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)
{
/*
* 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
* }
*
* To do this, when the buffer for a to-be-flattened rope is allocated, the
* allocation size is rounded up. Then, if the resulting flat string is the
* left-hand side of a new rope that gets flattened and there is enough
* capacity, the rope is flattened into the same buffer, thereby avoiding
* copying the left-hand side. Clearing the 'extensible' bit turns off this
* optimization. This is necessary, e.g., when the JSAPI hands out the raw
* null-terminated char array of a flat string.
*
* N.B. This optimization can create chains of dependent strings.
*/
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, jschar>::value) {
/*
* Simulate a left-most traversal from the root to leftMost->leftChild()
* via first_visit_node
*/
JS_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;
JS_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);
}
str->setNonInlineChars(left.nonInlineChars<CharT>(nogc));
wholeCapacity = capacity;
wholeChars = const_cast<CharT *>(left.nonInlineChars<CharT>(nogc));
pos = wholeChars + left.d.u1.length;
JS_STATIC_ASSERT(!(EXTENSIBLE_FLAGS & DEPENDENT_FLAGS));
left.d.u1.flags ^= (EXTENSIBLE_FLAGS | DEPENDENT_FLAGS);
left.d.s.u3.base = (JSLinearString *)this; /* will be true on exit */
StringWriteBarrierPostRemove(maybecx, &left.d.s.u2.left);
StringWriteBarrierPost(maybecx, (JSString **)&left.d.s.u3.base);
goto visit_right_child;
}
}
if (!AllocChars(maybecx, wholeLength, &wholeChars, &wholeCapacity))
return nullptr;
pos = wholeChars;
first_visit_node: {
if (b == WithIncrementalBarrier) {
JSString::writeBarrierPre(str->d.s.u2.left);
JSString::writeBarrierPre(str->d.s.u3.right);
}
JSString &left = *str->d.s.u2.left;
str->setNonInlineChars(pos);
StringWriteBarrierPostRemove(maybecx, &str->d.s.u2.left);
if (left.isRope()) {
/* Return to this node when 'left' done, then goto visit_right_child. */
left.d.u1.flattenData = uintptr_t(str) | Tag_VisitRightChild;
str = &left;
goto first_visit_node;
}
CopyChars(pos, left.asLinear());
pos += left.length();
}
visit_right_child: {
JSString &right = *str->d.s.u3.right;
if (right.isRope()) {
/* Return to this node when 'right' done, then goto finish_node. */
right.d.u1.flattenData = uintptr_t(str) | Tag_FinishNode;
str = &right;
goto first_visit_node;
}
CopyChars(pos, right.asLinear());
pos += right.length();
}
finish_node: {
if (str == this) {
JS_ASSERT(pos == wholeChars + wholeLength);
*pos = '\0';
str->d.u1.length = wholeLength;
if (IsSame<CharT, jschar>::value)
str->d.u1.flags = EXTENSIBLE_FLAGS;
else
str->d.u1.flags = EXTENSIBLE_FLAGS | LATIN1_CHARS_BIT;
str->setNonInlineChars(wholeChars);
str->d.s.u3.capacity = wholeCapacity;
StringWriteBarrierPostRemove(maybecx, &str->d.s.u2.left);
StringWriteBarrierPostRemove(maybecx, &str->d.s.u3.right);
return &this->asFlat();
}
uintptr_t flattenData = str->d.u1.flattenData;
if (IsSame<CharT, jschar>::value)
str->d.u1.flags = DEPENDENT_FLAGS;
else
str->d.u1.flags = DEPENDENT_FLAGS | LATIN1_CHARS_BIT;
str->d.u1.length = pos - str->asLinear().nonInlineChars<CharT>(nogc);
str->d.s.u3.base = (JSLinearString *)this; /* will be true on exit */
StringWriteBarrierPost(maybecx, (JSString **)&str->d.s.u3.base);
str = (JSString *)(flattenData & ~Tag_Mask);
if ((flattenData & Tag_Mask) == Tag_VisitRightChild)
goto visit_right_child;
JS_ASSERT((flattenData & Tag_Mask) == Tag_FinishNode);
goto finish_node;
}
}
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);
}
str->setNonInlineChars(left.nonInlineChars<CharT>(nogc));
wholeCapacity = capacity;
wholeChars = const_cast<CharT*>(left.nonInlineChars<CharT>(nogc));
pos = wholeChars + left.d.u1.length;
JS_STATIC_ASSERT(!(EXTENSIBLE_FLAGS & DEPENDENT_FLAGS));
left.d.u1.flags ^= (EXTENSIBLE_FLAGS | DEPENDENT_FLAGS);
left.d.s.u3.base = (JSLinearString*)this; /* will be true on exit */
StringWriteBarrierPostRemove(maybecx, &left.d.s.u2.left);
StringWriteBarrierPost(maybecx, (JSString**)&left.d.s.u3.base);
goto visit_right_child;
}
}
if (!AllocChars(this, wholeLength, &wholeChars, &wholeCapacity))
return nullptr;
pos = wholeChars;
first_visit_node: {
if (b == WithIncrementalBarrier) {
JSString::writeBarrierPre(str->d.s.u2.left);
JSString::writeBarrierPre(str->d.s.u3.right);
}
JSString& left = *str->d.s.u2.left;
str->setNonInlineChars(pos);
StringWriteBarrierPostRemove(maybecx, &str->d.s.u2.left);
if (left.isRope()) {
/* Return to this node when 'left' done, then goto visit_right_child. */
left.d.u1.flattenData = uintptr_t(str) | Tag_VisitRightChild;
str = &left;
goto first_visit_node;
}
CopyChars(pos, left.asLinear());
pos += left.length();
}
visit_right_child: {
JSString& right = *str->d.s.u3.right;
if (right.isRope()) {
/* Return to this node when 'right' done, then goto finish_node. */
right.d.u1.flattenData = uintptr_t(str) | Tag_FinishNode;
str = &right;
goto first_visit_node;
}
CopyChars(pos, right.asLinear());
pos += right.length();
}
finish_node: {
if (str == this) {
MOZ_ASSERT(pos == wholeChars + wholeLength);
*pos = '\0';
str->d.u1.length = wholeLength;
if (IsSame<CharT, char16_t>::value)
str->d.u1.flags = EXTENSIBLE_FLAGS;
else
str->d.u1.flags = EXTENSIBLE_FLAGS | LATIN1_CHARS_BIT;
str->setNonInlineChars(wholeChars);
str->d.s.u3.capacity = wholeCapacity;
StringWriteBarrierPostRemove(maybecx, &str->d.s.u2.left);
StringWriteBarrierPostRemove(maybecx, &str->d.s.u3.right);
return &this->asFlat();
}
uintptr_t flattenData = str->d.u1.flattenData;
if (IsSame<CharT, char16_t>::value)
str->d.u1.flags = DEPENDENT_FLAGS;
else
str->d.u1.flags = DEPENDENT_FLAGS | LATIN1_CHARS_BIT;
str->d.u1.length = pos - str->asLinear().nonInlineChars<CharT>(nogc);
str->d.s.u3.base = (JSLinearString*)this; /* will be true on exit */
StringWriteBarrierPost(maybecx, (JSString**)&str->d.s.u3.base);
str = (JSString*)(flattenData & ~Tag_Mask);
if ((flattenData & Tag_Mask) == Tag_VisitRightChild)
goto visit_right_child;
MOZ_ASSERT((flattenData & Tag_Mask) == Tag_FinishNode);
goto finish_node;
}
}
