/src/ast/ast-value-factory.cc

// Copyright 2014 the V8 project authors. All rights reserved.
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//
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#include "src/ast/ast-value-factory.h"

#include "src/api.h"
#include "src/objects.h"
#include "src/utils.h"

namespace v8 {
namespace internal {

namespace {

// For using StringToArrayIndex.
class OneByteStringStream {
 public:
  explicit OneByteStringStream(Vector<const byte> lb) :
      literal_bytes_(lb), pos_(0) {}

  bool HasMore() { return pos_ < literal_bytes_.length(); }
  uint16_t GetNext() { return literal_bytes_[pos_++]; }

 private:
  Vector<const byte> literal_bytes_;
  int pos_;
};

}  // namespace

class AstRawStringInternalizationKey : public HashTableKey {
 public:
  explicit AstRawStringInternalizationKey(const AstRawString* string)
      : string_(string) {}

  bool IsMatch(Object* other) override {
    if (string_->is_one_byte())
      return String::cast(other)->IsOneByteEqualTo(string_->literal_bytes_);
    return String::cast(other)->IsTwoByteEqualTo(
        Vector<const uint16_t>::cast(string_->literal_bytes_));
  }

  uint32_t Hash() override { return string_->hash() >> Name::kHashShift; }

  uint32_t HashForObject(Object* key) override {
    return String::cast(key)->Hash();
  }

  Handle<Object> AsHandle(Isolate* isolate) override {
    if (string_->is_one_byte())
      return isolate->factory()->NewOneByteInternalizedString(
          string_->literal_bytes_, string_->hash());
    return isolate->factory()->NewTwoByteInternalizedString(
        Vector<const uint16_t>::cast(string_->literal_bytes_), string_->hash());
  }

 private:
  const AstRawString* string_;
};

int AstString::length() const {
  if (IsRawStringBits::decode(bit_field_)) {
    return reinterpret_cast<const AstRawString*>(this)->length();
  }
  return reinterpret_cast<const AstConsString*>(this)->length();
}

void AstString::Internalize(Isolate* isolate) {
  if (IsRawStringBits::decode(bit_field_)) {
    return reinterpret_cast<AstRawString*>(this)->Internalize(isolate);
  }
  return reinterpret_cast<AstConsString*>(this)->Internalize(isolate);
}

void AstRawString::Internalize(Isolate* isolate) {
  if (literal_bytes_.length() == 0) {
    string_ = isolate->factory()->empty_string();
  } else {
    AstRawStringInternalizationKey key(this);
    string_ = StringTable::LookupKey(isolate, &key);
  }
}

bool AstRawString::AsArrayIndex(uint32_t* index) const {
  // The StringHasher will set up the hash in such a way that we can use it to
  // figure out whether the string is convertible to an array index.
  if ((hash_ & Name::kIsNotArrayIndexMask) != 0) return false;
  if (length() <= Name::kMaxCachedArrayIndexLength) {
    *index = Name::ArrayIndexValueBits::decode(hash_);
  } else {
    OneByteStringStream stream(literal_bytes_);
    CHECK(StringToArrayIndex(&stream, index));
  }
  return true;
}

bool AstRawString::IsOneByteEqualTo(const char* data) const {
  int length = static_cast<int>(strlen(data));
  if (is_one_byte() && literal_bytes_.length() == length) {
    const char* token = reinterpret_cast<const char*>(literal_bytes_.start());
    return !strncmp(token, data, length);
  }
  return false;
}


void AstConsString::Internalize(Isolate* isolate) {
  // AstRawStrings are internalized before AstConsStrings so left and right are
  // already internalized.
  string_ = isolate->factory()
                ->NewConsString(left_->string(), right_->string())
                .ToHandleChecked();
}

bool AstValue::IsPropertyName() const {
  if (type_ == STRING) {
    uint32_t index;
    return !string_->AsArrayIndex(&index);
  }
  return false;
}


bool AstValue::BooleanValue() const {
  switch (type_) {
    case STRING:
      DCHECK(string_ != NULL);
      return !string_->IsEmpty();
    case SYMBOL:
      UNREACHABLE();
      break;
    case NUMBER_WITH_DOT:
    case NUMBER:
      return DoubleToBoolean(number_);
    case SMI_WITH_DOT:
    case SMI:
      return smi_ != 0;
    case BOOLEAN:
      return bool_;
    case NULL_TYPE:
      return false;
    case THE_HOLE:
      UNREACHABLE();
      break;
    case UNDEFINED:
      return false;
  }
  UNREACHABLE();
  return false;
}


