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string.cc
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string.cc
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// Copyright 2019 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/objects/string.h"
#include "src/common/assert-scope.h"
#include "src/common/globals.h"
#include "src/execution/isolate-utils.h"
#include "src/execution/thread-id.h"
#include "src/handles/handles-inl.h"
#include "src/heap/heap-inl.h"
#include "src/heap/local-factory-inl.h"
#include "src/heap/local-heap-inl.h"
#include "src/heap/memory-chunk.h"
#include "src/heap/read-only-heap.h"
#include "src/numbers/conversions.h"
#include "src/objects/instance-type.h"
#include "src/objects/map.h"
#include "src/objects/oddball.h"
#include "src/objects/string-comparator.h"
#include "src/objects/string-inl.h"
#include "src/strings/char-predicates.h"
#include "src/strings/string-builder-inl.h"
#include "src/strings/string-hasher.h"
#include "src/strings/string-search.h"
#include "src/strings/string-stream.h"
#include "src/strings/unicode-inl.h"
#include "src/utils/ostreams.h"
namespace v8 {
namespace internal {
Handle<String> String::SlowFlatten(Isolate* isolate, Handle<ConsString> cons,
AllocationType allocation) {
DCHECK_NE(cons->second().length(), 0);
DCHECK(!cons->InSharedHeap());
// TurboFan can create cons strings with empty first parts.
while (cons->first().length() == 0) {
// We do not want to call this function recursively. Therefore we call
// String::Flatten only in those cases where String::SlowFlatten is not
// called again.
if (cons->second().IsConsString() && !cons->second().IsFlat()) {
cons = handle(ConsString::cast(cons->second()), isolate);
} else {
return String::Flatten(isolate, handle(cons->second(), isolate),
allocation);
}
}
DCHECK(AllowGarbageCollection::IsAllowed());
int length = cons->length();
if (allocation != AllocationType::kSharedOld) {
allocation =
ObjectInYoungGeneration(*cons) ? allocation : AllocationType::kOld;
}
Handle<SeqString> result;
if (cons->IsOneByteRepresentation()) {
Handle<SeqOneByteString> flat =
isolate->factory()
->NewRawOneByteString(length, allocation)
.ToHandleChecked();
DisallowGarbageCollection no_gc;
WriteToFlat(*cons, flat->GetChars(no_gc), 0, length);
result = flat;
} else {
Handle<SeqTwoByteString> flat =
isolate->factory()
->NewRawTwoByteString(length, allocation)
.ToHandleChecked();
DisallowGarbageCollection no_gc;
WriteToFlat(*cons, flat->GetChars(no_gc), 0, length);
result = flat;
}
cons->set_first(*result);
cons->set_second(ReadOnlyRoots(isolate).empty_string());
DCHECK(result->IsFlat());
return result;
}
Handle<String> String::SlowCopy(Isolate* isolate, Handle<SeqString> source,
AllocationType allocation) {
int length = source->length();
Handle<String> copy;
if (source->IsOneByteRepresentation()) {
copy = isolate->factory()
->NewRawOneByteString(length, allocation)
.ToHandleChecked();
DisallowGarbageCollection no_gc;
String::FlatContent content = source->GetFlatContent(no_gc);
CopyChars(SeqOneByteString::cast(*copy).GetChars(no_gc),
content.ToOneByteVector().begin(), length);
return copy;
} else {
copy = isolate->factory()
->NewRawTwoByteString(length, allocation)
.ToHandleChecked();
DisallowGarbageCollection no_gc;
String::FlatContent content = source->GetFlatContent(no_gc);
CopyChars(SeqTwoByteString::cast(*copy).GetChars(no_gc),
content.ToUC16Vector().begin(), length);
}
return copy;
}
namespace {
template <class StringClass>
void MigrateExternalStringResource(Isolate* isolate, ExternalString from,
StringClass to) {
Address to_resource_address = to.resource_as_address();
if (to_resource_address == kNullAddress) {
StringClass cast_from = StringClass::cast(from);
// |to| is a just-created internalized copy of |from|. Migrate the resource.
to.SetResource(isolate, cast_from.resource());
// Zap |from|'s resource pointer to reflect the fact that |from| has
// relinquished ownership of its resource.
isolate->heap()->UpdateExternalString(
from, ExternalString::cast(from).ExternalPayloadSize(), 0);
cast_from.SetResource(isolate, nullptr);
} else if (to_resource_address != from.resource_as_address()) {
// |to| already existed and has its own resource. Finalize |from|.
