// Copyright (c) 2012 The Chromium Authors. All rights reserved.

// Use of this source code is governed by a BSD-style license that can be

// found in the LICENSE file.

#pragma once

#include <cassert>

#include <cstddef>

#include <utility> // IWYU pragma: keep

#include "gutil/atomicops.h"

#include "butil/macros.h"

#include "gutil/threading/thread_collision_warner.h"

namespace doris {

namespace subtle {

typedef Atomic32 AtomicRefCount;

class RefCountedBase {

public:

    bool HasOneRef() const { return ref_count_ == 1; }

protected:

    RefCountedBase();

    ~RefCountedBase();

    void AddRef() const;

    // Returns true if the object should self-delete.

    bool Release() const;

private:

    mutable int ref_count_;

#ifndef NDEBUG

    mutable bool in_dtor_;

#endif

    DFAKE_MUTEX(add_release_);

    DISALLOW_COPY_AND_ASSIGN(RefCountedBase);

};

class RefCountedThreadSafeBase {

public:

    bool HasOneRef() const;

protected:

    RefCountedThreadSafeBase();

    ~RefCountedThreadSafeBase();

    void AddRef() const;

    // Returns true if the object should self-delete.

    bool Release() const;

private:

    mutable AtomicRefCount ref_count_;

#ifndef NDEBUG

    mutable bool in_dtor_;

#endif

    DISALLOW_COPY_AND_ASSIGN(RefCountedThreadSafeBase);

};

} // namespace subtle

//

// A base class for reference counted classes.  Otherwise, known as a cheap

// knock-off of WebKit's RefCounted<T> class.  To use this guy just extend your

// class from it like so:

//

//   class MyFoo : public RefCounted<MyFoo> {

//    ...

//    private:

//     friend class RefCounted<MyFoo>;

//     ~MyFoo();

//   };

//

// You should always make your destructor private, to avoid any code deleting

// the object accidentally while there are references to it.

template <class T>

class RefCounted : public subtle::RefCountedBase {

public:

    RefCounted() {}

    void AddRef() const { subtle::RefCountedBase::AddRef(); }

    void Release() const {

        if (subtle::RefCountedBase::Release()) {

            delete static_cast<const T*>(this);

        }

    }

protected:

    ~RefCounted() {}

};

// Forward declaration.

template <class T, typename Traits>

class RefCountedThreadSafe;

// Default traits for RefCountedThreadSafe<T>.  Deletes the object when its ref

// count reaches 0.  Overload to delete it on a different thread etc.

template <typename T>

struct DefaultRefCountedThreadSafeTraits {

    static void Destruct(const T* x) {

        // Delete through RefCountedThreadSafe to make child classes only need to be

        // friend with RefCountedThreadSafe instead of this struct, which is an

        // implementation detail.

        RefCountedThreadSafe<T, DefaultRefCountedThreadSafeTraits>::DeleteInternal(x);

    }

};

//

// A thread-safe variant of RefCounted<T>

//

//   class MyFoo : public RefCountedThreadSafe<MyFoo> {

//    ...

//   };

//

// If you're using the default trait, then you should add compile time

// asserts that no one else is deleting your object.  i.e.

//    private:

//     friend class RefCountedThreadSafe<MyFoo>;

//     ~MyFoo();

template <class T, typename Traits = DefaultRefCountedThreadSafeTraits<T>>

class RefCountedThreadSafe : public subtle::RefCountedThreadSafeBase {

public:

    RefCountedThreadSafe() {}

    void AddRef() const { subtle::RefCountedThreadSafeBase::AddRef(); }

    void Release() const {

        if (subtle::RefCountedThreadSafeBase::Release()) {

            Traits::Destruct(static_cast<const T*>(this));

        }

    }

protected:

    ~RefCountedThreadSafe() {}

private:

    friend struct DefaultRefCountedThreadSafeTraits<T>;

    static void DeleteInternal(const T* x) { delete x; }

    DISALLOW_COPY_AND_ASSIGN(RefCountedThreadSafe);

};

//

// A thread-safe wrapper for some piece of data so we can place other

// things in scoped_refptrs<>.

//

template <typename T>

class RefCountedData : public doris::RefCountedThreadSafe<doris::RefCountedData<T>> {

public:

    RefCountedData() : data() {}

    RefCountedData(const T& in_value) : data(in_value) {}

    T data;

private:

    friend class doris::RefCountedThreadSafe<doris::RefCountedData<T>>;

    ~RefCountedData() {}

};

} // namespace doris

//

// A smart pointer class for reference counted objects.  Use this class instead

// of calling AddRef and Release manually on a reference counted object to

// avoid common memory leaks caused by forgetting to Release an object

// reference.  Sample usage:

//

//   class MyFoo : public RefCounted<MyFoo> {

//    ...

