From c9afc2259d05d56c958ada024cb29c912640e42f Mon Sep 17 00:00:00 2001
From: Robert Sipka <rsipka.uszeged@partner.samsung.com>
Date: Fri, 13 Jan 2017 09:22:55 +0100
Subject: [PATCH] Refactor the ecma_string_substr function (#1517)

JerryScript-DCO-1.0-Signed-off-by: Robert Sipka rsipka.uszeged@partner.samsung.com
---
 jerry-core/ecma/base/ecma-helpers-string.c | 93 ++++++----------------
 1 file changed, 25 insertions(+), 68 deletions(-)

diff --git a/jerry-core/ecma/base/ecma-helpers-string.c b/jerry-core/ecma/base/ecma-helpers-string.c
index 7c222a88c..e7c1881b2 100644
--- a/jerry-core/ecma/base/ecma-helpers-string.c
+++ b/jerry-core/ecma/base/ecma-helpers-string.c
@@ -1779,87 +1779,44 @@ ecma_string_substr (const ecma_string_t *string_p, /**< pointer to an ecma strin
                     ecma_length_t start_pos, /**< start position, should be less or equal than string length */
                     ecma_length_t end_pos) /**< end position, should be less or equal than string length */
 {
-#ifndef JERRY_NDEBUG
   const ecma_length_t string_length = ecma_string_get_length (string_p);
   JERRY_ASSERT (start_pos <= string_length);
   JERRY_ASSERT (end_pos <= string_length);
-#endif /* !JERRY_NDEBUG */
 
-  if (start_pos < end_pos)
+  if (start_pos >= end_pos)
   {
-    lit_utf8_size_t buffer_size;
-    bool is_ascii;
-    const lit_utf8_byte_t *start_p = ecma_string_raw_chars (string_p, &buffer_size, &is_ascii);
+    return ecma_get_magic_string (LIT_MAGIC_STRING__EMPTY);
+  }
 
-    end_pos -= start_pos;
+  ecma_string_t *ecma_string_p = NULL;
+  end_pos -= start_pos;
 
-    if (start_p != NULL)
-    {
-      if (is_ascii)
-      {
-        return ecma_new_ecma_string_from_utf8 (start_p + start_pos,
-                                               (lit_utf8_size_t) end_pos);
-      }
+  ECMA_STRING_TO_UTF8_STRING (string_p, start_p, buffer_size);
 
-      while (start_pos--)
-      {
-        start_p += lit_get_unicode_char_size_by_utf8_first_byte (*start_p);
-      }
-
-      const lit_utf8_byte_t *end_p = start_p;
-      while (end_pos--)
-      {
-        end_p += lit_get_unicode_char_size_by_utf8_first_byte (*end_p);
-      }
-
-      return ecma_new_ecma_string_from_utf8 (start_p, (lit_utf8_size_t) (end_p - start_p));
-    }
-
-    /**
-     * I. Dump original string to plain buffer
-     */
-    ecma_string_t *ecma_string_p;
-
-    JMEM_DEFINE_LOCAL_ARRAY (utf8_str_p, buffer_size, lit_utf8_byte_t);
-
-    ecma_string_to_utf8_bytes (string_p, utf8_str_p, buffer_size);
-
-    /**
-     * II. Extract substring
-     */
-    start_p = utf8_str_p;
-
-    if (is_ascii)
-    {
-      ecma_string_p = ecma_new_ecma_string_from_utf8 (start_p + start_pos,
-                                                      (lit_utf8_size_t) end_pos);
-    }
-    else
-    {
-      while (start_pos--)
-      {
-        start_p += lit_get_unicode_char_size_by_utf8_first_byte (*start_p);
-      }
-
-      const lit_utf8_byte_t *end_p = start_p;
-      while (end_pos--)
-      {
-        end_p += lit_get_unicode_char_size_by_utf8_first_byte (*end_p);
-      }
-
-      ecma_string_p = ecma_new_ecma_string_from_utf8 (start_p, (lit_utf8_size_t) (end_p - start_p));
-    }
-
-    JMEM_FINALIZE_LOCAL_ARRAY (utf8_str_p);
-
-    return ecma_string_p;
+  if (string_length == buffer_size)
+  {
+    ecma_string_p = ecma_new_ecma_string_from_utf8 (start_p + start_pos,
+                                                    (lit_utf8_size_t) end_pos);
   }
   else
   {
-    return ecma_new_ecma_string_from_utf8 (NULL, 0);
+    while (start_pos--)
+    {
+      start_p += lit_get_unicode_char_size_by_utf8_first_byte (*start_p);
+    }
+
+    const lit_utf8_byte_t *end_p = start_p;
+    while (end_pos--)
+    {
+      end_p += lit_get_unicode_char_size_by_utf8_first_byte (*end_p);
+    }
+
+    ecma_string_p = ecma_new_ecma_string_from_utf8 (start_p, (lit_utf8_size_t) (end_p - start_p));
   }
 
-  JERRY_UNREACHABLE ();
+  ECMA_FINALIZE_UTF8_STRING (start_p, buffer_size);
+
+  return ecma_string_p;
 } /* ecma_string_substr */
 
 /**