forked from mirrors/gecko-dev
265e672179
# ignore-this-changeset --HG-- extra : amend_source : 4d301d3b0b8711c4692392aa76088ba7fd7d1022
85 lines
2.7 KiB
C++
85 lines
2.7 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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/*
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* A wrapper to contain either an nsAttrValue or an nsAString. This is useful
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* because constructing an nsAttrValue from an nsAString can be expensive when
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* the buffer of the string is not shared.
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*
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* This treats nsAttrValueOrString(nullptr) as the empty string,
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* to help with contexts where a null pointer denotes an empty value.
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*
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* Since a raw pointer to the passed-in string is kept, this class should only
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* be used on the stack.
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*/
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#ifndef nsAttrValueOrString_h___
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#define nsAttrValueOrString_h___
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#include "nsString.h"
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#include "nsAttrValue.h"
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class MOZ_STACK_CLASS nsAttrValueOrString {
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public:
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explicit nsAttrValueOrString(const nsAString& aValue)
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: mAttrValue(nullptr), mStringPtr(&aValue), mCheapString(nullptr) {}
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explicit nsAttrValueOrString(const nsAString* aValue)
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: mAttrValue(nullptr), mStringPtr(aValue), mCheapString(nullptr) {}
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explicit nsAttrValueOrString(const nsAttrValue& aValue)
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: mAttrValue(&aValue), mStringPtr(nullptr), mCheapString(nullptr) {}
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explicit nsAttrValueOrString(const nsAttrValue* aValue)
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: mAttrValue(aValue), mStringPtr(nullptr), mCheapString(nullptr) {}
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void ResetToAttrValue(const nsAttrValue& aValue) {
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mAttrValue = &aValue;
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mStringPtr = nullptr;
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// No need to touch mCheapString here. If we need to use it, we will reset
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// it to the rigthe value anyway.
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}
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/**
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* Returns a reference to the string value of the contents of this object.
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*
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* When this object points to a string or an nsAttrValue of string or atom
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* type this should be fairly cheap. Other nsAttrValue types will be
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* serialized the first time this is called and cached from thereon.
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*/
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const nsAString& String() const;
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/**
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* Compares the string representation of this object with the string
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* representation of an nsAttrValue.
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*/
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bool EqualsAsStrings(const nsAttrValue& aOther) const {
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if (mStringPtr) {
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return aOther.Equals(*mStringPtr, eCaseMatters);
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}
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return aOther.EqualsAsStrings(*mAttrValue);
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}
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/*
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* Returns true if the value stored is empty
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*/
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bool IsEmpty() const {
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if (mStringPtr) {
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return mStringPtr->IsEmpty();
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}
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if (mAttrValue) {
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return mAttrValue->IsEmptyString();
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}
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return true;
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}
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protected:
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const nsAttrValue* mAttrValue;
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mutable const nsAString* mStringPtr;
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mutable nsCheapString mCheapString;
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};
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#endif // nsAttrValueOrString_h___
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