deps: update V8 to 5.4.500.27

Pick up latest commit from the 5.4-lkgr branch.

deps: edit V8 gitignore to allow trace event copy
deps: update V8 trace event to 315bf1e2d45be7d53346c31cfcc37424a32c30c8
deps: edit V8 gitignore to allow gtest_prod.h copy
deps: update V8 gtest to 6f8a66431cb592dad629028a50b3dd418a408c87

PR-URL: https://github.com/nodejs/node/pull/8317
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

1 files changed, 812 insertions, 0 deletions

diff --git a/deps/v8/src/json-parser.cc b/deps/v8/src/json-parser.cc
new file mode 100644
index 0000000000..bf2fd0d673
--- /dev/null
+++ b/deps/v8/src/json-parser.cc
@@ -0,0 +1,812 @@
+// Copyright 2016 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/json-parser.h"
+
+#include "src/char-predicates-inl.h"
+#include "src/conversions.h"
+#include "src/debug/debug.h"
+#include "src/factory.h"
+#include "src/field-type.h"
+#include "src/messages.h"
+#include "src/objects-inl.h"
+#include "src/parsing/scanner.h"
+#include "src/parsing/token.h"
+#include "src/property-descriptor.h"
+#include "src/transitions.h"
+
+namespace v8 {
+namespace internal {
+
+MaybeHandle<Object> JsonParseInternalizer::Internalize(Isolate* isolate,
+                                                       Handle<Object> object,
+                                                       Handle<Object> reviver) {
+  DCHECK(reviver->IsCallable());
+  JsonParseInternalizer internalizer(isolate,
+                                     Handle<JSReceiver>::cast(reviver));
+  Handle<JSObject> holder =
+      isolate->factory()->NewJSObject(isolate->object_function());
+  Handle<String> name = isolate->factory()->empty_string();
+  JSObject::AddProperty(holder, name, object, NONE);
+  return internalizer.InternalizeJsonProperty(holder, name);
+}
+
+MaybeHandle<Object> JsonParseInternalizer::InternalizeJsonProperty(
+    Handle<JSReceiver> holder, Handle<String> name) {
+  HandleScope outer_scope(isolate_);
+  Handle<Object> value;
+  ASSIGN_RETURN_ON_EXCEPTION(
+      isolate_, value, Object::GetPropertyOrElement(holder, name), Object);
+  if (value->IsJSReceiver()) {
+    Handle<JSReceiver> object = Handle<JSReceiver>::cast(value);
+    Maybe<bool> is_array = Object::IsArray(object);
+    if (is_array.IsNothing()) return MaybeHandle<Object>();
+    if (is_array.FromJust()) {
+      Handle<Object> length_object;
+      ASSIGN_RETURN_ON_EXCEPTION(
+          isolate_, length_object,
+          Object::GetLengthFromArrayLike(isolate_, object), Object);
+      double length = length_object->Number();
+      for (double i = 0; i < length; i++) {
+        HandleScope inner_scope(isolate_);
+        Handle<Object> index = isolate_->factory()->NewNumber(i);
+        Handle<String> name = isolate_->factory()->NumberToString(index);
+        if (!RecurseAndApply(object, name)) return MaybeHandle<Object>();
+      }
+    } else {
+      Handle<FixedArray> contents;
+      ASSIGN_RETURN_ON_EXCEPTION(
+          isolate_, contents,
+          KeyAccumulator::GetKeys(object, KeyCollectionMode::kOwnOnly,
+                                  ENUMERABLE_STRINGS,
+                                  GetKeysConversion::kConvertToString),
+          Object);
+      for (int i = 0; i < contents->length(); i++) {
+        HandleScope inner_scope(isolate_);
+        Handle<String> name(String::cast(contents->get(i)), isolate_);
