1 // Copyright 2016 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #include "src/json-parser.h"
6 
7 #include "src/char-predicates-inl.h"
8 #include "src/conversions.h"
9 #include "src/debug/debug.h"
10 #include "src/factory.h"
11 #include "src/field-type.h"
12 #include "src/messages.h"
13 #include "src/objects-inl.h"
14 #include "src/parsing/token.h"
15 #include "src/property-descriptor.h"
16 #include "src/transitions.h"
17 #include "src/unicode-cache.h"
18 
19 namespace v8 {
20 namespace internal {
21 
Internalize(Isolate * isolate,Handle<Object> object,Handle<Object> reviver)22 MaybeHandle<Object> JsonParseInternalizer::Internalize(Isolate* isolate,
23                                                        Handle<Object> object,
24                                                        Handle<Object> reviver) {
25   DCHECK(reviver->IsCallable());
26   JsonParseInternalizer internalizer(isolate,
27                                      Handle<JSReceiver>::cast(reviver));
28   Handle<JSObject> holder =
29       isolate->factory()->NewJSObject(isolate->object_function());
30   Handle<String> name = isolate->factory()->empty_string();
31   JSObject::AddProperty(holder, name, object, NONE);
32   return internalizer.InternalizeJsonProperty(holder, name);
33 }
34 
InternalizeJsonProperty(Handle<JSReceiver> holder,Handle<String> name)35 MaybeHandle<Object> JsonParseInternalizer::InternalizeJsonProperty(
36     Handle<JSReceiver> holder, Handle<String> name) {
37   HandleScope outer_scope(isolate_);
38   Handle<Object> value;
39   ASSIGN_RETURN_ON_EXCEPTION(
40       isolate_, value, Object::GetPropertyOrElement(holder, name), Object);
41   if (value->IsJSReceiver()) {
42     Handle<JSReceiver> object = Handle<JSReceiver>::cast(value);
43     Maybe<bool> is_array = Object::IsArray(object);
44     if (is_array.IsNothing()) return MaybeHandle<Object>();
45     if (is_array.FromJust()) {
46       Handle<Object> length_object;
47       ASSIGN_RETURN_ON_EXCEPTION(
48           isolate_, length_object,
49           Object::GetLengthFromArrayLike(isolate_, object), Object);
50       double length = length_object->Number();
51       for (double i = 0; i < length; i++) {
52         HandleScope inner_scope(isolate_);
53         Handle<Object> index = isolate_->factory()->NewNumber(i);
54         Handle<String> name = isolate_->factory()->NumberToString(index);
55         if (!RecurseAndApply(object, name)) return MaybeHandle<Object>();
56       }
57     } else {
58       Handle<FixedArray> contents;
59       ASSIGN_RETURN_ON_EXCEPTION(
60           isolate_, contents,
61           KeyAccumulator::GetKeys(object, KeyCollectionMode::kOwnOnly,
62                                   ENUMERABLE_STRINGS,
63                                   GetKeysConversion::kConvertToString),
64           Object);
65       for (int i = 0; i < contents->length(); i++) {
66         HandleScope inner_scope(isolate_);
67         Handle<String> name(String::cast(contents->get(i)), isolate_);
68         if (!RecurseAndApply(object, name)) return MaybeHandle<Object>();
69       }
70     }
71   }
72   Handle<Object> argv[] = {name, value};
73   Handle<Object> result;
74   ASSIGN_RETURN_ON_EXCEPTION(
75       isolate_, result, Execution::Call(isolate_, reviver_, holder, 2, argv),
76       Object);
77   return outer_scope.CloseAndEscape(result);
78 }
79 
