Changeset 184866 in webkit for trunk/Source/JavaScriptCore

Timestamp:

May 26, 2015, 11:56:42 AM (10 years ago)

Author:

[email protected]

Message:

String.prototype.charCodeAt() should use StringView.
<​https://webkit.org/b/145353>

Reviewed by Darin Adler.

Use JSString::view() in charCodeAt() to avoid reifying the JSString if it's
a substring. This avoids StringImpl allocation in some cases and ref churn
in all cases.

• runtime/StringPrototype.cpp:

(JSC::stringProtoFuncCharCodeAt):

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• runtime/StringPrototype.cpp (modified) (1 diff)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2015-05-26  Andreas Kling  <[email protected]>
+
+        String.prototype.charCodeAt() should use StringView.
+        <https://webkit.org/b/145353>
+
+        Reviewed by Darin Adler.
+
+        Use JSString::view() in charCodeAt() to avoid reifying the JSString if it's
+        a substring. This avoids StringImpl allocation in some cases and ref churn
+        in all cases.
+
+        * runtime/StringPrototype.cpp:
+        (JSC::stringProtoFuncCharCodeAt):
+
 2015-05-26  Andreas Kling  <[email protected]>
 

trunk/Source/JavaScriptCore/runtime/StringPrototype.cpp

@@ -805 +805 @@
     if (!checkObjectCoercible(thisValue))
         return throwVMTypeError(exec);
-    String s = thisValue.toString(exec)->value(exec);
-    unsigned len = s.length();
+    StringView string = thisValue.toString(exec)->view(exec);
     JSValue a0 = exec->argument(0);
     if (a0.isUInt32()) {
         uint32_t i = a0.asUInt32();
-        if (i < len) {
-            if (s.is8Bit())
-                return JSValue::encode(jsNumber(s.characters8()[i]));
-            return JSValue::encode(jsNumber(s.characters16()[i]));
-        }
+        if (i < string.length())
+            return JSValue::encode(jsNumber(string[i]));
         return JSValue::encode(jsNaN());
     }
     double dpos = a0.toInteger(exec);
-    if (dpos >= 0 && dpos < len)
-        return JSValue::encode(jsNumber(s[static_cast<int>(dpos)]));
+    if (dpos >= 0 && dpos < string.length())
+        return JSValue::encode(jsNumber(string[static_cast<int>(dpos)]));
     return JSValue::encode(jsNaN());
 }