path: root/deps/v8/src/json-stringifier.cc

// 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-stringifier.h"

#include "src/conversions.h"
#include "src/heap/heap-inl.h"
#include "src/lookup.h"
#include "src/messages.h"
#include "src/objects-inl.h"
#include "src/objects/js-array-inl.h"
#include "src/string-builder-inl.h"
#include "src/utils.h"

namespace v8 {
namespace internal {

class JsonStringifier {
 public:
  explicit JsonStringifier(Isolate* isolate);

  ~JsonStringifier() { DeleteArray(gap_); }

  V8_WARN_UNUSED_RESULT MaybeHandle<Object> Stringify(Handle<Object> object,
                                                      Handle<Object> replacer,
                                                      Handle<Object> gap);

 private:
  enum Result { UNCHANGED, SUCCESS, EXCEPTION };

  bool InitializeReplacer(Handle<Object> replacer);
  bool InitializeGap(Handle<Object> gap);

  V8_WARN_UNUSED_RESULT MaybeHandle<Object> ApplyToJsonFunction(
      Handle<Object> object, Handle<Object> key);
  V8_WARN_UNUSED_RESULT MaybeHandle<Object> ApplyReplacerFunction(
      Handle<Object> value, Handle<Object> key, Handle<Object> initial_holder);

  // Entry point to serialize the object.
  V8_INLINE Result SerializeObject(Handle<Object> obj) {
    return Serialize_<false>(obj, false, factory()->empty_string());
  }

  // Serialize an array element.
  // The index may serve as argument for the toJSON function.
  V8_INLINE Result SerializeElement(Isolate* isolate, Handle<Object> object,
                                    int i) {
    return Serialize_<false>(object, false,
                             Handle<Object>(Smi::FromInt(i), isolate));
  }

  // Serialize a object property.
  // The key may or may not be serialized depending on the property.
  // The key may also serve as argument for the toJSON function.
  V8_INLINE Result SerializeProperty(Handle<Object> object, bool deferred_comma,
                                     Handle<String> deferred_key) {
    DCHECK(!deferred_key.is_null());
    return Serialize_<true>(object, deferred_comma, deferred_key);
  }

  template <bool deferred_string_key>
  Result Serialize_(Handle<Object> object, bool comma, Handle<Object> key);

  V8_INLINE void SerializeDeferredKey(bool deferred_comma,
                                      Handle<Object> deferred_key);

  Result SerializeSmi(Smi* object);

  Result SerializeDouble(double number);
  V8_INLINE Result SerializeHeapNumber(Handle<HeapNumber> object) {
    return SerializeDouble(object->value());
  }

  Result SerializeJSValue(Handle<JSValue> object);

  V8_INLINE Result SerializeJSArray(Handle<JSArray> object);
  V8_INLINE Result SerializeJSObject(Handle<JSObject> object);

  Result SerializeJSProxy(Handle<JSProxy> object);
  Result SerializeJSReceiverSlow(Handle<JSReceiver> object);
  Result SerializeArrayLikeSlow(Handle<JSReceiver> object, uint32_t start,
                                uint32_t length);

  void SerializeString(Handle<String> object);

  template <typename SrcChar, typename DestChar>
  V8_INLINE static void SerializeStringUnchecked_(
      Vector<const SrcChar> src,
      IncrementalStringBuilder::NoExtend<DestChar>* dest);

  template <typename SrcChar, typename DestChar>
  V8_INLINE void SerializeString_(Handle<String> string);

  template <typename Char>
  V8_INLINE static bool DoNotEscape(Char c);

  V8_INLINE void NewLine();
  V8_INLINE void Indent() { indent_++; }
  V8_INLINE void Unindent() { indent_--; }
  V8_INLINE void Separator(bool first);

  Handle<JSReceiver> CurrentHolder(Handle<Object> value,
                                   Handle<Object> inital_holder);

  Result StackPush(Handle<Object> object);
  void StackPop();

  Factory* factory() { return isolate_->factory(); }

  Isolate* isolate_;
  IncrementalStringBuilder builder_;
  Handle<String> tojson_string_;
  Handle<JSArray> stack_;
  Handle<FixedArray> property_list_;
  Handle<JSReceiver> replacer_function_;
  uc16* gap_;
  int indent_;

  static const int kJsonEscapeTableEntrySize = 8;
  static const char* const JsonEscapeTable;
};

MaybeHandle<Object> JsonStringify(Isolate* isolate, Handle<Object> object,
                                  Handle<Object> replacer, Handle<Object> gap) {
  JsonStringifier stringifier(isolate);
  return stringifier.Stringify(object, replacer, gap);
}