RecurseAndApply(Handle<JSReceiver> holder,Handle<String> name)80 bool JsonParseInternalizer::RecurseAndApply(Handle<JSReceiver> holder,
81                                             Handle<String> name) {
82   Handle<Object> result;
83   ASSIGN_RETURN_ON_EXCEPTION_VALUE(
84       isolate_, result, InternalizeJsonProperty(holder, name), false);
85   Maybe<bool> change_result = Nothing<bool>();
86   if (result->IsUndefined(isolate_)) {
87     change_result = JSReceiver::DeletePropertyOrElement(holder, name, SLOPPY);
88   } else {
89     PropertyDescriptor desc;
90     desc.set_value(result);
91     desc.set_configurable(true);
92     desc.set_enumerable(true);
93     desc.set_writable(true);
94     change_result = JSReceiver::DefineOwnProperty(isolate_, holder, name, &desc,
95                                                   Object::DONT_THROW);
96   }
97   MAYBE_RETURN(change_result, false);
98   return true;
99 }
100 
101 template <bool seq_one_byte>
JsonParser(Isolate * isolate,Handle<String> source)102 JsonParser<seq_one_byte>::JsonParser(Isolate* isolate, Handle<String> source)
103     : source_(source),
104       source_length_(source->length()),
105       isolate_(isolate),
106       factory_(isolate_->factory()),
107       zone_(isolate_->allocator(), ZONE_NAME),
108       object_constructor_(isolate_->native_context()->object_function(),
109                           isolate_),
110       position_(-1) {
111   source_ = String::Flatten(source_);
112   pretenure_ = (source_length_ >= kPretenureTreshold) ? TENURED : NOT_TENURED;
113 
114   // Optimized fast case where we only have Latin1 characters.
115   if (seq_one_byte) {
116     seq_source_ = Handle<SeqOneByteString>::cast(source_);
117   }
118 }
119 
120 template <bool seq_one_byte>
ParseJson()121 MaybeHandle<Object> JsonParser<seq_one_byte>::ParseJson() {
122   // Advance to the first character (possibly EOS)
123   AdvanceSkipWhitespace();
124   Handle<Object> result = ParseJsonValue();
125   if (result.is_null() || c0_ != kEndOfString) {
126     // Some exception (for example stack overflow) is already pending.
127     if (isolate_->has_pending_exception()) return Handle<Object>::null();
128 
129     // Parse failed. Current character is the unexpected token.
130     Factory* factory = this->factory();
131     MessageTemplate::Template message;
132     Handle<Object> arg1 = Handle<Smi>(Smi::FromInt(position_), isolate());
133     Handle<Object> arg2;
134 
135     switch (c0_) {
136       case kEndOfString:
137         message = MessageTemplate::kJsonParseUnexpectedEOS;
138         break;
139       case '-':
140       case '0':
141       case '1':
142       case '2':
143       case '3':
144       case '4':
145       case '5':
146       case '6':
147       case '7':
148       case '8':
149       case '9':
150         message = MessageTemplate::kJsonParseUnexpectedTokenNumber;
151         break;
152       case '"':
153         message = MessageTemplate::kJsonParseUnexpectedTokenString;
154         break;
155       default:
156         message = MessageTemplate::kJsonParseUnexpectedToken;
157         arg2 = arg1;
158         arg1 = factory->LookupSingleCharacterStringFromCode(c0_);
159         break;
160     }
161 
162     Handle<Script> script(factory->NewScript(source_));
163     // We should sent compile error event because we compile JSON object in
164     // separated source file.