isolate->heap()->FinalizeExternalString(from);
}
}
void MigrateExternalString(Isolate* isolate, String string,
String internalized) {
if (internalized.IsExternalOneByteString()) {
MigrateExternalStringResource(isolate, ExternalString::cast(string),
ExternalOneByteString::cast(internalized));
} else if (internalized.IsExternalTwoByteString()) {
MigrateExternalStringResource(isolate, ExternalString::cast(string),
ExternalTwoByteString::cast(internalized));
} else {
// If the external string is duped into an existing non-external
// internalized string, free its resource (it's about to be rewritten
// into a ThinString below).
isolate->heap()->FinalizeExternalString(string);
}
}
} // namespace
template <typename IsolateT>
void String::MakeThin(IsolateT* isolate, String internalized) {
DisallowGarbageCollection no_gc;
DCHECK_NE(*this, internalized);
DCHECK(internalized.IsInternalizedString());
// TODO(v8:12007): Make this method threadsafe.
DCHECK_IMPLIES(
InSharedWritableHeap(),
ThreadId::Current() == GetIsolateFromWritableObject(*this)->thread_id());
if (this->IsExternalString()) {
MigrateExternalString(isolate->AsIsolate(), *this, internalized);
}
bool has_pointers = StringShape(*this).IsIndirect();
int old_size = this->Size();
bool one_byte = internalized.IsOneByteRepresentation();
Handle<Map> map = one_byte ? isolate->factory()->thin_one_byte_string_map()
: isolate->factory()->thin_string_map();
// Update actual first and then do release store on the map word. This ensures
// that the concurrent marker will read the pointer when visiting a
// ThinString.
ThinString thin = ThinString::unchecked_cast(*this);
thin.set_actual(internalized);
DCHECK_GE(old_size, ThinString::kSize);
this->set_map(*map, kReleaseStore);
Address thin_end = thin.address() + ThinString::kSize;
int size_delta = old_size - ThinString::kSize;
if (size_delta != 0) {
if (!Heap::IsLargeObject(thin)) {
isolate->heap()->CreateFillerObjectAt(
thin_end, size_delta,
has_pointers ? ClearRecordedSlots::kYes : ClearRecordedSlots::kNo);
} else {
// We don't need special handling for the combination IsLargeObject &&
// has_pointers, because indirect strings never get that large.
DCHECK(!has_pointers);
}
}
}
template void String::MakeThin(Isolate* isolate, String internalized);
template void String::MakeThin(LocalIsolate* isolate, String internalized);
bool String::MakeExternal(v8::String::ExternalStringResource* resource) {
// Disallow garbage collection to avoid possible GC vs string access deadlock.
DisallowGarbageCollection no_gc;
// Externalizing twice leaks the external resource, so it's
// prohibited by the API.
DCHECK(this->SupportsExternalization());
DCHECK(resource->IsCacheable());
#ifdef ENABLE_SLOW_DCHECKS
if (FLAG_enable_slow_asserts) {
// Assert that the resource and the string are equivalent.
DCHECK(static_cast<size_t>(this->length()) == resource->length());
base::ScopedVector<base::uc16> smart_chars(this->length());
String::WriteToFlat(*this, smart_chars.begin(), 0, this->length());
DCHECK_EQ(0, memcmp(smart_chars.begin(), resource->data(),
resource->length() * sizeof(smart_chars[0])));
}
#endif // DEBUG
int size = this->Size(); // Byte size of the original string.
// Abort if size does not allow in-place conversion.
if (size < ExternalString::kUncachedSize) return false;
// Read-only strings cannot be made external, since that would mutate the
// string.
if (IsReadOnlyHeapObject(*this)) return false;
Isolate* isolate = GetIsolateFromWritableObject(*this);
bool is_internalized = this->IsInternalizedString();
bool has_pointers = StringShape(*this).IsIndirect();
if (has_pointers) {
isolate->heap()->NotifyObjectLayoutChange(*this, no_gc,
InvalidateRecordedSlots::kYes);
}
base::SharedMutexGuard<base::kExclusive> shared_mutex_guard(
isolate->internalized_string_access());
// Morph the string to an external string by replacing the map and
// reinitializing the fields. This won't work if the space the existing
// string occupies is too small for a regular external string. Instead, we
// resort to an uncached external string instead, omitting the field caching
// the address of the backing store. When we encounter uncached external
// strings in generated code, we need to bailout to runtime.
