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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
#include "vm/StringType-inl.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/HashFunctions.h"
#include "mozilla/Latin1.h"
#include "mozilla/MathAlgorithms.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/PodOperations.h"
#include "mozilla/RangedPtr.h"
#include "mozilla/TextUtils.h"
#include "mozilla/Utf8.h"
#include "mozilla/Vector.h"
#include <algorithm> // std::{all_of,copy_n,enable_if,is_const,move}
#include <iterator> // std::size
#include <type_traits> // std::is_same, std::is_unsigned
#include "jsfriendapi.h"
#include "jsnum.h"
#include "builtin/Boolean.h"
#ifdef ENABLE_RECORD_TUPLE
# include "builtin/RecordObject.h"
#endif
#include "frontend/BytecodeCompiler.h"
#include "gc/AllocKind.h"
#include "gc/MaybeRooted.h"
#include "gc/Nursery.h"
#include "js/CharacterEncoding.h"
#include "js/friend/ErrorMessages.h" // js::GetErrorMessage, JSMSG_*
#include "js/PropertyAndElement.h" // JS_DefineElement
#include "js/StableStringChars.h"
#include "js/UbiNode.h"
#include "util/Unicode.h"
#include "vm/GeckoProfiler.h"
#include "vm/StaticStrings.h"
#include "vm/ToSource.h" // js::ValueToSource
#include "gc/Marking-inl.h"
#include "vm/GeckoProfiler-inl.h"
#ifdef ENABLE_RECORD_TUPLE
# include "vm/RecordType.h"
# include "vm/TupleType.h"
#endif
using namespace js;
using mozilla::AsWritableChars;
using mozilla::ConvertLatin1toUtf16;
using mozilla::IsAsciiDigit;
using mozilla::IsUtf16Latin1;
using mozilla::LossyConvertUtf16toLatin1;
using mozilla::PodCopy;
using mozilla::RangedPtr;
using mozilla::RoundUpPow2;
using mozilla::Span;
using JS::AutoCheckCannotGC;
using JS::AutoStableStringChars;
using UniqueLatin1Chars = UniquePtr<Latin1Char[], JS::FreePolicy>;
size_t JSString::sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) {
// JSRope: do nothing, we'll count all children chars when we hit the leaf
// strings.
if (isRope()) {
return 0;
}
MOZ_ASSERT(isLinear());
// JSDependentString: do nothing, we'll count the chars when we hit the base
// string.
if (isDependent()) {
return 0;
}
// JSExternalString: Ask the embedding to tell us what's going on.
if (isExternal()) {
// Our callback isn't supposed to cause GC.
JS::AutoSuppressGCAnalysis nogc;
return asExternal().callbacks()->sizeOfBuffer(asExternal().twoByteChars(),
mallocSizeOf);
}
// JSExtensibleString: count the full capacity, not just the used space.
if (isExtensible()) {
JSExtensibleString& extensible = asExtensible();
return extensible.hasLatin1Chars()
? mallocSizeOf(extensible.rawLatin1Chars())
: mallocSizeOf(extensible.rawTwoByteChars());
}
// JSInlineString, JSFatInlineString [JSInlineAtom, JSFatInlineAtom]: the
// chars are inline.
if (isInline()) {
return 0;
}
// Everything else: measure the space for the chars.
JSLinearString& linear = asLinear();
MOZ_ASSERT(linear.ownsMallocedChars());
return linear.hasLatin1Chars() ? mallocSizeOf(linear.rawLatin1Chars())
: mallocSizeOf(linear.rawTwoByteChars());
}
JS::ubi::Node::Size JS::ubi::Concrete<JSString>::size(
mozilla::MallocSizeOf mallocSizeOf) const {
JSString& str = get();
size_t size;
if (str.isAtom()) {
size =
str.isFatInline() ? sizeof(js::FatInlineAtom) : sizeof(js::NormalAtom);
} else {
size = str.isFatInline() ? sizeof(JSFatInlineString) : sizeof(JSString);
}
if (IsInsideNursery(&str)) {
size += Nursery::nurseryCellHeaderSize();
}
size += str.sizeOfExcludingThis(mallocSizeOf);
return size;
}
const char16_t JS::ubi::Concrete<JSString>::concreteTypeName[] = u"JSString";
mozilla::Maybe<std::tuple<size_t, size_t> > JSString::encodeUTF8Partial(
const JS::AutoRequireNoGC& nogc, mozilla::Span<char> buffer) const {
mozilla::Vector<const JSString*, 16, SystemAllocPolicy> stack;
const JSString* current = this;
char16_t pendingLeadSurrogate = 0; // U+0000 means no pending lead surrogate
size_t totalRead = 0;
size_t totalWritten = 0;
for (;;) {
if (current->isRope()) {
JSRope& rope = current->asRope();
if (!stack.append(rope.rightChild())) {
// OOM
return mozilla::Nothing();
}
current = rope.leftChild();
continue;
}
JSLinearString& linear = current->asLinear();
if (MOZ_LIKELY(linear.hasLatin1Chars())) {
if (MOZ_UNLIKELY(pendingLeadSurrogate)) {
if (buffer.Length() < 3) {
return mozilla::Some(std::make_tuple(totalRead, totalWritten));
}
buffer[0] = '\xEF';
buffer[1] = '\xBF';
buffer[2] = '\xBD';
buffer = buffer.From(3);
totalRead += 1; // pendingLeadSurrogate
totalWritten += 3;
pendingLeadSurrogate = 0;
}
auto src = mozilla::AsChars(
mozilla::Span(linear.latin1Chars(nogc), linear.length()));
size_t read;
size_t written;
std::tie(read, written) =
mozilla::ConvertLatin1toUtf8Partial(src, buffer);
buffer = buffer.From(written);
totalRead += read;
totalWritten += written;
if (read < src.Length()) {
return mozilla::Some(std::make_tuple(totalRead, totalWritten));
}
} else {
auto src = mozilla::Span(linear.twoByteChars(nogc), linear.length());
if (MOZ_UNLIKELY(pendingLeadSurrogate)) {
char16_t first = 0;
if (!src.IsEmpty()) {
first = src[0];
}
if (unicode::IsTrailSurrogate(first)) {
// Got a surrogate pair
if (buffer.Length() < 4) {
return mozilla::Some(std::make_tuple(totalRead, totalWritten));
}
uint32_t astral = unicode::UTF16Decode(pendingLeadSurrogate, first);
buffer[0] = char(0b1111'0000 | (astral >> 18));
buffer[1] = char(0b1000'0000 | ((astral >> 12) & 0b11'1111));
buffer[2] = char(0b1000'0000 | ((astral >> 6) & 0b11'1111));
buffer[3] = char(0b1000'0000 | (astral & 0b11'1111));
src = src.From(1);
buffer = buffer.From(4);
totalRead += 2; // both pendingLeadSurrogate and first!