165     isolate()->debug()->OnCompileError(script);
166     MessageLocation location(script, position_, position_ + 1);
167     Handle<Object> error = factory->NewSyntaxError(message, arg1, arg2);
168     return isolate()->template Throw<Object>(error, &location);
169   }
170   return result;
171 }
172 
173 MaybeHandle<Object> InternalizeJsonProperty(Handle<JSObject> holder,
174                                             Handle<String> key);
175 
176 template <bool seq_one_byte>
Advance()177 void JsonParser<seq_one_byte>::Advance() {
178   position_++;
179   if (position_ >= source_length_) {
180     c0_ = kEndOfString;
181   } else if (seq_one_byte) {
182     c0_ = seq_source_->SeqOneByteStringGet(position_);
183   } else {
184     c0_ = source_->Get(position_);
185   }
186 }
187 
188 template <bool seq_one_byte>
AdvanceSkipWhitespace()189 void JsonParser<seq_one_byte>::AdvanceSkipWhitespace() {
190   do {
191     Advance();
192   } while (c0_ == ' ' || c0_ == '\t' || c0_ == '\n' || c0_ == '\r');
193 }
194 
195 template <bool seq_one_byte>
SkipWhitespace()196 void JsonParser<seq_one_byte>::SkipWhitespace() {
197   while (c0_ == ' ' || c0_ == '\t' || c0_ == '\n' || c0_ == '\r') {
198     Advance();
199   }
200 }
201 
202 template <bool seq_one_byte>
AdvanceGetChar()203 uc32 JsonParser<seq_one_byte>::AdvanceGetChar() {
204   Advance();
205   return c0_;
206 }
207 
208 template <bool seq_one_byte>
MatchSkipWhiteSpace(uc32 c)209 bool JsonParser<seq_one_byte>::MatchSkipWhiteSpace(uc32 c) {
210   if (c0_ == c) {
211     AdvanceSkipWhitespace();
212     return true;
213   }
214   return false;
215 }
216 
217 template <bool seq_one_byte>
ParseJsonString(Handle<String> expected)218 bool JsonParser<seq_one_byte>::ParseJsonString(Handle<String> expected) {
219   int length = expected->length();
220   if (source_->length() - position_ - 1 > length) {
221     DisallowHeapAllocation no_gc;
222     String::FlatContent content = expected->GetFlatContent();
223     if (content.IsOneByte()) {
224       DCHECK_EQ('"', c0_);
225       const uint8_t* input_chars = seq_source_->GetChars() + position_ + 1;
226       const uint8_t* expected_chars = content.ToOneByteVector().start();
227       for (int i = 0; i < length; i++) {
228         uint8_t c0 = input_chars[i];
229         if (c0 != expected_chars[i] || c0 == '"' || c0 < 0x20 || c0 == '\\') {
230           return false;
231         }
232       }
233       if (input_chars[length] == '"') {
234         position_ = position_ + length + 1;
235         AdvanceSkipWhitespace();
236         return true;
237       }
238     }
239   }
240   return false;
241 }
242 
243 // Parse any JSON value.
244 template <bool seq_one_byte>
ParseJsonValue()245 Handle<Object> JsonParser<seq_one_byte>::ParseJsonValue() {
246   StackLimitCheck stack_check(isolate_);
247   if (stack_check.HasOverflowed()) {
248     isolate_->StackOverflow();
249     return Handle<Object>::null();
250   }
251 
252   if (stack_check.InterruptRequested() &&
253       isolate_->stack_guard()->HandleInterrupts()->IsException(isolate_)) {
254     return Handle<Object>::null();
255   }
256 
257   if (c0_ == '"') return ParseJsonString();
258   if ((c0_ >= '0' && c0_ <= '9') || c0_ == '-') return ParseJsonNumber();
259   if (c0_ == '{') return ParseJsonObject();
260   if (c0_ == '[') return ParseJsonArray();
261   if (c0_ == 'f') {
262     if (AdvanceGetChar() == 'a' && AdvanceGetChar() == 'l' &&
263         AdvanceGetChar() == 's' && AdvanceGetChar() == 'e') {
264       AdvanceSkipWhitespace();
265       return factory()->false_value();
266     }
267     return ReportUnexpectedCharacter();
268   }
269   if (c0_ == 't') {
270     if (AdvanceGetChar() == 'r' && AdvanceGetChar() == 'u' &&
271         AdvanceGetChar() == 'e') {
272       AdvanceSkipWhitespace();
273       return factory()->true_value();
274     }
275     return ReportUnexpectedCharacter();
276   }
277   if (c0_ == 'n') {
278     if (AdvanceGetChar() == 'u' && AdvanceGetChar() == 'l' &&
279         AdvanceGetChar() == 'l') {
280       AdvanceSkipWhitespace();
281       return factory()->null_value();
282     }
283     return ReportUnexpectedCharacter();
284   }
285   return ReportUnexpectedCharacter();
286 }
287 
288 template <bool seq_one_byte>
ParseElement(Handle<JSObject> json_object)289 ParseElementResult JsonParser<seq_one_byte>::ParseElement(
290     Handle<JSObject> json_object) {
291   uint32_t index = 0;
292   // Maybe an array index, try to parse it.
