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-rw-r--r--dom/base/nsAttrValueOrString.h95
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diff --git a/dom/base/nsAttrValueOrString.h b/dom/base/nsAttrValueOrString.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+/*
+ * A wrapper to contain either an nsAttrValue or an nsAString. This is useful
+ * because constructing an nsAttrValue from an nsAString can be expensive when
+ * the buffer of the string is not shared.
+ *
+ * This treats nsAttrValueOrString(nullptr) as the empty string,
+ * to help with contexts where a null pointer denotes an empty value.
+ *
+ * Since a raw pointer to the passed-in string is kept, this class should only
+ * be used on the stack.
+ */
+
+#ifndef nsAttrValueOrString_h___
+#define nsAttrValueOrString_h___
+
+#include "nsString.h"
+#include "nsAttrValue.h"
+
+class MOZ_STACK_CLASS nsAttrValueOrString
+{
+public:
+ explicit nsAttrValueOrString(const nsAString& aValue)
+ : mAttrValue(nullptr)
+ , mStringPtr(&aValue)
+ , mCheapString(nullptr)
+ { }
+
+ explicit nsAttrValueOrString(const nsAString* aValue)
+ : mAttrValue(nullptr)
+ , mStringPtr(aValue)
+ , mCheapString(nullptr)
+ { }
+
+ explicit nsAttrValueOrString(const nsAttrValue& aValue)
+ : mAttrValue(&aValue)
+ , mStringPtr(nullptr)
+ , mCheapString(nullptr)
+ { }
+
+ explicit nsAttrValueOrString(const nsAttrValue* aValue)
+ : mAttrValue(aValue)
+ , mStringPtr(nullptr)
+ , mCheapString(nullptr)
+ { }
+
+ void TakeParsedValue(nsAttrValue& aValue)
+ {
+ mStoredAttrValue.SwapValueWith(aValue);
+ mAttrValue = &mStoredAttrValue;
+ mStringPtr = nullptr;
+ }
+ /**
+ * If TakeParsedValue has been called, returns the value that it set.
+ */
+ nsAttrValue* GetStoredAttrValue()
+ {
+ return mAttrValue == &mStoredAttrValue ? &mStoredAttrValue : nullptr;
+ }
+ const nsAttrValue* GetAttrValue() { return mAttrValue; }
+
+ /**
+ * Returns a reference to the string value of the contents of this object.
+ *
+ * When this object points to a string or an nsAttrValue of string or atom
+ * type this should be fairly cheap. Other nsAttrValue types will be
+ * serialized the first time this is called and cached from thereon.
+ */
+ const nsAString& String() const;
+
+ /**
+ * Compares the string representation of this object with the string
+ * representation of an nsAttrValue.
+ */
+ bool EqualsAsStrings(const nsAttrValue& aOther) const
+ {
+ if (mStringPtr) {
+ return aOther.Equals(*mStringPtr, eCaseMatters);
+ }
+ return aOther.EqualsAsStrings(*mAttrValue);
+ }
+
+protected:
+ const nsAttrValue* mAttrValue;
+ mutable const nsAString* mStringPtr;
+ mutable nsCheapString mCheapString;
+ nsAttrValue mStoredAttrValue;
+};
+
+#endif // nsAttrValueOrString_h___