File constructor understands lastModified.

Source/bindings/v8/custom/V8BlobCustomHelpers.cpp

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 20 matching lines @@
 #include "config.h"
 #include "V8BlobCustomHelpers.h"
 
 #include "V8Blob.h"
 #include "bindings/v8/Dictionary.h"
 #include "bindings/v8/V8Binding.h"
 #include "bindings/v8/V8Utilities.h"
 #include "bindings/v8/custom/V8ArrayBufferCustom.h"
 #include "bindings/v8/custom/V8ArrayBufferViewCustom.h"
 #include "core/fileapi/BlobBuilder.h"
+#include "wtf/DateMath.h"
 
 namespace WebCore {
 
 namespace V8BlobCustomHelpers {
 
-bool processBlobPropertyBag(v8::Local<v8::Value> propertyBag, const char* blobClassName, String& contentType, String& endings, v8::Isolate* isolate)
+ParsedProperties::ParsedProperties(bool hasFileProperties)
+    : endings("transparent")
+    , hasFileProperties(hasFileProperties)
+#ifndef NDEBUG
+    , m_hasLastModifiedDate(false)
+#endif // NDEBUG
 {
-    ASSERT(endings == "transparent");
+}
+
+double ParsedProperties::lastModifiedDate()
+{
+    ASSERT(this->hasFileProperties);
+    ASSERT(this->m_hasLastModifiedDate);
+    return m_lastModifiedDate;
+}
+
+void ParsedProperties::setLastModifiedDate(double lastModifiedDate)
+{
+    ASSERT(this->hasFileProperties);
+    ASSERT(!this->m_hasLastModifiedDate);
+    m_lastModifiedDate = lastModifiedDate;
+#ifndef NDEBUG
+    m_hasLastModifiedDate = true;
+#endif // NDEBUG
+}
+
+void ParsedProperties::setDefaultLastModifiedDate()
+{
+    setLastModifiedDate(currentTime());
+}
+
+bool processBlobPropertyBag(v8::Local<v8::Value> propertyBag, const char* blobClassName, ParsedProperties& parsedProperties, v8::Isolate* isolate)
+{
+    ASSERT(parsedProperties.endings == "transparent");
+    String& endings = parsedProperties.endings;
 
     V8TRYCATCH_RETURN(Dictionary, dictionary, Dictionary(propertyBag, isolate), false);
 
     V8TRYCATCH_RETURN(bool, containsEndings, dictionary.get("endings", endings), false);
     if (containsEndings) {
         if (endings != "transparent" && endings != "native") {
             throwTypeError(ExceptionMessages::failedToConstruct(blobClassName, "The \"endings\" property must be either \"transparent\" or \"native\"."), isolate);
             return false;
         }
     }
 
+    String& contentType = parsedProperties.contentType;
     V8TRYCATCH_RETURN(bool, containsType, dictionary.get("type", contentType), false);
     if (containsType) {
         if (!contentType.containsOnlyASCII()) {
             throwError(v8SyntaxError, ExceptionMessages::failedToConstruct(blobClassName, "The \"type\" property must consist of ASCII characters."), isolate);
             return false;
         }
         contentType = contentType.lower();
     }
+
+    if (!parsedProperties.hasFileProperties)
+        return true;
+
+    v8::Local<v8::Value> lastModifiedDate;
+    V8TRYCATCH_RETURN(bool, containsLastModifiedDate, dictionary.get("lastModifiedDate", lastModifiedDate), false);
+    if (containsLastModifiedDate) {
+        if (!lastModifiedDate->IsDate()) {
+            throwTypeError(ExceptionMessages::failedToConstruct(blobClassName, "The \"lastModifiedDate\" property must be a Date instance."), isolate);
+            return false;
+        }
+        double dateValue = static_cast<double>(v8::Local<v8::Date>::Cast(lastModifiedDate)->ValueOf());

[haraken, 2013/11/18 10:27:48]

You can use toWebCoreDate() in V8Binding.h.

[pwnall-personal, 2013/11/18 11:23:45]

I avoided toWebCoreDate() because it does an unnecessary check for the value's
type and then it uses NumberValue(), and the v8::Date class definition in
src/v8/include/v8.h says that ValueOf() should be preferred instead of
NumberValue().

Is there a general rule for navigating this kind of clarity/performance
trade-offs in the bindings code?

[haraken, 2013/11/18 11:29:07]

We want to use utility methods in V8Binding.h as much as possible, since direct
use of V8 APIs are error-prone.

Would you update the implementation of toWebCoreDate() so that it uses
ValueOf(), and use toWebCoreDate() here? I agree it's doing an extra check but
this code wouldn't be performance-sensitive.

[pwnall-personal, 2013/11/18 12:48:57]

Done.

+        parsedProperties.setLastModifiedDate(dateValue / msPerSecond);
+    } else {
+        parsedProperties.setDefaultLastModifiedDate();
+    }
+
     return true;
 }
 
 bool processBlobParts(v8::Local<v8::Object> blobParts, uint32_t blobPartsLength, const String& endings, BlobBuilder& blobBuilder, v8::Isolate* isolate)
 {
     ASSERT(endings == "transparent" || endings == "native");
 
     for (uint32_t i = 0; i < blobPartsLength; ++i) {
         v8::Local<v8::Value> item = blobParts->Get(v8::Uint32::New(i, isolate));
         if (item.IsEmpty())
@@ skipping 15 matching lines @@
             V8TRYCATCH_FOR_V8STRINGRESOURCE_RETURN(V8StringResource<>, stringValue, item, false);
             blobBuilder.append(stringValue, endings);
         }
     }
     return true;
 }
 
 } // namespace V8BlobCustomHelpers
 
 } // namespace WebCore