+        if (!RecurseAndApply(object, name)) return MaybeHandle<Object>();
+      }
+    }
+  }
+  Handle<Object> argv[] = {name, value};
+  Handle<Object> result;
+  ASSIGN_RETURN_ON_EXCEPTION(
+      isolate_, result, Execution::Call(isolate_, reviver_, holder, 2, argv),
+      Object);
+  return outer_scope.CloseAndEscape(result);
+}
+
+bool JsonParseInternalizer::RecurseAndApply(Handle<JSReceiver> holder,
+                                            Handle<String> name) {
+  Handle<Object> result;
+  ASSIGN_RETURN_ON_EXCEPTION_VALUE(
+      isolate_, result, InternalizeJsonProperty(holder, name), false);
+  Maybe<bool> change_result = Nothing<bool>();
+  if (result->IsUndefined(isolate_)) {
+    change_result = JSReceiver::DeletePropertyOrElement(holder, name, SLOPPY);
+  } else {
+    PropertyDescriptor desc;
+    desc.set_value(result);
+    desc.set_configurable(true);
+    desc.set_enumerable(true);
+    desc.set_writable(true);
+    change_result = JSReceiver::DefineOwnProperty(isolate_, holder, name, &desc,
+                                                  Object::DONT_THROW);
+  }
+  MAYBE_RETURN(change_result, false);
+  return true;
+}
+
+template <bool seq_one_byte>
+JsonParser<seq_one_byte>::JsonParser(Isolate* isolate, Handle<String> source)
+    : source_(source),
+      source_length_(source->length()),
+      isolate_(isolate),
+      factory_(isolate_->factory()),
+      zone_(isolate_->allocator()),
+      object_constructor_(isolate_->native_context()->object_function(),
+                          isolate_),
+      position_(-1) {
+  source_ = String::Flatten(source_);
+  pretenure_ = (source_length_ >= kPretenureTreshold) ? TENURED : NOT_TENURED;
+
+  // Optimized fast case where we only have Latin1 characters.
+  if (seq_one_byte) {
+    seq_source_ = Handle<SeqOneByteString>::cast(source_);
+  }
+}
+
+template <bool seq_one_byte>
+MaybeHandle<Object> JsonParser<seq_one_byte>::ParseJson() {
+  // Advance to the first character (possibly EOS)
+  AdvanceSkipWhitespace();
+  Handle<Object> result = ParseJsonValue();
+  if (result.is_null() || c0_ != kEndOfString) {
+    // Some exception (for example stack overflow) is already pending.
+    if (isolate_->has_pending_exception()) return Handle<Object>::null();
+
+    // Parse failed. Current character is the unexpected token.
+    Factory* factory = this->factory();
+    MessageTemplate::Template message;
+    Handle<Object> arg1 = Handle<Smi>(Smi::FromInt(position_), isolate());
+    Handle<Object> arg2;
+
+    switch (c0_) {
+      case kEndOfString:
+        message = MessageTemplate::kJsonParseUnexpectedEOS;
+        break;
+      case '-':
+      case '0':
+      case '1':
+      case '2':
+      case '3':
+      case '4':
+      case '5':
+      case '6':
+      case '7':
+      case '8':
+      case '9':
+        message = MessageTemplate::kJsonParseUnexpectedTokenNumber;
+        break;
+      case '"':
+        message = MessageTemplate::kJsonParseUnexpectedTokenString;
+        break;
+      default:
+        message = MessageTemplate::kJsonParseUnexpectedToken;
+        arg2 = arg1;
+        arg1 = factory->LookupSingleCharacterStringFromCode(c0_);
+        break;
+    }
+
+    Handle<Script> script(factory->NewScript(source_));
+    // We should sent compile error event because we compile JSON object in
+    // separated source file.
