* io.c (rb_io_external_encoding): new method.

* encoding.c (rb_enc_from_encoding): returns Qnil for NULL
  encoding.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@14397 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,10 @@
+Fri Dec 21 13:10:57 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* io.c (rb_io_external_encoding): new method.
+
+	* encoding.c (rb_enc_from_encoding): returns Qnil for NULL
+	  encoding.
+
 Fri Dec 21 13:09:11 2007  Tanaka Akira  <akr@fsij.org>
 
 	* encoding.c (rb_locale_charmap): return nil if no locale information.

encoding.c

@@ -51,7 +51,7 @@ enc_new(rb_encoding *encoding)
 VALUE
 rb_enc_from_encoding(rb_encoding *encoding)
 {
-    if (!encoding) return 0;
+    if (!encoding) return Qnil;
     if (enc_initialized_p(encoding))
 	return ENC_FROM_ENCODING(encoding);
     return enc_new(encoding);

io.c

@@ -5657,6 +5657,24 @@ rb_io_s_read(int argc, VALUE *argv, VALUE io)
     return rb_ensure(io_s_read, (VALUE)&arg, rb_io_close, arg.io);
 }
 
+
+/*
+ *  call-seq:
+ *     io.externalencoding   => encoding
+ *
+ *  Returns the Encoding object that represents the encoding of the file.
+ */
+
+static VALUE
+rb_io_external_encoding(VALUE io)
+{
+    rb_io_t *fptr;
+
+    GetOpenFile(io, fptr);
+    return rb_enc_from_encoding(fptr->enc);
+}
+
+
 static VALUE
 argf_tell(void)
 {
@@ -6232,6 +6250,8 @@ Init_IO(void)
     rb_define_method(rb_cIO, "pid", rb_io_pid, 0);
     rb_define_method(rb_cIO, "inspect",  rb_io_inspect, 0);
 
+    rb_define_method(rb_cIO, "external_encoding", rb_io_external_encoding, 0);
+
     rb_define_variable("$stdin", &rb_stdin);
     rb_stdin = prep_stdio(stdin, FMODE_READABLE, rb_cIO, "<STDIN>");
     rb_define_hooked_variable("$stdout", &rb_stdout, 0, stdout_setter);