293   if (c0_ == '0') {
294     // With a leading zero, the string has to be "0" only to be an index.
295     Advance();
296   } else {
297     do {
298       int d = c0_ - '0';
299       if (index > 429496729U - ((d + 3) >> 3)) break;
300       index = (index * 10) + d;
301       Advance();
302     } while (IsDecimalDigit(c0_));
303   }
304 
305   if (c0_ == '"') {
306     // Successfully parsed index, parse and store element.
307     AdvanceSkipWhitespace();
308 
309     if (c0_ == ':') {
310       AdvanceSkipWhitespace();
311       Handle<Object> value = ParseJsonValue();
312       if (!value.is_null()) {
313         JSObject::SetOwnElementIgnoreAttributes(json_object, index, value, NONE)
314             .Assert();
315         return kElementFound;
316       } else {
317         return kNullHandle;
318       }
319     }
320   }
321   return kElementNotFound;
322 }
323 
324 // Parse a JSON object. Position must be right at '{'.
325 template <bool seq_one_byte>
ParseJsonObject()326 Handle<Object> JsonParser<seq_one_byte>::ParseJsonObject() {
327   HandleScope scope(isolate());
328   Handle<JSObject> json_object =
329       factory()->NewJSObject(object_constructor(), pretenure_);
330   Handle<Map> map(json_object->map());
331   int descriptor = 0;
332   ZoneList<Handle<Object> > properties(8, zone());
333   DCHECK_EQ(c0_, '{');
334 
335   bool transitioning = true;
336 
337   AdvanceSkipWhitespace();
338   if (c0_ != '}') {
339     do {
340       if (c0_ != '"') return ReportUnexpectedCharacter();
341 
342       int start_position = position_;
343       Advance();
344 
345       if (IsDecimalDigit(c0_)) {
346         ParseElementResult element_result = ParseElement(json_object);
347         if (element_result == kNullHandle) return Handle<Object>::null();
348         if (element_result == kElementFound) continue;
349       }
350       // Not an index, fallback to the slow path.
351 
352       position_ = start_position;
353 #ifdef DEBUG
354       c0_ = '"';
355 #endif
356 
357       Handle<String> key;
358       Handle<Object> value;
359 
360       // Try to follow existing transitions as long as possible. Once we stop
361       // transitioning, no transition can be found anymore.
362       DCHECK(transitioning);
363       // First check whether there is a single expected transition. If so, try
364       // to parse it first.
365       bool follow_expected = false;
366       Handle<Map> target;
367       if (seq_one_byte) {
368         key = TransitionArray::ExpectedTransitionKey(map);
369         follow_expected = !key.is_null() && ParseJsonString(key);
370       }
371       // If the expected transition hits, follow it.
372       if (follow_expected) {
373         target = TransitionArray::ExpectedTransitionTarget(map);
374       } else {
375         // If the expected transition failed, parse an internalized string and
376         // try to find a matching transition.
377         key = ParseJsonInternalizedString();
378         if (key.is_null()) return ReportUnexpectedCharacter();
379 
380         target = TransitionArray::FindTransitionToField(map, key);
381         // If a transition was found, follow it and continue.
382         transitioning = !target.is_null();
383       }
384       if (c0_ != ':') return ReportUnexpectedCharacter();
385 
386       AdvanceSkipWhitespace();
387       value = ParseJsonValue();
388       if (value.is_null()) return ReportUnexpectedCharacter();
389 
390       if (transitioning) {
391         PropertyDetails details =
392             target->instance_descriptors()->GetDetails(descriptor);
393         Representation expected_representation = details.representation();
394 
395         if (value->FitsRepresentation(expected_representation)) {
396           if (expected_representation.IsHeapObject() &&
397               !target->instance_descriptors()
398                    ->GetFieldType(descriptor)
399                    ->NowContains(value)) {
400             Handle<FieldType> value_type(
401                 value->OptimalType(isolate(), expected_representation));
402             Map::GeneralizeFieldType(target, descriptor,
403                                      expected_representation, value_type);
404           }
405           DCHECK(target->instance_descriptors()
406                      ->GetFieldType(descriptor)
407                      ->NowContains(value));
408           properties.Add(value, zone());
409           map = target;
410           descriptor++;
411           continue;
412         } else {
413           transitioning = false;
414         }
415       }
416 
417       DCHECK(!transitioning);
418 
419       // Commit the intermediate state to the object and stop transitioning.