+    isolate()->debug()->OnCompileError(script);
+    MessageLocation location(script, position_, position_ + 1);
+    Handle<Object> error = factory->NewSyntaxError(message, arg1, arg2);
+    return isolate()->template Throw<Object>(error, &location);
+  }
+  return result;
+}
+
+MaybeHandle<Object> InternalizeJsonProperty(Handle<JSObject> holder,
+                                            Handle<String> key);
+
+template <bool seq_one_byte>
+void JsonParser<seq_one_byte>::Advance() {
+  position_++;
+  if (position_ >= source_length_) {
+    c0_ = kEndOfString;
+  } else if (seq_one_byte) {
+    c0_ = seq_source_->SeqOneByteStringGet(position_);
+  } else {
+    c0_ = source_->Get(position_);
+  }
+}
+
+template <bool seq_one_byte>
+void JsonParser<seq_one_byte>::AdvanceSkipWhitespace() {
+  do {
+    Advance();
+  } while (c0_ == ' ' || c0_ == '\t' || c0_ == '\n' || c0_ == '\r');
+}
+
+template <bool seq_one_byte>
+void JsonParser<seq_one_byte>::SkipWhitespace() {
+  while (c0_ == ' ' || c0_ == '\t' || c0_ == '\n' || c0_ == '\r') {
+    Advance();
+  }
+}
+
+template <bool seq_one_byte>
+uc32 JsonParser<seq_one_byte>::AdvanceGetChar() {
+  Advance();
+  return c0_;
+}
+
+template <bool seq_one_byte>
+bool JsonParser<seq_one_byte>::MatchSkipWhiteSpace(uc32 c) {
+  if (c0_ == c) {
+    AdvanceSkipWhitespace();
+    return true;
+  }
+  return false;
+}
+
+template <bool seq_one_byte>
+bool JsonParser<seq_one_byte>::ParseJsonString(Handle<String> expected) {
+  int length = expected->length();
+  if (source_->length() - position_ - 1 > length) {
+    DisallowHeapAllocation no_gc;
+    String::FlatContent content = expected->GetFlatContent();
+    if (content.IsOneByte()) {
+      DCHECK_EQ('"', c0_);
+      const uint8_t* input_chars = seq_source_->GetChars() + position_ + 1;
+      const uint8_t* expected_chars = content.ToOneByteVector().start();
+      for (int i = 0; i < length; i++) {
+        uint8_t c0 = input_chars[i];
+        if (c0 != expected_chars[i] || c0 == '"' || c0 < 0x20 || c0 == '\\') {
+          return false;
+        }
+      }
+      if (input_chars[length] == '"') {
+        position_ = position_ + length + 1;
+        AdvanceSkipWhitespace();
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+// Parse any JSON value.
+template <bool seq_one_byte>
+Handle<Object> JsonParser<seq_one_byte>::ParseJsonValue() {
+  StackLimitCheck stack_check(isolate_);
+  if (stack_check.HasOverflowed()) {
+    isolate_->StackOverflow();
+    return Handle<Object>::null();
+  }
+
+  if (stack_check.InterruptRequested() &&
+      isolate_->stack_guard()->HandleInterrupts()->IsException(isolate_)) {
+    return Handle<Object>::null();
+  }
+
+  if (c0_ == '"') return ParseJsonString();
+  if ((c0_ >= '0' && c0_ <= '9') || c0_ == '-') return ParseJsonNumber();
+  if (c0_ == '{') return ParseJsonObject();
+  if (c0_ == '[') return ParseJsonArray();
+  if (c0_ == 'f') {
+    if (AdvanceGetChar() == 'a' && AdvanceGetChar() == 'l' &&
+        AdvanceGetChar() == 's' && AdvanceGetChar() == 'e') {
+      AdvanceSkipWhitespace();
+      return factory()->false_value();
+    }
+    return ReportUnexpectedCharacter();
+  }
+  if (c0_ == 't') {
+    if (AdvanceGetChar() == 'r' && AdvanceGetChar() == 'u' &&
+        AdvanceGetChar() == 'e') {
+      AdvanceSkipWhitespace();
+      return factory()->true_value();
+    }
+    return ReportUnexpectedCharacter();
+  }
+  if (c0_ == 'n') {
+    if (AdvanceGetChar() == 'u' && AdvanceGetChar() == 'l' &&
+        AdvanceGetChar() == 'l') {
+      AdvanceSkipWhitespace();
+      return factory()->null_value();
+    }
+    return ReportUnexpectedCharacter();
+  }
+  return ReportUnexpectedCharacter();
+}
+
+template <bool seq_one_byte>
+ParseElementResult JsonParser<seq_one_byte>::ParseElement(
+    Handle<JSObject> json_object) {
+  uint32_t index = 0;
+  // Maybe an array index, try to parse it.