//   };

//

//   void some_function() {

//     scoped_refptr<MyFoo> foo = new MyFoo();

//     foo->Method(param);

//     // |foo| is released when this function returns

//   }

//

//   void some_other_function() {

//     scoped_refptr<MyFoo> foo = new MyFoo();

//     ...

//     foo = NULL;  // explicitly releases |foo|

//     ...

//     if (foo)

//       foo->Method(param);

//   }

//

// The above examples show how scoped_refptr<T> acts like a pointer to T.

// Given two scoped_refptr<T> classes, it is also possible to exchange

// references between the two objects, like so:

//

//   {

//     scoped_refptr<MyFoo> a = new MyFoo();

//     scoped_refptr<MyFoo> b;

//

//     b.swap(a);

//     // now, |b| references the MyFoo object, and |a| references NULL.

//   }

//

// To make both |a| and |b| in the above example reference the same MyFoo

// object, simply use the assignment operator:

//

//   {

//     scoped_refptr<MyFoo> a = new MyFoo();

//     scoped_refptr<MyFoo> b;

//

//     b = a;

//     // now, |a| and |b| each own a reference to the same MyFoo object.

//   }

//

template <class T>

class scoped_refptr {

public:

    typedef T element_type;

    scoped_refptr() : ptr_(NULL) {}

    scoped_refptr(T* p) : ptr_(p) {

        if (ptr_) ptr_->AddRef();

    }

    // Copy constructor.

    scoped_refptr(const scoped_refptr<T>& r) : ptr_(r.ptr_) {

        if (ptr_) ptr_->AddRef();

    }

    // Copy conversion constructor.

    template <typename U>

    scoped_refptr(const scoped_refptr<U>& r) : ptr_(r.get()) {

        if (ptr_) ptr_->AddRef();

    }

    // Move constructor. This is required in addition to the conversion

    // constructor below in order for clang to warn about pessimizing moves.

    scoped_refptr(scoped_refptr&& r) noexcept : ptr_(r.get()) { // NOLINT

        r.ptr_ = nullptr;

    }

    // Move conversion constructor.

    template <typename U>

    scoped_refptr(scoped_refptr<U>&& r) noexcept : ptr_(r.get()) { // NOLINT

        r.ptr_ = nullptr;

    }

    ~scoped_refptr() {

        if (ptr_) ptr_->Release();

    }

    T* get() const { return ptr_; }

    typedef T* scoped_refptr::*Testable;

    operator Testable() const { return ptr_ ? &scoped_refptr::ptr_ : NULL; }

    T* operator->() const {

        assert(ptr_ != NULL);

        return ptr_;

    }

    scoped_refptr<T>& operator=(T* p) {

        // AddRef first so that self assignment should work

        if (p) p->AddRef();

        T* old_ptr = ptr_;

        ptr_ = p;

        if (old_ptr) old_ptr->Release();

        return *this;

    }

    scoped_refptr<T>& operator=(const scoped_refptr<T>& r) { return *this = r.ptr_; }

    template <typename U>

    scoped_refptr<T>& operator=(const scoped_refptr<U>& r) {

        return *this = r.get();

    }

    scoped_refptr<T>& operator=(scoped_refptr<T>&& r) {

        scoped_refptr<T>(std::move(r)).swap(*this);

        return *this;

    }

    template <typename U>

    scoped_refptr<T>& operator=(scoped_refptr<U>&& r) {

        scoped_refptr<T>(std::move(r)).swap(*this);

        return *this;

    }

    void swap(T** pp) {

        T* p = ptr_;

        ptr_ = *pp;

        *pp = p;

    }

    void swap(scoped_refptr<T>& r) { swap(&r.ptr_); }

    // Like gscoped_ptr::reset(), drops a reference on the currently held object

    // (if any), and adds a reference to the passed-in object (if not NULL).

    void reset(T* p = NULL) { *this = p; }

protected:

    T* ptr_ = nullptr;

private:

    template <typename U>

    friend class scoped_refptr;

};

// Handy utility for creating a scoped_refptr<T> out of a T* explicitly without

// having to retype all the template arguments

template <typename T>

scoped_refptr<T> make_scoped_refptr(T* t) {

    return scoped_refptr<T>(t);

}

// equal_to and hash implementations for templated scoped_refptrs suitable for

// use with STL unordered_* containers.

template <class T>

struct ScopedRefPtrEqualToFunctor {

    bool operator()(const scoped_refptr<T>& x, const scoped_refptr<T>& y) const {

        return x.get() == y.get();

    }

};

template <class T>

struct ScopedRefPtrHashFunctor {

    size_t operator()(const scoped_refptr<T>& p) const { return reinterpret_cast<size_t>(p.get()); }

};