420       CommitStateToJsonObject(json_object, map, &properties);
421 
422       JSObject::DefinePropertyOrElementIgnoreAttributes(json_object, key, value)
423           .Check();
424     } while (transitioning && MatchSkipWhiteSpace(','));
425 
426     // If we transitioned until the very end, transition the map now.
427     if (transitioning) {
428       CommitStateToJsonObject(json_object, map, &properties);
429     } else {
430       while (MatchSkipWhiteSpace(',')) {
431         HandleScope local_scope(isolate());
432         if (c0_ != '"') return ReportUnexpectedCharacter();
433 
434         int start_position = position_;
435         Advance();
436 
437         if (IsDecimalDigit(c0_)) {
438           ParseElementResult element_result = ParseElement(json_object);
439           if (element_result == kNullHandle) return Handle<Object>::null();
440           if (element_result == kElementFound) continue;
441         }
442         // Not an index, fallback to the slow path.
443 
444         position_ = start_position;
445 #ifdef DEBUG
446         c0_ = '"';
447 #endif
448 
449         Handle<String> key;
450         Handle<Object> value;
451 
452         key = ParseJsonInternalizedString();
453         if (key.is_null() || c0_ != ':') return ReportUnexpectedCharacter();
454 
455         AdvanceSkipWhitespace();
456         value = ParseJsonValue();
457         if (value.is_null()) return ReportUnexpectedCharacter();
458 
459         JSObject::DefinePropertyOrElementIgnoreAttributes(json_object, key,
460                                                           value)
461             .Check();
462       }
463     }
464 
465     if (c0_ != '}') {
466       return ReportUnexpectedCharacter();
467     }
468   }
469   AdvanceSkipWhitespace();
470   return scope.CloseAndEscape(json_object);
471 }
472 
473 template <bool seq_one_byte>
CommitStateToJsonObject(Handle<JSObject> json_object,Handle<Map> map,ZoneList<Handle<Object>> * properties)474 void JsonParser<seq_one_byte>::CommitStateToJsonObject(
475     Handle<JSObject> json_object, Handle<Map> map,
476     ZoneList<Handle<Object> >* properties) {
477   JSObject::AllocateStorageForMap(json_object, map);
478   DCHECK(!json_object->map()->is_dictionary_map());
479 
480   DisallowHeapAllocation no_gc;
481 
482   int length = properties->length();
483   for (int i = 0; i < length; i++) {
484     Handle<Object> value = (*properties)[i];
485     json_object->WriteToField(i, *value);
486   }
487 }
488 
489 // Parse a JSON array. Position must be right at '['.
490 template <bool seq_one_byte>
ParseJsonArray()491 Handle<Object> JsonParser<seq_one_byte>::ParseJsonArray() {
492   HandleScope scope(isolate());
493   ZoneList<Handle<Object> > elements(4, zone());
494   DCHECK_EQ(c0_, '[');
495 
496   AdvanceSkipWhitespace();
497   if (c0_ != ']') {
498     do {
499       Handle<Object> element = ParseJsonValue();
500       if (element.is_null()) return ReportUnexpectedCharacter();
501       elements.Add(element, zone());
502     } while (MatchSkipWhiteSpace(','));
503     if (c0_ != ']') {
504       return ReportUnexpectedCharacter();
505     }
506   }
507   AdvanceSkipWhitespace();
508   // Allocate a fixed array with all the elements.
