* transcode.c (econv_s_stateless_encoding): new method.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@19156 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,7 @@
+Sat Sep  6 02:23:18 2008  Tanaka Akira  <akr@fsij.org>
+
+	* transcode.c (econv_s_stateless_encoding): new method.
+
 Sat Sep  6 02:01:59 2008  Tanaka Akira  <akr@fsij.org>
 
 	* transcode.c (enc_arg): extracted from str_transcode_enc_args.

test/ruby/test_econv.rb

@@ -27,6 +27,15 @@ class TestEncodingConverter < Test::Unit::TestCase
                  ec.primitive_errinfo)
   end
 
+  def test_s_stateless_encoding
+    assert_equal(Encoding::EUC_JP, Encoding::Converter.stateless_encoding("ISO-2022-JP"))
+    assert_equal(Encoding::EUC_JP, Encoding::Converter.stateless_encoding(Encoding::ISO_2022_JP))
+    assert_nil(Encoding::Converter.stateless_encoding("EUC-JP"))
+    assert_nil(Encoding::Converter.stateless_encoding("UTF-8"))
+    assert_nil(Encoding::Converter.stateless_encoding("UTF-16BE"))
+    assert_nil(Encoding::Converter.stateless_encoding(Encoding::UTF_8))
+  end
+
   def test_new
     assert_kind_of(Encoding::Converter, Encoding::Converter.new("UTF-8", "EUC-JP"))
     assert_kind_of(Encoding::Converter, Encoding::Converter.new(Encoding::UTF_8, Encoding::EUC_JP))

transcode.c

@@ -2334,6 +2334,47 @@ make_dummy_encoding(const char *name)
     return enc;
 }
 
+/*
+ * call-seq:
+ *   Encoding::Converter.stateless_encoding(string) => encoding or nil
+ *   Encoding::Converter.stateless_encoding(encoding) => encoding or nil
+ *
+ * returns the corresponding stateless encoding.
+ *
+ * It returns nil if the argument is stateless encoding.
+ *
+ * "corresponding stateless encoding" is a stateless encoding which
+ * can represent all characters in the statefull encoding.
+ *
+ * So, no conversion undefined error occur from the stateful encoding to the stateless encoding.
+ *
+ * Currently, EUC-JP is the corresponding stateless encoding of ISO-2022-JP.
+ *
+ *   Encoding::Converter.stateless_encoding("ISO-2022-JP") #=> #<Encoding:EUC-JP>
+ *
+ * (This may be changed in future because EUC-JP cannot distinguish JIS X 0208 1978 and 1983.)
+ */
+static VALUE
+econv_s_stateless_encoding(VALUE klass, VALUE arg)
+{
+    const char *stateful_name, *stateless_name;
+    rb_encoding *stateful_enc, *stateless_enc;
+
+    enc_arg(arg, &stateful_name, &stateful_enc);
+
+    stateless_name = rb_econv_stateless_encoding(stateful_name);
+
+    if (stateless_name == NULL)
+        return Qnil;
+
+    stateless_enc = rb_enc_find(stateless_name);
+
+    if (!stateless_enc)
+        stateless_enc = make_dummy_encoding(stateless_name);
+
+    return rb_enc_from_encoding(stateless_enc);
+}
+
 /*
  * call-seq:
  *   Encoding::Converter.new(source_encoding, destination_encoding)
@@ -3346,6 +3387,7 @@ Init_transcode(void)
 
     rb_cEncodingConverter = rb_define_class_under(rb_cEncoding, "Converter", rb_cData);
     rb_define_alloc_func(rb_cEncodingConverter, econv_s_allocate);
+    rb_define_singleton_method(rb_cEncodingConverter, "stateless_encoding", econv_s_stateless_encoding, 1);
     rb_define_method(rb_cEncodingConverter, "initialize", econv_init, -1);
     rb_define_method(rb_cEncodingConverter, "inspect", econv_inspect, 0);
     rb_define_method(rb_cEncodingConverter, "source_encoding", econv_source_encoding, 0);