// Translation table to escape Latin1 characters.
// Table entries start at a multiple of 8 and are null-terminated.
const char* const JsonStringifier::JsonEscapeTable =
    "\\u0000\0 \\u0001\0 \\u0002\0 \\u0003\0 "
    "\\u0004\0 \\u0005\0 \\u0006\0 \\u0007\0 "
    "\\b\0     \\t\0     \\n\0     \\u000b\0 "
    "\\f\0     \\r\0     \\u000e\0 \\u000f\0 "
    "\\u0010\0 \\u0011\0 \\u0012\0 \\u0013\0 "
    "\\u0014\0 \\u0015\0 \\u0016\0 \\u0017\0 "
    "\\u0018\0 \\u0019\0 \\u001a\0 \\u001b\0 "
    "\\u001c\0 \\u001d\0 \\u001e\0 \\u001f\0 "
    " \0      !\0      \\\"\0     #\0      "
    "$\0      %\0      &\0      '\0      "
    "(\0      )\0      *\0      +\0      "
    ",\0      -\0      .\0      /\0      "
    "0\0      1\0      2\0      3\0      "
    "4\0      5\0      6\0      7\0      "
    "8\0      9\0      :\0      ;\0      "
    "<\0      =\0      >\0      ?\0      "
    "@\0      A\0      B\0      C\0      "
    "D\0      E\0      F\0      G\0      "
    "H\0      I\0      J\0      K\0      "
    "L\0      M\0      N\0      O\0      "
    "P\0      Q\0      R\0      S\0      "
    "T\0      U\0      V\0      W\0      "
    "X\0      Y\0      Z\0      [\0      "
    "\\\\\0     ]\0      ^\0      _\0      "
    "`\0      a\0      b\0      c\0      "
    "d\0      e\0      f\0      g\0      "
    "h\0      i\0      j\0      k\0      "
    "l\0      m\0      n\0      o\0      "
    "p\0      q\0      r\0      s\0      "
    "t\0      u\0      v\0      w\0      "
    "x\0      y\0      z\0      {\0      "
    "|\0      }\0      ~\0      \x7F\0      "
    "\x80\0      \x81\0      \x82\0      \x83\0      "
    "\x84\0      \x85\0      \x86\0      \x87\0      "
    "\x88\0      \x89\0      \x8A\0      \x8B\0      "
    "\x8C\0      \x8D\0      \x8E\0      \x8F\0      "
    "\x90\0      \x91\0      \x92\0      \x93\0      "
    "\x94\0      \x95\0      \x96\0      \x97\0      "
    "\x98\0      \x99\0      \x9A\0      \x9B\0      "
    "\x9C\0      \x9D\0      \x9E\0      \x9F\0      "
    "\xA0\0      \xA1\0      \xA2\0      \xA3\0      "
    "\xA4\0      \xA5\0      \xA6\0      \xA7\0      "
    "\xA8\0      \xA9\0      \xAA\0      \xAB\0      "
    "\xAC\0      \xAD\0      \xAE\0      \xAF\0      "
    "\xB0\0      \xB1\0      \xB2\0      \xB3\0      "
    "\xB4\0      \xB5\0      \xB6\0      \xB7\0      "
    "\xB8\0      \xB9\0      \xBA\0      \xBB\0      "
    "\xBC\0      \xBD\0      \xBE\0      \xBF\0      "
    "\xC0\0      \xC1\0      \xC2\0      \xC3\0      "
    "\xC4\0      \xC5\0      \xC6\0      \xC7\0      "
    "\xC8\0      \xC9\0      \xCA\0      \xCB\0      "
    "\xCC\0      \xCD\0      \xCE\0      \xCF\0      "
    "\xD0\0      \xD1\0      \xD2\0      \xD3\0      "
    "\xD4\0      \xD5\0      \xD6\0      \xD7\0      "
    "\xD8\0      \xD9\0      \xDA\0      \xDB\0      "
    "\xDC\0      \xDD\0      \xDE\0      \xDF\0      "
    "\xE0\0      \xE1\0      \xE2\0      \xE3\0      "
    "\xE4\0      \xE5\0      \xE6\0      \xE7\0      "
    "\xE8\0      \xE9\0      \xEA\0      \xEB\0      "
    "\xEC\0      \xED\0      \xEE\0      \xEF\0      "
    "\xF0\0      \xF1\0      \xF2\0      \xF3\0      "
    "\xF4\0      \xF5\0      \xF6\0      \xF7\0      "
    "\xF8\0      \xF9\0      \xFA\0      \xFB\0      "
    "\xFC\0      \xFD\0      \xFE\0      \xFF\0      ";

JsonStringifier::JsonStringifier(Isolate* isolate)
    : isolate_(isolate), builder_(isolate), gap_(nullptr), indent_(0) {
  tojson_string_ = factory()->toJSON_string();
  stack_ = factory()->NewJSArray(8);
}