Map new_map;
ReadOnlyRoots roots(isolate);
if (size < ExternalString::kSizeOfAllExternalStrings) {
if (is_internalized) {
new_map = roots.uncached_external_internalized_string_map();
} else {
new_map = roots.uncached_external_string_map();
}
} else {
new_map = is_internalized ? roots.external_internalized_string_map()
: roots.external_string_map();
}
// Byte size of the external String object.
int new_size = this->SizeFromMap(new_map);
if (!isolate->heap()->IsLargeObject(*this)) {
isolate->heap()->CreateFillerObjectAt(
this->address() + new_size, size - new_size,
has_pointers ? ClearRecordedSlots::kYes : ClearRecordedSlots::kNo);
} else {
// We don't need special handling for the combination IsLargeObject &&
// has_pointers, because indirect strings never get that large.
DCHECK(!has_pointers);
}
// We are storing the new map using release store after creating a filler for
// the left-over space to avoid races with the sweeper thread.
this->set_map(new_map, kReleaseStore);
ExternalTwoByteString self = ExternalTwoByteString::cast(*this);
self.AllocateExternalPointerEntries(isolate);
self.SetResource(isolate, resource);
isolate->heap()->RegisterExternalString(*this);
// Force regeneration of the hash value.
if (is_internalized) self.EnsureHash();
return true;
}
bool String::MakeExternal(v8::String::ExternalOneByteStringResource* resource) {
// Disallow garbage collection to avoid possible GC vs string access deadlock.
DisallowGarbageCollection no_gc;
// Externalizing twice leaks the external resource, so it's
// prohibited by the API.
DCHECK(this->SupportsExternalization());
DCHECK(resource->IsCacheable());
#ifdef ENABLE_SLOW_DCHECKS
if (FLAG_enable_slow_asserts) {
// Assert that the resource and the string are equivalent.
DCHECK(static_cast<size_t>(this->length()) == resource->length());
if (this->IsTwoByteRepresentation()) {
base::ScopedVector<uint16_t> smart_chars(this->length());
String::WriteToFlat(*this, smart_chars.begin(), 0, this->length());
DCHECK(String::IsOneByte(smart_chars.begin(), this->length()));
}
base::ScopedVector<char> smart_chars(this->length());
String::WriteToFlat(*this, smart_chars.begin(), 0, this->length());
DCHECK_EQ(0, memcmp(smart_chars.begin(), resource->data(),
resource->length() * sizeof(smart_chars[0])));
}
#endif // DEBUG
int size = this->Size(); // Byte size of the original string.
// Abort if size does not allow in-place conversion.
if (size < ExternalString::kUncachedSize) return false;
// Read-only strings cannot be made external, since that would mutate the
// string.
if (IsReadOnlyHeapObject(*this)) return false;
Isolate* isolate = GetIsolateFromWritableObject(*this);
bool is_internalized = this->IsInternalizedString();
bool has_pointers = StringShape(*this).IsIndirect();
if (has_pointers) {
isolate->heap()->NotifyObjectLayoutChange(*this, no_gc,
InvalidateRecordedSlots::kYes);
}
base::SharedMutexGuard<base::kExclusive> shared_mutex_guard(
isolate->internalized_string_access());
// Morph the string to an external string by replacing the map and
// reinitializing the fields. This won't work if the space the existing
// string occupies is too small for a regular external string. Instead, we
// resort to an uncached external string instead, omitting the field caching
// the address of the backing store. When we encounter uncached external
// strings in generated code, we need to bailout to runtime.
Map new_map;
ReadOnlyRoots roots(isolate);
if (size < ExternalString::kSizeOfAllExternalStrings) {
new_map = is_internalized
? roots.uncached_external_one_byte_internalized_string_map()
: roots.uncached_external_one_byte_string_map();
} else {
new_map = is_internalized
? roots.external_one_byte_internalized_string_map()
: roots.external_one_byte_string_map();
}
if (!isolate->heap()->IsLargeObject(*this)) {
// Byte size of the external String object.
int new_size = this->SizeFromMap(new_map);
isolate->heap()->CreateFillerObjectAt(
this->address() + new_size, size - new_size,
has_pointers ? ClearRecordedSlots::kYes : ClearRecordedSlots::kNo);
} else {
// We don't need special handling for the combination IsLargeObject &&
// has_pointers, because indirect strings never get that large.
