C++ JSString::isRope方法代码示例

void JSString::visitChildren(JSCell* cell, SlotVisitor& visitor)
{
    JSString* thisObject = jsCast<JSString*>(cell);
    Base::visitChildren(thisObject, visitor);
    
    MARK_LOG_MESSAGE1("[%u]: ", thisObject->length());

#if ENABLE(OBJECT_MARK_LOGGING)
    if (!thisObject->isRope()) {
        WTF::StringImpl* ourImpl = thisObject->m_value.impl();
        if (ourImpl->is8Bit())
            MARK_LOG_MESSAGE1("[8 %p]", ourImpl->characters8());
        else
            MARK_LOG_MESSAGE1("[16 %p]", ourImpl->characters16());
    } else
        MARK_LOG_MESSAGE0("[rope]: ");
#endif

    if (thisObject->isRope())
        static_cast<JSRopeString*>(thisObject)->visitFibers(visitor);
    else {
        StringImpl* impl = thisObject->m_value.impl();
        ASSERT(impl);
        visitor.reportExtraMemoryUsage(impl->costDuringGC());
    }
}

void JSRopeString::resolveRopeSlowCase(UChar* buffer) const
{
    UChar* position = buffer + m_length; // We will be working backwards over the rope.
    Vector<JSString*, 32, UnsafeVectorOverflow> workQueue; // These strings are kept alive by the parent rope, so using a Vector is OK.

    for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i)
        workQueue.append(m_fibers[i].get());

    while (!workQueue.isEmpty()) {
        JSString* currentFiber = workQueue.last();
        workQueue.removeLast();

        if (currentFiber->isRope()) {
            JSRopeString* currentFiberAsRope = static_cast<JSRopeString*>(currentFiber);
            for (size_t i = 0; i < s_maxInternalRopeLength && currentFiberAsRope->m_fibers[i]; ++i)
                workQueue.append(currentFiberAsRope->m_fibers[i].get());
            continue;
        }

        StringImpl* string = static_cast<StringImpl*>(currentFiber->m_value.impl());
        unsigned length = string->length();
        position -= length;
        if (string->is8Bit())
            StringImpl::copyChars(position, string->characters8(), length);
        else
            StringImpl::copyChars(position, string->characters16(), length);
    }

    ASSERT(buffer == position);
    ASSERT(!isRope());
}

// Overview: These functions convert a JSString from holding a string in rope form
// down to a simple String representation. It does so by building up the string
// backwards, since we want to avoid recursion, we expect that the tree structure
// representing the rope is likely imbalanced with more nodes down the left side
// (since appending to the string is likely more common) - and as such resolving
// in this fashion should minimize work queue size.  (If we built the queue forwards
// we would likely have to place all of the constituent StringImpls into the
// Vector before performing any concatenation, but by working backwards we likely
// only fill the queue with the number of substrings at any given level in a
// rope-of-ropes.)    
void JSRopeString::resolveRopeSlowCase8(LChar* buffer) const
{
    LChar* position = buffer + m_length; // We will be working backwards over the rope.
    Vector<JSString*, 32, UnsafeVectorOverflow> workQueue; // Putting strings into a Vector is only OK because there are no GC points in this method.
    
    for (size_t i = 0; i < s_maxInternalRopeLength && m_fibers[i]; ++i) {
        workQueue.append(m_fibers[i].get());
        // Clearing here works only because there are no GC points in this method.
        m_fibers[i].clear();
    }

    while (!workQueue.isEmpty()) {
        JSString* currentFiber = workQueue.last();
        workQueue.removeLast();

        if (currentFiber->isRope()) {
            JSRopeString* currentFiberAsRope = static_cast<JSRopeString*>(currentFiber);
            for (size_t i = 0; i < s_maxInternalRopeLength && currentFiberAsRope->m_fibers[i]; ++i)
                workQueue.append(currentFiberAsRope->m_fibers[i].get());
            continue;
        }

        StringImpl* string = static_cast<StringImpl*>(currentFiber->m_value.impl());
        unsigned length = string->length();
        position -= length;
        StringImpl::copyChars(position, string->characters8(), length);
    }

    ASSERT(buffer == position);
    ASSERT(!isRope());
}

size_t JSString::estimatedSize(JSCell* cell)
{
    JSString* thisObject = asString(cell);
    if (thisObject->isRope())
        return Base::estimatedSize(cell);
    return Base::estimatedSize(cell) + thisObject->m_value.impl()->costDuringGC();
}