totalWritten += 4;
} else {
// unpaired surrogate
if (buffer.Length() < 3) {
return mozilla::Some(std::make_tuple(totalRead, totalWritten));
}
buffer[0] = '\xEF';
buffer[1] = '\xBF';
buffer[2] = '\xBD';
buffer = buffer.From(3);
totalRead += 1; // pendingLeadSurrogate
totalWritten += 3;
}
pendingLeadSurrogate = 0;
}
if (!src.IsEmpty()) {
char16_t last = src[src.Length() - 1];
if (unicode::IsLeadSurrogate(last)) {
src = src.To(src.Length() - 1);
pendingLeadSurrogate = last;
} else {
MOZ_ASSERT(!pendingLeadSurrogate);
}
size_t read;
size_t written;
std::tie(read, written) =
mozilla::ConvertUtf16toUtf8Partial(src, buffer);
buffer = buffer.From(written);
totalRead += read;
totalWritten += written;
if (read < src.Length()) {
return mozilla::Some(std::make_tuple(totalRead, totalWritten));
}
}
}
if (stack.empty()) {
break;
}
current = stack.popCopy();
}
if (MOZ_UNLIKELY(pendingLeadSurrogate)) {
if (buffer.Length() < 3) {
return mozilla::Some(std::make_tuple(totalRead, totalWritten));
}
buffer[0] = '\xEF';
buffer[1] = '\xBF';
buffer[2] = '\xBD';
// No need to update buffer and pendingLeadSurrogate anymore
totalRead += 1;
totalWritten += 3;
}
return mozilla::Some(std::make_tuple(totalRead, totalWritten));
}
#if defined(DEBUG) || defined(JS_JITSPEW) || defined(JS_CACHEIR_SPEW)
template <typename CharT>
/*static */
void JSString::dumpChars(const CharT* s, size_t n, js::GenericPrinter& out) {
if (n == SIZE_MAX) {
n = 0;
while (s[n]) {
n++;
}
}
out.put("\"");
dumpCharsNoQuote(s, n, out);
out.putChar('"');
}
template void JSString::dumpChars(const Latin1Char* s, size_t n,
js::GenericPrinter& out);
template void JSString::dumpChars(const char16_t* s, size_t n,
js::GenericPrinter& out);
template <typename CharT>
/*static */
void JSString::dumpCharsNoQuote(const CharT* s, size_t n,
js::GenericPrinter& out) {
for (size_t i = 0; i < n; i++) {
char16_t c = s[i];
if (c == '\n') {
out.put("\\n");
} else if (c == '\t') {
out.put("\\t");
} else if (c >= 32 && c < 127) {
out.putChar((char)s[i]);
} else if (c <= 255) {
out.printf("\\x%02x", unsigned(c));
} else {
out.printf("\\u%04x", unsigned(c));
}
}
}
template void JSString::dumpCharsNoQuote(const Latin1Char* s, size_t n,
js::GenericPrinter& out);
template void JSString::dumpCharsNoQuote(const char16_t* s, size_t n,
js::GenericPrinter& out);
void JSString::dumpCharsNoNewline(js::GenericPrinter& out) {
if (JSLinearString* linear = ensureLinear(nullptr)) {
AutoCheckCannotGC nogc;
if (hasLatin1Chars()) {
out.put("[Latin 1]");
dumpChars(linear->latin1Chars(nogc), length(), out);
} else {
out.put("[2 byte]");
dumpChars(linear->twoByteChars(nogc), length(), out);
}
} else {
out.put("(oom in JSString::dumpCharsNoNewline)");
}
}
void JSString::dumpCharsNoQuote(js::GenericPrinter& out) {
if (JSLinearString* linear = ensureLinear(nullptr)) {
AutoCheckCannotGC nogc;
if (hasLatin1Chars()) {
dumpCharsNoQuote(linear->latin1Chars(nogc), length(), out);
} else {
dumpCharsNoQuote(linear->twoByteChars(nogc), length(), out);
}
} else {
out.put("(oom in JSString::dumpCharsNoNewline)");
}
}
void JSString::dump() {
js::Fprinter out(stderr);
dump(out);
}
void JSString::dump(js::GenericPrinter& out) {
dumpNoNewline(out);
out.putChar('\n');
}
void JSString::dumpNoNewline(js::GenericPrinter& out) {
if (JSLinearString* linear = ensureLinear(nullptr)) {
AutoCheckCannotGC nogc;
if (hasLatin1Chars()) {
const Latin1Char* chars = linear->latin1Chars(nogc);
out.printf("JSString* (%p) = Latin1Char * (%p) = ", (void*)this,
(void*)chars);
dumpChars(chars, length(), out);
} else {
const char16_t* chars = linear->twoByteChars(nogc);
out.printf("JSString* (%p) = char16_t * (%p) = ", (void*)this,
(void*)chars);
dumpChars(chars, length(), out);
}
} else {
out.put("(oom in JSString::dump)");
}
}
void JSString::dumpRepresentation(js::GenericPrinter& out, int indent) const {
if (isRope()) {
asRope().dumpRepresentation(out, indent);
} else if (isDependent()) {
asDependent().dumpRepresentation(out, indent);
} else if (isExternal()) {
asExternal().dumpRepresentation(out, indent);
} else if (isExtensible()) {
asExtensible().dumpRepresentation(out, indent);
} else if (isInline()) {
asInline().dumpRepresentation(out, indent);
} else if (isLinear()) {
asLinear().dumpRepresentation(out, indent);
} else {
MOZ_CRASH("Unexpected JSString representation");
}
}
void JSString::dumpRepresentationHeader(js::GenericPrinter& out,
const char* subclass) const {
uint32_t flags = JSString::flags();
// Print the string's address as an actual C++ expression, to facilitate
// copy-and-paste into a debugger.
