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356 lines (320 loc) · 11.8 KB
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// Copyright 2014 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/base/strings.h"
#include "src/execution/isolate-inl.h"
#include "src/objects/fixed-array-inl.h"
#include "src/objects/js-array-inl.h"
#include "src/strings/string-builder-inl.h"
namespace v8 {
namespace internal {
template <typename sinkchar>
void StringBuilderConcatHelper(Tagged<String> special, sinkchar* sink,
Tagged<FixedArray> fixed_array,
int array_length) {
DisallowGarbageCollection no_gc;
int position = 0;
for (int i = 0; i < array_length; i++) {
Tagged<Object> element = fixed_array->get(i);
if (IsSmi(element)) {
// Smi encoding of position and length.
int encoded_slice = Smi::ToInt(element);
int pos;
int len;
if (encoded_slice > 0) {
// Position and length encoded in one smi.
pos = StringBuilderSubstringPosition::decode(encoded_slice);
len = StringBuilderSubstringLength::decode(encoded_slice);
} else {
// Position and length encoded in two smis.
Tagged<Object> obj = fixed_array->get(++i);
DCHECK(IsSmi(obj));
pos = Smi::ToInt(obj);
len = -encoded_slice;
}
String::WriteToFlat(special, sink + position, pos, len);
position += len;
} else {
Tagged<String> string = String::cast(element);
int element_length = string->length();
String::WriteToFlat(string, sink + position, 0, element_length);
position += element_length;
}
}
}
template void StringBuilderConcatHelper<uint8_t>(Tagged<String> special,
uint8_t* sink,
Tagged<FixedArray> fixed_array,
int array_length);
template void StringBuilderConcatHelper<base::uc16>(
Tagged<String> special, base::uc16* sink, Tagged<FixedArray> fixed_array,
int array_length);
int StringBuilderConcatLength(int special_length,
Tagged<FixedArray> fixed_array, int array_length,
bool* one_byte) {
DisallowGarbageCollection no_gc;
int position = 0;
for (int i = 0; i < array_length; i++) {
int increment = 0;
Tagged<Object> elt = fixed_array->get(i);
if (IsSmi(elt)) {
// Smi encoding of position and length.
int smi_value = Smi::ToInt(elt);
int pos;
int len;
if (smi_value > 0) {
// Position and length encoded in one smi.
pos = StringBuilderSubstringPosition::decode(smi_value);
len = StringBuilderSubstringLength::decode(smi_value);
} else {
// Position and length encoded in two smis.
len = -smi_value;
// Get the position and check that it is a positive smi.
i++;
if (i >= array_length) return -1;
Tagged<Object> next_smi = fixed_array->get(i);
if (!IsSmi(next_smi)) return -1;
pos = Smi::ToInt(next_smi);
if (pos < 0) return -1;
}
DCHECK_GE(pos, 0);
DCHECK_GE(len, 0);
if (pos > special_length || len > special_length - pos) return -1;
increment = len;
} else if (IsString(elt)) {
Tagged<String> element = String::cast(elt);
int element_length = element->length();
increment = element_length;
if (*one_byte && !element->IsOneByteRepresentation()) {
*one_byte = false;
}
} else {
return -1;
}
if (increment > String::kMaxLength - position) {
return kMaxInt; // Provoke throw on allocation.
}
position += increment;
}
return position;
}
FixedArrayBuilder::FixedArrayBuilder(Isolate* isolate, int initial_capacity)
: array_(isolate->factory()->NewFixedArrayWithHoles(initial_capacity)),
length_(0),
has_non_smi_elements_(false) {
// Require a non-zero initial size. Ensures that doubling the size to
// extend the array will work.
DCHECK_GT(initial_capacity, 0);
}
FixedArrayBuilder::FixedArrayBuilder(Handle<FixedArray> backing_store)
: array_(backing_store), length_(0), has_non_smi_elements_(false) {
// Require a non-zero initial size. Ensures that doubling the size to
// extend the array will work.
