setting the encoding twice is not allowed

3 files changed, 19 insertions, 0 deletions

diff --git a/ext/psych/parser.c b/ext/psych/parser.c
index 41260ab..c8b92a0 100644
--- a/ext/psych/parser.c
+++ b/ext/psych/parser.c
@@ -293,8 +293,15 @@ static VALUE parse(VALUE self, VALUE yaml)
 static VALUE set_external_encoding(VALUE self, VALUE encoding)
 {
     yaml_parser_t * parser;
+    VALUE exception;
 
     Data_Get_Struct(self, yaml_parser_t, parser);
+
+    if(parser->encoding) {
+	exception = rb_const_get_at(mPsych, rb_intern("Exception"));
+	rb_raise(exception, "don't set the encoding twice!");
+    }
+
     yaml_parser_set_encoding(parser, NUM2INT(encoding));
 
     return encoding;
diff --git a/lib/psych.rb b/lib/psych.rb
index 464fae4..a73b892 100644
--- a/lib/psych.rb
+++ b/lib/psych.rb
@@ -94,6 +94,9 @@ module Psych
   # The version of libyaml Psych is using
   LIBYAML_VERSION = Psych.libyaml_version.join '.'
 
+  class Exception < RuntimeError
+  end
+
   ###
   # Load +yaml+ in to a Ruby data structure.  If multiple documents are
   # provided, the object contained in the first document will be returned.
diff --git a/test/psych/test_parser.rb b/test/psych/test_parser.rb
index 8c44833..0b1e92e 100644
--- a/test/psych/test_parser.rb
+++ b/test/psych/test_parser.rb
@@ -26,6 +26,15 @@ module Psych
       @parser = Psych::Parser.new EventCatcher.new
     end
 
+    def test_set_encoding_twice
+      @parser.external_encoding = Psych::Parser::UTF16LE
+
+      e = assert_raises(Psych::Exception) do
+        @parser.external_encoding = Psych::Parser::UTF16LE
+      end
+      assert_equal "don't set the encoding twice!", e.message
+    end
+
     def test_bom
       tadpole = 'おたまじゃくし'