out.printf("((%s*) %p) length: %zu flags: 0x%x", subclass, this, length(),
flags);
if (flags & LINEAR_BIT) out.put(" LINEAR");
if (flags & DEPENDENT_BIT) out.put(" DEPENDENT");
if (flags & INLINE_CHARS_BIT) out.put(" INLINE_CHARS");
if (flags & ATOM_BIT)
out.put(" ATOM");
else
out.put(" (NON ATOM)");
if (isPermanentAtom()) out.put(" PERMANENT");
if (flags & LATIN1_CHARS_BIT) out.put(" LATIN1");
if (flags & INDEX_VALUE_BIT) out.printf(" INDEX_VALUE(%u)", getIndexValue());
if (!isTenured()) out.put(" NURSERY");
out.putChar('\n');
}
void JSLinearString::dumpRepresentationChars(js::GenericPrinter& out,
int indent) const {
if (hasLatin1Chars()) {
out.printf("%*schars: ((Latin1Char*) %p) ", indent, "", rawLatin1Chars());
dumpChars(rawLatin1Chars(), length(), out);
} else {
out.printf("%*schars: ((char16_t*) %p) ", indent, "", rawTwoByteChars());
dumpChars(rawTwoByteChars(), length(), out);
}
out.putChar('\n');
}
bool JSString::equals(const char* s) {
JSLinearString* linear = ensureLinear(nullptr);
if (!linear) {
// This is DEBUG-only code.
fprintf(stderr, "OOM in JSString::equals!\n");
return false;
}
return StringEqualsAscii(linear, s);
}
#endif /* defined(DEBUG) || defined(JS_JITSPEW) || defined(JS_CACHEIR_SPEW) */
JSExtensibleString& JSLinearString::makeExtensible(size_t capacity) {
MOZ_ASSERT(!isDependent());
MOZ_ASSERT(!isInline());
MOZ_ASSERT(!isAtom());
MOZ_ASSERT(!isExternal());
MOZ_ASSERT(capacity >= length());
js::RemoveCellMemory(this, allocSize(), js::MemoryUse::StringContents);
setLengthAndFlags(length(), flags() | EXTENSIBLE_FLAGS);
d.s.u3.capacity = capacity;
js::AddCellMemory(this, allocSize(), js::MemoryUse::StringContents);
return asExtensible();
}
template <typename CharT>
static MOZ_ALWAYS_INLINE bool AllocChars(JSString* str, size_t length,
CharT** chars, size_t* capacity) {
/*
* Grow by 12.5% if the buffer is very large. Otherwise, round up to the
* next power of 2. This is similar to what we do with arrays; see
* JSObject::ensureDenseArrayElements.
*/
static const size_t DOUBLING_MAX = 1024 * 1024;
*capacity =
length > DOUBLING_MAX ? length + (length / 8) : RoundUpPow2(length);
static_assert(JSString::MAX_LENGTH * sizeof(CharT) <= UINT32_MAX);
*chars =
str->zone()->pod_arena_malloc<CharT>(js::StringBufferArena, *capacity);
return *chars != nullptr;
}
UniqueLatin1Chars JSRope::copyLatin1Chars(JSContext* maybecx,
arena_id_t destArenaId) const {
return copyCharsInternal<Latin1Char>(maybecx, destArenaId);
}
UniqueTwoByteChars JSRope::copyTwoByteChars(JSContext* maybecx,
arena_id_t destArenaId) const {
return copyCharsInternal<char16_t>(maybecx, destArenaId);
}
template <typename CharT>
UniquePtr<CharT[], JS::FreePolicy> JSRope::copyCharsInternal(
JSContext* maybecx, arena_id_t destArenaId) const {
// Left-leaning ropes are far more common than right-leaning ropes, so
// perform a non-destructive traversal of the rope, right node first,
// splatting each node's characters into a contiguous buffer.
size_t n = length();
UniquePtr<CharT[], JS::FreePolicy> out;
if (maybecx) {
out.reset(maybecx->pod_arena_malloc<CharT>(destArenaId, n));
} else {
out.reset(js_pod_arena_malloc<CharT>(destArenaId, n));
}
if (!out) {
return nullptr;
}
Vector<const JSString*, 8, SystemAllocPolicy> nodeStack;
const JSString* str = this;
CharT* end = out.get() + str->length();
while (true) {
if (str->isRope()) {
if (!nodeStack.append(str->asRope().leftChild())) {
if (maybecx) {
ReportOutOfMemory(maybecx);
}
return nullptr;
}
str = str->asRope().rightChild();
} else {
end -= str->length();
CopyChars(end, str->asLinear());
if (nodeStack.empty()) {
break;
}
str = nodeStack.popCopy();
}
}
MOZ_ASSERT(end == out.get());
return out;
}
template <typename CharT>
void AddStringToHash(uint32_t* hash, const CharT* chars, size_t len) {
// It's tempting to use |HashString| instead of this loop, but that's
// slightly different than our existing implementation for non-ropes. We
// want to pretend we have a contiguous set of chars so we need to
// accumulate char by char rather than generate a new hash for substring
// and then accumulate that.