DCHECK(!has_pointers);
}
// We are storing the new map using release store after creating a filler for
// the left-over space to avoid races with the sweeper thread.
this->set_map(new_map, kReleaseStore);
ExternalOneByteString self = ExternalOneByteString::cast(*this);
self.AllocateExternalPointerEntries(isolate);
self.SetResource(isolate, resource);
isolate->heap()->RegisterExternalString(*this);
// Force regeneration of the hash value.
if (is_internalized) self.EnsureHash();
return true;
}
bool String::SupportsExternalization() {
if (this->IsThinString()) {
return i::ThinString::cast(*this).actual().SupportsExternalization();
}
// RO_SPACE strings cannot be externalized.
if (IsReadOnlyHeapObject(*this)) {
return false;
}
// Already an external string.
if (StringShape(*this).IsExternal()) {
return false;
}
#ifdef V8_COMPRESS_POINTERS
// Small strings may not be in-place externalizable.
if (this->Size() < ExternalString::kUncachedSize) return false;
#else
DCHECK_LE(ExternalString::kUncachedSize, this->Size());
#endif
Isolate* isolate = GetIsolateFromWritableObject(*this);
return !isolate->heap()->IsInGCPostProcessing();
}
const char* String::PrefixForDebugPrint() const {
StringShape shape(*this);
if (IsTwoByteRepresentation()) {
StringShape shape(*this);
if (shape.IsInternalized()) {
return "u#";
} else if (shape.IsCons()) {
return "uc\"";
} else if (shape.IsThin()) {
return "u>\"";
} else if (shape.IsExternal()) {
return "ue\"";
} else {
return "u\"";
}
} else {
StringShape shape(*this);
if (shape.IsInternalized()) {
return "#";
} else if (shape.IsCons()) {
return "c\"";
} else if (shape.IsThin()) {
return ">\"";
} else if (shape.IsExternal()) {
return "e\"";
} else {
return "\"";
}
}
UNREACHABLE();
}
const char* String::SuffixForDebugPrint() const {
StringShape shape(*this);
if (shape.IsInternalized()) return "";
return "\"";
}
void String::StringShortPrint(StringStream* accumulator) {
if (!LooksValid()) {
accumulator->Add("<Invalid String>");
return;
}
const int len = length();
accumulator->Add("<String[%u]: ", len);
accumulator->Add(PrefixForDebugPrint());
if (len > kMaxShortPrintLength) {
accumulator->Add("...<truncated>>");
accumulator->Add(SuffixForDebugPrint());
accumulator->Put('>');
return;
}
PrintUC16(accumulator, 0, len);
accumulator->Add(SuffixForDebugPrint());
accumulator->Put('>');
}
void String::PrintUC16(std::ostream& os, int start, int end) {
if (end < 0) end = length();
StringCharacterStream stream(*this, start);
for (int i = start; i < end && stream.HasMore(); i++) {
os << AsUC16(stream.GetNext());
}
}
void String::PrintUC16(StringStream* accumulator, int start, int end) {
if (end < 0) end = length();
StringCharacterStream stream(*this, start);
for (int i = start; i < end && stream.HasMore(); i++) {
uint16_t c = stream.GetNext();
if (c == '\n') {
accumulator->Add("\\n");
} else if (c == '\r') {
accumulator->Add("\\r");
} else if (c == '\\') {
accumulator->Add("\\\\");
} else if (!std::isprint(c)) {
accumulator->Add("\\x%02x", c);
} else {
accumulator->Put(static_cast<char>(c));
}
}
}
int32_t String::ToArrayIndex(Address addr) {
DisallowGarbageCollection no_gc;
String key(addr);
uint32_t index;
if (!key.AsArrayIndex(&index)) return -1;
if (index <= INT_MAX) return index;
return -1;
}
bool String::LooksValid() {
// TODO(leszeks): Maybe remove this check entirely, Heap::Contains uses
// basically the same logic as the way we access the heap in the first place.
