Source/JavaScriptCore/runtime/SmallStrings.cpp

/*
 * Copyright (C) 2008, 2010 Apple 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:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"
#include "SmallStrings.h"

#include "JSGlobalObject.h"
#include "JSString.h"
#include "JSCInlines.h"
#include <wtf/Noncopyable.h>
#include <wtf/text/StringImpl.h>

namespace JSC {

SmallStrings::SmallStrings()
{
    COMPILE_ASSERT(singleCharacterStringCount == sizeof(m_singleCharacterStrings) / sizeof(m_singleCharacterStrings[0]), IsNumCharactersConstInSyncWithClassUsage);

    for (unsigned i = 0; i < singleCharacterStringCount; ++i)
        m_singleCharacterStrings[i] = nullptr;
}

void SmallStrings::initializeCommonStrings(VM& vm)
{
    ASSERT(!m_emptyString);
    m_emptyString = JSString::createEmptyString(vm);
    ASSERT(m_needsToBeVisited);

    for (unsigned i = 0; i < singleCharacterStringCount; ++i) {
        ASSERT(!m_singleCharacterStrings[i]);
        const LChar string[] = { static_cast<LChar>(i) };
        m_singleCharacterStrings[i] = JSString::createHasOtherOwner(vm, AtomStringImpl::add(string, 1).releaseNonNull());
        ASSERT(m_needsToBeVisited);
    }

#define JSC_COMMON_STRINGS_ATTRIBUTE_INITIALIZE(name) initialize(&vm, m_##name, #name);
    JSC_COMMON_STRINGS_EACH_NAME(JSC_COMMON_STRINGS_ATTRIBUTE_INITIALIZE)
#undef JSC_COMMON_STRINGS_ATTRIBUTE_INITIALIZE
    initialize(&vm, m_objectStringStart, "[object ");
    initialize(&vm, m_nullObjectString, "[object Null]");
    initialize(&vm, m_undefinedObjectString, "[object Undefined]");

    setIsInitialized(true);
}

void SmallStrings::visitStrongReferences(SlotVisitor& visitor)
{
    m_needsToBeVisited = false;
    visitor.appendUnbarriered(m_emptyString);
    for (unsigned i = 0; i <= maxSingleCharacterString; ++i)
        visitor.appendUnbarriered(m_singleCharacterStrings[i]);
#define JSC_COMMON_STRINGS_ATTRIBUTE_VISIT(name) visitor.appendUnbarriered(m_##name);
    JSC_COMMON_STRINGS_EACH_NAME(JSC_COMMON_STRINGS_ATTRIBUTE_VISIT)
#undef JSC_COMMON_STRINGS_ATTRIBUTE_VISIT
    visitor.appendUnbarriered(m_objectStringStart);
    visitor.appendUnbarriered(m_nullObjectString);
    visitor.appendUnbarriered(m_undefinedObjectString);
}

SmallStrings::~SmallStrings()
{
}

Ref<StringImpl> SmallStrings::singleCharacterStringRep(unsigned char character)
{
    if (LIKELY(m_isInitialized))
        return *const_cast<StringImpl*>(m_singleCharacterStrings[character]->tryGetValueImpl());
    const LChar string[] = { static_cast<LChar>(character) };
    return AtomStringImpl::add(string, 1).releaseNonNull();
}

void SmallStrings::initialize(VM* vm, JSString*& string, const char* value)
{
    string = JSString::create(*vm, AtomStringImpl::add(value).releaseNonNull());
    ASSERT(m_needsToBeVisited);
}

} // namespace JSC