Changeset 44984 in webkit for trunk/JavaScriptCore/runtime/LiteralParser.cpp

Timestamp:

Jun 23, 2009, 2:14:40 AM (16 years ago)

Author:

[email protected]

Message:

Fix stupid performance problem in the LiteralParser

Reviewed by Alexey Proskuryakov.

The LiteralParser was making a new UString in order to use
toDouble, however UString's toDouble allows a much wider range
of numberic strings than the LiteralParser accepts, and requires
an additional heap allocation or two for the construciton of the
UString. To rectify this we just call WTF::dtoa directly using
a stack allocated buffer to hold the validated numeric literal.

File:

• trunk/JavaScriptCore/runtime/LiteralParser.cpp (modified) (3 diffs)

trunk/JavaScriptCore/runtime/LiteralParser.cpp

@@ -31 +31 @@
 #include "Lexer.h"
 #include <wtf/ASCIICType.h>
+#include <wtf/dtoa.h>
 
 namespace JSC {
@@ -264 +265 @@
     token.type = TokNumber;
     token.end = m_ptr;
+    Vector<char, 64> buffer(token.end - token.start + 1);
+    int i;
+    for (i = 0; i < token.end - token.start; i++) {
+        ASSERT(static_cast<char>(token.start[i]) == token.start[i]);
+        buffer[i] = static_cast<char>(token.start[i]);
+    }
+    buffer[i] = 0;
+    char* end;
+    token.numberToken = WTF::strtod(buffer.data(), &end);
+    ASSERT(buffer.data() + (token.end - token.start) == end);
     return TokNumber;
 }
@@ -377 +388 @@
                         Lexer::LiteralParserToken numberToken = m_lexer.currentToken();
                         m_lexer.next();
-                        lastValue = jsNumber(m_exec, UString(numberToken.start, numberToken.end - numberToken.start).toDouble());
+                        lastValue = jsNumber(m_exec, numberToken.numberToken);
                         break;
                     }