for (size_t i = 0; i < len; i++) {
*hash = mozilla::AddToHash(*hash, chars[i]);
}
}
void AddStringToHash(uint32_t* hash, const JSString* str) {
AutoCheckCannotGC nogc;
const auto& s = str->asLinear();
if (s.hasLatin1Chars()) {
AddStringToHash(hash, s.latin1Chars(nogc), s.length());
} else {
AddStringToHash(hash, s.twoByteChars(nogc), s.length());
}
}
bool JSRope::hash(uint32_t* outHash) const {
Vector<const JSString*, 8, SystemAllocPolicy> nodeStack;
const JSString* str = this;
*outHash = 0;
while (true) {
if (str->isRope()) {
if (!nodeStack.append(str->asRope().rightChild())) {
return false;
}
str = str->asRope().leftChild();
} else {
AddStringToHash(outHash, str);
if (nodeStack.empty()) {
break;
}
str = nodeStack.popCopy();
}
}
return true;
}
#if defined(DEBUG) || defined(JS_JITSPEW) || defined(JS_CACHEIR_SPEW)
void JSRope::dumpRepresentation(js::GenericPrinter& out, int indent) const {
dumpRepresentationHeader(out, "JSRope");
indent += 2;
out.printf("%*sleft: ", indent, "");
leftChild()->dumpRepresentation(out, indent);
out.printf("%*sright: ", indent, "");
rightChild()->dumpRepresentation(out, indent);
}
#endif
namespace js {
template <>
void CopyChars(char16_t* dest, const JSLinearString& str) {
AutoCheckCannotGC nogc;
if (str.hasTwoByteChars()) {
PodCopy(dest, str.twoByteChars(nogc), str.length());
} else {
CopyAndInflateChars(dest, str.latin1Chars(nogc), str.length());
}
}
template <>
void CopyChars(Latin1Char* dest, const JSLinearString& str) {
AutoCheckCannotGC nogc;
if (str.hasLatin1Chars()) {
PodCopy(dest, str.latin1Chars(nogc), str.length());
} else {
/*
* When we flatten a TwoByte rope, we turn child ropes (including Latin1
* ropes) into TwoByte dependent strings. If one of these strings is
* also part of another Latin1 rope tree, we can have a Latin1 rope with
* a TwoByte descendent and we end up here when we flatten it. Although
* the chars are stored as TwoByte, we know they must be in the Latin1
* range, so we can safely deflate here.
*/
size_t len = str.length();
const char16_t* chars = str.twoByteChars(nogc);
auto src = Span(chars, len);
MOZ_ASSERT(IsUtf16Latin1(src));
LossyConvertUtf16toLatin1(src, AsWritableChars(Span(dest, len)));
}
}
} /* namespace js */
template <typename CharT>
static constexpr uint32_t StringFlagsForCharType(uint32_t baseFlags) {
if constexpr (std::is_same_v<CharT, char16_t>) {
return baseFlags;
}
return baseFlags | JSString::LATIN1_CHARS_BIT;
}
static bool UpdateNurseryBuffersOnTransfer(js::Nursery& nursery, JSString* from,
JSString* to, void* buffer,
size_t size) {
// Update the list of buffers associated with nursery cells when |buffer| is
// moved from string |from| to string |to|, depending on whether those strings
// are in the nursery or not.
if (from->isTenured() && !to->isTenured()) {
// Tenured leftmost child is giving its chars buffer to the
// nursery-allocated root node.
if (!nursery.registerMallocedBuffer(buffer, size)) {
return false;
}
} else if (!from->isTenured() && to->isTenured()) {
// Leftmost child is giving its nursery-held chars buffer to a
// tenured string.
nursery.removeMallocedBuffer(buffer, size);
}
return true;
}
static bool CanReuseLeftmostBuffer(JSString* leftmostChild, size_t wholeLength,
bool hasTwoByteChars) {
if (!leftmostChild->isExtensible()) {
return false;
}
JSExtensibleString& str = leftmostChild->asExtensible();
return str.capacity() >= wholeLength &&
str.hasTwoByteChars() == hasTwoByteChars;
}
JSLinearString* JSRope::flatten(JSContext* maybecx) {
MOZ_ASSERT_IF(maybecx, maybecx->isMainThreadContext());
mozilla::Maybe<AutoGeckoProfilerEntry> entry;
if (maybecx) {
entry.emplace(maybecx, "JSRope::flatten");
}
JSLinearString* str = flattenInternal();
if (!str && maybecx) {
ReportOutOfMemory(maybecx);
}
return str;
}
JSLinearString* JSRope::flattenInternal() {
if (zone()->needsIncrementalBarrier()) {
return flattenInternal<WithIncrementalBarrier>();
}
return flattenInternal<NoBarrier>();
}
template <JSRope::UsingBarrier usingBarrier>
JSLinearString* JSRope::flattenInternal() {
if (hasTwoByteChars()) {
return flattenInternal<usingBarrier, char16_t>(this);
}
return flattenInternal<usingBarrier, Latin1Char>(this);
}
template <JSRope::UsingBarrier usingBarrier, typename CharT>
/* static */
JSLinearString* JSRope::flattenInternal(JSRope* root) {
/*
* Consider the DAG of JSRopes rooted at |root|, 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 = root->length();
size_t wholeCapacity;
CharT* wholeChars;
AutoCheckCannotGC nogc;
Nursery& nursery = root->runtimeFromMainThread()->gc.nursery();
/* Find the left most string, containing the first string. */
JSRope* leftmostRope = root;
while (leftmostRope->leftChild()->isRope()) {
leftmostRope = &leftmostRope->leftChild()->asRope();
}
JSString* leftmostChild = leftmostRope->leftChild();
bool reuseLeftmostBuffer = CanReuseLeftmostBuffer(
leftmostChild, wholeLength, std::is_same_v<CharT, char16_t>);
if (reuseLeftmostBuffer) {
JSExtensibleString& left = leftmostChild->asExtensible();
wholeCapacity = left.capacity();
wholeChars = const_cast<CharT*>(left.nonInlineChars<CharT>(nogc));
// Nursery::registerMallocedBuffer is fallible, so attempt it first before
// doing anything irreversible.
if (!UpdateNurseryBuffersOnTransfer(nursery, &left, root, wholeChars,
wholeCapacity * sizeof(CharT))) {
return nullptr;
}
} else {
// If we can't reuse the leftmost child's buffer, allocate a new one.