509   Handle<FixedArray> fast_elements =
510       factory()->NewFixedArray(elements.length(), pretenure_);
511   for (int i = 0, n = elements.length(); i < n; i++) {
512     fast_elements->set(i, *elements[i]);
513   }
514   Handle<Object> json_array = factory()->NewJSArrayWithElements(
515       fast_elements, FAST_ELEMENTS, pretenure_);
516   return scope.CloseAndEscape(json_array);
517 }
518 
519 template <bool seq_one_byte>
ParseJsonNumber()520 Handle<Object> JsonParser<seq_one_byte>::ParseJsonNumber() {
521   bool negative = false;
522   int beg_pos = position_;
523   if (c0_ == '-') {
524     Advance();
525     negative = true;
526   }
527   if (c0_ == '0') {
528     Advance();
529     // Prefix zero is only allowed if it's the only digit before
530     // a decimal point or exponent.
531     if (IsDecimalDigit(c0_)) return ReportUnexpectedCharacter();
532   } else {
533     int i = 0;
534     int digits = 0;
535     if (c0_ < '1' || c0_ > '9') return ReportUnexpectedCharacter();
536     do {
537       i = i * 10 + c0_ - '0';
538       digits++;
539       Advance();
540     } while (IsDecimalDigit(c0_));
541     if (c0_ != '.' && c0_ != 'e' && c0_ != 'E' && digits < 10) {
542       SkipWhitespace();
543       return Handle<Smi>(Smi::FromInt((negative ? -i : i)), isolate());
544     }
545   }
546   if (c0_ == '.') {
547     Advance();
548     if (!IsDecimalDigit(c0_)) return ReportUnexpectedCharacter();
549     do {
550       Advance();
551     } while (IsDecimalDigit(c0_));
552   }
553   if (AsciiAlphaToLower(c0_) == 'e') {
554     Advance();
555     if (c0_ == '-' || c0_ == '+') Advance();
556     if (!IsDecimalDigit(c0_)) return ReportUnexpectedCharacter();
557     do {
558       Advance();
559     } while (IsDecimalDigit(c0_));
560   }
561   int length = position_ - beg_pos;
562   double number;
563   if (seq_one_byte) {
564     Vector<const uint8_t> chars(seq_source_->GetChars() + beg_pos, length);
565     number = StringToDouble(isolate()->unicode_cache(), chars,
566                             NO_FLAGS,  // Hex, octal or trailing junk.
567                             std::numeric_limits<double>::quiet_NaN());
568   } else {
569     Vector<uint8_t> buffer = Vector<uint8_t>::New(length);
570     String::WriteToFlat(*source_, buffer.start(), beg_pos, position_);
571     Vector<const uint8_t> result =
572         Vector<const uint8_t>(buffer.start(), length);
573     number = StringToDouble(isolate()->unicode_cache(), result,
574                             NO_FLAGS,  // Hex, octal or trailing junk.
575                             0.0);
576     buffer.Dispose();
577   }
578   SkipWhitespace();
579   return factory()->NewNumber(number, pretenure_);
580 }
581 
582 template <typename StringType>
583 inline void SeqStringSet(Handle<StringType> seq_str, int i, uc32 c);
584 
585 template <>
SeqStringSet(Handle<SeqTwoByteString> seq_str,int i,uc32 c)586 inline void SeqStringSet(Handle<SeqTwoByteString> seq_str, int i, uc32 c) {
587   seq_str->SeqTwoByteStringSet(i, c);
588 }
589 
590 template <>
SeqStringSet(Handle<SeqOneByteString> seq_str,int i,uc32 c)591 inline void SeqStringSet(Handle<SeqOneByteString> seq_str, int i, uc32 c) {
592   seq_str->SeqOneByteStringSet(i, c);
593 }
594 
595 template <typename StringType>
596 inline Handle<StringType> NewRawString(Factory* factory, int length,
597                                        PretenureFlag pretenure);
598 
599 template <>
NewRawString(Factory * factory,int length,PretenureFlag pretenure)600 inline Handle<SeqTwoByteString> NewRawString(Factory* factory, int length,
601                                              PretenureFlag pretenure) {
602   return factory->NewRawTwoByteString(length, pretenure).ToHandleChecked();
603 }
604 
605 template <>
NewRawString(Factory * factory,int length,PretenureFlag pretenure)606 inline Handle<SeqOneByteString> NewRawString(Factory* factory, int length,
607                                              PretenureFlag pretenure) {
608   return factory->NewRawOneByteString(length, pretenure).ToHandleChecked();
609 }
610 
611 // Scans the rest of a JSON string starting from position_ and writes
612 // prefix[start..end] along with the scanned characters into a
613 // sequential string of type StringType.