DCHECK_GT(backing_store->length(), 0);
}
FixedArrayBuilder::FixedArrayBuilder(Isolate* isolate)
: array_(isolate->factory()->empty_fixed_array()),
length_(0),
has_non_smi_elements_(false) {}
// static
FixedArrayBuilder FixedArrayBuilder::Lazy(Isolate* isolate) {
return FixedArrayBuilder(isolate);
}
bool FixedArrayBuilder::HasCapacity(int elements) {
int length = array_->length();
int required_length = length_ + elements;
return (length >= required_length);
}
void FixedArrayBuilder::EnsureCapacity(Isolate* isolate, int elements) {
int length = array_->length();
int required_length = length_ + elements;
if (length < required_length) {
if (length == 0) {
constexpr int kInitialCapacityForLazy = 16;
array_ = isolate->factory()->NewFixedArrayWithHoles(
std::max(kInitialCapacityForLazy, elements));
return;
}
int new_length = length;
do {
new_length *= 2;
} while (new_length < required_length);
Handle<FixedArray> extended_array =
isolate->factory()->NewFixedArrayWithHoles(new_length);
FixedArray::CopyElements(isolate, *extended_array, 0, *array_, 0, length_);
array_ = extended_array;
}
}
void FixedArrayBuilder::Add(Tagged<Object> value) {
DCHECK(!IsSmi(value));
array_->set(length_, value);
length_++;
has_non_smi_elements_ = true;
}
void FixedArrayBuilder::Add(Tagged<Smi> value) {
DCHECK(IsSmi(value));
array_->set(length_, value);
length_++;
}
int FixedArrayBuilder::capacity() { return array_->length(); }
ReplacementStringBuilder::ReplacementStringBuilder(Heap* heap,
Handle<String> subject,
int estimated_part_count)
: heap_(heap),
array_builder_(Isolate::FromHeap(heap), estimated_part_count),
subject_(subject),
character_count_(0),
is_one_byte_(subject->IsOneByteRepresentation()) {
// Require a non-zero initial size. Ensures that doubling the size to
// extend the array will work.
DCHECK_GT(estimated_part_count, 0);
}
void ReplacementStringBuilder::EnsureCapacity(int elements) {
array_builder_.EnsureCapacity(Isolate::FromHeap(heap_), elements);
}
void ReplacementStringBuilder::AddString(Handle<String> string) {
int length = string->length();
DCHECK_GT(length, 0);
AddElement(string);
if (!string->IsOneByteRepresentation()) {
is_one_byte_ = false;
}
IncrementCharacterCount(length);
}
MaybeHandle<String> ReplacementStringBuilder::ToString() {
Isolate* isolate = Isolate::FromHeap(heap_);
if (array_builder_.length() == 0) {
return isolate->factory()->empty_string();
}
Handle<String> joined_string;
if (is_one_byte_) {
Handle<SeqOneByteString> seq;
ASSIGN_RETURN_ON_EXCEPTION(
isolate, seq, isolate->factory()->NewRawOneByteString(character_count_),
String);
DisallowGarbageCollection no_gc;
uint8_t* char_buffer = seq->GetChars(no_gc);
StringBuilderConcatHelper(*subject_, char_buffer, *array_builder_.array(),
array_builder_.length());
joined_string = Handle<String>::cast(seq);
} else {
// Two-byte.
Handle<SeqTwoByteString> seq;
ASSIGN_RETURN_ON_EXCEPTION(
isolate, seq, isolate->factory()->NewRawTwoByteString(character_count_),
String);
DisallowGarbageCollection no_gc;
base::uc16* char_buffer = seq->GetChars(no_gc);
StringBuilderConcatHelper(*subject_, char_buffer, *array_builder_.array(),
array_builder_.length());
joined_string = Handle<String>::cast(seq);
}
return joined_string;
}
void ReplacementStringBuilder::AddElement(Handle<Object> element) {
DCHECK(IsSmi(*element) || IsString(*element));
EnsureCapacity(1);
DisallowGarbageCollection no_gc;
array_builder_.Add(*element);
}
IncrementalStringBuilder::IncrementalStringBuilder(Isolate* isolate)
: isolate_(isolate),
encoding_(String::ONE_BYTE_ENCODING),
overflowed_(false),
part_length_(kInitialPartLength),
current_index_(0) {
// Create an accumulator handle starting with the empty string.