if (!AllocChars(root, wholeLength, &wholeChars, &wholeCapacity)) {
return nullptr;
}
if (!root->isTenured()) {
if (!nursery.registerMallocedBuffer(wholeChars,
wholeCapacity * sizeof(CharT))) {
js_free(wholeChars);
return nullptr;
}
}
}
JSRope* str = root;
CharT* pos = wholeChars;
JSRope* parent = nullptr;
uint32_t parentFlag = 0;
first_visit_node : {
MOZ_ASSERT_IF(str != root, parent && parentFlag);
MOZ_ASSERT(!str->asRope().isBeingFlattened());
ropeBarrierDuringFlattening<usingBarrier>(str);
JSString& left = *str->d.s.u2.left;
str->d.s.u2.parent = parent;
str->setFlagBit(parentFlag);
parent = nullptr;
parentFlag = 0;
if (left.isRope()) {
/* Return to this node when 'left' done, then goto visit_right_child. */
parent = str;
parentFlag = FLATTEN_VISIT_RIGHT;
str = &left.asRope();
goto first_visit_node;
}
if (!(reuseLeftmostBuffer && pos == wholeChars)) {
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. */
parent = str;
parentFlag = FLATTEN_FINISH_NODE;
str = &right.asRope();
goto first_visit_node;
}
CopyChars(pos, right.asLinear());
pos += right.length();
}
finish_node : {
if (str == root) {
goto finish_root;
}
MOZ_ASSERT(pos >= wholeChars);
CharT* chars = pos - str->length();
JSRope* strParent = str->d.s.u2.parent;
str->setNonInlineChars(chars);
MOZ_ASSERT(str->asRope().isBeingFlattened());
mozilla::DebugOnly<bool> visitRight = str->flags() & FLATTEN_VISIT_RIGHT;
bool finishNode = str->flags() & FLATTEN_FINISH_NODE;
MOZ_ASSERT(visitRight != finishNode);
// This also clears the flags related to flattening.
str->setLengthAndFlags(str->length(),
StringFlagsForCharType<CharT>(INIT_DEPENDENT_FLAGS));
str->d.s.u3.base =
reinterpret_cast<JSLinearString*>(root); /* will be true on exit */
// Every interior (rope) node in the rope's tree will be visited during
// the traversal and post-barriered here, so earlier additions of
// dependent.base -> root pointers are handled by this barrier as well.
//
// The only time post-barriers need do anything is when the root is in
// the nursery. Note that the root was a rope but will be an extensible
// string when we return, so it will not point to any strings and need
// not be barriered.
if (str->isTenured() && !root->isTenured()) {
root->storeBuffer()->putWholeCell(str);
}
str = strParent;
if (finishNode) {
goto finish_node;
}
MOZ_ASSERT(visitRight);
goto visit_right_child;
}
finish_root:
// We traversed all the way back up to the root so we're finished.
MOZ_ASSERT(str == root);
MOZ_ASSERT(pos == wholeChars + wholeLength);
root->setLengthAndFlags(wholeLength,
StringFlagsForCharType<CharT>(EXTENSIBLE_FLAGS));
root->setNonInlineChars(wholeChars);
root->d.s.u3.capacity = wholeCapacity;
AddCellMemory(root, root->asLinear().allocSize(), MemoryUse::StringContents);
if (reuseLeftmostBuffer) {
// Remove memory association for left node we're about to make into a
// dependent string.
JSString& left = *leftmostChild;
RemoveCellMemory(&left, left.allocSize(), MemoryUse::StringContents);
uint32_t flags = INIT_DEPENDENT_FLAGS;
if (left.inStringToAtomCache()) {
flags |= IN_STRING_TO_ATOM_CACHE;
}
left.setLengthAndFlags(left.length(), StringFlagsForCharType<CharT>(flags));
left.d.s.u3.base = &root->asLinear();
if (left.isTenured() && !root->isTenured()) {
// leftmost child -> root is a tenured -> nursery edge.
root->storeBuffer()->putWholeCell(&left);
}
}
return &root->asLinear();
}
template <JSRope::UsingBarrier usingBarrier>
/* static */
inline void JSRope::ropeBarrierDuringFlattening(JSRope* rope) {
MOZ_ASSERT(!rope->isBeingFlattened());
if constexpr (usingBarrier) {
gc::PreWriteBarrierDuringFlattening(rope->leftChild());
gc::PreWriteBarrierDuringFlattening(rope->rightChild());
}
}
template <AllowGC allowGC>
static JSLinearString* EnsureLinear(
JSContext* cx,
typename MaybeRooted<JSString*, allowGC>::HandleType string) {
JSLinearString* linear = string->ensureLinear(cx);
// Don't report an exception if GC is not allowed, just return nullptr.
if (!linear && !allowGC) {
cx->recoverFromOutOfMemory();
}
return linear;
}
template <AllowGC allowGC>
JSString* js::ConcatStrings(
JSContext* cx, typename MaybeRooted<JSString*, allowGC>::HandleType left,
typename MaybeRooted<JSString*, allowGC>::HandleType right,
gc::InitialHeap heap) {
MOZ_ASSERT_IF(!left->isAtom(), cx->isInsideCurrentZone(left));
MOZ_ASSERT_IF(!right->isAtom(), cx->isInsideCurrentZone(right));
size_t leftLen = left->length();
if (leftLen == 0) {
return right;
}
size_t rightLen = right->length();
if (rightLen == 0) {
return left;
}
size_t wholeLength = leftLen + rightLen;
if (MOZ_UNLIKELY(wholeLength > JSString::MAX_LENGTH)) {
// Don't report an exception if GC is not allowed, just return nullptr.
if (allowGC) {
js::ReportOversizedAllocation(cx, JSMSG_ALLOC_OVERFLOW);
}
return nullptr;
}
bool isLatin1 = left->hasLatin1Chars() && right->hasLatin1Chars();
bool canUseInline = isLatin1
? JSInlineString::lengthFits<Latin1Char>(wholeLength)
: JSInlineString::lengthFits<char16_t>(wholeLength);
if (canUseInline) {
Latin1Char* latin1Buf = nullptr; // initialize to silence GCC warning
char16_t* twoByteBuf = nullptr; // initialize to silence GCC warning
JSInlineString* str =
isLatin1
? AllocateInlineString<allowGC>(cx, wholeLength, &latin1Buf, heap)
: AllocateInlineString<allowGC>(cx, wholeLength, &twoByteBuf, heap);
if (!str) {
return nullptr;
}
AutoCheckCannotGC nogc;
JSLinearString* leftLinear = EnsureLinear<allowGC>(cx, left);
if (!leftLinear) {
return nullptr;
}
JSLinearString* rightLinear = EnsureLinear<allowGC>(cx, right);
if (!rightLinear) {
return nullptr;
}
if (isLatin1) {
PodCopy(latin1Buf, leftLinear->latin1Chars(nogc), leftLen);
PodCopy(latin1Buf + leftLen, rightLinear->latin1Chars(nogc), rightLen);
} else {
if (leftLinear->hasTwoByteChars()) {
PodCopy(twoByteBuf, leftLinear->twoByteChars(nogc), leftLen);
} else {
CopyAndInflateChars(twoByteBuf, leftLinear->latin1Chars(nogc), leftLen);
}
if (rightLinear->hasTwoByteChars()) {
PodCopy(twoByteBuf + leftLen, rightLinear->twoByteChars(nogc),
rightLen);
} else {
CopyAndInflateChars(twoByteBuf + leftLen,
rightLinear->latin1Chars(nogc), rightLen);
}
}
return str;
}
return JSRope::new_<allowGC>(cx, left, right, wholeLength, heap);
}
template JSString* js::ConcatStrings<CanGC>(JSContext* cx, HandleString left,
HandleString right,
gc::InitialHeap heap);
template JSString* js::ConcatStrings<NoGC>(JSContext* cx, JSString* const& left,
JSString* const& right,
gc::InitialHeap heap);
/**
* Copy |src[0..length]| to |dest[0..length]| when copying doesn't narrow and
* therefore can't lose information.