void AstValue::Internalize(Isolate* isolate) {
  switch (type_) {
    case STRING:
      DCHECK(string_ != NULL);
      // Strings are already internalized.
      DCHECK(!string_->string().is_null());
      break;
    case SYMBOL:
      if (symbol_name_[0] == 'i') {
        DCHECK_EQ(0, strcmp(symbol_name_, "iterator_symbol"));
        value_ = isolate->factory()->iterator_symbol();
      } else if (strcmp(symbol_name_, "hasInstance_symbol") == 0) {
        value_ = isolate->factory()->has_instance_symbol();
      } else {
        DCHECK_EQ(0, strcmp(symbol_name_, "home_object_symbol"));
        value_ = isolate->factory()->home_object_symbol();
      }
      break;
    case NUMBER_WITH_DOT:
    case NUMBER:
      value_ = isolate->factory()->NewNumber(number_, TENURED);
      break;
    case SMI_WITH_DOT:
    case SMI:
      value_ = handle(Smi::FromInt(smi_), isolate);
      break;
    case BOOLEAN:
      if (bool_) {
        value_ = isolate->factory()->true_value();
      } else {
        value_ = isolate->factory()->false_value();
      }
      break;
    case NULL_TYPE:
      value_ = isolate->factory()->null_value();
      break;
    case THE_HOLE:
      value_ = isolate->factory()->the_hole_value();
      break;
    case UNDEFINED:
      value_ = isolate->factory()->undefined_value();
      break;
  }
}


AstRawString* AstValueFactory::GetOneByteStringInternal(
    Vector<const uint8_t> literal) {
  uint32_t hash = StringHasher::HashSequentialString<uint8_t>(
      literal.start(), literal.length(), hash_seed_);
  return GetString(hash, true, literal);
}


AstRawString* AstValueFactory::GetTwoByteStringInternal(
    Vector<const uint16_t> literal) {
  uint32_t hash = StringHasher::HashSequentialString<uint16_t>(
      literal.start(), literal.length(), hash_seed_);
  return GetString(hash, false, Vector<const byte>::cast(literal));
}


const AstRawString* AstValueFactory::GetString(Handle<String> literal) {
  // For the FlatContent to stay valid, we shouldn't do any heap
  // allocation. Make sure we won't try to internalize the string in GetString.
  AstRawString* result = NULL;
  Isolate* saved_isolate = isolate_;
  isolate_ = NULL;
  {
    DisallowHeapAllocation no_gc;
    String::FlatContent content = literal->GetFlatContent();
    if (content.IsOneByte()) {
      result = GetOneByteStringInternal(content.ToOneByteVector());
    } else {
      DCHECK(content.IsTwoByte());
      result = GetTwoByteStringInternal(content.ToUC16Vector());
    }
  }
  isolate_ = saved_isolate;
  if (strings_ != nullptr && isolate_) {
    // Only the string we are creating is uninternalized at this point.
    DCHECK_EQ(result, strings_);
    DCHECK_NULL(strings_->next());
    result->Internalize(isolate_);
    ResetStrings();
  }
  return result;
}


const AstConsString* AstValueFactory::NewConsString(
    const AstString* left, const AstString* right) {
  // This Vector will be valid as long as the Collector is alive (meaning that
  // the AstRawString will not be moved).
  AstConsString* new_string = new (zone_) AstConsString(left, right);
  CHECK(new_string != nullptr);
  AddString(new_string);
  return new_string;
}


void AstValueFactory::Internalize(Isolate* isolate) {
  if (isolate_) {
    DCHECK_NULL(strings_);
    DCHECK_NULL(values_);
    // Everything is already internalized.
    return;
  }

