Source/JavaScriptCore/API/OpaqueJSString.cpp

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 * Copyright (C) 2008-2019 Apple Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *
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 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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#include "config.h"
#include "OpaqueJSString.h"

#include "CallFrame.h"
#include "Identifier.h"
#include "IdentifierInlines.h"
#include "JSGlobalObject.h"
#include <wtf/text/StringView.h>

using namespace JSC;

RefPtr<OpaqueJSString> OpaqueJSString::tryCreate(const String& string)
{
    if (string.isNull())
        return nullptr;

    return adoptRef(new OpaqueJSString(string));
}

RefPtr<OpaqueJSString> OpaqueJSString::tryCreate(String&& string)
{
    if (string.isNull())
        return nullptr;

    return adoptRef(new OpaqueJSString(WTFMove(string)));
}

OpaqueJSString::~OpaqueJSString()
{
    // m_characters is put in a local here to avoid an extra atomic load.
    UChar* characters = m_characters;
    if (!characters)
        return;

    if (!m_string.is8Bit() && m_string.characters16() == characters)
        return;

    fastFree(characters);
}

String OpaqueJSString::string() const
{
    // Return a copy of the wrapped string, because the caller may make it an Identifier.
    return m_string.isolatedCopy();
}

Identifier OpaqueJSString::identifier(VM* vm) const
{
    if (m_string.isNull())
        return Identifier();

    if (m_string.isEmpty())
        return Identifier(Identifier::EmptyIdentifier);

    if (m_string.is8Bit())
        return Identifier::fromString(*vm, m_string.characters8(), m_string.length());

    return Identifier::fromString(*vm, m_string.characters16(), m_string.length());
}

const UChar* OpaqueJSString::characters()
{
    // m_characters is put in a local here to avoid an extra atomic load.
    UChar* characters = m_characters;
    if (characters)
        return characters;

    if (m_string.isNull())
        return nullptr;

    unsigned length = m_string.length();
    UChar* newCharacters = static_cast<UChar*>(fastMalloc(length * sizeof(UChar)));
    StringView(m_string).getCharactersWithUpconvert(newCharacters);

    if (!m_characters.compare_exchange_strong(characters, newCharacters)) {
        fastFree(newCharacters);
        return characters;
    }

    return newCharacters;
}

bool OpaqueJSString::equal(const OpaqueJSString* a, const OpaqueJSString* b)
{
    if (a == b)
        return true;

    if (!a || !b)
        return false;

    return a->m_string == b->m_string;
}