*/
static inline void FillChars(char16_t* dest, const unsigned char* src,
size_t length) {
ConvertLatin1toUtf16(AsChars(Span(src, length)), Span(dest, length));
}
static inline void FillChars(char16_t* dest, const char16_t* src,
size_t length) {
PodCopy(dest, src, length);
}
static inline void FillChars(unsigned char* dest, const unsigned char* src,
size_t length) {
PodCopy(dest, src, length);
}
/**
* Copy |src[0..length]| to |dest[0..length]| when copying *does* narrow, but
* the user guarantees every runtime |src[i]| value can be stored without change
* of value in |dest[i]|.
*/
static inline void FillFromCompatible(unsigned char* dest, const char16_t* src,
size_t length) {
LossyConvertUtf16toLatin1(Span(src, length),
AsWritableChars(Span(dest, length)));
}
#if defined(DEBUG) || defined(JS_JITSPEW) || defined(JS_CACHEIR_SPEW)
void JSDependentString::dumpRepresentation(js::GenericPrinter& out,
int indent) const {
dumpRepresentationHeader(out, "JSDependentString");
indent += 2;
out.printf("%*soffset: %zu\n", indent, "", baseOffset());
out.printf("%*sbase: ", indent, "");
base()->dumpRepresentation(out, indent);
}
#endif
bool js::EqualChars(const JSLinearString* str1, const JSLinearString* str2) {
MOZ_ASSERT(str1->length() == str2->length());
size_t len = str1->length();
AutoCheckCannotGC nogc;
if (str1->hasTwoByteChars()) {
if (str2->hasTwoByteChars()) {
return EqualChars(str1->twoByteChars(nogc), str2->twoByteChars(nogc),
len);
}
return EqualChars(str2->latin1Chars(nogc), str1->twoByteChars(nogc), len);
}
if (str2->hasLatin1Chars()) {
return EqualChars(str1->latin1Chars(nogc), str2->latin1Chars(nogc), len);
}
return EqualChars(str1->latin1Chars(nogc), str2->twoByteChars(nogc), len);
}
bool js::HasSubstringAt(JSLinearString* text, JSLinearString* pat,
size_t start) {
MOZ_ASSERT(start + pat->length() <= text->length());
size_t patLen = pat->length();
AutoCheckCannotGC nogc;
if (text->hasLatin1Chars()) {
const Latin1Char* textChars = text->latin1Chars(nogc) + start;
if (pat->hasLatin1Chars()) {
return EqualChars(textChars, pat->latin1Chars(nogc), patLen);
}
return EqualChars(textChars, pat->twoByteChars(nogc), patLen);
}
const char16_t* textChars = text->twoByteChars(nogc) + start;
if (pat->hasTwoByteChars()) {
return EqualChars(textChars, pat->twoByteChars(nogc), patLen);
}
return EqualChars(pat->latin1Chars(nogc), textChars, patLen);
}
bool js::EqualStrings(JSContext* cx, JSString* str1, JSString* str2,
bool* result) {
if (str1 == str2) {
*result = true;
return true;
}
size_t length1 = str1->length();
if (length1 != str2->length()) {
*result = false;
return true;
}
JSLinearString* linear1 = str1->ensureLinear(cx);
if (!linear1) {
return false;
}
JSLinearString* linear2 = str2->ensureLinear(cx);
if (!linear2) {
return false;
}
*result = EqualChars(linear1, linear2);
return true;
}
bool js::EqualStrings(const JSLinearString* str1, const JSLinearString* str2) {
if (str1 == str2) {
return true;
}
size_t length1 = str1->length();
if (length1 != str2->length()) {
return false;
}
return EqualChars(str1, str2);
}
int32_t js::CompareChars(const char16_t* s1, size_t len1, JSLinearString* s2) {
AutoCheckCannotGC nogc;
return s2->hasLatin1Chars()
? CompareChars(s1, len1, s2->latin1Chars(nogc), s2->length())
: CompareChars(s1, len1, s2->twoByteChars(nogc), s2->length());
}
static int32_t CompareStringsImpl(const JSLinearString* str1,
const JSLinearString* str2) {
size_t len1 = str1->length();
size_t len2 = str2->length();
AutoCheckCannotGC nogc;
if (str1->hasLatin1Chars()) {
const Latin1Char* chars1 = str1->latin1Chars(nogc);
return str2->hasLatin1Chars()
? CompareChars(chars1, len1, str2->latin1Chars(nogc), len2)
: CompareChars(chars1, len1, str2->twoByteChars(nogc), len2);
}
const char16_t* chars1 = str1->twoByteChars(nogc);
return str2->hasLatin1Chars()
? CompareChars(chars1, len1, str2->latin1Chars(nogc), len2)
: CompareChars(chars1, len1, str2->twoByteChars(nogc), len2);
}
bool js::CompareStrings(JSContext* cx, JSString* str1, JSString* str2,
int32_t* result) {
MOZ_ASSERT(str1);
MOZ_ASSERT(str2);
if (str1 == str2) {
*result = 0;
return true;
}
JSLinearString* linear1 = str1->ensureLinear(cx);
if (!linear1) {
return false;
}
JSLinearString* linear2 = str2->ensureLinear(cx);
if (!linear2) {
return false;
}
*result = CompareStringsImpl(linear1, linear2);
return true;
}
int32_t js::CompareStrings(const JSLinearString* str1,
const JSLinearString* str2) {
MOZ_ASSERT(str1);
