base/src/refbase.cpp

/*
 * Copyright (c) 2021 Huawei Device Co., Ltd.
 * 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.
 */

#include "refbase.h"
#ifdef DEBUG_REFBASE
#include "utils_log.h"
#include <unistd.h>
#endif

namespace OHOS {

WeakRefCounter::WeakRefCounter(RefCounter *counter, void *cookie)
    : atomicWeak_(0), refCounter_(counter), cookie_(cookie)
{
    if (refCounter_ != nullptr) {
        refCounter_->IncRefCount();
    }
}

WeakRefCounter::~WeakRefCounter()
{
    if (refCounter_ != nullptr) {
        refCounter_->DecRefCount();
    }
}

int WeakRefCounter::GetWeakRefCount() const
{
    return atomicWeak_.load(std::memory_order_relaxed);
}

void* WeakRefCounter::GetRefPtr()
{
    if ((cookie_ != nullptr) && (!refCounter_->IsRefPtrValid())) {
        cookie_ = nullptr;
    }
    return cookie_;
}

void WeakRefCounter::IncWeakRefCount(const void *objectId)
{
    if (atomicWeak_.fetch_add(1, std::memory_order_relaxed) == 0) {
        refCounter_->IncWeakRefCount(objectId);
    }
}

void WeakRefCounter::DecWeakRefCount(const void *objectId)
{
    if (atomicWeak_.fetch_sub(1, std::memory_order_release) == 1) {
        refCounter_->DecWeakRefCount(objectId);
        delete this;
    }
}

bool WeakRefCounter::AttemptIncStrongRef(const void *objectId)
{
    int unuse = 0;
    return refCounter_->AttemptIncStrongRef(objectId, unuse);
}

#if ((defined DEBUG_REFBASE) && (!defined PRINT_TRACK_AT_ONCE))
// RefTracker is a debug tool, used to record the trace of RefBase.
// RefTracker will save the information about the count of RefBase,
// including the pointer of sptr/wptr(The pointer of itself, not the pointer
// it manages), the amount of strong/weak/refcout and the PID&TID.
// The Tracker can live with RefCounter.
// User should keep thread-safety of RefTracker.
class RefTracker {
public:
    RefTracker(RefTracker* exTracker, const void* id, int strong, int weak, int ref, int pid, int tid);

    void PrintTrace(const void* refCounterPtr);

    RefTracker* PopTrace(const void* refCounterPtr);

private:
    const void* ptrID;
    int strongRefCnt;
    int weakRefCnt;
    int refCnt;
    int PID;
    int TID;
    RefTracker* exTrace;
};

RefTracker::RefTracker(RefTracker* exTracker, const void* id, int strong, int weak, int ref, int pid, int tid)
    : ptrID (id), strongRefCnt (strong), weakRefCnt (weak), refCnt (ref), PID (pid), TID (tid), exTrace (exTracker)
{
}

void RefTracker::PrintTrace(const void* refCounterPtr)
{
    UTILS_LOGI("%{public}p call %{public}p. strong: %{public}d weak: %{public}d " \
        "refcnt: %{public}d PID: %{public}d TID: %{public}d",
        ptrID, refCounterPtr, strongRefCnt, weakRefCnt, refCnt, PID, TID);
}

RefTracker* RefTracker::PopTrace(const void* refCounterPtr)
{
    RefTracker* ref = exTrace;
    PrintTrace(refCounterPtr);
    delete this;
    return ref;
}
#endif

#ifdef DEBUG_REFBASE
#ifdef PRINT_TRACK_AT_ONCE
void RefCounter::PrintRefs(const void* objectId)
{
    std::lock_guard<std::mutex> lock(trackerMutex);
    UTILS_LOGI("%{public}p call %{public}p. strong: %{public}d weak: %{public}d " \
        "refcnt: %{public}d", objectId, this, atomicStrong_.load(std::memory_order_relaxed),
        atomicWeak_.load(std::memory_order_relaxed), atomicRefCount_.load(std::memory_order_relaxed));
}
#else
void RefCounter::GetNewTrace(const void* objectId)
{
    std::lock_guard<std::mutex> lock(trackerMutex);
    RefTracker* newTracker = new RefTracker(refTracker, objectId, atomicStrong_,
        atomicWeak_, atomicRefCount_, getpid(), gettid());
    refTracker = newTracker;
}

void RefCounter::PrintTracker()
{
    std::lock_guard<std::mutex> lock(trackerMutex);
    if (refTracker) {
        UTILS_LOGI("%{public}p start backtrace", this);
        while (refTracker) {
            refTracker = refTracker->PopTrace(this);
        }
        UTILS_LOGI("%{public}p end backtrace", this);
    }
}
#endif

