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

Source/bindings/v8/V8StringResource.h

Index: Source/bindings/v8/V8StringResource.h
diff --git a/Source/bindings/v8/V8StringResource.h b/Source/bindings/v8/V8StringResource.h
index e11002e5b0492b719f3bb4e560c5610ef63c0dce..1ad98b093f4c5644e86ddae8effb7b6eab8bb6b2 100644
--- a/Source/bindings/v8/V8StringResource.h
+++ b/Source/bindings/v8/V8StringResource.h
@@ -158,6 +158,56 @@ 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 {
@@ -176,16 +226,20 @@ public:
     {
     }
 
-    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;
 
@@ -193,18 +247,16 @@ private:
             setString(int32ToWebCoreString(m_v8Object->Int32Value()));
             return true;
         }
-
         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;
+        return V8StringResourceToString<initMode>::call(stringifier, &m_v8Object);
     }
 
+    operator String() const { return toString<String>(); }
+    operator AtomicString() const { return toString<AtomicString>(); }
+
+private:
+    bool isValid();
+
     void setString(const String& string)
     {
         m_string = string;
@@ -225,27 +277,19 @@ private:
     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