MOZ_ASSERT(str2);
if (str1 == str2) {
return 0;
}
return CompareStringsImpl(str1, str2);
}
bool js::StringIsAscii(JSLinearString* str) {
JS::AutoCheckCannotGC nogc;
if (str->hasLatin1Chars()) {
return mozilla::IsAscii(
AsChars(Span(str->latin1Chars(nogc), str->length())));
}
return mozilla::IsAscii(Span(str->twoByteChars(nogc), str->length()));
}
bool js::StringEqualsAscii(JSLinearString* str, const char* asciiBytes) {
return StringEqualsAscii(str, asciiBytes, strlen(asciiBytes));
}
bool js::StringEqualsAscii(JSLinearString* str, const char* asciiBytes,
size_t length) {
MOZ_ASSERT(JS::StringIsASCII(Span(asciiBytes, length)));
if (length != str->length()) {
return false;
}
const Latin1Char* latin1 = reinterpret_cast<const Latin1Char*>(asciiBytes);
AutoCheckCannotGC nogc;
return str->hasLatin1Chars()
? EqualChars(latin1, str->latin1Chars(nogc), length)
: EqualChars(latin1, str->twoByteChars(nogc), length);
}
template <typename CharT>
bool js::CheckStringIsIndex(const CharT* s, size_t length, uint32_t* indexp) {
MOZ_ASSERT(length > 0);
MOZ_ASSERT(length <= UINT32_CHAR_BUFFER_LENGTH);
MOZ_ASSERT(IsAsciiDigit(*s),
"caller's fast path must have checked first char");
RangedPtr<const CharT> cp(s, length);
const RangedPtr<const CharT> end(s + length, s, length);
uint32_t index = AsciiDigitToNumber(*cp++);
uint32_t oldIndex = 0;
uint32_t c = 0;
if (index != 0) {
// Consume remaining characters only if the first character isn't '0'.
while (cp < end && IsAsciiDigit(*cp)) {
oldIndex = index;
c = AsciiDigitToNumber(*cp);
index = 10 * index + c;
cp++;
}
}
// It's not an integer index if there are characters after the number.
if (cp != end) {
return false;
}
// Look out for "4294967295" and larger-number strings that fit in
// UINT32_CHAR_BUFFER_LENGTH: only unsigned 32-bit integers less than or equal
// to MAX_ARRAY_INDEX shall pass.
if (oldIndex < MAX_ARRAY_INDEX / 10 ||
(oldIndex == MAX_ARRAY_INDEX / 10 && c <= (MAX_ARRAY_INDEX % 10))) {
MOZ_ASSERT(index <= MAX_ARRAY_INDEX);
*indexp = index;
return true;
}
return false;
}
template bool js::CheckStringIsIndex(const Latin1Char* s, size_t length,
uint32_t* indexp);
template bool js::CheckStringIsIndex(const char16_t* s, size_t length,
uint32_t* indexp);
template <typename CharT>
static uint32_t AtomCharsToIndex(const CharT* s, size_t length) {
// Chars are known to be a valid index value (as determined by
// CheckStringIsIndex) that didn't fit in the "index value" bits in the
// header.
MOZ_ASSERT(length > 0);
MOZ_ASSERT(length <= UINT32_CHAR_BUFFER_LENGTH);
RangedPtr<const CharT> cp(s, length);
const RangedPtr<const CharT> end(s + length, s, length);
MOZ_ASSERT(IsAsciiDigit(*cp));
uint32_t index = AsciiDigitToNumber(*cp++);
MOZ_ASSERT(index != 0);
while (cp < end) {
MOZ_ASSERT(IsAsciiDigit(*cp));
index = 10 * index + AsciiDigitToNumber(*cp);
cp++;
}
MOZ_ASSERT(index <= MAX_ARRAY_INDEX);
return index;
}
uint32_t JSAtom::getIndexSlow() const {
MOZ_ASSERT(isIndex());
MOZ_ASSERT(!hasIndexValue());
size_t len = length();
AutoCheckCannotGC nogc;
return hasLatin1Chars() ? AtomCharsToIndex(latin1Chars(nogc), len)
: AtomCharsToIndex(twoByteChars(nogc), len);
}
static void MarkStringAndBasesNonDeduplicatable(JSLinearString* s) {
while (true) {
if (!s->isTenured()) {
s->setNonDeduplicatable();
}
if (!s->hasBase()) {
break;
}
s = s->base();
}
}
bool AutoStableStringChars::init(JSContext* cx, JSString* s) {
Rooted<JSLinearString*> linearString(cx, s->ensureLinear(cx));
if (!linearString) {
return false;
}
MOZ_ASSERT(state_ == Uninitialized);
// If the chars are inline then we need to copy them since they may be moved
// by a compacting GC.
if (baseIsInline(linearString)) {
return linearString->hasTwoByteChars() ? copyTwoByteChars(cx, linearString)
: copyLatin1Chars(cx, linearString);
}
if (linearString->hasLatin1Chars()) {
state_ = Latin1;
latin1Chars_ = linearString->rawLatin1Chars();
} else {
state_ = TwoByte;
twoByteChars_ = linearString->rawTwoByteChars();
}
MarkStringAndBasesNonDeduplicatable(linearString);
s_ = linearString;
return true;
}
bool AutoStableStringChars::initTwoByte(JSContext* cx, JSString* s) {
Rooted<JSLinearString*> linearString(cx, s->ensureLinear(cx));
if (!linearString) {
return false;
}
MOZ_ASSERT(state_ == Uninitialized);
if (linearString->hasLatin1Chars()) {
return copyAndInflateLatin1Chars(cx, linearString);
}
// If the chars are inline then we need to copy them since they may be moved
// by a compacting GC.