MaybeHandle<Object> JsonStringifier::Stringify(Handle<Object> object,
                                               Handle<Object> replacer,
                                               Handle<Object> gap) {
  if (!InitializeReplacer(replacer)) return MaybeHandle<Object>();
  if (!gap->IsUndefined(isolate_) && !InitializeGap(gap)) {
    return MaybeHandle<Object>();
  }
  Result result = SerializeObject(object);
  if (result == UNCHANGED) return factory()->undefined_value();
  if (result == SUCCESS) return builder_.Finish();
  DCHECK(result == EXCEPTION);
  return MaybeHandle<Object>();
}

bool JsonStringifier::InitializeReplacer(Handle<Object> replacer) {
  DCHECK(property_list_.is_null());
  DCHECK(replacer_function_.is_null());
  Maybe<bool> is_array = Object::IsArray(replacer);
  if (is_array.IsNothing()) return false;
  if (is_array.FromJust()) {
    HandleScope handle_scope(isolate_);
    Handle<OrderedHashSet> set = factory()->NewOrderedHashSet();
    Handle<Object> length_obj;
    ASSIGN_RETURN_ON_EXCEPTION_VALUE(
        isolate_, length_obj,
        Object::GetLengthFromArrayLike(isolate_,
                                       Handle<JSReceiver>::cast(replacer)),
        false);
    uint32_t length;
    if (!length_obj->ToUint32(&length)) length = kMaxUInt32;
    for (uint32_t i = 0; i < length; i++) {
      Handle<Object> element;
      Handle<String> key;
      ASSIGN_RETURN_ON_EXCEPTION_VALUE(
          isolate_, element, Object::GetElement(isolate_, replacer, i), false);
      if (element->IsNumber() || element->IsString()) {
        ASSIGN_RETURN_ON_EXCEPTION_VALUE(
            isolate_, key, Object::ToString(isolate_, element), false);
      } else if (element->IsJSValue()) {
        Handle<Object> value(Handle<JSValue>::cast(element)->value(), isolate_);
        if (value->IsNumber() || value->IsString()) {
          ASSIGN_RETURN_ON_EXCEPTION_VALUE(
              isolate_, key, Object::ToString(isolate_, element), false);
        }
      }
      if (key.is_null()) continue;
      // Object keys are internalized, so do it here.
      key = factory()->InternalizeString(key);
      set = OrderedHashSet::Add(isolate_, set, key);
    }
    property_list_ = OrderedHashSet::ConvertToKeysArray(
        isolate_, set, GetKeysConversion::kKeepNumbers);
    property_list_ = handle_scope.CloseAndEscape(property_list_);
  } else if (replacer->IsCallable()) {
    replacer_function_ = Handle<JSReceiver>::cast(replacer);
  }
  return true;
}

bool JsonStringifier::InitializeGap(Handle<Object> gap) {
  DCHECK_NULL(gap_);
  HandleScope scope(isolate_);
  if (gap->IsJSValue()) {
    Handle<Object> value(Handle<JSValue>::cast(gap)->value(), isolate_);
    if (value->IsString()) {
      ASSIGN_RETURN_ON_EXCEPTION_VALUE(isolate_, gap,
                                       Object::ToString(isolate_, gap), false);
    } else if (value->IsNumber()) {
      ASSIGN_RETURN_ON_EXCEPTION_VALUE(isolate_, gap,
                                       Object::ToNumber(isolate_, gap), false);
    }
  }

  if (gap->IsString()) {
    Handle<String> gap_string = Handle<String>::cast(gap);
    if (gap_string->length() > 0) {
      int gap_length = std::min(gap_string->length(), 10);
      gap_ = NewArray<uc16>(gap_length + 1);
      String::WriteToFlat(*gap_string, gap_, 0, gap_length);
      for (int i = 0; i < gap_length; i++) {
        if (gap_[i] > String::kMaxOneByteCharCode) {
          builder_.ChangeEncoding();
          break;
        }
      }
      gap_[gap_length] = '\0';
    }
  } else if (gap->IsNumber()) {
    int num_value = DoubleToInt32(gap->Number());
    if (num_value > 0) {
      int gap_length = std::min(num_value, 10);
      gap_ = NewArray<uc16>(gap_length + 1);
      for (int i = 0; i < gap_length; i++) gap_[i] = ' ';
      gap_[gap_length] = '\0';
    }
  }
  return true;
}

MaybeHandle<Object> JsonStringifier::ApplyToJsonFunction(Handle<Object> object,
                                                         Handle<Object> key) {
  HandleScope scope(isolate_);

  Handle<Object> object_for_lookup = object;
  if (object->IsBigInt()) {
    ASSIGN_RETURN_ON_EXCEPTION(isolate_, object_for_lookup,
                               Object::ToObject(isolate_, object), Object);
  }
  DCHECK(object_for_lookup->IsJSReceiver());