// RO_SPACE objects should always be valid.
if (V8_ENABLE_THIRD_PARTY_HEAP_BOOL) return true;
if (ReadOnlyHeap::Contains(*this)) return true;
BasicMemoryChunk* chunk = BasicMemoryChunk::FromHeapObject(*this);
if (chunk->heap() == nullptr) return false;
return chunk->heap()->Contains(*this);
}
namespace {
bool AreDigits(const uint8_t* s, int from, int to) {
for (int i = from; i < to; i++) {
if (s[i] < '0' || s[i] > '9') return false;
}
return true;
}
int ParseDecimalInteger(const uint8_t* s, int from, int to) {
DCHECK_LT(to - from, 10); // Overflow is not possible.
DCHECK(from < to);
int d = s[from] - '0';
for (int i = from + 1; i < to; i++) {
d = 10 * d + (s[i] - '0');
}
return d;
}
} // namespace
// static
Handle<Object> String::ToNumber(Isolate* isolate, Handle<String> subject) {
// Flatten {subject} string first.
subject = String::Flatten(isolate, subject);
// Fast array index case.
uint32_t index;
if (subject->AsArrayIndex(&index)) {
return isolate->factory()->NewNumberFromUint(index);
}
// Fast case: short integer or some sorts of junk values.
if (subject->IsSeqOneByteString()) {
int len = subject->length();
if (len == 0) return handle(Smi::zero(), isolate);
DisallowGarbageCollection no_gc;
uint8_t const* data =
Handle<SeqOneByteString>::cast(subject)->GetChars(no_gc);
bool minus = (data[0] == '-');
int start_pos = (minus ? 1 : 0);
if (start_pos == len) {
return isolate->factory()->nan_value();
} else if (data[start_pos] > '9') {
// Fast check for a junk value. A valid string may start from a
// whitespace, a sign ('+' or '-'), the decimal point, a decimal digit
// or the 'I' character ('Infinity'). All of that have codes not greater
// than '9' except 'I' and .
if (data[start_pos] != 'I' && data[start_pos] != 0xA0) {
return isolate->factory()->nan_value();
}
} else if (len - start_pos < 10 && AreDigits(data, start_pos, len)) {
// The maximal/minimal smi has 10 digits. If the string has less digits
// we know it will fit into the smi-data type.
int d = ParseDecimalInteger(data, start_pos, len);
if (minus) {
if (d == 0) return isolate->factory()->minus_zero_value();
d = -d;
} else if (!subject->HasHashCode() && len <= String::kMaxArrayIndexSize &&
(len == 1 || data[0] != '0')) {
// String hash is not calculated yet but all the data are present.
// Update the hash field to speed up sequential convertions.
uint32_t raw_hash_field = StringHasher::MakeArrayIndexHash(d, len);
#ifdef DEBUG
subject->EnsureHash(); // Force hash calculation.
DCHECK_EQ(subject->raw_hash_field(), raw_hash_field);
#endif
subject->set_raw_hash_field(raw_hash_field);
}
return handle(Smi::FromInt(d), isolate);
}
}
// Slower case.
int flags = ALLOW_HEX | ALLOW_OCTAL | ALLOW_BINARY;
return isolate->factory()->NewNumber(StringToDouble(isolate, subject, flags));
}
String::FlatContent String::GetFlatContent(
const DisallowGarbageCollection& no_gc) {
#if DEBUG
// Check that this method is called only from the main thread.
{
Isolate* isolate;
// We don't have to check read only strings as those won't move.
DCHECK_IMPLIES(GetIsolateFromHeapObject(*this, &isolate),
ThreadId::Current() == isolate->thread_id());
}
#endif
USE(no_gc);
PtrComprCageBase cage_base = GetPtrComprCageBase(*this);
int length = this->length();
StringShape shape(*this, cage_base);
String string = *this;
int offset = 0;
if (shape.representation_tag() == kConsStringTag) {
ConsString cons = ConsString::cast(string);
if (cons.second(cage_base).length() != 0) {
return FlatContent(no_gc);
}
string = cons.first(cage_base);
shape = StringShape(string, cage_base);
} else if (shape.representation_tag() == kSlicedStringTag) {
SlicedString slice = SlicedString::cast(string);
offset = slice.offset();
string = slice.parent(cage_base);
shape = StringShape(string, cage_base);
DCHECK(shape.representation_tag() != kConsStringTag &&
shape.representation_tag() != kSlicedStringTag);
}
if (shape.representation_tag() == kThinStringTag) {
ThinString thin = ThinString::cast(string);
string = thin.actual(cage_base);
shape = StringShape(string, cage_base);
DCHECK(!shape.IsCons());
DCHECK(!shape.IsSliced());
}
if (shape.encoding_tag() == kOneByteStringTag) {
const uint8_t* start;
if (shape.representation_tag() == kSeqStringTag) {
start = SeqOneByteString::cast(string).GetChars(no_gc);
} else {
start = ExternalOneByteString::cast(string).GetChars(cage_base);
}
return FlatContent(start + offset, length, no_gc);
} else {
DCHECK_EQ(shape.encoding_tag(), kTwoByteStringTag);
const base::uc16* start;
if (shape.representation_tag() == kSeqStringTag) {
start = SeqTwoByteString::cast(string).GetChars(no_gc);
} else {
start = ExternalTwoByteString::cast(string).GetChars(cage_base);
}
return FlatContent(start + offset, length, no_gc);
}
}
std::unique_ptr<char[]> String::ToCString(AllowNullsFlag allow_nulls,
RobustnessFlag robust_flag,
int offset, int length,
int* length_return) {
if (robust_flag == ROBUST_STRING_TRAVERSAL && !LooksValid()) {
return std::unique_ptr<char[]>();
}
// Negative length means the to the end of the string.
