[ABANDONED] Add exception handling options to V8StringResource<T>::prepare.

Source/bindings/v8/V8StringResource.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 140 matching lines @@
 
 enum ExternalMode {
     Externalize,
     DoNotExternalize
 };
 
 template <typename StringType>
 StringType v8StringToWebCoreString(v8::Handle<v8::String>, ExternalMode);
 String int32ToWebCoreString(int value);
 
+enum V8StringResourceInitMode {
+    V8StringResourceDoNotCatchException,
+    V8StringResourceRethrowException,
+    V8StringResourceStoreException,
+};
+
+template<V8StringResourceInitMode>
+struct V8StringResourceToString;

[yhirano, 2014/04/24 06:52:51]

I know this is a bit complex, but It is needed to avoid size / speed
regressions.

+
+template<>
+struct V8StringResourceToString<V8StringResourceDoNotCatchException> {
+    typedef V8StringResourceToString<V8StringResourceDoNotCatchException> ThisClass;
+    static bool call(ThisClass*, v8::Handle<v8::Value>* value)
+    {
+        *value = (*value)->ToString();
+        return !value->IsEmpty();
+    }
+};
+
+template<>
+struct V8StringResourceToString<V8StringResourceRethrowException> {
+    typedef V8StringResourceToString<V8StringResourceRethrowException> ThisClass;
+    static bool call(ThisClass*, v8::Handle<v8::Value>* value)
+    {
+        v8::TryCatch block;
+        *value = (*value)->ToString();
+        if (block.HasCaught()) {
+            block.ReThrow();
+            return false;
+        }
+        return true;
+    }
+};
+
+template<>
+struct V8StringResourceToString<V8StringResourceStoreException> {

[yhirano, 2014/04/24 06:52:51]

Nobody uses this class yet, but I wrote it as a preparation for the following CL
https://codereview.chromium.org/232563003/ .

+    typedef V8StringResourceToString<V8StringResourceStoreException> ThisClass;
+    bool call(ThisClass* context, v8::Handle<v8::Value>* value)
+    {
+        v8::TryCatch block;
+        *value = (*value)->ToString();
+        if (block.HasCaught()) {
+            context->exception = block.Exception();
+            return false;
+        }
+        return true;
+    }
+    v8::Handle<v8::Value> exception;
+};
+
 // V8StringResource is an adapter class that converts V8 values to Strings
 // or AtomicStrings as appropriate, using multiple typecast operators.
 enum V8StringResourceMode {
     DefaultMode,
     WithNullCheck,
     WithUndefinedOrNullCheck
 };
 
 template <V8StringResourceMode Mode = DefaultMode>
 class V8StringResource {
 public:
     V8StringResource(v8::Handle<v8::Value> object)
         : m_v8Object(object)
         , m_mode(Externalize)
         , m_string()
     {
     }
 
-    bool prepare();
-    operator String() const { return toString<String>(); }
-    operator AtomicString() const { return toString<AtomicString>(); }
-
-private:
-    bool prepareBase()
+    // Initializes this object, which means sets m_v8Object, m_mode and
+    // m_string appropriately.
+    // This function returns true if intialization is done successfully.
+    template<V8StringResourceInitMode initMode>
+    bool init(V8StringResourceToString<initMode>* stringifier)
     {
         if (m_v8Object.IsEmpty())
             return true;
 
+        if (!isValid()) {
+            setString(String());
+            return true;
+        }
+
         if (LIKELY(m_v8Object->IsString()))
             return true;
 
         if (LIKELY(m_v8Object->IsInt32())) {
             setString(int32ToWebCoreString(m_v8Object->Int32Value()));
             return true;
         }
+        m_mode = DoNotExternalize;
+        return V8StringResourceToString<initMode>::call(stringifier, &m_v8Object);
+    }
 
-        m_mode = DoNotExternalize;
-        v8::TryCatch block;
-        m_v8Object = m_v8Object->ToString();
-        // Handle the case where an exception is thrown as part of invoking toString on the object.
-        if (block.HasCaught()) {
-            block.ReThrow();
-            return false;
-        }
-        return true;
-    }
+    operator String() const { return toString<String>(); }
+    operator AtomicString() const { return toString<AtomicString>(); }
+
+private:
+    bool isValid();
 
     void setString(const String& string)
     {
         m_string = string;
         m_v8Object.Clear(); // To signal that String is ready.
     }
 
     template <class StringType>
     StringType toString() const
     {
         if (LIKELY(!m_v8Object.IsEmpty()))
             return v8StringToWebCoreString<StringType>(const_cast<v8::Handle<v8::Value>*>(&m_v8Object)->As<v8::String>(), m_mode);
 
         return StringType(m_string);
     }
 
     v8::Handle<v8::Value> m_v8Object;
     ExternalMode m_mode;
     String m_string;
 };
 
-template<> inline bool V8StringResource<DefaultMode>::prepare()
+template<> inline bool V8StringResource<DefaultMode>::isValid()
 {
-    return prepareBase();
+    return true;
 }
 
-template<> inline bool V8StringResource<WithNullCheck>::prepare()
+template<> inline bool V8StringResource<WithNullCheck>::isValid()
 {
-    if (m_v8Object.IsEmpty() || m_v8Object->IsNull()) {
-        setString(String());
-        return true;
-    }
-    return prepareBase();
+    return !m_v8Object->IsNull();
 }
 
-template<> inline bool V8StringResource<WithUndefinedOrNullCheck>::prepare()
+template<> inline bool V8StringResource<WithUndefinedOrNullCheck>::isValid()
 {
-    if (m_v8Object.IsEmpty() || m_v8Object->IsNull() || m_v8Object->IsUndefined()) {
-        setString(String());
-        return true;
-    }
-    return prepareBase();
+    return !m_v8Object->IsNull() && !m_v8Object->IsUndefined();
 }
 
 } // namespace WebCore
 
 #endif // V8StringResource_h