+  if (c0_ == '0') {
+    // With a leading zero, the string has to be "0" only to be an index.
+    Advance();
+  } else {
+    do {
+      int d = c0_ - '0';
+      if (index > 429496729U - ((d + 3) >> 3)) break;
+      index = (index * 10) + d;
+      Advance();
+    } while (IsDecimalDigit(c0_));
+  }
+
+  if (c0_ == '"') {
+    // Successfully parsed index, parse and store element.
+    AdvanceSkipWhitespace();
+
+    if (c0_ == ':') {
+      AdvanceSkipWhitespace();
+      Handle<Object> value = ParseJsonValue();
+      if (!value.is_null()) {
+        JSObject::SetOwnElementIgnoreAttributes(json_object, index, value, NONE)
+            .Assert();
+        return kElementFound;
+      } else {
+        return kNullHandle;
+      }
+    }
+  }
+  return kElementNotFound;
+}
+
+// Parse a JSON object. Position must be right at '{'.
+template <bool seq_one_byte>
+Handle<Object> JsonParser<seq_one_byte>::ParseJsonObject() {
+  HandleScope scope(isolate());
+  Handle<JSObject> json_object =
+      factory()->NewJSObject(object_constructor(), pretenure_);
+  Handle<Map> map(json_object->map());
+  int descriptor = 0;
+  ZoneList<Handle<Object> > properties(8, zone());
+  DCHECK_EQ(c0_, '{');
+
+  bool transitioning = true;
+
+  AdvanceSkipWhitespace();
+  if (c0_ != '}') {
+    do {
+      if (c0_ != '"') return ReportUnexpectedCharacter();
+
+      int start_position = position_;
+      Advance();
+
+      if (IsDecimalDigit(c0_)) {
+        ParseElementResult element_result = ParseElement(json_object);
+        if (element_result == kNullHandle) return Handle<Object>::null();
+        if (element_result == kElementFound) continue;
+      }
+      // Not an index, fallback to the slow path.
+
+      position_ = start_position;
+#ifdef DEBUG
+      c0_ = '"';
+#endif
+
+      Handle<String> key;
+      Handle<Object> value;
+
+      // Try to follow existing transitions as long as possible. Once we stop
+      // transitioning, no transition can be found anymore.
+      DCHECK(transitioning);
+      // First check whether there is a single expected transition. If so, try
+      // to parse it first.
+      bool follow_expected = false;
+      Handle<Map> target;
+      if (seq_one_byte) {
+        key = TransitionArray::ExpectedTransitionKey(map);
+        follow_expected = !key.is_null() && ParseJsonString(key);
+      }
+      // If the expected transition hits, follow it.
+      if (follow_expected) {
+        target = TransitionArray::ExpectedTransitionTarget(map);
+      } else {
+        // If the expected transition failed, parse an internalized string and
+        // try to find a matching transition.
+        key = ParseJsonInternalizedString();
+        if (key.is_null()) return ReportUnexpectedCharacter();
+
+        target = TransitionArray::FindTransitionToField(map, key);
+        // If a transition was found, follow it and continue.