  // Retrieve toJSON function.
  Handle<Object> fun;
  {
    LookupIterator it(isolate_, object_for_lookup, tojson_string_,
                      LookupIterator::PROTOTYPE_CHAIN_SKIP_INTERCEPTOR);
    ASSIGN_RETURN_ON_EXCEPTION(isolate_, fun, Object::GetProperty(&it), Object);
    if (!fun->IsCallable()) return object;
  }

  // Call toJSON function.
  if (key->IsSmi()) key = factory()->NumberToString(key);
  Handle<Object> argv[] = {key};
  ASSIGN_RETURN_ON_EXCEPTION(isolate_, object,
                             Execution::Call(isolate_, fun, object, 1, argv),
                             Object);
  return scope.CloseAndEscape(object);
}

MaybeHandle<Object> JsonStringifier::ApplyReplacerFunction(
    Handle<Object> value, Handle<Object> key, Handle<Object> initial_holder) {
  HandleScope scope(isolate_);
  if (key->IsSmi()) key = factory()->NumberToString(key);
  Handle<Object> argv[] = {key, value};
  Handle<JSReceiver> holder = CurrentHolder(value, initial_holder);
  ASSIGN_RETURN_ON_EXCEPTION(
      isolate_, value,
      Execution::Call(isolate_, replacer_function_, holder, 2, argv), Object);
  return scope.CloseAndEscape(value);
}

Handle<JSReceiver> JsonStringifier::CurrentHolder(
    Handle<Object> value, Handle<Object> initial_holder) {
  int length = Smi::ToInt(stack_->length());
  if (length == 0) {
    Handle<JSObject> holder =
        factory()->NewJSObject(isolate_->object_function());
    JSObject::AddProperty(isolate_, holder, factory()->empty_string(),
                          initial_holder, NONE);
    return holder;
  } else {
    FixedArray* elements = FixedArray::cast(stack_->elements());
    return Handle<JSReceiver>(JSReceiver::cast(elements->get(length - 1)),
                              isolate_);
  }
}

JsonStringifier::Result JsonStringifier::StackPush(Handle<Object> object) {
  StackLimitCheck check(isolate_);
  if (check.HasOverflowed()) {
    isolate_->StackOverflow();
    return EXCEPTION;
  }

  int length = Smi::ToInt(stack_->length());
  {
    DisallowHeapAllocation no_allocation;
    FixedArray* elements = FixedArray::cast(stack_->elements());
    for (int i = 0; i < length; i++) {
      if (elements->get(i) == *object) {
        AllowHeapAllocation allow_to_return_error;
        Handle<Object> error =
            factory()->NewTypeError(MessageTemplate::kCircularStructure);
        isolate_->Throw(*error);
        return EXCEPTION;
      }
    }
  }
  JSArray::SetLength(stack_, length + 1);
  FixedArray::cast(stack_->elements())->set(length, *object);
  return SUCCESS;
}

void JsonStringifier::StackPop() {
  int length = Smi::ToInt(stack_->length());
  stack_->set_length(Smi::FromInt(length - 1));
}

template <bool deferred_string_key>
JsonStringifier::Result JsonStringifier::Serialize_(Handle<Object> object,
                                                    bool comma,
                                                    Handle<Object> key) {
  StackLimitCheck interrupt_check(isolate_);
  Handle<Object> initial_value = object;
  if (interrupt_check.InterruptRequested() &&
      isolate_->stack_guard()->HandleInterrupts()->IsException(isolate_)) {
    return EXCEPTION;
  }
  if (object->IsJSReceiver() || object->IsBigInt()) {
    ASSIGN_RETURN_ON_EXCEPTION_VALUE(
        isolate_, object, ApplyToJsonFunction(object, key), EXCEPTION);
  }
  if (!replacer_function_.is_null()) {
    ASSIGN_RETURN_ON_EXCEPTION_VALUE(
        isolate_, object, ApplyReplacerFunction(object, key, initial_value),
        EXCEPTION);
  }

  if (object->IsSmi()) {
    if (deferred_string_key) SerializeDeferredKey(comma, key);
    return SerializeSmi(Smi::cast(*object));
  }

