compile.c: fix performance of strconcat

* compile.c (compile_dstr_fragments): fix performance by omitting
  the first empty string only for keeping literal encoding if
  other literals are too.  [ruby-core:70930] [Bug #11556]
* string.c (rb_str_append_literal): append but keep encoding non
  US-ASCII.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51970 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 12 insertions, 0 deletions

diff --git a/string.c b/string.c
index e93af5cece..728676c159 100644
--- a/string.c
+++ b/string.c
@@ -2460,6 +2460,18 @@ rb_str_append(VALUE str, VALUE str2)
     return rb_str_buf_append(str, str2);
 }
 
+VALUE
+rb_str_append_literal(VALUE str, VALUE str2)
+{
+    int encidx = rb_enc_get_index(str2);
+    rb_str_buf_append(str, str2);
+    if (encidx != ENCINDEX_US_ASCII) {
+	if (rb_enc_get_index(str) == ENCINDEX_US_ASCII)
+	    rb_enc_associate_index(str, encidx);
+    }
+    return str;
+}
+
 /*
  *  call-seq:
  *     str << integer       -> str