+        transitioning = !target.is_null();
+      }
+      if (c0_ != ':') return ReportUnexpectedCharacter();
+
+      AdvanceSkipWhitespace();
+      value = ParseJsonValue();
+      if (value.is_null()) return ReportUnexpectedCharacter();
+
+      if (transitioning) {
+        PropertyDetails details =
+            target->instance_descriptors()->GetDetails(descriptor);
+        Representation expected_representation = details.representation();
+
+        if (value->FitsRepresentation(expected_representation)) {
+          if (expected_representation.IsHeapObject() &&
+              !target->instance_descriptors()
+                   ->GetFieldType(descriptor)
+                   ->NowContains(value)) {
+            Handle<FieldType> value_type(
+                value->OptimalType(isolate(), expected_representation));
+            Map::GeneralizeFieldType(target, descriptor,
+                                     expected_representation, value_type);
+          }
+          DCHECK(target->instance_descriptors()
+                     ->GetFieldType(descriptor)
+                     ->NowContains(value));
+          properties.Add(value, zone());
+          map = target;
+          descriptor++;
+          continue;
+        } else {
+          transitioning = false;
+        }
+      }
+
+      DCHECK(!transitioning);
+
+      // Commit the intermediate state to the object and stop transitioning.
+      CommitStateToJsonObject(json_object, map, &properties);
+
+      JSObject::DefinePropertyOrElementIgnoreAttributes(json_object, key, value)
+          .Check();
+    } while (transitioning && MatchSkipWhiteSpace(','));
+
+    // If we transitioned until the very end, transition the map now.
+    if (transitioning) {
+      CommitStateToJsonObject(json_object, map, &properties);
+    } else {
+      while (MatchSkipWhiteSpace(',')) {
+        HandleScope local_scope(isolate());
+        if (c0_ != '"') return ReportUnexpectedCharacter();
+
+        int start_position = position_;
+        Advance();
+
+        if (IsDecimalDigit(c0_)) {
+          ParseElementResult element_result = ParseElement(json_object);
+          if (element_result == kNullHandle) return Handle<Object>::null();
+          if (element_result == kElementFound) continue;
+        }
+        // Not an index, fallback to the slow path.
+
+        position_ = start_position;
+#ifdef DEBUG
+        c0_ = '"';
+#endif
+
+        Handle<String> key;
+        Handle<Object> value;
+
+        key = ParseJsonInternalizedString();
+        if (key.is_null() || c0_ != ':') return ReportUnexpectedCharacter();
+
+        AdvanceSkipWhitespace();
+        value = ParseJsonValue();
+        if (value.is_null()) return ReportUnexpectedCharacter();
+
+        JSObject::DefinePropertyOrElementIgnoreAttributes(json_object, key,
+                                                          value)
+            .Check();
+      }
+    }
+
+    if (c0_ != '}') {
+      return ReportUnexpectedCharacter();
+    }
+  }
+  AdvanceSkipWhitespace();
+  return scope.CloseAndEscape(json_object);
+}
+
+template <bool seq_one_byte>
+void JsonParser<seq_one_byte>::CommitStateToJsonObject(
+    Handle<JSObject> json_object, Handle<Map> map,
+    ZoneList<Handle<Object> >* properties) {
+  JSObject::AllocateStorageForMap(json_object, map);
+  DCHECK(!json_object->map()->is_dictionary_map());
+
+  DisallowHeapAllocation no_gc;
+
+  int length = properties->length();
+  for (int i = 0; i < length; i++) {
+    Handle<Object> value = (*properties)[i];
+    json_object->WriteToField(i, *value);
+  }
+}
+
+// Parse a JSON array. Position must be right at '['.
+template <bool seq_one_byte>
+Handle<Object> JsonParser<seq_one_byte>::ParseJsonArray() {
+  HandleScope scope(isolate());
+  ZoneList<Handle<Object> > elements(4, zone());
+  DCHECK_EQ(c0_, '[');
+
+  AdvanceSkipWhitespace();
+  if (c0_ != ']') {
+    do {
+      Handle<Object> element = ParseJsonValue();
+      if (element.is_null()) return ReportUnexpectedCharacter();
+      elements.Add(element, zone());
+    } while (MatchSkipWhiteSpace(','));
+    if (c0_ != ']') {
+      return ReportUnexpectedCharacter();
+    }
+  }
+  AdvanceSkipWhitespace();
+  // Allocate a fixed array with all the elements.
