heap.cc.svn-base

Google浏览器V8内核代码

Object* Heap::AllocateArgumentsObject(Object* callee, int length) {
  // To get fast allocation and map sharing for arguments objects we
  // allocate them based on an arguments boilerplate.

  // This calls Copy directly rather than using Heap::AllocateRaw so we
  // duplicate the check here.
  ASSERT(allocation_allowed_ && gc_state_ == NOT_IN_GC);

  JSObject* boilerplate =
      Top::context()->global_context()->arguments_boilerplate();
  Object* result = boilerplate->Copy();
  if (result->IsFailure()) return result;

  Object* obj = JSObject::cast(result)->properties();
  FixedArray::cast(obj)->set(arguments_callee_index, callee);
  FixedArray::cast(obj)->set(arguments_length_index, Smi::FromInt(length));

  // Allocate the fixed array.
  obj = Heap::AllocateFixedArray(length);
  if (obj->IsFailure()) return obj;
  JSObject::cast(result)->set_elements(FixedArray::cast(obj));

  // Check the state of the object
  ASSERT(JSObject::cast(result)->HasFastProperties());
  ASSERT(JSObject::cast(result)->HasFastElements());

  return result;
}


Object* Heap::AllocateInitialMap(JSFunction* fun) {
  ASSERT(!fun->has_initial_map());

  // First create a new map.
  Object* map_obj = Heap::AllocateMap(JS_OBJECT_TYPE, JSObject::kHeaderSize);
  if (map_obj->IsFailure()) return map_obj;

  // Fetch or allocate prototype.
  Object* prototype;
  if (fun->has_instance_prototype()) {
    prototype = fun->instance_prototype();
  } else {
    prototype = AllocateFunctionPrototype(fun);
    if (prototype->IsFailure()) return prototype;
  }
  Map* map = Map::cast(map_obj);
  map->set_unused_property_fields(fun->shared()->expected_nof_properties());
  map->set_prototype(prototype);
  return map;
}


void Heap::InitializeJSObjectFromMap(JSObject* obj,
                                     FixedArray* properties,
                                     Map* map) {
  obj->set_properties(properties);
  obj->initialize_elements();
  // TODO(1240798): Initialize the object's body using valid initial values
  // according to the object's initial map.  For example, if the map's
  // instance type is JS_ARRAY_TYPE, the length field should be initialized
  // to a number (eg, Smi::FromInt(0)) and the elements initialized to a
  // fixed array (eg, Heap::empty_fixed_array()).  Currently, the object
  // verification code has to cope with (temporarily) invalid objects.  See
  // for example, JSArray::JSArrayVerify).
  obj->InitializeBody(map->instance_size());
}


Object* Heap::AllocateJSObjectFromMap(Map* map, PretenureFlag pretenure) {
  // JSFunctions should be allocated using AllocateFunction to be
  // properly initialized.
  ASSERT(map->instance_type() != JS_FUNCTION_TYPE);

  // Allocate the backing storage for the properties.
  Object* properties = AllocateFixedArray(map->unused_property_fields());
  if (properties->IsFailure()) return properties;

  // Allocate the JSObject.
  AllocationSpace space =
      (pretenure == TENURED) ? OLD_POINTER_SPACE : NEW_SPACE;
  if (map->instance_size() > MaxHeapObjectSize()) space = LO_SPACE;
  Object* obj = Allocate(map, space);
  if (obj->IsFailure()) return obj;

  // Initialize the JSObject.
  InitializeJSObjectFromMap(JSObject::cast(obj),
                            FixedArray::cast(properties),
                            map);
  return obj;
}


Object* Heap::AllocateJSObject(JSFunction* constructor,
                               PretenureFlag pretenure) {
  // Allocate the initial map if absent.
  if (!constructor->has_initial_map()) {
    Object* initial_map = AllocateInitialMap(constructor);
    if (initial_map->IsFailure()) return initial_map;
    constructor->set_initial_map(Map::cast(initial_map));
    Map::cast(initial_map)->set_constructor(constructor);
  }
  // Allocate the object based on the constructors initial map.
  return AllocateJSObjectFromMap(constructor->initial_map(), pretenure);
}


Object* Heap::ReinitializeJSGlobalObject(JSFunction* constructor,
                                         JSGlobalObject* object) {
  // Allocate initial map if absent.
  if (!constructor->has_initial_map()) {
    Object* initial_map = AllocateInitialMap(constructor);
    if (initial_map->IsFailure()) return initial_map;
    constructor->set_initial_map(Map::cast(initial_map));
    Map::cast(initial_map)->set_constructor(constructor);
  }

  Map* map = constructor->initial_map();

  // Check that the already allocated object has the same size as
  // objects allocated using the constructor.
  ASSERT(map->instance_size() == object->map()->instance_size());