if (length < 0) length = kMaxInt - offset;
// Compute the size of the UTF-8 string. Start at the specified offset.
StringCharacterStream stream(*this, offset);
int character_position = offset;
int utf8_bytes = 0;
int last = unibrow::Utf16::kNoPreviousCharacter;
while (stream.HasMore() && character_position++ < offset + length) {
uint16_t character = stream.GetNext();
utf8_bytes += unibrow::Utf8::Length(character, last);
last = character;
}
if (length_return) {
*length_return = utf8_bytes;
}
char* result = NewArray<char>(utf8_bytes + 1);
// Convert the UTF-16 string to a UTF-8 buffer. Start at the specified offset.
stream.Reset(*this, offset);
character_position = offset;
int utf8_byte_position = 0;
last = unibrow::Utf16::kNoPreviousCharacter;
while (stream.HasMore() && character_position++ < offset + length) {
uint16_t character = stream.GetNext();
if (allow_nulls == DISALLOW_NULLS && character == 0) {
character = ' ';
}
utf8_byte_position +=
unibrow::Utf8::Encode(result + utf8_byte_position, character, last);
last = character;
}
result[utf8_byte_position] = 0;
return std::unique_ptr<char[]>(result);
}
std::unique_ptr<char[]> String::ToCString(AllowNullsFlag allow_nulls,
RobustnessFlag robust_flag,
int* length_return) {
return ToCString(allow_nulls, robust_flag, 0, -1, length_return);
}
// static
template <typename sinkchar>
void String::WriteToFlat(String source, sinkchar* sink, int start, int length) {
DCHECK(!SharedStringAccessGuardIfNeeded::IsNeeded(source));
return WriteToFlat(source, sink, start, length, GetPtrComprCageBase(source),
SharedStringAccessGuardIfNeeded::NotNeeded());
}
// static
template <typename sinkchar>
void String::WriteToFlat(String source, sinkchar* sink, int start, int length,
PtrComprCageBase cage_base,
const SharedStringAccessGuardIfNeeded& access_guard) {
DisallowGarbageCollection no_gc;
if (length == 0) return;
while (true) {
DCHECK_LT(0, length);
DCHECK_LE(0, start);
DCHECK_LE(length, source.length());
switch (StringShape(source, cage_base).full_representation_tag()) {
case kOneByteStringTag | kExternalStringTag:
CopyChars(
sink,
ExternalOneByteString::cast(source).GetChars(cage_base) + start,
length);
return;
case kTwoByteStringTag | kExternalStringTag:
CopyChars(
sink,
ExternalTwoByteString::cast(source).GetChars(cage_base) + start,
length);
return;
case kOneByteStringTag | kSeqStringTag:
CopyChars(sink,
SeqOneByteString::cast(source).GetChars(no_gc, access_guard) +
start,
length);
return;
case kTwoByteStringTag | kSeqStringTag:
CopyChars(sink,
SeqTwoByteString::cast(source).GetChars(no_gc, access_guard) +
start,
length);
return;
case kOneByteStringTag | kConsStringTag:
case kTwoByteStringTag | kConsStringTag: {
ConsString cons_string = ConsString::cast(source);
String first = cons_string.first(cage_base);
int boundary = first.length();
int first_length = boundary - start;
int second_length = start + length - boundary;
if (second_length >= first_length) {
// Right hand side is longer. Recurse over left.
