bug#31138: Native json slower than json.el

[Eli Zaretskii]

> Date: Mon, 22 Apr 2019 19:49:28 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: p.stephani2@gmail.com, sebastien@chapu.is, yyoncho@gmail.com,
>       31138@debbugs.gnu.org
> 
> Btw, we could somewhat speed up even the case where we do call
> code_convert_string, by avoiding the call to make_specified_string.

Like this:

diff --git a/src/json.c b/src/json.c
index 16500bc..48aeccf 100644
--- a/src/json.c
+++ b/src/json.c
@@ -225,8 +225,12 @@ json_has_suffix (const char *string, const char *suffix)
 static Lisp_Object
 json_make_string (const char *data, ptrdiff_t size)
 {
-  return code_convert_string (make_specified_string (data, -1, size, false),
-                              Qutf_8_unix, Qt, false, true, true);
+  struct coding_system coding;
+  setup_coding_system (Qutf_8_unix, &coding);
+  coding.mode |= CODING_MODE_LAST_BLOCK;
+  coding.source = data;
+  decode_coding_object (&coding, Qnil, 0, 0, size, size, Qt);
+  return coding.dst_object;
 }
 
 /* Create a multibyte Lisp string from the NUL-terminated UTF-8


How does this fare in your benchmarks?