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// Copyright 2011 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_SMALL_POINTER_LIST_H_
#define V8_SMALL_POINTER_LIST_H_
#include "src/base/logging.h"
#include "src/globals.h"
#include "src/zone/zone.h"
namespace v8 {
namespace internal {
// SmallPointerList is a list optimized for storing no or just a
// single value. When more values are given it falls back to ZoneList.
//
// The interface tries to be as close to List from list.h as possible.
template <typename T>
class SmallPointerList {
public:
SmallPointerList() : data_(kEmptyTag) {}
SmallPointerList(int capacity, Zone* zone) : data_(kEmptyTag) {
Reserve(capacity, zone);
}
void Reserve(int capacity, Zone* zone) {
if (capacity < 2) return;
if ((data_ & kTagMask) == kListTag) {
if (list()->capacity() >= capacity) return;
int old_length = list()->length();
list()->AddBlock(NULL, capacity - list()->capacity(), zone);
list()->Rewind(old_length);
return;
}
PointerList* list = new(zone) PointerList(capacity, zone);
if ((data_ & kTagMask) == kSingletonTag) {
list->Add(single_value(), zone);
}
DCHECK(IsAligned(reinterpret_cast<intptr_t>(list), kPointerAlignment));
data_ = reinterpret_cast<intptr_t>(list) | kListTag;
}
void Clear() {
data_ = kEmptyTag;
}
void Sort() {
if ((data_ & kTagMask) == kListTag) {
list()->Sort(compare_value);
}
}
bool is_empty() const { return length() == 0; }
int length() const {
if ((data_ & kTagMask) == kEmptyTag) return 0;
if ((data_ & kTagMask) == kSingletonTag) return 1;
return list()->length();
}
void Add(T* pointer, Zone* zone) {
DCHECK(IsAligned(reinterpret_cast<intptr_t>(pointer), kPointerAlignment));
if ((data_ & kTagMask) == kEmptyTag) {
data_ = reinterpret_cast<intptr_t>(pointer) | kSingletonTag;
return;
}
if ((data_ & kTagMask) == kSingletonTag) {
PointerList* list = new(zone) PointerList(2, zone);
list->Add(single_value(), zone);
list->Add(pointer, zone);
DCHECK(IsAligned(reinterpret_cast<intptr_t>(list), kPointerAlignment));
data_ = reinterpret_cast<intptr_t>(list) | kListTag;
return;
}
list()->Add(pointer, zone);
}
// Note: returns T* and not T*& (unlike List from list.h).
// This makes the implementation simpler and more const correct.
T* at(int i) const {
DCHECK((data_ & kTagMask) != kEmptyTag);
if ((data_ & kTagMask) == kSingletonTag) {
DCHECK(i == 0);
return single_value();
}
return list()->at(i);
}
// See the note above.
T* operator[](int i) const { return at(i); }
// Remove the given element from the list (if present).
void RemoveElement(T* pointer) {
if ((data_ & kTagMask) == kEmptyTag) return;
if ((data_ & kTagMask) == kSingletonTag) {
if (pointer == single_value()) {
data_ = kEmptyTag;
}
return;
}
list()->RemoveElement(pointer);
}
T* RemoveLast() {
DCHECK((data_ & kTagMask) != kEmptyTag);
if ((data_ & kTagMask) == kSingletonTag) {
T* result = single_value();
data_ = kEmptyTag;
return result;
}
return list()->RemoveLast();
}
void Rewind(int pos) {
if ((data_ & kTagMask) == kEmptyTag) {
DCHECK(pos == 0);
return;
}
if ((data_ & kTagMask) == kSingletonTag) {
DCHECK(pos == 0 || pos == 1);
if (pos == 0) {
data_ = kEmptyTag;
}
return;
}
list()->Rewind(pos);
}
int CountOccurrences(T* pointer, int start, int end) const {
if ((data_ & kTagMask) == kEmptyTag) return 0;
if ((data_ & kTagMask) == kSingletonTag) {
if (start == 0 && end >= 0) {
return (single_value() == pointer) ? 1 : 0;
}
return 0;
}
return list()->CountOccurrences(pointer, start, end);
}
private:
typedef ZoneList<T*> PointerList;
static int compare_value(T* const* a, T* const* b) {
return Compare<T>(**a, **b);
}
static const intptr_t kEmptyTag = 1;
static const intptr_t kSingletonTag = 0;
static const intptr_t kListTag = 2;
static const intptr_t kTagMask = 3;
static const intptr_t kValueMask = ~kTagMask;
STATIC_ASSERT(kTagMask + 1 <= kPointerAlignment);
T* single_value() const {
DCHECK((data_ & kTagMask) == kSingletonTag);
STATIC_ASSERT(kSingletonTag == 0);
return reinterpret_cast<T*>(data_);
}
PointerList* list() const {
DCHECK((data_ & kTagMask) == kListTag);
return reinterpret_cast<PointerList*>(data_ & kValueMask);
}
intptr_t data_;
DISALLOW_COPY_AND_ASSIGN(SmallPointerList);
};
} // namespace internal
} // namespace v8
#endif // V8_SMALL_POINTER_LIST_H_
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