+  Handle<FixedArray> fast_elements =
+      factory()->NewFixedArray(elements.length(), pretenure_);
+  for (int i = 0, n = elements.length(); i < n; i++) {
+    fast_elements->set(i, *elements[i]);
+  }
+  Handle<Object> json_array = factory()->NewJSArrayWithElements(
+      fast_elements, FAST_ELEMENTS, pretenure_);
+  return scope.CloseAndEscape(json_array);
+}
+
+template <bool seq_one_byte>
+Handle<Object> JsonParser<seq_one_byte>::ParseJsonNumber() {
+  bool negative = false;
+  int beg_pos = position_;
+  if (c0_ == '-') {
+    Advance();
+    negative = true;
+  }
+  if (c0_ == '0') {
+    Advance();
+    // Prefix zero is only allowed if it's the only digit before
+    // a decimal point or exponent.
+    if (IsDecimalDigit(c0_)) return ReportUnexpectedCharacter();
+  } else {
+    int i = 0;
+    int digits = 0;
+    if (c0_ < '1' || c0_ > '9') return ReportUnexpectedCharacter();
+    do {
+      i = i * 10 + c0_ - '0';
+      digits++;
+      Advance();
+    } while (IsDecimalDigit(c0_));
+    if (c0_ != '.' && c0_ != 'e' && c0_ != 'E' && digits < 10) {
+      SkipWhitespace();
+      return Handle<Smi>(Smi::FromInt((negative ? -i : i)), isolate());
+    }
+  }
+  if (c0_ == '.') {
+    Advance();
+    if (!IsDecimalDigit(c0_)) return ReportUnexpectedCharacter();
+    do {
+      Advance();
+    } while (IsDecimalDigit(c0_));
+  }
+  if (AsciiAlphaToLower(c0_) == 'e') {
+    Advance();
+    if (c0_ == '-' || c0_ == '+') Advance();
+    if (!IsDecimalDigit(c0_)) return ReportUnexpectedCharacter();
+    do {
+      Advance();
+    } while (IsDecimalDigit(c0_));
+  }
+  int length = position_ - beg_pos;
+  double number;
+  if (seq_one_byte) {
+    Vector<const uint8_t> chars(seq_source_->GetChars() + beg_pos, length);
+    number = StringToDouble(isolate()->unicode_cache(), chars,
+                            NO_FLAGS,  // Hex, octal or trailing junk.
+                            std::numeric_limits<double>::quiet_NaN());
+  } else {
+    Vector<uint8_t> buffer = Vector<uint8_t>::New(length);
+    String::WriteToFlat(*source_, buffer.start(), beg_pos, position_);
+    Vector<const uint8_t> result =
+        Vector<const uint8_t>(buffer.start(), length);
+    number = StringToDouble(isolate()->unicode_cache(), result,
+                            NO_FLAGS,  // Hex, octal or trailing junk.
+                            0.0);
+    buffer.Dispose();
+  }
+  SkipWhitespace();
+  return factory()->NewNumber(number, pretenure_);
+}
+
+template <typename StringType>
+inline void SeqStringSet(Handle<StringType> seq_str, int i, uc32 c);
+
+template <>
+inline void SeqStringSet(Handle<SeqTwoByteString> seq_str, int i, uc32 c) {
+  seq_str->SeqTwoByteStringSet(i, c);
+}
+
+template <>
+inline void SeqStringSet(Handle<SeqOneByteString> seq_str, int i, uc32 c) {
+  seq_str->SeqOneByteStringSet(i, c);
+}
+
+template <typename StringType>
+inline Handle<StringType> NewRawString(Factory* factory, int length,
+                                       PretenureFlag pretenure);
+
+template <>
+inline Handle<SeqTwoByteString> NewRawString(Factory* factory, int length,
+                                             PretenureFlag pretenure) {
+  return factory->NewRawTwoByteString(length, pretenure).ToHandleChecked();
+}
+
+template <>
+inline Handle<SeqOneByteString> NewRawString(Factory* factory, int length,
+                                             PretenureFlag pretenure) {
+  return factory->NewRawOneByteString(length, pretenure).ToHandleChecked();
+}
+
+// Scans the rest of a JSON string starting from position_ and writes
+// prefix[start..end] along with the scanned characters into a
+// sequential string of type StringType.