  // Strings need to be internalized before values, because values refer to
  // strings.
  for (AstString* current = strings_; current != nullptr;) {
    AstString* next = current->next();
    current->Internalize(isolate);
    current = next;
  }
  for (AstValue* current = values_; current != nullptr;) {
    AstValue* next = current->next();
    current->Internalize(isolate);
    current = next;
  }
  isolate_ = isolate;
  ResetStrings();
  values_ = nullptr;
}


const AstValue* AstValueFactory::NewString(const AstRawString* string) {
  AstValue* value = new (zone_) AstValue(string);
  CHECK(string != nullptr);
  return AddValue(value);
}


const AstValue* AstValueFactory::NewSymbol(const char* name) {
  AstValue* value = new (zone_) AstValue(name);
  return AddValue(value);
}


const AstValue* AstValueFactory::NewNumber(double number, bool with_dot) {
  AstValue* value = new (zone_) AstValue(number, with_dot);
  return AddValue(value);
}


const AstValue* AstValueFactory::NewSmi(int number) {
  AstValue* value =
      new (zone_) AstValue(AstValue::SMI, number);
  return AddValue(value);
}

#define GENERATE_VALUE_GETTER(value, initializer)        \
  if (!value) {                                          \
    value = AddValue(new (zone_) AstValue(initializer)); \
  }                                                      \
  return value;

const AstValue* AstValueFactory::NewBoolean(bool b) {
  if (b) {
    GENERATE_VALUE_GETTER(true_value_, true);
  } else {
    GENERATE_VALUE_GETTER(false_value_, false);
  }
}


const AstValue* AstValueFactory::NewNull() {
  GENERATE_VALUE_GETTER(null_value_, AstValue::NULL_TYPE);
}


const AstValue* AstValueFactory::NewUndefined() {
  GENERATE_VALUE_GETTER(undefined_value_, AstValue::UNDEFINED);
}


const AstValue* AstValueFactory::NewTheHole() {
  GENERATE_VALUE_GETTER(the_hole_value_, AstValue::THE_HOLE);
}


#undef GENERATE_VALUE_GETTER

AstRawString* AstValueFactory::GetString(uint32_t hash, bool is_one_byte,
                                         Vector<const byte> literal_bytes) {
  // literal_bytes here points to whatever the user passed, and this is OK
  // because we use vector_compare (which checks the contents) to compare
  // against the AstRawStrings which are in the string_table_. We should not
  // return this AstRawString.
  AstRawString key(is_one_byte, literal_bytes, hash);
  base::HashMap::Entry* entry = string_table_.LookupOrInsert(&key, hash);
  if (entry->value == NULL) {
    // Copy literal contents for later comparison.
    int length = literal_bytes.length();
    byte* new_literal_bytes = zone_->NewArray<byte>(length);
    memcpy(new_literal_bytes, literal_bytes.start(), length);
    AstRawString* new_string = new (zone_) AstRawString(
        is_one_byte, Vector<const byte>(new_literal_bytes, length), hash);
    CHECK(new_string != nullptr);
    entry->key = new_string;
    AddString(new_string);
    entry->value = reinterpret_cast<void*>(1);
  }
  return reinterpret_cast<AstRawString*>(entry->key);
}


bool AstValueFactory::AstRawStringCompare(void* a, void* b) {
  const AstRawString* lhs = static_cast<AstRawString*>(a);
  const AstRawString* rhs = static_cast<AstRawString*>(b);
  DCHECK_EQ(lhs->hash(), rhs->hash());
  if (lhs->length() != rhs->length()) return false;
  const unsigned char* l = lhs->raw_data();
  const unsigned char* r = rhs->raw_data();
  size_t length = rhs->length();
  if (lhs->is_one_byte()) {
    if (rhs->is_one_byte()) {
      return CompareCharsUnsigned(reinterpret_cast<const uint8_t*>(l),
                                  reinterpret_cast<const uint8_t*>(r),
                                  length) == 0;
    } else {
      return CompareCharsUnsigned(reinterpret_cast<const uint8_t*>(l),
                                  reinterpret_cast<const uint16_t*>(r),
                                  length) == 0;
    }
  } else {
    if (rhs->is_one_byte()) {
      return CompareCharsUnsigned(reinterpret_cast<const uint16_t*>(l),
                                  reinterpret_cast<const uint8_t*>(r),
                                  length) == 0;
    } else {
      return CompareCharsUnsigned(reinterpret_cast<const uint16_t*>(l),
                                  reinterpret_cast<const uint16_t*>(r),
                                  length) == 0;
    }
  }
}
}  // namespace internal
}  // namespace v8