Simplify and speed up string-to-multibyte

* src/character.h (str_to_multibyte):
* src/character.c (str_to_multibyte): Change signature and simplify;
the conversion is no longer done in-place.
* src/fns.c (string_to_multibyte): Drop temporary buffer and memcpy;
adapt to new str_to_multibyte signature.
* src/print.c (print_string): Drop memcpy; adapt call to str_to_multibyte.
* test/src/fns-tests.el (fns--string-to-unibyte): Rename to...
(fns--string-to-unibyte-multibyte): ... this and strengthen, so that
the test covers string-to-multibyte reasonably well.

1 files changed, 1 insertions, 2 deletions

diff --git a/src/print.c b/src/print.c
index 4d7e42df1e8..9a31e386f5e 100644
--- a/src/print.c
+++ b/src/print.c
@@ -467,8 +467,7 @@ print_string (Lisp_Object string, Lisp_Object printcharfun)
 	  if (chars < bytes)
 	    {
 	      newstr = make_uninit_multibyte_string (chars, bytes);
-	      memcpy (SDATA (newstr), SDATA (string), chars);
-	      str_to_multibyte (SDATA (newstr), bytes, chars);
+	      str_to_multibyte (SDATA (newstr), SDATA (string), chars, bytes);
 	      string = newstr;
 	    }
 	}