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// Copyright 2017 The Cobalt Authors. All Rights Reserved.
//
// 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 STARBOARD_COMMON_LOCKED_PTR_H_
#define STARBOARD_COMMON_LOCKED_PTR_H_
#include "starboard/common/log.h"
#include "starboard/common/mutex.h"
#include "starboard/common/scoped_ptr.h"
namespace starboard {
// This class adds thread-safety to any class. Note when using LockedPtr<T>,
// the caller should use the returned object directly as a pointer without
// holding on it. This is enforced by making the ctors of Impl private.
template <typename Type>
class LockedPtr {
public:
template <typename ImplType>
class Impl {
public:
~Impl() {
if (mutex_) {
mutex_->Release();
}
}
ImplType* operator->() {
SB_DCHECK(ptr_);
return ptr_;
}
private:
friend class LockedPtr<Type>;
Impl(Mutex* mutex, ImplType* ptr) : mutex_(mutex), ptr_(ptr) {
SB_DCHECK(mutex);
}
// The copy ctor transfers the ownership. So only the last one holds the
// lock. This is safe as long as the user won't hold a reference to the
// returned object.
Impl(Impl& that) {
mutex_ = that.mutex_;
ptr_ = that.ptr_;
that.mutex_ = NULL;
that.ptr_ = NULL;
}
Mutex* mutex_;
ImplType* ptr_;
};
LockedPtr() : ptr_(NULL) {}
explicit LockedPtr(scoped_ptr<Type> ptr) : ptr_(ptr) {
SB_DCHECK(ptr != NULL);
}
// This function is solely used to set the pointer to a valid value when it is
// not convenient to construct the object directly. So it checks if the
// existing |ptr_| is NULL.
void set(scoped_ptr<Type> ptr) {
starboard::ScopedLock scoped_lock(mutex_);
SB_DCHECK(ptr_ == NULL);
ptr_ = ptr.Pass();
}
void reset() {
starboard::ScopedLock scoped_lock(mutex_);
ptr_.reset();
}
bool is_valid() const {
starboard::ScopedLock scoped_lock(mutex_);
return ptr_ != NULL;
}
Impl<Type> operator->() {
mutex_.Acquire();
Impl<Type> impl(&mutex_, ptr_.get());
return impl;
}
Impl<const Type> operator->() const {
mutex_.Acquire();
Impl<const Type> impl(&mutex_, ptr_.get());
return impl;
}
private:
mutable Mutex mutex_;
scoped_ptr<Type> ptr_;
};
} // namespace starboard
#endif // STARBOARD_COMMON_LOCKED_PTR_H_