#ifndef TRACK_ALL
void RefCounter::EnableTracker()
{
    std::lock_guard<std::mutex> lock(trackerMutex);
#ifdef PRINT_TRACK_AT_ONCE
    UTILS_LOGI("%{public}p start tracking", this);
#endif
    enableTrack = true;
}
#endif
#endif

RefCounter::RefCounter()
    : atomicStrong_(INITIAL_PRIMARY_VALUE), atomicWeak_(0), atomicRefCount_(0), atomicFlags_(0), atomicAttempt_(0)
{
}

int RefCounter::GetRefCount()
{
    return atomicRefCount_.load(std::memory_order_relaxed);
}

void RefCounter::IncRefCount()
{
    atomicRefCount_.fetch_add(1, std::memory_order_relaxed);
}

void RefCounter::DecRefCount()
{
    if (atomicRefCount_.load(std::memory_order_relaxed) > 0) {
        if (atomicRefCount_.fetch_sub(1, std::memory_order_release) == 1) {
            delete (this);
        }
    }
}

void RefCounter::SetCallback(const RefPtrCallback& callback)
{
    callback_ = callback;
}

void RefCounter::RemoveCallback()
{
    callback_ = nullptr;
}

bool RefCounter::IsRefPtrValid()
{
    return callback_ != nullptr;
}

RefCounter::~RefCounter()
{
#ifdef DEBUG_REFBASE
    if (enableTrack) {
#ifdef PRINT_TRACK_AT_ONCE
        UTILS_LOGI("%{public}p end tracking", this);
#else
        PrintTracker();
#endif
    }
#endif
}

int RefCounter::IncStrongRefCount(const void* objectId)
{
#ifdef DEBUG_REFBASE
    if (enableTrack) {
#ifdef PRINT_TRACK_AT_ONCE
        PrintRefs(objectId);
#else
        GetNewTrace(objectId);
#endif
    }
#endif
    int curCount = atomicStrong_.load(std::memory_order_relaxed);
    if (curCount >= 0) {
        curCount = atomicStrong_.fetch_add(1, std::memory_order_relaxed);
        if (curCount == INITIAL_PRIMARY_VALUE) {
            atomicStrong_.fetch_sub(INITIAL_PRIMARY_VALUE, std::memory_order_release);
        }
    }

    return curCount;
}

int RefCounter::DecStrongRefCount(const void* objectId)
{
#ifdef DEBUG_REFBASE
    if (enableTrack) {
#ifdef PRINT_TRACK_AT_ONCE
        PrintRefs(objectId);
#else
        GetNewTrace(objectId);
#endif
    }
#endif
    int curCount = GetStrongRefCount();
    if (curCount == INITIAL_PRIMARY_VALUE) {
        // unexpected case: there had never a strong reference.
    } else if (curCount > 0) {
        // we should update the current count here.
        // it may be changed after last operation.
        curCount = atomicStrong_.fetch_sub(1, std::memory_order_release);
    }

    return curCount;
}

int RefCounter::GetStrongRefCount()
{
    return atomicStrong_.load(std::memory_order_relaxed);
}

int RefCounter::IncWeakRefCount(const void* objectId)
{
#ifdef DEBUG_REFBASE
    if (enableTrack) {
#ifdef PRINT_TRACK_AT_ONCE
        PrintRefs(objectId);
#else
        GetNewTrace(objectId);
#endif
    }
#endif
    return atomicWeak_.fetch_add(1, std::memory_order_relaxed);
}

int RefCounter::DecWeakRefCount(const void* objectId)
{
#ifdef DEBUG_REFBASE
    if (enableTrack) {
#ifdef PRINT_TRACK_AT_ONCE
        PrintRefs(objectId);
#else
        GetNewTrace(objectId);
#endif
    }
#endif
    int curCount = GetWeakRefCount();
    if (curCount > 0) {
        curCount = atomicWeak_.fetch_sub(1, std::memory_order_release);
    }

    if (curCount != 1) {
        return curCount;
    }

    if (IsLifeTimeExtended() && GetStrongRefCount() == 0) {
        if (callback_) {
            callback_();
        }
    } else {
        // only weak ptr case: no strong reference, delete the object
        if (GetStrongRefCount() == INITIAL_PRIMARY_VALUE) {
            if (callback_) {
                callback_();
            }
        } else {
            // free RefCounter
            DecRefCount();
        }
    }

    return curCount;
}

int RefCounter::GetWeakRefCount()
{
    return atomicWeak_.load(std::memory_order_relaxed);
}

void RefCounter::SetAttemptAcquire()
{
    (void)atomicAttempt_.fetch_add(1, std::memory_order_relaxed);
}

bool RefCounter::IsAttemptAcquireSet()
{
    return static_cast<bool>(atomicAttempt_.load(std::memory_order_relaxed) > 0);
}

void RefCounter::ClearAttemptAcquire()
{
    atomicAttempt_.fetch_sub(1, std::memory_order_relaxed);
}

void RefCounter::ExtendObjectLifetime()
{
    atomicFlags_.fetch_or(FLAG_EXTEND_LIFE_TIME, std::memory_order_relaxed);
}

bool RefCounter::IsLifeTimeExtended()
{
    return static_cast<bool>(atomicFlags_.load(std::memory_order_relaxed) & FLAG_EXTEND_LIFE_TIME);
}

bool RefCounter::AttemptIncStrongRef(const void *objectId, int &outCount)
{
    int curCount = GetStrongRefCount();
    IncWeakRefCount(objectId);

