Improve performance of search in the list of the magic strings.

JerryScript-DCO-1.0-Signed-off-by: Robert Sipka [email protected]

Author: robertsipka

jerry-core/lit/lit-magic-strings.c

@@ -37,14 +37,6 @@ lit_get_magic_string_ex_count (void)
 const lit_utf8_byte_t *
 lit_get_magic_string_utf8 (lit_magic_string_id_t id) /**< magic string id */
 {
-  static const lit_utf8_byte_t * const magic_strings[] JERRY_CONST_DATA =
-  {
-#define LIT_MAGIC_STRING_DEF(id, utf8_string) \
-    (const lit_utf8_byte_t *) utf8_string,
-#include "lit-magic-strings.inc.h"
-#undef LIT_MAGIC_STRING_DEF
-  };
-
   JERRY_ASSERT (id < LIT_MAGIC_STRING__COUNT);
 
   return magic_strings[id];
@@ -145,22 +137,32 @@ lit_is_utf8_string_magic (const lit_utf8_byte_t *string_p, /**< utf-8 string */
                           lit_utf8_size_t string_size, /**< string size in bytes */
                           lit_magic_string_id_t *out_id_p) /**< [out] magic string's id */
 {
-  /* TODO: Improve performance of search */
+  *out_id_p = LIT_MAGIC_STRING__COUNT;
 
-  for (lit_magic_string_id_t id = (lit_magic_string_id_t) 0;
-       id < LIT_MAGIC_STRING__COUNT;
-       id = (lit_magic_string_id_t) (id + 1))
+  int first = 0; /**< First magic string element */
+  int last = (int) (LIT_MAGIC_STRING__COUNT - 1); /**< Last magic string element */
+
+  while (first <= last)
   {
-    if (lit_compare_utf8_string_and_magic_string (string_p, string_size, id))
-    {
-      *out_id_p = id;
+    int middle = ((first + last) / 2); /**< mid point of search */
+
+    int compare = lit_compare_utf8_string_and_magic_string (string_p, string_size, magic_strings[middle]);
 
+    if (compare == 0)
+    {
+      *out_id_p = (lit_magic_string_id_t) middle;
       return true;
     }
+    else if (compare < 0)
+    {
+      last = middle - 1;
+    }
+    else
+    {
+      first = middle + 1;
+    }
   }
 
-  *out_id_p = LIT_MAGIC_STRING__COUNT;
-
   return false;
 } /* lit_is_utf8_string_magic */
 
@@ -197,18 +199,40 @@ bool lit_is_ex_utf8_string_magic (const lit_utf8_byte_t *string_p, /**< utf-8 st
 /**
  * Compare utf-8 string and magic string for equality
  *
- * @return true if strings are equal
- *         false otherwise
+ * @return 0, if areas are equal;
+ *         <0, if string's content is lexicographically less, than magic string's content;
+ *         >0, otherwise
  */
-bool
+int
 lit_compare_utf8_string_and_magic_string (const lit_utf8_byte_t *string_p, /**< utf-8 string */
-                                          lit_utf8_size_t string_size, /**< string size in bytes */
-                                          lit_magic_string_id_t magic_string_id) /**< magic string's id */
+                                          const lit_utf8_size_t buf_size, /**< string size */
+                                          const lit_utf8_byte_t *magic_string_p) /**< magic string */
 {
-  return lit_compare_utf8_strings (string_p,
-                                   string_size,
-                                   lit_get_magic_string_utf8 (magic_string_id),
-                                   lit_get_magic_string_size (magic_string_id));
+  lit_utf8_size_t position = 0;
+
+  while (position < buf_size)
+  {
+    if (magic_string_p[position] == '\0')
+    {
+      return 1;
+    }
+
+    int diff = ((int) string_p[position]) - ((int) magic_string_p[position]);
+
+    if (diff)
+    {
+      return diff;
+    }
+
+    position++;
+  }
+
+  if (magic_string_p[position] == '\0')
+  {
+    return 0;
+  }
+
+  return -1;
 } /* lit_compare_utf8_string_and_magic_string */
 
 /**

jerry-core/lit/lit-magic-strings.h

@@ -36,6 +36,18 @@ typedef enum
   LIT_MAGIC_STRING__COUNT /**< number of magic strings */
 } lit_magic_string_id_t;
 
+/**
+ *
+ * List of ECMA and implementation-defined magic string constants
+ */
+static const lit_utf8_byte_t * const magic_strings[] JERRY_CONST_DATA =
+{
+#define LIT_MAGIC_STRING_DEF(id, utf8_string) \
+  (const lit_utf8_byte_t *) utf8_string,
+#include "lit-magic-strings.inc.h"
+#undef LIT_MAGIC_STRING_DEF
+};
+
 /**
  * Identifiers of implementation-defined external magic string constants
  */
@@ -52,11 +64,12 @@ extern lit_utf8_size_t lit_get_magic_string_ex_size (lit_magic_string_ex_id_t);
 extern void lit_magic_strings_ex_set (const lit_utf8_byte_t **, uint32_t, const lit_utf8_size_t *);
 
 extern bool lit_is_utf8_string_magic (const lit_utf8_byte_t *, lit_utf8_size_t, lit_magic_string_id_t *);
-extern bool lit_is_ex_utf8_string_magic (const lit_utf8_byte_t *, lit_utf8_size_t, lit_magic_string_ex_id_t *);
 
-extern bool lit_compare_utf8_string_and_magic_string (const lit_utf8_byte_t *, lit_utf8_size_t,
-                                                      lit_magic_string_id_t);
+extern bool lit_is_ex_utf8_string_magic (const lit_utf8_byte_t *, lit_utf8_size_t, lit_magic_string_ex_id_t *);
 
+extern int lit_compare_utf8_string_and_magic_string (const lit_utf8_byte_t *,
+                                                     const lit_utf8_size_t,
+                                                     const lit_utf8_byte_t *magic_string_p);
 extern bool lit_compare_utf8_string_and_magic_string_ex (const lit_utf8_byte_t *, lit_utf8_size_t,
                                                          lit_magic_string_ex_id_t);