  switch (HeapObject::cast(*object)->map()->instance_type()) {
    case HEAP_NUMBER_TYPE:
    case MUTABLE_HEAP_NUMBER_TYPE:
      if (deferred_string_key) SerializeDeferredKey(comma, key);
      return SerializeHeapNumber(Handle<HeapNumber>::cast(object));
    case BIGINT_TYPE:
      isolate_->Throw(
          *factory()->NewTypeError(MessageTemplate::kBigIntSerializeJSON));
      return EXCEPTION;
    case ODDBALL_TYPE:
      switch (Oddball::cast(*object)->kind()) {
        case Oddball::kFalse:
          if (deferred_string_key) SerializeDeferredKey(comma, key);
          builder_.AppendCString("false");
          return SUCCESS;
        case Oddball::kTrue:
          if (deferred_string_key) SerializeDeferredKey(comma, key);
          builder_.AppendCString("true");
          return SUCCESS;
        case Oddball::kNull:
          if (deferred_string_key) SerializeDeferredKey(comma, key);
          builder_.AppendCString("null");
          return SUCCESS;
        default:
          return UNCHANGED;
      }
    case JS_ARRAY_TYPE:
      if (deferred_string_key) SerializeDeferredKey(comma, key);
      return SerializeJSArray(Handle<JSArray>::cast(object));
    case JS_VALUE_TYPE:
      if (deferred_string_key) SerializeDeferredKey(comma, key);
      return SerializeJSValue(Handle<JSValue>::cast(object));
    case SYMBOL_TYPE:
      return UNCHANGED;
    default:
      if (object->IsString()) {
        if (deferred_string_key) SerializeDeferredKey(comma, key);
        SerializeString(Handle<String>::cast(object));
        return SUCCESS;
      } else {
        DCHECK(object->IsJSReceiver());
        if (object->IsCallable()) return UNCHANGED;
        // Go to slow path for global proxy and objects requiring access checks.
        if (deferred_string_key) SerializeDeferredKey(comma, key);
        if (object->IsJSProxy()) {
          return SerializeJSProxy(Handle<JSProxy>::cast(object));
        }
        return SerializeJSObject(Handle<JSObject>::cast(object));
      }
  }

  UNREACHABLE();
}

JsonStringifier::Result JsonStringifier::SerializeJSValue(
    Handle<JSValue> object) {
  Object* raw = object->value();
  if (raw->IsString()) {
    Handle<Object> value;
    ASSIGN_RETURN_ON_EXCEPTION_VALUE(
        isolate_, value, Object::ToString(isolate_, object), EXCEPTION);
    SerializeString(Handle<String>::cast(value));
  } else if (raw->IsNumber()) {
    Handle<Object> value;
    ASSIGN_RETURN_ON_EXCEPTION_VALUE(
        isolate_, value, Object::ToNumber(isolate_, object), EXCEPTION);
    if (value->IsSmi()) return SerializeSmi(Smi::cast(*value));
    SerializeHeapNumber(Handle<HeapNumber>::cast(value));
  } else if (raw->IsBigInt()) {
    isolate_->Throw(
        *factory()->NewTypeError(MessageTemplate::kBigIntSerializeJSON));
    return EXCEPTION;
  } else if (raw->IsBoolean()) {
    builder_.AppendCString(raw->IsTrue(isolate_) ? "true" : "false");
  } else {
    // ES6 24.3.2.1 step 10.c, serialize as an ordinary JSObject.
    return SerializeJSObject(object);
  }
  return SUCCESS;
}

JsonStringifier::Result JsonStringifier::SerializeSmi(Smi* object) {
  static const int kBufferSize = 100;
  char chars[kBufferSize];
  Vector<char> buffer(chars, kBufferSize);
  builder_.AppendCString(IntToCString(object->value(), buffer));
  return SUCCESS;
}

JsonStringifier::Result JsonStringifier::SerializeDouble(double number) {
  if (std::isinf(number) || std::isnan(number)) {
    builder_.AppendCString("null");
    return SUCCESS;
  }
  static const int kBufferSize = 100;
  char chars[kBufferSize];
  Vector<char> buffer(chars, kBufferSize);
  builder_.AppendCString(DoubleToCString(number, buffer));
  return SUCCESS;
}