614 template <bool seq_one_byte>
615 template <typename StringType, typename SinkChar>
SlowScanJsonString(Handle<String> prefix,int start,int end)616 Handle<String> JsonParser<seq_one_byte>::SlowScanJsonString(
617     Handle<String> prefix, int start, int end) {
618   int count = end - start;
619   int max_length = count + source_length_ - position_;
620   int length = Min(max_length, Max(kInitialSpecialStringLength, 2 * count));
621   Handle<StringType> seq_string =
622       NewRawString<StringType>(factory(), length, pretenure_);
623   // Copy prefix into seq_str.
624   SinkChar* dest = seq_string->GetChars();
625   String::WriteToFlat(*prefix, dest, start, end);
626 
627   while (c0_ != '"') {
628     // Check for control character (0x00-0x1f) or unterminated string (<0).
629     if (c0_ < 0x20) return Handle<String>::null();
630     if (count >= length) {
631       // We need to create a longer sequential string for the result.
632       return SlowScanJsonString<StringType, SinkChar>(seq_string, 0, count);
633     }
634     if (c0_ != '\\') {
635       // If the sink can contain UC16 characters, or source_ contains only
636       // Latin1 characters, there's no need to test whether we can store the
637       // character. Otherwise check whether the UC16 source character can fit
638       // in the Latin1 sink.
639       if (sizeof(SinkChar) == kUC16Size || seq_one_byte ||
640           c0_ <= String::kMaxOneByteCharCode) {
641         SeqStringSet(seq_string, count++, c0_);
642         Advance();
643       } else {
644         // StringType is SeqOneByteString and we just read a non-Latin1 char.
645         return SlowScanJsonString<SeqTwoByteString, uc16>(seq_string, 0, count);
646       }
647     } else {
648       Advance();  // Advance past the \.
649       switch (c0_) {
650         case '"':
651         case '\\':
652         case '/':
653           SeqStringSet(seq_string, count++, c0_);
654           break;
655         case 'b':
656           SeqStringSet(seq_string, count++, '\x08');
657           break;
658         case 'f':
659           SeqStringSet(seq_string, count++, '\x0c');
660           break;
661         case 'n':
662           SeqStringSet(seq_string, count++, '\x0a');
663           break;
664         case 'r':
665           SeqStringSet(seq_string, count++, '\x0d');
666           break;
667         case 't':
668           SeqStringSet(seq_string, count++, '\x09');
669           break;
670         case 'u': {
671           uc32 value = 0;
672           for (int i = 0; i < 4; i++) {
673             Advance();
674             int digit = HexValue(c0_);
675             if (digit < 0) {
676               return Handle<String>::null();
677             }
678             value = value * 16 + digit;
679           }
680           if (sizeof(SinkChar) == kUC16Size ||
681               value <= String::kMaxOneByteCharCode) {
682             SeqStringSet(seq_string, count++, value);
683             break;
684           } else {
685             // StringType is SeqOneByteString and we just read a non-Latin1
686             // char.
687             position_ -= 6;  // Rewind position_ to \ in \uxxxx.
688             Advance();
689             return SlowScanJsonString<SeqTwoByteString, uc16>(seq_string, 0,
690                                                               count);
691           }
692         }
693         default:
694           return Handle<String>::null();
695       }
696       Advance();
697     }
698   }
699 
700   DCHECK_EQ('"', c0_);
701   // Advance past the last '"'.
702   AdvanceSkipWhitespace();
703 
704   // Shrink seq_string length to count and return.
