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// Copyright 2012 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#ifndef V8_TRANSITIONS_H_
#define V8_TRANSITIONS_H_
#include "elements-kind.h"
#include "heap.h"
#include "isolate.h"
#include "objects.h"
#include "v8checks.h"
namespace v8 {
namespace internal {
// TransitionArrays are fixed arrays used to hold map transitions for property,
// constant, and element changes. They can either be simple transition arrays
// that store a single property transition, or a full transition array that has
// space for elements transitions, prototype transitions and multiple property
// transitons. The details related to property transitions are accessed in the
// descriptor array of the target map. In the case of a simple transition, the
// key is also read from the descriptor array of the target map.
//
// The simple format of the these objects is:
// [0] Undefined or back pointer map
// [1] Single transition
//
// The full format is:
// [0] Undefined or back pointer map
// [1] Smi(0) or elements transition map
// [2] Smi(0) or fixed array of prototype transitions
// [3] First transition
// [length() - kTransitionSize] Last transition
class TransitionArray: public FixedArray {
public:
// Accessors for fetching instance transition at transition number.
inline String* GetKey(int transition_number);
inline void SetKey(int transition_number, String* value);
inline Object** GetKeySlot(int transition_number);
int GetSortedKeyIndex(int transition_number) { return transition_number; }
String* GetSortedKey(int transition_number) {
return GetKey(transition_number);
}
inline Map* GetTarget(int transition_number);
inline void SetTarget(int transition_number, Map* target);
inline PropertyDetails GetTargetDetails(int transition_number);
inline Map* elements_transition();
inline void set_elements_transition(
Map* target,
WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
inline bool HasElementsTransition();
inline void ClearElementsTransition();
inline Object* back_pointer_storage();
inline void set_back_pointer_storage(
Object* back_pointer,
WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
inline FixedArray* GetPrototypeTransitions();
inline void SetPrototypeTransitions(
FixedArray* prototype_transitions,
WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
inline Object** GetPrototypeTransitionsSlot();
inline bool HasPrototypeTransitions();
inline HeapObject* UncheckedPrototypeTransitions();
// Returns the number of transitions in the array.
int number_of_transitions() {
if (IsSimpleTransition()) return 1;
int len = length();
return len <= kFirstIndex ? 0 : (len - kFirstIndex) / kTransitionSize;
}
inline int number_of_entries() { return number_of_transitions(); }
// Allocate a new transition array with a single entry.
static MUST_USE_RESULT MaybeObject* NewWith(
SimpleTransitionFlag flag,
String* key,
Map* target,
Object* back_pointer);
MUST_USE_RESULT MaybeObject* ExtendToFullTransitionArray();
// Copy the transition array, inserting a new transition.
// TODO(verwaest): This should not cause an existing transition to be
// overwritten.
MUST_USE_RESULT MaybeObject* CopyInsert(String* name, Map* target);
// Copy a single transition from the origin array.
inline void NoIncrementalWriteBarrierCopyFrom(TransitionArray* origin,
int origin_transition,
int target_transition);
// Search a transition for a given property name.
inline int Search(String* name);
// Allocates a TransitionArray.
MUST_USE_RESULT static MaybeObject* Allocate(int number_of_transitions);
bool IsSimpleTransition() { return length() == kSimpleTransitionSize; }
bool IsFullTransitionArray() { return length() >= kFirstIndex; }
// Casting.
static inline TransitionArray* cast(Object* obj);
// Constant for denoting key was not found.
static const int kNotFound = -1;
static const int kBackPointerStorageIndex = 0;
// Layout for full transition arrays.
static const int kElementsTransitionIndex = 1;
static const int kPrototypeTransitionsIndex = 2;
static const int kFirstIndex = 3;
// Layout for simple transition arrays.
static const int kSimpleTransitionTarget = 1;
static const int kSimpleTransitionSize = 2;
static const int kSimpleTransitionIndex = 0;
STATIC_ASSERT(kSimpleTransitionIndex != kNotFound);
static const int kBackPointerStorageOffset = FixedArray::kHeaderSize;
// Layout for the full transition array header.
static const int kElementsTransitionOffset = kBackPointerStorageOffset +
kPointerSize;
static const int kPrototypeTransitionsOffset = kElementsTransitionOffset +
kPointerSize;
// Layout of map transition entries in full transition arrays.
static const int kTransitionKey = 0;
static const int kTransitionTarget = 1;
static const int kTransitionSize = 2;
#ifdef OBJECT_PRINT
// Print all the transitions.
inline void PrintTransitions() {
PrintTransitions(stdout);
}
void PrintTransitions(FILE* out);
#endif
#ifdef DEBUG
bool IsSortedNoDuplicates(int valid_entries = -1);
bool IsConsistentWithBackPointers(Map* current_map);
bool IsEqualTo(TransitionArray* other);
#endif
// The maximum number of transitions we want in a transition array (should
// fit in a page).
static const int kMaxNumberOfTransitions = 1024 + 512;
private:
// Conversion from transition number to array indices.
static int ToKeyIndex(int transition_number) {
return kFirstIndex +
(transition_number * kTransitionSize) +
kTransitionKey;
}
static int ToTargetIndex(int transition_number) {
return kFirstIndex +
(transition_number * kTransitionSize) +
kTransitionTarget;
}
inline void NoIncrementalWriteBarrierSet(int transition_number,
String* key,
Map* target);
DISALLOW_IMPLICIT_CONSTRUCTORS(TransitionArray);
};
} } // namespace v8::internal
#endif // V8_TRANSITIONS_H_
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