JsonStringifier::Result JsonStringifier::SerializeJSArray(
    Handle<JSArray> object) {
  HandleScope handle_scope(isolate_);
  Result stack_push = StackPush(object);
  if (stack_push != SUCCESS) return stack_push;
  uint32_t length = 0;
  CHECK(object->length()->ToArrayLength(&length));
  DCHECK(!object->IsAccessCheckNeeded());
  builder_.AppendCharacter('[');
  Indent();
  uint32_t i = 0;
  if (replacer_function_.is_null()) {
    switch (object->GetElementsKind()) {
      case PACKED_SMI_ELEMENTS: {
        Handle<FixedArray> elements(FixedArray::cast(object->elements()),
                                    isolate_);
        StackLimitCheck interrupt_check(isolate_);
        while (i < length) {
          if (interrupt_check.InterruptRequested() &&
              isolate_->stack_guard()->HandleInterrupts()->IsException(
                  isolate_)) {
            return EXCEPTION;
          }
          Separator(i == 0);
          SerializeSmi(Smi::cast(elements->get(i)));
          i++;
        }
        break;
      }
      case PACKED_DOUBLE_ELEMENTS: {
        // Empty array is FixedArray but not FixedDoubleArray.
        if (length == 0) break;
        Handle<FixedDoubleArray> elements(
            FixedDoubleArray::cast(object->elements()), isolate_);
        StackLimitCheck interrupt_check(isolate_);
        while (i < length) {
          if (interrupt_check.InterruptRequested() &&
              isolate_->stack_guard()->HandleInterrupts()->IsException(
                  isolate_)) {
            return EXCEPTION;
          }
          Separator(i == 0);
          SerializeDouble(elements->get_scalar(i));
          i++;
        }
        break;
      }
      case PACKED_ELEMENTS: {
        Handle<Object> old_length(object->length(), isolate_);
        while (i < length) {
          if (object->length() != *old_length ||
              object->GetElementsKind() != PACKED_ELEMENTS) {
            // Fall back to slow path.
            break;
          }
          Separator(i == 0);
          Result result = SerializeElement(
              isolate_,
              Handle<Object>(FixedArray::cast(object->elements())->get(i),
                             isolate_),
              i);
          if (result == UNCHANGED) {
            builder_.AppendCString("null");
          } else if (result != SUCCESS) {
            return result;
          }
          i++;
        }
        break;
      }
      // The FAST_HOLEY_* cases could be handled in a faster way. They resemble
      // the non-holey cases except that a lookup is necessary for holes.
      default:
        break;
    }
  }
  if (i < length) {
    // Slow path for non-fast elements and fall-back in edge case.
    Result result = SerializeArrayLikeSlow(object, i, length);
    if (result != SUCCESS) return result;
  }
  Unindent();
  if (length > 0) NewLine();
  builder_.AppendCharacter(']');
  StackPop();
  return SUCCESS;
}

JsonStringifier::Result JsonStringifier::SerializeArrayLikeSlow(
    Handle<JSReceiver> object, uint32_t start, uint32_t length) {
  // We need to write out at least two characters per array element.
  static const int kMaxSerializableArrayLength = String::kMaxLength / 2;
  if (length > kMaxSerializableArrayLength) {
    isolate_->Throw(*isolate_->factory()->NewInvalidStringLengthError());
    return EXCEPTION;
  }
  for (uint32_t i = start; i < length; i++) {
    Separator(i == 0);
    Handle<Object> element;
    ASSIGN_RETURN_ON_EXCEPTION_VALUE(
        isolate_, element, JSReceiver::GetElement(isolate_, object, i),
        EXCEPTION);
    Result result = SerializeElement(isolate_, element, i);
    if (result == SUCCESS) continue;
    if (result == UNCHANGED) {
      // Detect overflow sooner for large sparse arrays.
      if (builder_.HasOverflowed()) return EXCEPTION;
      builder_.AppendCString("null");
    } else {
      return result;
    }
  }
  return SUCCESS;
}

JsonStringifier::Result JsonStringifier::SerializeJSObject(
    Handle<JSObject> object) {
  HandleScope handle_scope(isolate_);
  Result stack_push = StackPush(object);
  if (stack_push != SUCCESS) return stack_push;

  if (property_list_.is_null() &&
      !object->map()->IsCustomElementsReceiverMap() &&
      object->HasFastProperties() &&
      Handle<JSObject>::cast(object)->elements()->length() == 0) {
    DCHECK(object->IsJSObject());
    DCHECK(!object->IsJSGlobalProxy());
    Handle<JSObject> js_obj = Handle<JSObject>::cast(object);
    DCHECK(!js_obj->HasIndexedInterceptor());
    DCHECK(!js_obj->HasNamedInterceptor());
    Handle<Map> map(js_obj->map(), isolate_);
    builder_.AppendCharacter('{');
    Indent();
    bool comma = false;
    for (int i = 0; i < map->NumberOfOwnDescriptors(); i++) {
      Handle<Name> name(map->instance_descriptors()->GetKey(i), isolate_);
      // TODO(rossberg): Should this throw?
      if (!name->IsString()) continue;
      Handle<String> key = Handle<String>::cast(name);
      PropertyDetails details = map->instance_descriptors()->GetDetails(i);
      if (details.IsDontEnum()) continue;
      Handle<Object> property;
      if (details.location() == kField && *map == js_obj->map()) {
        DCHECK_EQ(kData, details.kind());
        FieldIndex field_index = FieldIndex::ForDescriptor(*map, i);
        property = JSObject::FastPropertyAt(js_obj, details.representation(),
                                            field_index);
      } else {
        ASSIGN_RETURN_ON_EXCEPTION_VALUE(
            isolate_, property,
            Object::GetPropertyOrElement(isolate_, js_obj, key), EXCEPTION);
      }
      Result result = SerializeProperty(property, comma, key);
      if (!comma && result == SUCCESS) comma = true;
      if (result == EXCEPTION) return result;
    }
    Unindent();
    if (comma) NewLine();
    builder_.AppendCharacter('}');
  } else {
    Result result = SerializeJSReceiverSlow(object);
    if (result != SUCCESS) return result;
  }
  StackPop();
  return SUCCESS;
}