if (first_length > 0) {
WriteToFlat(first, sink, start, first_length, cage_base,
access_guard);
if (start == 0 && cons_string.second(cage_base) == first) {
CopyChars(sink + boundary, sink, boundary);
return;
}
sink += boundary - start;
start = 0;
length -= first_length;
} else {
start -= boundary;
}
source = cons_string.second(cage_base);
} else {
// Left hand side is longer. Recurse over right.
if (second_length > 0) {
String second = cons_string.second(cage_base);
// When repeatedly appending to a string, we get a cons string that
// is unbalanced to the left, a list, essentially. We inline the
// common case of sequential one-byte right child.
if (second_length == 1) {
sink[boundary - start] =
static_cast<sinkchar>(second.Get(0, cage_base, access_guard));
} else if (second.IsSeqOneByteString(cage_base)) {
CopyChars(
sink + boundary - start,
SeqOneByteString::cast(second).GetChars(no_gc, access_guard),
second_length);
} else {
WriteToFlat(second, sink + boundary - start, 0, second_length,
cage_base, access_guard);
}
length -= second_length;
}
source = first;
}
if (length == 0) return;
continue;
}
case kOneByteStringTag | kSlicedStringTag:
case kTwoByteStringTag | kSlicedStringTag: {
SlicedString slice = SlicedString::cast(source);
unsigned offset = slice.offset();
source = slice.parent(cage_base);
start += offset;
continue;
}
case kOneByteStringTag | kThinStringTag:
case kTwoByteStringTag | kThinStringTag:
source = ThinString::cast(source).actual(cage_base);
continue;
}
UNREACHABLE();
}
UNREACHABLE();
}
template <typename SourceChar>
static void CalculateLineEndsImpl(std::vector<int>* line_ends,
base::Vector<const SourceChar> src,
bool include_ending_line) {
const int src_len = src.length();
for (int i = 0; i < src_len - 1; i++) {
SourceChar current = src[i];
SourceChar next = src[i + 1];
if (IsLineTerminatorSequence(current, next)) line_ends->push_back(i);
}
if (src_len > 0 && IsLineTerminatorSequence(src[src_len - 1], 0)) {
line_ends->push_back(src_len - 1);
}
if (include_ending_line) {
// Include one character beyond the end of script. The rewriter uses that
// position for the implicit return statement.
line_ends->push_back(src_len);
}
}
template <typename IsolateT>
Handle<FixedArray> String::CalculateLineEnds(IsolateT* isolate,
Handle<String> src,
bool include_ending_line) {
src = Flatten(isolate, src);
// Rough estimate of line count based on a roughly estimated average
// length of (unpacked) code.
int line_count_estimate = src->length() >> 4;
std::vector<int> line_ends;
line_ends.reserve(line_count_estimate);
{
DisallowGarbageCollection no_gc; // ensure vectors stay valid.
// Dispatch on type of strings.
String::FlatContent content = src->GetFlatContent(no_gc);
DCHECK(content.IsFlat());
if (content.IsOneByte()) {
CalculateLineEndsImpl(&line_ends, content.ToOneByteVector(),
include_ending_line);
} else {
CalculateLineEndsImpl(&line_ends, content.ToUC16Vector(),
include_ending_line);
}
}
int line_count = static_cast<int>(line_ends.size());
Handle<FixedArray> array =
isolate->factory()->NewFixedArray(line_count, AllocationType::kOld);
for (int i = 0; i < line_count; i++) {
array->set(i, Smi::FromInt(line_ends[i]));
}
return array;
}
template Handle<FixedArray> String::CalculateLineEnds(Isolate* isolate,
Handle<String> src,
bool include_ending_line);
template Handle<FixedArray> String::CalculateLineEnds(LocalIsolate* isolate,
Handle<String> src,
bool include_ending_line);
bool String::SlowEquals(String other) const {
DCHECK(!SharedStringAccessGuardIfNeeded::IsNeeded(*this));
DCHECK(!SharedStringAccessGuardIfNeeded::IsNeeded(other));
return SlowEquals(other, SharedStringAccessGuardIfNeeded::NotNeeded());
}
bool String::SlowEquals(
String other, const SharedStringAccessGuardIfNeeded& access_guard) const {
DisallowGarbageCollection no_gc;
// Fast check: negative check with lengths.