  // Allocate the backing storage for the properties.
  Object* properties = AllocateFixedArray(map->unused_property_fields());
  if (properties->IsFailure()) return properties;

  // Reset the map for the object.
  object->set_map(constructor->initial_map());

  // Reinitialize the object from the constructor map.
  InitializeJSObjectFromMap(object, FixedArray::cast(properties), map);
  return object;
}


Object* Heap::AllocateStringFromAscii(Vector<const char> string,
                                      PretenureFlag pretenure) {
  Object* result = AllocateRawAsciiString(string.length(), pretenure);
  if (result->IsFailure()) return result;

  // Copy the characters into the new object.
  AsciiString* string_result = AsciiString::cast(result);
  for (int i = 0; i < string.length(); i++) {
    string_result->AsciiStringSet(i, string[i]);
  }
  return result;
}


Object* Heap::AllocateStringFromUtf8(Vector<const char> string,
                                     PretenureFlag pretenure) {
  // Count the number of characters in the UTF-8 string and check if
  // it is an ASCII string.
  Access<Scanner::Utf8Decoder> decoder(Scanner::utf8_decoder());
  decoder->Reset(string.start(), string.length());
  int chars = 0;
  bool is_ascii = true;
  while (decoder->has_more()) {
    uc32 r = decoder->GetNext();
    if (r > String::kMaxAsciiCharCode) is_ascii = false;
    chars++;
  }

  // If the string is ascii, we do not need to convert the characters
  // since UTF8 is backwards compatible with ascii.
  if (is_ascii) return AllocateStringFromAscii(string, pretenure);

  Object* result = AllocateRawTwoByteString(chars, pretenure);
  if (result->IsFailure()) return result;

  // Convert and copy the characters into the new object.
  String* string_result = String::cast(result);
  decoder->Reset(string.start(), string.length());
  for (int i = 0; i < chars; i++) {
    uc32 r = decoder->GetNext();
    string_result->Set(i, r);
  }
  return result;
}


Object* Heap::AllocateStringFromTwoByte(Vector<const uc16> string,
                                        PretenureFlag pretenure) {
  // Check if the string is an ASCII string.
  int i = 0;
  while (i < string.length() && string[i] <= String::kMaxAsciiCharCode) i++;

  Object* result;
  if (i == string.length()) {  // It's an ASCII string.
    result = AllocateRawAsciiString(string.length(), pretenure);
  } else {  // It's not an ASCII string.
    result = AllocateRawTwoByteString(string.length(), pretenure);
  }
  if (result->IsFailure()) return result;

  // Copy the characters into the new object, which may be either ASCII or
  // UTF-16.
  String* string_result = String::cast(result);
  for (int i = 0; i < string.length(); i++) {
    string_result->Set(i, string[i]);
  }
  return result;
}


Map* Heap::SymbolMapForString(String* string) {
  // If the string is in new space it cannot be used as a symbol.
  if (InNewSpace(string)) return NULL;

  // Find the corresponding symbol map for strings.
  Map* map = string->map();

  if (map == short_ascii_string_map()) return short_ascii_symbol_map();
  if (map == medium_ascii_string_map()) return medium_ascii_symbol_map();
  if (map == long_ascii_string_map()) return long_ascii_symbol_map();

  if (map == short_string_map()) return short_symbol_map();
  if (map == medium_string_map()) return medium_symbol_map();
  if (map == long_string_map()) return long_symbol_map();

  if (map == short_cons_string_map()) return short_cons_symbol_map();
  if (map == medium_cons_string_map()) return medium_cons_symbol_map();
  if (map == long_cons_string_map()) return long_cons_symbol_map();

  if (map == short_cons_ascii_string_map()) {
    return short_cons_ascii_symbol_map();
  }
  if (map == medium_cons_ascii_string_map()) {
    return medium_cons_ascii_symbol_map();
  }
  if (map == long_cons_ascii_string_map()) {
    return long_cons_ascii_symbol_map();
  }

  if (map == short_sliced_string_map()) return short_sliced_symbol_map();
  if (map == medium_sliced_string_map()) return short_sliced_symbol_map();
  if (map == long_sliced_string_map()) return short_sliced_symbol_map();

  if (map == short_sliced_ascii_string_map()) {
    return short_sliced_ascii_symbol_map();
  }
  if (map == medium_sliced_ascii_string_map()) {
    return short_sliced_ascii_symbol_map();
  }
  if (map == long_sliced_ascii_string_map()) {
    return short_sliced_ascii_symbol_map();
  }

  if (map == short_external_string_map()) return short_external_string_map();
  if (map == medium_external_string_map()) return medium_external_string_map();
  if (map == long_external_string_map()) return long_external_string_map();

  if (map == short_external_ascii_string_map()) {
    return short_external_ascii_string_map();
  }
  if (map == medium_external_ascii_string_map()) {
    return medium_external_ascii_string_map();
  }
  if (map == long_external_ascii_string_map()) {
    return long_external_ascii_string_map();
  }