JsonStringifier::Result JsonStringifier::SerializeJSReceiverSlow(
    Handle<JSReceiver> object) {
  Handle<FixedArray> contents = property_list_;
  if (contents.is_null()) {
    ASSIGN_RETURN_ON_EXCEPTION_VALUE(
        isolate_, contents,
        KeyAccumulator::GetKeys(object, KeyCollectionMode::kOwnOnly,
                                ENUMERABLE_STRINGS,
                                GetKeysConversion::kConvertToString),
        EXCEPTION);
  }
  builder_.AppendCharacter('{');
  Indent();
  bool comma = false;
  for (int i = 0; i < contents->length(); i++) {
    Handle<String> key(String::cast(contents->get(i)), isolate_);
    Handle<Object> property;
    ASSIGN_RETURN_ON_EXCEPTION_VALUE(
        isolate_, property, Object::GetPropertyOrElement(isolate_, object, key),
        EXCEPTION);
    Result result = SerializeProperty(property, comma, key);
    if (!comma && result == SUCCESS) comma = true;
    if (result == EXCEPTION) return result;
  }
  Unindent();
  if (comma) NewLine();
  builder_.AppendCharacter('}');
  return SUCCESS;
}

JsonStringifier::Result JsonStringifier::SerializeJSProxy(
    Handle<JSProxy> object) {
  HandleScope scope(isolate_);
  Result stack_push = StackPush(object);
  if (stack_push != SUCCESS) return stack_push;
  Maybe<bool> is_array = Object::IsArray(object);
  if (is_array.IsNothing()) return EXCEPTION;
  if (is_array.FromJust()) {
    Handle<Object> length_object;
    ASSIGN_RETURN_ON_EXCEPTION_VALUE(
        isolate_, length_object,
        Object::GetLengthFromArrayLike(isolate_,
                                       Handle<JSReceiver>::cast(object)),
        EXCEPTION);
    uint32_t length;
    if (!length_object->ToUint32(&length)) {
      // Technically, we need to be able to handle lengths outside the
      // uint32_t range. However, we would run into string size overflow
      // if we tried to stringify such an array.
      isolate_->Throw(*isolate_->factory()->NewInvalidStringLengthError());
      return EXCEPTION;
    }
    builder_.AppendCharacter('[');
    Indent();
    Result result = SerializeArrayLikeSlow(object, 0, length);
    if (result != SUCCESS) return result;
    Unindent();
    if (length > 0) NewLine();
    builder_.AppendCharacter(']');
  } else {
    Result result = SerializeJSReceiverSlow(object);
    if (result != SUCCESS) return result;
  }
  StackPop();
  return SUCCESS;
}

template <typename SrcChar, typename DestChar>
void JsonStringifier::SerializeStringUnchecked_(
    Vector<const SrcChar> src,
    IncrementalStringBuilder::NoExtend<DestChar>* dest) {
  // Assert that uc16 character is not truncated down to 8 bit.
  // The <uc16, char> version of this method must not be called.
  DCHECK(sizeof(DestChar) >= sizeof(SrcChar));
  for (int i = 0; i < src.length(); i++) {
    SrcChar c = src[i];
    if (DoNotEscape(c)) {
      dest->Append(c);
    } else if (FLAG_harmony_json_stringify && c >= 0xD800 && c <= 0xDFFF) {
      // The current character is a surrogate.
      if (c <= 0xDBFF) {
        // The current character is a leading surrogate.
        if (i + 1 < src.length()) {
          // There is a next character.
          SrcChar next = src[i + 1];
          if (next >= 0xDC00 && next <= 0xDFFF) {
            // The next character is a trailing surrogate, meaning this is a
            // surrogate pair.
            dest->Append(c);
            dest->Append(next);
            i++;
          } else {
            // The next character is not a trailing surrogate. Thus, the
            // current character is a lone leading surrogate.
            dest->AppendCString("\\u");
            char* const hex = DoubleToRadixCString(c, 16);
            dest->AppendCString(hex);
            DeleteArray(hex);
          }
        } else {
          // There is no next character. Thus, the current character is a lone
          // leading surrogate.
          dest->AppendCString("\\u");
          char* const hex = DoubleToRadixCString(c, 16);
          dest->AppendCString(hex);
          DeleteArray(hex);
        }
      } else {
        // The current character is a lone trailing surrogate. (If it had been
        // preceded by a leading surrogate, we would've ended up in the other
        // branch earlier on, and the current character would've been handled
        // as part of the surrogate pair already.)
        dest->AppendCString("\\u");
        char* const hex = DoubleToRadixCString(c, 16);
        dest->AppendCString(hex);
        DeleteArray(hex);
      }
    } else {
      dest->AppendCString(&JsonEscapeTable[c * kJsonEscapeTableEntrySize]);
    }
  }
}