if (baseIsInline(linearString)) {
return copyTwoByteChars(cx, linearString);
}
state_ = TwoByte;
twoByteChars_ = linearString->rawTwoByteChars();
MarkStringAndBasesNonDeduplicatable(linearString);
s_ = linearString;
return true;
}
bool AutoStableStringChars::baseIsInline(Handle<JSLinearString*> linearString) {
JSString* base = linearString;
while (base->isDependent()) {
base = base->asDependent().base();
}
return base->isInline();
}
template <typename T>
T* AutoStableStringChars::allocOwnChars(JSContext* cx, size_t count) {
static_assert(
InlineCapacity >=
sizeof(JS::Latin1Char) * JSFatInlineString::MAX_LENGTH_LATIN1 &&
InlineCapacity >=
sizeof(char16_t) * JSFatInlineString::MAX_LENGTH_TWO_BYTE,
"InlineCapacity too small to hold fat inline strings");
static_assert((JSString::MAX_LENGTH &
mozilla::tl::MulOverflowMask<sizeof(T)>::value) == 0,
"Size calculation can overflow");
MOZ_ASSERT(count <= JSString::MAX_LENGTH);
size_t size = sizeof(T) * count;
ownChars_.emplace(cx);
if (!ownChars_->resize(size)) {
ownChars_.reset();
return nullptr;
}
return reinterpret_cast<T*>(ownChars_->begin());
}
bool AutoStableStringChars::copyAndInflateLatin1Chars(
JSContext* cx, Handle<JSLinearString*> linearString) {
char16_t* chars = allocOwnChars<char16_t>(cx, linearString->length());
if (!chars) {
return false;
}
FillChars(chars, linearString->rawLatin1Chars(), linearString->length());
state_ = TwoByte;
twoByteChars_ = chars;
s_ = linearString;
return true;
}
bool AutoStableStringChars::copyLatin1Chars(
JSContext* cx, Handle<JSLinearString*> linearString) {
size_t length = linearString->length();
JS::Latin1Char* chars = allocOwnChars<JS::Latin1Char>(cx, length);
if (!chars) {
return false;
}
FillChars(chars, linearString->rawLatin1Chars(), length);
state_ = Latin1;
latin1Chars_ = chars;
s_ = linearString;
return true;
}
bool AutoStableStringChars::copyTwoByteChars(
JSContext* cx, Handle<JSLinearString*> linearString) {
size_t length = linearString->length();
char16_t* chars = allocOwnChars<char16_t>(cx, length);
if (!chars) {
return false;
}
FillChars(chars, linearString->rawTwoByteChars(), length);
state_ = TwoByte;
twoByteChars_ = chars;
s_ = linearString;
return true;
}
template <>
bool JS::SourceText<char16_t>::initMaybeBorrowed(
JSContext* cx, JS::AutoStableStringChars& linearChars) {
MOZ_ASSERT(linearChars.isTwoByte(),
"AutoStableStringChars must be initialized with char16_t");
const char16_t* chars = linearChars.twoByteChars();
size_t length = linearChars.length();
JS::SourceOwnership ownership = linearChars.maybeGiveOwnershipToCaller()
? JS::SourceOwnership::TakeOwnership
: JS::SourceOwnership::Borrowed;
return initImpl(cx, chars, length, ownership);
}
template <>
bool JS::SourceText<char16_t>::initMaybeBorrowed(
JS::FrontendContext* fc, JS::AutoStableStringChars& linearChars) {
MOZ_ASSERT(linearChars.isTwoByte(),
"AutoStableStringChars must be initialized with char16_t");
const char16_t* chars = linearChars.twoByteChars();
size_t length = linearChars.length();
JS::SourceOwnership ownership = linearChars.maybeGiveOwnershipToCaller()
? JS::SourceOwnership::TakeOwnership
: JS::SourceOwnership::Borrowed;
return initImpl(fc, chars, length, ownership);
}
#if defined(DEBUG) || defined(JS_JITSPEW) || defined(JS_CACHEIR_SPEW)
void JSAtom::dump(js::GenericPrinter& out) {
out.printf("JSAtom* (%p) = ", (void*)this);
this->JSString::dump(out);
}
void JSAtom::dump() {
Fprinter out(stderr);
dump(out);
}
void JSExternalString::dumpRepresentation(js::GenericPrinter& out,
int indent) const {
dumpRepresentationHeader(out, "JSExternalString");
indent += 2;
out.printf("%*sfinalizer: ((JSExternalStringCallbacks*) %p)\n", indent, "",
callbacks());
dumpRepresentationChars(out, indent);
}
#endif /* defined(DEBUG) || defined(JS_JITSPEW) || defined(JS_CACHEIR_SPEW) */
JSLinearString* js::NewDependentString(JSContext* cx, JSString* baseArg,
size_t start, size_t length,
gc::InitialHeap heap) {
if (length == 0) {
return cx->emptyString();
}
JSLinearString* base = baseArg->ensureLinear(cx);
if (!base) {
return nullptr;
}
if (start == 0 && length == base->length()) {
return base;
}
if (base->hasTwoByteChars()) {
AutoCheckCannotGC nogc;
const char16_t* chars = base->twoByteChars(nogc) + start;
if (JSLinearString* staticStr = cx->staticStrings().lookup(chars, length)) {
return staticStr;
}
} else {
AutoCheckCannotGC nogc;
const Latin1Char* chars = base->latin1Chars(nogc) + start;
if (JSLinearString* staticStr = cx->staticStrings().lookup(chars, length)) {
return staticStr;
}
}
return JSDependentString::new_(cx, base, start, length, heap);
}
static inline bool CanStoreCharsAsLatin1(const char16_t* s, size_t length) {
return IsUtf16Latin1(Span(s, length));
}
template <AllowGC allowGC>
static MOZ_ALWAYS_INLINE JSInlineString* NewInlineStringDeflated(
JSContext* cx, const mozilla::Range<const char16_t>& chars,
gc::InitialHeap heap = gc::DefaultHeap) {
size_t len = chars.length();
Latin1Char* storage;
JSInlineString* str = AllocateInlineString<allowGC>(cx, len, &storage, heap);
if (!str) {
return nullptr;
}
MOZ_ASSERT(CanStoreCharsAsLatin1(chars.begin().get(), len));
FillFromCompatible(storage, chars.begin().get(), len);
return str;
}
template <AllowGC allowGC>
static JSLinearString* NewStringDeflated(JSContext* cx, const char16_t* s,
size_t n, gc::InitialHeap heap) {
if (JSLinearString* str = TryEmptyOrStaticString(cx, s, n)) {