// Overview: These functions convert a JSString from holding a string in rope form
// down to a simple String representation. It does so by building up the string
// backwards, since we want to avoid recursion, we expect that the tree structure
// representing the rope is likely imbalanced with more nodes down the left side
// (since appending to the string is likely more common) - and as such resolving
// in this fashion should minimize work queue size.  (If we built the queue forwards
// we would likely have to place all of the constituent StringImpls into the
// Vector before performing any concatenation, but by working backwards we likely
// only fill the queue with the number of substrings at any given level in a
// rope-of-ropes.)    
void JSRopeString::resolveRopeSlowCase8(LChar* buffer) const
{
    LChar* position = buffer + length(); // We will be working backwards over the rope.
    Vector<JSString*, 32, UnsafeVectorOverflow> workQueue; // Putting strings into a Vector is only OK because there are no GC points in this method.
    
    for (size_t i = 0; i < s_maxInternalRopeLength && fiber(i); ++i)
        workQueue.append(fiber(i).get());

    while (!workQueue.isEmpty()) {
        JSString* currentFiber = workQueue.last();
        workQueue.removeLast();

        const LChar* characters;
        
        if (currentFiber->isRope()) {
            JSRopeString* currentFiberAsRope = static_cast<JSRopeString*>(currentFiber);
            if (!currentFiberAsRope->isSubstring()) {
                for (size_t i = 0; i < s_maxInternalRopeLength && currentFiberAsRope->fiber(i); ++i)
                    workQueue.append(currentFiberAsRope->fiber(i).get());
                continue;
            }
            ASSERT(!currentFiberAsRope->substringBase()->isRope());
            characters =
                currentFiberAsRope->substringBase()->m_value.characters8() +
                currentFiberAsRope->substringOffset();
        } else
            characters = currentFiber->m_value.characters8();
        
        unsigned length = currentFiber->length();
        position -= length;
        StringImpl::copyChars(position, characters, length);
    }

    ASSERT(buffer == position);
}

void JSString::visitChildren(JSCell* cell, SlotVisitor& visitor)
{
    JSString* thisObject = asString(cell);
    Base::visitChildren(thisObject, visitor);
    
    if (thisObject->isRope())
        static_cast<JSRopeString*>(thisObject)->visitFibers(visitor);
    if (StringImpl* impl = thisObject->m_value.impl())
        visitor.reportExtraMemoryVisited(impl->costDuringGC());
}

void JSString::visitChildren(JSCell* cell, SlotVisitor& visitor)
{
    JSString* thisObject = jsCast<JSString*>(cell);
    Base::visitChildren(thisObject, visitor);
    
    if (thisObject->isRope())
        static_cast<JSRopeString*>(thisObject)->visitFibers(visitor);
    else {
        StringImpl* impl = thisObject->m_value.impl();
        ASSERT(impl);
        visitor.reportExtraMemoryUsage(thisObject, impl->costDuringGC());
    }
}

void JSValue::dumpInContextAssumingStructure(
    PrintStream& out, DumpContext* context, Structure* structure) const
{
    if (!*this)
        out.print("<JSValue()>");
    else if (isInt32())
        out.printf("Int32: %d", asInt32());
    else if (isDouble()) {
#if USE(JSVALUE64)
        out.printf("Double: %lld, %lf", (long long)reinterpretDoubleToInt64(asDouble()), asDouble());
#else
        union {
            double asDouble;
            uint32_t asTwoInt32s[2];
        } u;
        u.asDouble = asDouble();
        out.printf("Double: %08x:%08x, %lf", u.asTwoInt32s[1], u.asTwoInt32s[0], asDouble());
#endif
    } else if (isCell()) {
        if (structure->classInfo()->isSubClassOf(JSString::info())) {
            JSString* string = jsCast<JSString*>(asCell());
            out.print("String");
            if (string->isRope())
                out.print(" (rope)");
            const StringImpl* impl = string->tryGetValueImpl();
            if (impl) {
                if (impl->isAtomic())
                    out.print(" (atomic)");
                if (impl->isAtomic())
                    out.print(" (identifier)");
                if (impl->isSymbol())
                    out.print(" (symbol)");
            } else
                out.print(" (unresolved)");
            out.print(": ", impl);
        } else if (structure->classInfo()->isSubClassOf(Symbol::info()))
            out.print("Symbol: ", RawPointer(asCell()));
        else if (structure->classInfo()->isSubClassOf(Structure::info()))
            out.print("Structure: ", inContext(*jsCast<Structure*>(asCell()), context));
        else if (structure->classInfo()->isSubClassOf(JSObject::info())) {
            out.print("Object: ", RawPointer(asCell()));
            out.print(" with butterfly ", RawPointer(asObject(asCell())->butterfly()));
            out.print(" (", inContext(*structure, context), ")");
        } else {
            out.print("Cell: ", RawPointer(asCell()));
            out.print(" (", inContext(*structure, context), ")");
        }
#if USE(JSVALUE64)
        out.print(", ID: ", asCell()->structureID());
#endif
    } else if (isTrue())
        out.print("True");
    else if (isFalse())
        out.print("False");
    else if (isNull())
        out.print("Null");
    else if (isUndefined())
        out.print("Undefined");
    else
        out.print("INVALID");
}