accumulator_ =
Handle<String>::New(ReadOnlyRoots(isolate).empty_string(), isolate);
current_part_ =
factory()->NewRawOneByteString(part_length_).ToHandleChecked();
}
int IncrementalStringBuilder::Length() const {
return accumulator_->length() + current_index_;
}
bool IncrementalStringBuilder::HasValidCurrentIndex() const {
return current_index_ < part_length_;
}
void IncrementalStringBuilder::Accumulate(Handle<String> new_part) {
Handle<String> new_accumulator;
if (accumulator()->length() + new_part->length() > String::kMaxLength) {
// Set the flag and carry on. Delay throwing the exception till the end.
new_accumulator = factory()->empty_string();
overflowed_ = true;
} else {
new_accumulator =
factory()->NewConsString(accumulator(), new_part).ToHandleChecked();
}
set_accumulator(new_accumulator);
}
void IncrementalStringBuilder::Extend() {
DCHECK_EQ(current_index_, current_part()->length());
Accumulate(current_part());
if (part_length_ <= kMaxPartLength / kPartLengthGrowthFactor) {
part_length_ *= kPartLengthGrowthFactor;
}
Handle<String> new_part;
if (encoding_ == String::ONE_BYTE_ENCODING) {
new_part = factory()->NewRawOneByteString(part_length_).ToHandleChecked();
} else {
new_part = factory()->NewRawTwoByteString(part_length_).ToHandleChecked();
}
// Reuse the same handle to avoid being invalidated when exiting handle scope.
set_current_part(new_part);
current_index_ = 0;
}
MaybeHandle<String> IncrementalStringBuilder::Finish() {
ShrinkCurrentPart();
Accumulate(current_part());
if (overflowed_) {
THROW_NEW_ERROR(isolate_, NewInvalidStringLengthError(), String);
}
if (isolate()->serializer_enabled()) {
return factory()->InternalizeString(accumulator());
}
return accumulator();
}
// Short strings can be copied directly to {current_part_}.
// Requires the IncrementalStringBuilder to either have two byte encoding or
// the incoming string to have one byte representation "underneath" (The
// one byte check requires the string to be flat).
bool IncrementalStringBuilder::CanAppendByCopy(Handle<String> string) {
const bool representation_ok =
encoding_ == String::TWO_BYTE_ENCODING ||
(string->IsFlat() && String::IsOneByteRepresentationUnderneath(*string));
return representation_ok && CurrentPartCanFit(string->length());
}
void IncrementalStringBuilder::AppendStringByCopy(Handle<String> string) {
DCHECK(CanAppendByCopy(string));
{
DisallowGarbageCollection no_gc;
if (encoding_ == String::ONE_BYTE_ENCODING) {
String::WriteToFlat(
*string,
Handle<SeqOneByteString>::cast(current_part())->GetChars(no_gc) +
current_index_,
0, string->length());
} else {
String::WriteToFlat(
*string,
Handle<SeqTwoByteString>::cast(current_part())->GetChars(no_gc) +
current_index_,
0, string->length());
}
}
current_index_ += string->length();
DCHECK(current_index_ <= part_length_);
if (current_index_ == part_length_) Extend();
}
void IncrementalStringBuilder::AppendString(Handle<String> string) {
if (CanAppendByCopy(string)) {
AppendStringByCopy(string);
return;
}
ShrinkCurrentPart();
part_length_ = kInitialPartLength; // Allocate conservatively.
Extend(); // Attach current part and allocate new part.
Accumulate(string);
}
} // namespace internal
} // namespace v8