template <typename SrcChar, typename DestChar>
void JsonStringifier::SerializeString_(Handle<String> string) {
  int length = string->length();
  builder_.Append<uint8_t, DestChar>('"');
  // We might be able to fit the whole escaped string in the current string
  // part, or we might need to allocate.
  if (int worst_case_length = builder_.EscapedLengthIfCurrentPartFits(length)) {
    DisallowHeapAllocation no_gc;
    Vector<const SrcChar> vector = string->GetCharVector<SrcChar>();
    IncrementalStringBuilder::NoExtendBuilder<DestChar> no_extend(
        &builder_, worst_case_length);
    SerializeStringUnchecked_(vector, &no_extend);
  } else {
    FlatStringReader reader(isolate_, string);
    for (int i = 0; i < reader.length(); i++) {
      SrcChar c = reader.Get<SrcChar>(i);
      if (DoNotEscape(c)) {
        builder_.Append<SrcChar, DestChar>(c);
      } else if (FLAG_harmony_json_stringify && c >= 0xD800 && c <= 0xDFFF) {
        // The current character is a surrogate.
        if (c <= 0xDBFF) {
          // The current character is a leading surrogate.
          if (i + 1 < reader.length()) {
            // There is a next character.
            SrcChar next = reader.Get<SrcChar>(i + 1);
            if (next >= 0xDC00 && next <= 0xDFFF) {
              // The next character is a trailing surrogate, meaning this is a
              // surrogate pair.
              builder_.Append<SrcChar, DestChar>(c);
              builder_.Append<SrcChar, DestChar>(next);
              i++;
            } else {
              // The next character is not a trailing surrogate. Thus, the
              // current character is a lone leading surrogate.
              builder_.AppendCString("\\u");
              char* const hex = DoubleToRadixCString(c, 16);
              builder_.AppendCString(hex);
              DeleteArray(hex);
            }
          } else {
            // There is no next character. Thus, the current character is a
            // lone leading surrogate.
            builder_.AppendCString("\\u");
            char* const hex = DoubleToRadixCString(c, 16);
            builder_.AppendCString(hex);
            DeleteArray(hex);
          }
        } else {
          // The current character is a lone trailing surrogate. (If it had
          // been preceded by a leading surrogate, we would've ended up in the
          // other branch earlier on, and the current character would've been
          // handled as part of the surrogate pair already.)
          builder_.AppendCString("\\u");
          char* const hex = DoubleToRadixCString(c, 16);
          builder_.AppendCString(hex);
          DeleteArray(hex);
        }
      } else {
        builder_.AppendCString(&JsonEscapeTable[c * kJsonEscapeTableEntrySize]);
      }
    }
  }
  builder_.Append<uint8_t, DestChar>('"');
}

template <>
bool JsonStringifier::DoNotEscape(uint8_t c) {
  // https://tc39.github.io/ecma262/#table-json-single-character-escapes
  return c >= 0x23 && c <= 0x7E && c != 0x5C;
}

template <>
bool JsonStringifier::DoNotEscape(uint16_t c) {
  // https://tc39.github.io/ecma262/#table-json-single-character-escapes
  return c >= 0x23 && c != 0x5C && c != 0x7F &&
         (!FLAG_harmony_json_stringify || (c < 0xD800 || c > 0xDFFF));
}

void JsonStringifier::NewLine() {
  if (gap_ == nullptr) return;
  builder_.AppendCharacter('\n');
  for (int i = 0; i < indent_; i++) builder_.AppendCString(gap_);
}

void JsonStringifier::Separator(bool first) {
  if (!first) builder_.AppendCharacter(',');
  NewLine();
}

void JsonStringifier::SerializeDeferredKey(bool deferred_comma,
                                           Handle<Object> deferred_key) {
  Separator(!deferred_comma);
  SerializeString(Handle<String>::cast(deferred_key));
  builder_.AppendCharacter(':');
  if (gap_ != nullptr) builder_.AppendCharacter(' ');
}

void JsonStringifier::SerializeString(Handle<String> object) {
  object = String::Flatten(isolate_, object);
  if (builder_.CurrentEncoding() == String::ONE_BYTE_ENCODING) {
    if (object->IsOneByteRepresentationUnderneath()) {
      SerializeString_<uint8_t, uint8_t>(object);
    } else {
      builder_.ChangeEncoding();
      SerializeString(object);
    }
  } else {
    if (object->IsOneByteRepresentationUnderneath()) {
      SerializeString_<uint8_t, uc16>(object);
    } else {
      SerializeString_<uc16, uc16>(object);
    }
  }
}

}  // namespace internal
}  // namespace v8