::Emitter to emit the same
+  # document that was parsed.
+  #
+  # See Psych::Handler for documentation on the events that Psych::Parser emits.
+  #
+  # Here is an example that prints out ever scalar found in a YAML document:
+  #
+  #   # Handler for detecting scalar values
+  #   class ScalarHandler < Psych::Handler
+  #     def scalar value, anchor, tag, plain, quoted, style
+  #       puts value
+  #     end
+  #   end
+  #
+  #   parser = Psych::Parser.new(ScalarHandler.new)
+  #   parser.parse(yaml_document)
+  #
+  # Here is an example that feeds the parser back in to Psych::Emitter.  The
+  # YAML document is read from STDIN and written back out to STDERR:
+  #
+  #   parser = Psych::Parser.new(Psych::Emitter.new($stderr))
+  #   parser.parse($stdin)
+  #
+  # Psych uses Psych::Parser in combination with Psych::TreeBuilder to
+  # construct an AST of the parsed YAML document.
+
+  class Parser
+    # The handler on which events will be called
+    attr_accessor :handler
+
+    ###
+    # Creates a new Psych::Parser instance with +handler+.  YAML events will
+    # be called on +handler+.  See Psych::Parser for more details.
+
+    def initialize handler = Handler.new
+      @handler = handler
+    end
+  end
+end