src/ast/ast-value-factory.cc

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

#include "src/char-predicates-inl.h"
#include "src/objects-inl.h"
#include "src/objects.h"
#include "src/string-hasher.h"
#include "src/utils-inl.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 StringTableKey {
 public:
  explicit AstRawStringInternalizationKey(const AstRawString* string)
      : StringTableKey(string->hash_field()), 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_));
  }

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

 private:
  const AstRawString* string_;
};

void AstRawString::Internalize(Isolate* isolate) {
  DCHECK(!has_string_);
  if (literal_bytes_.length() == 0) {
    set_string(isolate->factory()->empty_string());
  } else {
    AstRawStringInternalizationKey key(this);
    set_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_field_ & Name::kIsNotArrayIndexMask) != 0) return false;
  if (length() <= Name::kMaxCachedArrayIndexLength) {
    *index = Name::ArrayIndexValueBits::decode(hash_field_);
  } else {
    OneByteStringStream stream(literal_bytes_);
    CHECK(StringToArrayIndex(&stream, index));
  }
  return true;
}

bool AstRawString::IsOneByteEqualTo(const char* data) const {
  if (!is_one_byte()) return false;

  size_t length = static_cast<size_t>(literal_bytes_.length());
  if (length != strlen(data)) return false;

  return 0 == strncmp(reinterpret_cast<const char*>(literal_bytes_.start()),
                      data, length);
}

uint16_t AstRawString::FirstCharacter() const {
  if (is_one_byte()) return literal_bytes_[0];
  const uint16_t* c = reinterpret_cast<const uint16_t*>(literal_bytes_.start());
  return *c;
}

bool AstRawString::Compare(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;
    }
  }
}

void AstConsString::Internalize(Isolate* isolate) {
  if (IsEmpty()) {
    set_string(isolate->factory()->empty_string());
    return;
  }
  // AstRawStrings are internalized before AstConsStrings, so
  // AstRawString::string() will just work.
  Handle<String> tmp(segment_.string->string());
  for (AstConsString::Segment* current = segment_.next; current != nullptr;
       current = current->next) {
    tmp = isolate->factory()
              ->NewConsString(current->string->string(), tmp)
              .ToHandleChecked();
  }
  set_string(tmp);
}

std::forward_list<const AstRawString*> AstConsString::ToRawStrings() const {
  std::forward_list<const AstRawString*> result;
  if (IsEmpty()) {
    return result;
  }

  result.emplace_front(segment_.string);
  for (AstConsString::Segment* current = segment_.next; current != nullptr;
       current = current->next) {
    result.emplace_front(current->string);
  }
  return result;
}

AstStringConstants::AstStringConstants(Isolate* isolate, uint64_t hash_seed)
    : zone_(isolate->allocator(), ZONE_NAME),
      string_table_(AstRawString::Compare),
      hash_seed_(hash_seed) {
  DCHECK(ThreadId::Current().Equals(isolate->thread_id()));
#define F(name, str)                                                       \
  {                                                                        \
    const char* data = str;                                                \
    Vector<const uint8_t> literal(reinterpret_cast<const uint8_t*>(data),  \
                                  static_cast<int>(strlen(data)));         \
    uint32_t hash_field = StringHasher::HashSequentialString<uint8_t>(     \
        literal.start(), literal.length(), hash_seed_);                    \
    name##_string_ = new (&zone_) AstRawString(true, literal, hash_field); \
    /* The Handle returned by the factory is located on the roots */       \
    /* array, not on the temporary HandleScope, so this is safe.  */       \
    name##_string_->set_string(isolate->factory()->name##_string());       \
    base::HashMap::Entry* entry =                                          \
        string_table_.InsertNew(name##_string_, name##_string_->Hash());   \
    DCHECK_NULL(entry->value);                                             \
    entry->value = reinterpret_cast<void*>(1);                             \
  }
  AST_STRING_CONSTANTS(F)
#undef F
}

AstRawString* AstValueFactory::GetOneByteStringInternal(
    Vector<const uint8_t> literal) {
  if (literal.length() == 1 && IsInRange(literal[0], 'a', 'z')) {
    int key = literal[0] - 'a';
    if (one_character_strings_[key] == nullptr) {
      uint32_t hash_field = StringHasher::HashSequentialString<uint8_t>(
          literal.start(), literal.length(), hash_seed_);
      one_character_strings_[key] = GetString(hash_field, true, literal);
    }
    return one_character_strings_[key];
  }
  uint32_t hash_field = StringHasher::HashSequentialString<uint8_t>(
      literal.start(), literal.length(), hash_seed_);
  return GetString(hash_field, true, literal);
}

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

const AstRawString* AstValueFactory::GetString(Handle<String> literal) {
  AstRawString* result = nullptr;
  DisallowHeapAllocation no_gc;
  String::FlatContent content = literal->GetFlatContent();
  if (content.IsOneByte()) {
    result = GetOneByteStringInternal(content.ToOneByteVector());
  } else {
    DCHECK(content.IsTwoByte());
    result = GetTwoByteStringInternal(content.ToUC16Vector());
  }
  return result;
}

AstConsString* AstValueFactory::NewConsString() {
  AstConsString* new_string = new (zone_) AstConsString;
  DCHECK_NOT_NULL(new_string);
  AddConsString(new_string);
  return new_string;
}

AstConsString* AstValueFactory::NewConsString(const AstRawString* str) {
  return NewConsString()->AddString(zone_, str);
}

AstConsString* AstValueFactory::NewConsString(const AstRawString* str1,
                                              const AstRawString* str2) {
  return NewConsString()->AddString(zone_, str1)->AddString(zone_, str2);
}

void AstValueFactory::Internalize(Isolate* isolate) {
  // Strings need to be internalized before values, because values refer to
  // strings.
  for (AstRawString* current = strings_; current != nullptr;) {
    AstRawString* next = current->next();
    current->Internalize(isolate);
    current = next;
  }

  // AstConsStrings refer to AstRawStrings.
  for (AstConsString* current = cons_strings_; current != nullptr;) {
    AstConsString* next = current->next();
    current->Internalize(isolate);
    current = next;
  }

  ResetStrings();
}

AstRawString* AstValueFactory::GetString(uint32_t hash_field, 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_field);
  base::HashMap::Entry* entry = string_table_.LookupOrInsert(&key, key.Hash());
  if (entry->value == nullptr) {
    // 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_field);
    CHECK_NOT_NULL(new_string);
    AddString(new_string);
    entry->key = new_string;
    entry->value = reinterpret_cast<void*>(1);
  }
  return reinterpret_cast<AstRawString*>(entry->key);
}

}  // namespace internal
}  // namespace v8