Merge pull request #4524 from dearblue/reverse-utf8

Change to UTF-8 string reversing with in place

src/string.c

@@ -1674,6 +1674,18 @@ mrb_ptr_to_str(mrb_state *mrb, void *p)
   return mrb_obj_value(p_str);
 }
 
+static inline void
+str_reverse(char *p, char *e)
+{
+  char c;
+
+  while (p < e) {
+    c = *p;
+    *p++ = *e;
+    *e-- = c;
+  }
+}
+
 /* 15.2.10.5.30 */
 /*
  *  call-seq:
@@ -1684,53 +1696,35 @@ mrb_ptr_to_str(mrb_state *mrb, void *p)
 static mrb_value
 mrb_str_reverse_bang(mrb_state *mrb, mrb_value str)
 {
+  struct RString *s = mrb_str_ptr(str);
+  char *p, *e;
+
 #ifdef MRB_UTF8_STRING
   mrb_int utf8_len = RSTRING_CHAR_LEN(str);
-  mrb_int len = RSTRING_LEN(str);
-
-  if (utf8_len == len) goto bytes;
-  if (utf8_len > 1) {
-    char *buf;
-    char *p, *e, *r;
-
-    mrb_str_modify(mrb, mrb_str_ptr(str));
-    len = RSTRING_LEN(str);
-    buf = (char*)mrb_malloc(mrb, (size_t)len);
-    p = buf;
-    e = buf + len;
-
-    memcpy(buf, RSTRING_PTR(str), len);
-    r = RSTRING_PTR(str) + len;
+  mrb_int len = RSTR_LEN(s);
 
+  if (utf8_len < 2) return str;
+  if (utf8_len < len) {
+    mrb_str_modify(mrb, s);
+    p = RSTR_PTR(s);
+    e = p + RSTR_LEN(s);
     while (p<e) {
       mrb_int clen = utf8len(p, e);
-      r -= clen;
-      memcpy(r, p, clen);
+      str_reverse(p, p + clen - 1);
       p += clen;
     }
-    mrb_free(mrb, buf);
+    goto bytes;
   }
-  return str;
-
- bytes:
 #endif
-  {
-    struct RString *s = mrb_str_ptr(str);
-    char *p, *e;
-    char c;
 
-    mrb_str_modify(mrb, s);
   if (RSTR_LEN(s) > 1) {
+    mrb_str_modify(mrb, s);
+   bytes:
     p = RSTR_PTR(s);
     e = p + RSTR_LEN(s) - 1;
-      while (p < e) {
-      c = *p;
-      *p++ = *e;
-      *e-- = c;
-      }
+    str_reverse(p, e);
   }
   return str;
-  }
 }
 
 /* ---------------------------------- */

test/t/string.rb

@@ -479,6 +479,7 @@ assert('String#reverse(UTF-8)', '15.2.10.5.29') do
 
   assert_equal 'こんにちは世界!', a
   assert_equal '!界世はちにんこ', 'こんにちは世界!'.reverse
+  assert_equal 'あ', 'あ'.reverse
 end if UTF8STRING
 
 assert('String#reverse!', '15.2.10.5.30') do
@@ -495,6 +496,10 @@ assert('String#reverse!(UTF-8)', '15.2.10.5.30') do
 
   assert_equal '!界世はちにんこ', a
   assert_equal '!界世はちにんこ', 'こんにちは世界!'.reverse!
+
+  b = 'あ'
+  b.reverse!
+  assert_equal 'あ', b
 end if UTF8STRING
 
 assert('String#rindex', '15.2.10.5.31') do