int len = length();
if (len != other.length()) return false;
if (len == 0) return true;
PtrComprCageBase cage_base = GetPtrComprCageBase(*this);
// Fast check: if at least one ThinString is involved, dereference it/them
// and restart.
if (this->IsThinString(cage_base) || other.IsThinString(cage_base)) {
if (other.IsThinString(cage_base))
other = ThinString::cast(other).actual(cage_base);
if (this->IsThinString(cage_base)) {
return ThinString::cast(*this).actual(cage_base).Equals(other);
} else {
return this->Equals(other);
}
}
// Fast check: if hash code is computed for both strings
// a fast negative check can be performed.
if (HasHashCode() && other.HasHashCode()) {
#ifdef ENABLE_SLOW_DCHECKS
if (FLAG_enable_slow_asserts) {
if (hash() != other.hash()) {
bool found_difference = false;
for (int i = 0; i < len; i++) {
if (Get(i) != other.Get(i)) {
found_difference = true;
break;
}
}
DCHECK(found_difference);
}
}
#endif
if (hash() != other.hash()) return false;
}
// We know the strings are both non-empty. Compare the first chars
// before we try to flatten the strings.
if (this->Get(0, cage_base, access_guard) !=
other.Get(0, cage_base, access_guard))
return false;
if (IsSeqOneByteString() && other.IsSeqOneByteString()) {
const uint8_t* str1 =
SeqOneByteString::cast(*this).GetChars(no_gc, access_guard);
const uint8_t* str2 =
SeqOneByteString::cast(other).GetChars(no_gc, access_guard);
return CompareCharsEqual(str1, str2, len);
}
StringComparator comparator;
return comparator.Equals(*this, other, access_guard);
}
// static
bool String::SlowEquals(Isolate* isolate, Handle<String> one,
Handle<String> two) {
// Fast check: negative check with lengths.
int one_length = one->length();
if (one_length != two->length()) return false;
if (one_length == 0) return true;
// Fast check: if at least one ThinString is involved, dereference it/them
// and restart.
if (one->IsThinString() || two->IsThinString()) {
if (one->IsThinString())
one = handle(ThinString::cast(*one).actual(), isolate);
if (two->IsThinString())
two = handle(ThinString::cast(*two).actual(), isolate);
return String::Equals(isolate, one, two);
}
// Fast check: if hash code is computed for both strings
// a fast negative check can be performed.
if (one->HasHashCode() && two->HasHashCode()) {
#ifdef ENABLE_SLOW_DCHECKS
if (FLAG_enable_slow_asserts) {
if (one->hash() != two->hash()) {
bool found_difference = false;
for (int i = 0; i < one_length; i++) {
if (one->Get(i) != two->Get(i)) {
found_difference = true;
break;
}
}
DCHECK(found_difference);
}
}
#endif
if (one->hash() != two->hash()) return false;
}
// We know the strings are both non-empty. Compare the first chars
// before we try to flatten the strings.
if (one->Get(0) != two->Get(0)) return false;
one = String::Flatten(isolate, one);
two = String::Flatten(isolate, two);
DisallowGarbageCollection no_gc;
String::FlatContent flat1 = one->GetFlatContent(no_gc);
String::FlatContent flat2 = two->GetFlatContent(no_gc);
if (flat1.IsOneByte() && flat2.IsOneByte()) {
return CompareCharsEqual(flat1.ToOneByteVector().begin(),
flat2.ToOneByteVector().begin(), one_length);
} else {
for (int i = 0; i < one_length; i++) {
if (flat1.Get(i) != flat2.Get(i)) return false;
}
return true;
}
}
// static
ComparisonResult String::Compare(Isolate* isolate, Handle<String> x,
Handle<String> y) {
// A few fast case tests before we flatten.
if (x.is_identical_to(y)) {
return ComparisonResult::kEqual;
} else if (y->length() == 0) {
return x->length() == 0 ? ComparisonResult::kEqual
: ComparisonResult::kGreaterThan;
} else if (x->length() == 0) {
return ComparisonResult::kLessThan;
}
int const d = x->Get(0) - y->Get(0);
if (d < 0) {
return ComparisonResult::kLessThan;
} else if (d > 0) {
return ComparisonResult::kGreaterThan;
}
// Slow case.
x = String::Flatten(isolate, x);
y = String::Flatten(isolate, y);