JSFlatString*
JSRope::flattenInternal(ExclusiveContext* maybecx)
{
    /*
     * Consider the DAG of JSRopes rooted at this JSRope, with non-JSRopes as
     * its leaves. Mutate the root JSRope into a JSExtensibleString containing
     * the full flattened text that the root represents, and mutate all other
     * JSRopes in the interior of the DAG into JSDependentStrings that refer to
     * this new JSExtensibleString.
     *
     * If the leftmost leaf of our DAG is a JSExtensibleString, consider
     * stealing its buffer for use in our new root, and transforming it into a
     * JSDependentString too. Do not mutate any of the other leaves.
     *
     * Perform a depth-first dag traversal, splatting each node's characters
     * into a contiguous buffer. Visit each rope node three times:
     *   1. record position in the buffer and recurse into left child;
     *   2. recurse into the right child;
     *   3. transform the node into a dependent string.
     * To avoid maintaining a stack, tree nodes are mutated to indicate how many
     * times they have been visited. Since ropes can be dags, a node may be
     * encountered multiple times during traversal. However, step 3 above leaves
     * a valid dependent string, so everything works out.
     *
     * While ropes avoid all sorts of quadratic cases with string concatenation,
     * they can't help when ropes are immediately flattened. One idiomatic case
     * that we'd like to keep linear (and has traditionally been linear in SM
     * and other JS engines) is:
     *
     *   while (...) {
     *     s += ...
     *     s.flatten
     *   }
     *
     * Two behaviors accomplish this:
     *
     * - When the leftmost non-rope in the DAG we're flattening is a
     *   JSExtensibleString with sufficient capacity to hold the entire
     *   flattened string, we just flatten the DAG into its buffer. Then, when
     *   we transform the root of the DAG from a JSRope into a
     *   JSExtensibleString, we steal that buffer, and change the victim from a
     *   JSExtensibleString to a JSDependentString. In this case, the left-hand
     *   side of the string never needs to be copied.
     *
     * - Otherwise, we round up the total flattened size and create a fresh
     *   JSExtensibleString with that much capacity. If this in turn becomes the
     *   leftmost leaf of a subsequent flatten, we will hopefully be able to
     *   fill it, as in the case above.
     *
     * Note that, even though the code for creating JSDependentStrings avoids
     * creating dependents of dependents, we can create that situation here: the
     * JSExtensibleStrings we transform into JSDependentStrings might have
     * JSDependentStrings pointing to them already. Stealing the buffer doesn't
     * change its address, only its owning JSExtensibleString, so all chars()
     * pointers in the JSDependentStrings are still valid.
     */
    const size_t wholeLength = length();
    size_t wholeCapacity;
    CharT* wholeChars;
    JSString* str = this;
    CharT* pos;

    /*
     * JSString::flattenData is a tagged pointer to the parent node.
     * The tag indicates what to do when we return to the parent.
     */
    static const uintptr_t Tag_Mask = 0x3;
    static const uintptr_t Tag_FinishNode = 0x0;
    static const uintptr_t Tag_VisitRightChild = 0x1;

    AutoCheckCannotGC nogc;

    /* Find the left most string, containing the first string. */
    JSRope* leftMostRope = this;
    while (leftMostRope->leftChild()->isRope())
        leftMostRope = &leftMostRope->leftChild()->asRope();

    if (leftMostRope->leftChild()->isExtensible()) {
        JSExtensibleString& left = leftMostRope->leftChild()->asExtensible();
        size_t capacity = left.capacity();
        if (capacity >= wholeLength && left.hasTwoByteChars() == IsSame<CharT, char16_t>::value) {
            /*
             * Simulate a left-most traversal from the root to leftMost->leftChild()
             * via first_visit_node
             */
            MOZ_ASSERT(str->isRope());
            while (str != leftMostRope) {
                if (b == WithIncrementalBarrier) {
                    JSString::writeBarrierPre(str->d.s.u2.left);
                    JSString::writeBarrierPre(str->d.s.u3.right);
                }
                JSString* child = str->d.s.u2.left;
                MOZ_ASSERT(child->isRope());
                str->setNonInlineChars(left.nonInlineChars<CharT>(nogc));
                child->d.u1.flattenData = uintptr_t(str) | Tag_VisitRightChild;
                str = child;
            }
            if (b == WithIncrementalBarrier) {
                JSString::writeBarrierPre(str->d.s.u2.left);
                JSString::writeBarrierPre(str->d.s.u3.right);
//.........这里部分代码省略.........