+template <bool seq_one_byte>
+template <typename StringType, typename SinkChar>
+Handle<String> JsonParser<seq_one_byte>::SlowScanJsonString(
+    Handle<String> prefix, int start, int end) {
+  int count = end - start;
+  int max_length = count + source_length_ - position_;
+  int length = Min(max_length, Max(kInitialSpecialStringLength, 2 * count));
+  Handle<StringType> seq_string =
+      NewRawString<StringType>(factory(), length, pretenure_);
+  // Copy prefix into seq_str.
+  SinkChar* dest = seq_string->GetChars();
+  String::WriteToFlat(*prefix, dest, start, end);
+
+  while (c0_ != '"') {
+    // Check for control character (0x00-0x1f) or unterminated string (<0).
+    if (c0_ < 0x20) return Handle<String>::null();
+    if (count >= length) {
+      // We need to create a longer sequential string for the result.
+      return SlowScanJsonString<StringType, SinkChar>(seq_string, 0, count);
+    }
+    if (c0_ != '\\') {
+      // If the sink can contain UC16 characters, or source_ contains only
+      // Latin1 characters, there's no need to test whether we can store the
+      // character. Otherwise check whether the UC16 source character can fit
+      // in the Latin1 sink.
+      if (sizeof(SinkChar) == kUC16Size || seq_one_byte ||
+          c0_ <= String::kMaxOneByteCharCode) {
+        SeqStringSet(seq_string, count++, c0_);
+        Advance();
+      } else {
+        // StringType is SeqOneByteString and we just read a non-Latin1 char.
+        return SlowScanJsonString<SeqTwoByteString, uc16>(seq_string, 0, count);
+      }
+    } else {
+      Advance();  // Advance past the \.
+      switch (c0_) {
+        case '"':
+        case '\\':
+        case '/':
+          SeqStringSet(seq_string, count++, c0_);
+          break;
+        case 'b':
+          SeqStringSet(seq_string, count++, '\x08');
+          break;
+        case 'f':
+          SeqStringSet(seq_string, count++, '\x0c');
+          break;
+        case 'n':
+          SeqStringSet(seq_string, count++, '\x0a');
+          break;
+        case 'r':
+          SeqStringSet(seq_string, count++, '\x0d');
+          break;
+        case 't':
+          SeqStringSet(seq_string, count++, '\x09');
+          break;
+        case 'u': {
+          uc32 value = 0;
+          for (int i = 0; i < 4; i++) {
+            Advance();
+            int digit = HexValue(c0_);
+            if (digit < 0) {
+              return Handle<String>::null();
+            }
+            value = value * 16 + digit;
+          }
+          if (sizeof(SinkChar) == kUC16Size ||
+              value <= String::kMaxOneByteCharCode) {
+            SeqStringSet(seq_string, count++, value);
+            break;
+          } else {
+            // StringType is SeqOneByteString and we just read a non-Latin1
+            // char.
+            position_ -= 6;  // Rewind position_ to \ in \uxxxx.
+            Advance();
+            return SlowScanJsonString<SeqTwoByteString, uc16>(seq_string, 0,
+                                                              count);
+          }
+        }
+        default:
+          return Handle<String>::null();
+      }
+      Advance();
+    }
+  }
+
+  DCHECK_EQ('"', c0_);
+  // Advance past the last '"'.
+  AdvanceSkipWhitespace();
+
+  // Shrink seq_string length to count and return.
