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/*
* Copyright (C) 2012 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_SRC_GC_ACCOUNTING_ATOMIC_STACK_H_
#define ART_SRC_GC_ACCOUNTING_ATOMIC_STACK_H_
#include <string>
#include "atomic_integer.h"
#include "base/logging.h"
#include "base/macros.h"
#include "UniquePtr.h"
#include "mem_map.h"
#include "utils.h"
namespace art {
namespace gc {
namespace accounting {
template <typename T>
class AtomicStack {
public:
// Capacity is how many elements we can store in the stack.
static AtomicStack* Create(const std::string& name, size_t capacity) {
UniquePtr<AtomicStack> mark_stack(new AtomicStack(name, capacity));
mark_stack->Init();
return mark_stack.release();
}
~AtomicStack() {}
void Reset() {
DCHECK(mem_map_.get() != NULL);
DCHECK(begin_ != NULL);
front_index_ = 0;
back_index_ = 0;
is_sorted_ = true;
int result = madvise(begin_, sizeof(T) * capacity_, MADV_DONTNEED);
if (result == -1) {
PLOG(WARNING) << "madvise failed";
}
}
// Beware: Mixing atomic pushes and atomic pops will cause ABA problem.
// Returns false if we overflowed the stack.
bool AtomicPushBack(const T& value) {
int32_t index;
is_sorted_ = false;
do {
index = back_index_;
if (UNLIKELY(static_cast<size_t>(index) >= capacity_)) {
// Stack overflow.
return false;
}
} while(!back_index_.CompareAndSwap(index, index + 1));
begin_[index] = value;
return true;
}
void PushBack(const T& value) {
is_sorted_ = false;
int32_t index = back_index_;
DCHECK_LT(static_cast<size_t>(index), capacity_);
back_index_ = index + 1;
begin_[index] = value;
}
T PopBack() {
DCHECK_GT(back_index_, front_index_);
// Decrement the back index non atomically.
back_index_ = back_index_ - 1;
return begin_[back_index_];
}
// Take an item from the front of the stack.
T PopFront() {
int32_t index = front_index_;
DCHECK_LT(index, back_index_.get());
front_index_ = front_index_ + 1;
return begin_[index];
}
bool IsEmpty() const {
return Size() == 0;
}
size_t Size() const {
DCHECK_LE(front_index_, back_index_);
return back_index_ - front_index_;
}
T* Begin() const {
return const_cast<mirror::Object**>(begin_ + front_index_);
}
T* End() const {
return const_cast<mirror::Object**>(begin_ + back_index_);
}
size_t Capacity() const {
return capacity_;
}
// Will clear the stack.
void Resize(size_t new_capacity) {
capacity_ = new_capacity;
Init();
}
void Sort() {
if (!is_sorted_) {
int32_t start_back_index = back_index_.get();
int32_t start_front_index = front_index_.get();
is_sorted_ = true;
std::sort(Begin(), End());
CHECK_EQ(start_back_index, back_index_.get());
CHECK_EQ(start_front_index, front_index_.get());
}
}
bool Contains(const T& value) const {
if (is_sorted_) {
return std::binary_search(Begin(), End(), value);
} else {
return std::find(Begin(), End(), value) != End();
}
}
private:
AtomicStack(const std::string& name, const size_t capacity)
: name_(name),
back_index_(0),
front_index_(0),
begin_(NULL),
capacity_(capacity),
is_sorted_(true) {
}
// Size in number of elements.
void Init() {
mem_map_.reset(MemMap::MapAnonymous(name_.c_str(), NULL, capacity_ * sizeof(T), PROT_READ | PROT_WRITE));
CHECK(mem_map_.get() != NULL) << "couldn't allocate mark stack";
byte* addr = mem_map_->Begin();
CHECK(addr != NULL);
begin_ = reinterpret_cast<T*>(addr);
Reset();
}
// Name of the mark stack.
std::string name_;
// Memory mapping of the atomic stack.
UniquePtr<MemMap> mem_map_;
// Back index (index after the last element pushed).
AtomicInteger back_index_;
// Front index, used for implementing PopFront.
AtomicInteger front_index_;
// Base of the atomic stack.
T* begin_;
// Maximum number of elements.
size_t capacity_;
bool is_sorted_;
DISALLOW_COPY_AND_ASSIGN(AtomicStack);
};
typedef AtomicStack<mirror::Object*> ObjectStack;
} // namespace accounting
} // namespace gc
} // namespace art
#endif // ART_SRC_GC_ACCOUNTING_ATOMIC_STACK_H_
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