705   return SeqString::Truncate(seq_string, count);
706 }
707 
708 template <bool seq_one_byte>
709 template <bool is_internalized>
ScanJsonString()710 Handle<String> JsonParser<seq_one_byte>::ScanJsonString() {
711   DCHECK_EQ('"', c0_);
712   Advance();
713   if (c0_ == '"') {
714     AdvanceSkipWhitespace();
715     return factory()->empty_string();
716   }
717 
718   if (seq_one_byte && is_internalized) {
719     // Fast path for existing internalized strings.  If the the string being
720     // parsed is not a known internalized string, contains backslashes or
721     // unexpectedly reaches the end of string, return with an empty handle.
722     uint32_t running_hash = isolate()->heap()->HashSeed();
723     int position = position_;
724     uc32 c0 = c0_;
725     do {
726       if (c0 == '\\') {
727         c0_ = c0;
728         int beg_pos = position_;
729         position_ = position;
730         return SlowScanJsonString<SeqOneByteString, uint8_t>(source_, beg_pos,
731                                                              position_);
732       }
733       if (c0 < 0x20) return Handle<String>::null();
734       running_hash = StringHasher::AddCharacterCore(running_hash,
735                                                     static_cast<uint16_t>(c0));
736       position++;
737       if (position >= source_length_) return Handle<String>::null();
738       c0 = seq_source_->SeqOneByteStringGet(position);
739     } while (c0 != '"');
740     int length = position - position_;
741     uint32_t hash = (length <= String::kMaxHashCalcLength)
742                         ? StringHasher::GetHashCore(running_hash)
743                         : static_cast<uint32_t>(length);
744     Vector<const uint8_t> string_vector(seq_source_->GetChars() + position_,
745                                         length);
746     StringTable* string_table = isolate()->heap()->string_table();
747     uint32_t capacity = string_table->Capacity();
748     uint32_t entry = StringTable::FirstProbe(hash, capacity);
749     uint32_t count = 1;
750     Handle<String> result;
751     while (true) {
752       Object* element = string_table->KeyAt(entry);
753       if (element->IsUndefined(isolate())) {
754         // Lookup failure.
755         result =
756             factory()->InternalizeOneByteString(seq_source_, position_, length);
757         break;
758       }
759       if (!element->IsTheHole(isolate()) &&
760           String::cast(element)->IsOneByteEqualTo(string_vector)) {
761         result = Handle<String>(String::cast(element), isolate());
762 #ifdef DEBUG
763         uint32_t hash_field =
764             (hash << String::kHashShift) | String::kIsNotArrayIndexMask;
765         DCHECK_EQ(static_cast<int>(result->Hash()),
766                   static_cast<int>(hash_field >> String::kHashShift));
767 #endif
768         break;
769       }
770       entry = StringTable::NextProbe(entry, count++, capacity);
771     }
772     position_ = position;
773     // Advance past the last '"'.
774     AdvanceSkipWhitespace();
775     return result;
776   }
777 
778   int beg_pos = position_;
779   // Fast case for Latin1 only without escape characters.
780   do {
781     // Check for control character (0x00-0x1f) or unterminated string (<0).
782     if (c0_ < 0x20) return Handle<String>::null();
783     if (c0_ != '\\') {
784       if (seq_one_byte || c0_ <= String::kMaxOneByteCharCode) {
785         Advance();
786       } else {
787         return SlowScanJsonString<SeqTwoByteString, uc16>(source_, beg_pos,
788                                                           position_);
789       }
790     } else {
791       return SlowScanJsonString<SeqOneByteString, uint8_t>(source_, beg_pos,
792                                                            position_);
793     }
794   } while (c0_ != '"');
795   int length = position_ - beg_pos;
796   Handle<String> result =
797       factory()->NewRawOneByteString(length, pretenure_).ToHandleChecked();
798   uint8_t* dest = SeqOneByteString::cast(*result)->GetChars();
799   String::WriteToFlat(*source_, dest, beg_pos, position_);
800 
801   DCHECK_EQ('"', c0_);
802   // Advance past the last '"'.
803   AdvanceSkipWhitespace();
804   return result;
805 }
806 
807 // Explicit instantiation.
808 template class JsonParser<true>;
809 template class JsonParser<false>;
810 
811 }  // namespace internal
812 }  // namespace v8
813