+  return SeqString::Truncate(seq_string, count);
+}
+
+template <bool seq_one_byte>
+template <bool is_internalized>
+Handle<String> JsonParser<seq_one_byte>::ScanJsonString() {
+  DCHECK_EQ('"', c0_);
+  Advance();
+  if (c0_ == '"') {
+    AdvanceSkipWhitespace();
+    return factory()->empty_string();
+  }
+
+  if (seq_one_byte && is_internalized) {
+    // Fast path for existing internalized strings.  If the the string being
+    // parsed is not a known internalized string, contains backslashes or
+    // unexpectedly reaches the end of string, return with an empty handle.
+    uint32_t running_hash = isolate()->heap()->HashSeed();
+    int position = position_;
+    uc32 c0 = c0_;
+    do {
+      if (c0 == '\\') {
+        c0_ = c0;
+        int beg_pos = position_;
+        position_ = position;
+        return SlowScanJsonString<SeqOneByteString, uint8_t>(source_, beg_pos,
+                                                             position_);
+      }
+      if (c0 < 0x20) return Handle<String>::null();
+      running_hash = StringHasher::AddCharacterCore(running_hash,
+                                                    static_cast<uint16_t>(c0));
+      position++;
+      if (position >= source_length_) return Handle<String>::null();
+      c0 = seq_source_->SeqOneByteStringGet(position);
+    } while (c0 != '"');
+    int length = position - position_;
+    uint32_t hash = (length <= String::kMaxHashCalcLength)
+                        ? StringHasher::GetHashCore(running_hash)
+                        : static_cast<uint32_t>(length);
+    Vector<const uint8_t> string_vector(seq_source_->GetChars() + position_,
+                                        length);
+    StringTable* string_table = isolate()->heap()->string_table();
+    uint32_t capacity = string_table->Capacity();
+    uint32_t entry = StringTable::FirstProbe(hash, capacity);
+    uint32_t count = 1;
+    Handle<String> result;
+    while (true) {
+      Object* element = string_table->KeyAt(entry);
+      if (element->IsUndefined(isolate())) {
+        // Lookup failure.
+        result =
+            factory()->InternalizeOneByteString(seq_source_, position_, length);
+        break;
+      }
+      if (!element->IsTheHole(isolate()) &&
+          String::cast(element)->IsOneByteEqualTo(string_vector)) {
+        result = Handle<String>(String::cast(element), isolate());
+#ifdef DEBUG
+        uint32_t hash_field =
+            (hash << String::kHashShift) | String::kIsNotArrayIndexMask;
+        DCHECK_EQ(static_cast<int>(result->Hash()),
+                  static_cast<int>(hash_field >> String::kHashShift));
+#endif
+        break;
+      }
+      entry = StringTable::NextProbe(entry, count++, capacity);
+    }
+    position_ = position;
+    // Advance past the last '"'.
+    AdvanceSkipWhitespace();
+    return result;
+  }
+
+  int beg_pos = position_;
+  // Fast case for Latin1 only without escape characters.
+  do {
+    // Check for control character (0x00-0x1f) or unterminated string (<0).
+    if (c0_ < 0x20) return Handle<String>::null();
+    if (c0_ != '\\') {
+      if (seq_one_byte || c0_ <= String::kMaxOneByteCharCode) {
+        Advance();
+      } else {
+        return SlowScanJsonString<SeqTwoByteString, uc16>(source_, beg_pos,
+                                                          position_);
+      }
+    } else {
+      return SlowScanJsonString<SeqOneByteString, uint8_t>(source_, beg_pos,
+                                                           position_);
+    }
+  } while (c0_ != '"');
+  int length = position_ - beg_pos;
+  Handle<String> result =
+      factory()->NewRawOneByteString(length, pretenure_).ToHandleChecked();
+  uint8_t* dest = SeqOneByteString::cast(*result)->GetChars();
+  String::WriteToFlat(*source_, dest, beg_pos, position_);
+
+  DCHECK_EQ('"', c0_);
+  // Advance past the last '"'.
+  AdvanceSkipWhitespace();
+  return result;
+}
+
+// Explicit instantiation.
+template class JsonParser<true>;
+template class JsonParser<false>;
+
+}  // namespace internal
+}  // namespace v8