diff -r 000000000000 -r 6474c204b198 dom/smil/nsSMILValue.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/smil/nsSMILValue.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,144 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsSMILValue.h"
+#include "nsDebug.h"
+#include <string.h>
+
+//----------------------------------------------------------------------
+// Public methods
+
+nsSMILValue::nsSMILValue(const nsISMILType* aType)
+  : mType(nsSMILNullType::Singleton())
+{
+  if (!aType) {
+    NS_ERROR("Trying to construct nsSMILValue with null mType pointer");
+    return;
+  }
+
+  InitAndCheckPostcondition(aType);
+}
+
+nsSMILValue::nsSMILValue(const nsSMILValue& aVal)
+  : mType(nsSMILNullType::Singleton())
+{
+  InitAndCheckPostcondition(aVal.mType);
+  mType->Assign(*this, aVal);
+}
+
+const nsSMILValue&
+nsSMILValue::operator=(const nsSMILValue& aVal)
+{
+  if (&aVal == this)
+    return *this;
+
+  if (mType != aVal.mType) {
+    DestroyAndReinit(aVal.mType);
+  }
+
+  mType->Assign(*this, aVal);
+
+  return *this;
+}
+
+bool
+nsSMILValue::operator==(const nsSMILValue& aVal) const
+{
+  if (&aVal == this)
+    return true;
+
+  return mType == aVal.mType && mType->IsEqual(*this, aVal);
+}
+
+void
+nsSMILValue::Swap(nsSMILValue& aOther)
+{
+  nsSMILValue tmp;
+  memcpy(&tmp,    &aOther, sizeof(nsSMILValue));  // tmp    = aOther
+  memcpy(&aOther, this,    sizeof(nsSMILValue));  // aOther = this
+  memcpy(this,    &tmp,    sizeof(nsSMILValue));  // this   = tmp
+
+  // |tmp| is about to die -- we need to clear its mType, so that its
+  // destructor doesn't muck with the data we just transferred out of it.
+  tmp.mType = nsSMILNullType::Singleton();
+}
+
+nsresult
+nsSMILValue::Add(const nsSMILValue& aValueToAdd, uint32_t aCount)
+{
+  if (aValueToAdd.mType != mType) {
+    NS_ERROR("Trying to add incompatible types");
+    return NS_ERROR_FAILURE;
+  }
+
+  return mType->Add(*this, aValueToAdd, aCount);
+}
+
+nsresult
+nsSMILValue::SandwichAdd(const nsSMILValue& aValueToAdd)
+{
+  if (aValueToAdd.mType != mType) {
+    NS_ERROR("Trying to add incompatible types");
+    return NS_ERROR_FAILURE;
+  }
+
+  return mType->SandwichAdd(*this, aValueToAdd);
+}
+
+nsresult
+nsSMILValue::ComputeDistance(const nsSMILValue& aTo, double& aDistance) const
+{
+  if (aTo.mType != mType) {
+    NS_ERROR("Trying to calculate distance between incompatible types");
+    return NS_ERROR_FAILURE;
+  }
+
+  return mType->ComputeDistance(*this, aTo, aDistance);
+}
+
+nsresult
+nsSMILValue::Interpolate(const nsSMILValue& aEndVal,
+                         double aUnitDistance,
+                         nsSMILValue& aResult) const
+{
+  if (aEndVal.mType != mType) {
+    NS_ERROR("Trying to interpolate between incompatible types");
+    return NS_ERROR_FAILURE;
+  }
+
+  if (aResult.mType != mType) {
+    // Outparam has wrong type
+    aResult.DestroyAndReinit(mType);
+  }
+
+  return mType->Interpolate(*this, aEndVal, aUnitDistance, aResult);
+}
+
+//----------------------------------------------------------------------
+// Helper methods
+
+// Wrappers for nsISMILType::Init & ::Destroy that verify their postconditions
+void
+nsSMILValue::InitAndCheckPostcondition(const nsISMILType* aNewType)
+{
+  aNewType->Init(*this);
+  NS_ABORT_IF_FALSE(mType == aNewType,
+                    "Post-condition of Init failed. nsSMILValue is invalid");
+}
+                
+void
+nsSMILValue::DestroyAndCheckPostcondition()
+{
+  mType->Destroy(*this);
+  NS_ABORT_IF_FALSE(IsNull(), "Post-condition of Destroy failed. "
+                    "nsSMILValue not null after destroying");
+}
+
+void
+nsSMILValue::DestroyAndReinit(const nsISMILType* aNewType)
+{
+  DestroyAndCheckPostcondition();
+  InitAndCheckPostcondition(aNewType);
+}