  // No match found.
  return NULL;
}


Object* Heap::AllocateSymbol(unibrow::CharacterStream* buffer,
                             int chars,
                             int hash) {
  // Ensure the chars matches the number of characters in the buffer.
  ASSERT(static_cast<unsigned>(chars) == buffer->Length());
  // Determine whether the string is ascii.
  bool is_ascii = true;
  while (buffer->has_more()) {
    if (buffer->GetNext() > unibrow::Utf8::kMaxOneByteChar) is_ascii = false;
  }
  buffer->Rewind();

  // Compute map and object size.
  int size;
  Map* map;

  if (is_ascii) {
    if (chars <= String::kMaxShortStringSize) {
      map = short_ascii_symbol_map();
    } else if (chars <= String::kMaxMediumStringSize) {
      map = medium_ascii_symbol_map();
    } else {
      map = long_ascii_symbol_map();
    }
    size = AsciiString::SizeFor(chars);
  } else {
    if (chars <= String::kMaxShortStringSize) {
      map = short_symbol_map();
    } else if (chars <= String::kMaxMediumStringSize) {
      map = medium_symbol_map();
    } else {
      map = long_symbol_map();
    }
    size = TwoByteString::SizeFor(chars);
  }

  // Allocate string.
  AllocationSpace space =
      (size > MaxHeapObjectSize()) ? LO_SPACE : OLD_DATA_SPACE;
  Object* result = AllocateRaw(size, space);
  if (result->IsFailure()) return result;

  reinterpret_cast<HeapObject*>(result)->set_map(map);
  // The hash value contains the length of the string.
  String::cast(result)->set_length_field(hash);

  ASSERT_EQ(size, String::cast(result)->Size());

  // Fill in the characters.
  for (int i = 0; i < chars; i++) {
    String::cast(result)->Set(i, buffer->GetNext());
  }
  return result;
}


Object* Heap::AllocateRawAsciiString(int length, PretenureFlag pretenure) {
  AllocationSpace space = (pretenure == TENURED) ? OLD_DATA_SPACE : NEW_SPACE;
  int size = AsciiString::SizeFor(length);
  if (size > MaxHeapObjectSize()) {
    space = LO_SPACE;
  }

  // Use AllocateRaw rather than Allocate because the object's size cannot be
  // determined from the map.
  Object* result = AllocateRaw(size, space);
  if (result->IsFailure()) return result;

  // Determine the map based on the string's length.
  Map* map;
  if (length <= String::kMaxShortStringSize) {
    map = short_ascii_string_map();
  } else if (length <= String::kMaxMediumStringSize) {
    map = medium_ascii_string_map();
  } else {
    map = long_ascii_string_map();
  }

  // Partially initialize the object.
  HeapObject::cast(result)->set_map(map);
  String::cast(result)->set_length(length);
  ASSERT_EQ(size, HeapObject::cast(result)->Size());
  return result;
}


Object* Heap::AllocateRawTwoByteString(int length, PretenureFlag pretenure) {
  AllocationSpace space = (pretenure == TENURED) ? OLD_DATA_SPACE : NEW_SPACE;
  int size = TwoByteString::SizeFor(length);
  if (size > MaxHeapObjectSize()) {
    space = LO_SPACE;
  }

  // Use AllocateRaw rather than Allocate because the object's size cannot be
  // determined from the map.
  Object* result = AllocateRaw(size, space);
  if (result->IsFailure()) return result;

  // Determine the map based on the string's length.
  Map* map;
  if (length <= String::kMaxShortStringSize) {
    map = short_string_map();
  } else if (length <= String::kMaxMediumStringSize) {
    map = medium_string_map();
  } else {
    map = long_string_map();
  }

  // Partially initialize the object.
  HeapObject::cast(result)->set_map(map);
  String::cast(result)->set_length(length);
  ASSERT_EQ(size, HeapObject::cast(result)->Size());
  return result;
}


Object* Heap::AllocateEmptyFixedArray() {
  int size = FixedArray::SizeFor(0);
  Object* result = AllocateRaw(size, OLD_DATA_SPACE);
  if (result->IsFailure()) return result;
  // Initialize the object.
  reinterpret_cast<Array*>(result)->set_map(fixed_array_map());
  reinterpret_cast<Array*>(result)->set_length(0);
  return result;
}


Object* Heap::AllocateFixedArray(int length, PretenureFlag pretenure) {
  ASSERT(empty_fixed_array()->IsFixedArray());
  if (length == 0) return empty_fixed_array();

  int size =