    // if the object already had strong references.just promoting it.
    while ((curCount > 0) && (curCount != INITIAL_PRIMARY_VALUE)) {
        if (atomicStrong_.compare_exchange_weak(curCount, curCount + 1, std::memory_order_relaxed)) {
            goto ATTEMPT_SUCCESS;
        }
        // someone else changed the counter.re-acquire the counter value.
        curCount = atomicStrong_.load(std::memory_order_relaxed);
    }

    if ((curCount == INITIAL_PRIMARY_VALUE) && !IsLifeTimeExtended()) {
        // this object has a "normal" life-time,
        while (curCount > 0) {
            if (atomicStrong_.compare_exchange_weak(curCount, curCount + 1, std::memory_order_relaxed)) {
                goto ATTEMPT_SUCCESS;
            }
            curCount = atomicStrong_.load(std::memory_order_relaxed);
        }
    }

    if (IsLifeTimeExtended()) {
        curCount = atomicStrong_.fetch_add(1, std::memory_order_relaxed);
    }

ATTEMPT_SUCCESS:
    if (curCount >= INITIAL_PRIMARY_VALUE) {
        outCount = curCount;
        atomicStrong_.fetch_sub(INITIAL_PRIMARY_VALUE, std::memory_order_release);
        return true;
    }

    if (curCount < 0 || (!IsLifeTimeExtended() && curCount == 0)) {
        // the object destroyed on strong reference count reduce to zero.
        DecWeakRefCount(objectId);
        return false;
    }

    return true;
}

bool RefCounter::AttemptIncStrong(const void *objectId)
{
    IncWeakRefCount(objectId);
    int curCount = GetStrongRefCount();
    while (curCount > 0) {
        if (atomicStrong_.compare_exchange_weak(curCount, curCount + 1, std::memory_order_relaxed)) {
            break;
        }
        // curCount has been updated.
    }
    if (curCount <= 0) {
        DecWeakRefCount(objectId);
    }
    return curCount > 0;
}

RefBase::RefBase() : refs_(new RefCounter())
{
    refs_->IncRefCount();
    refs_->SetCallback(std::bind(&RefBase::RefPtrCallback, this));
}

RefBase::RefBase(const RefBase &)
{
    refs_ = new (std::nothrow) RefCounter();
    if (refs_ != nullptr) {
        refs_->IncRefCount();
        refs_->SetCallback(std::bind(&RefBase::RefPtrCallback, this));
    }
}

void RefBase::RefPtrCallback()
{
    delete this;
}

/*
 * The two ends of the assignment are two independent and exclusive,
 * and the application should not share the reference counter.
 * RISK: If there is a reference count on the left of the equal sign,
 * it may cause a reference count exception
 */
RefBase &RefBase::operator=(const RefBase &)
{
    if (refs_ != nullptr) {
        refs_->RemoveCallback();
        refs_->DecRefCount();
    }

    refs_ = new (std::nothrow) RefCounter();
    if (refs_ != nullptr) {
        refs_->IncRefCount();
        refs_->SetCallback(std::bind(&RefBase::RefPtrCallback, this));
    }

    return *this;
}

RefBase::RefBase(RefBase &&other) noexcept
{
    refs_ = other.refs_;
    other.refs_ = nullptr;
}

RefBase &RefBase::operator=(RefBase &&other) noexcept
{
    if (refs_ == other.refs_) {
        return *this;
    }

    if (refs_ != nullptr) {
        refs_->RemoveCallback();
        refs_->DecRefCount();
    }

    refs_ = other.refs_;
    other.refs_ = nullptr;
    return *this;
}

RefBase::~RefBase()
{
    if (refs_ != nullptr) {
        refs_->RemoveCallback();
        if ((refs_->IsLifeTimeExtended() && refs_->GetWeakRefCount() == 0) ||
             refs_->GetStrongRefCount() == INITIAL_PRIMARY_VALUE) {
            refs_->DecRefCount();
        }
        refs_ = nullptr;
    }
}

void RefBase::ExtendObjectLifetime()
{
    refs_->ExtendObjectLifetime();
}

void RefBase::IncStrongRef(const void *objectId)
{
    if (refs_ == nullptr) {
        return;
    }

    IncWeakRef(objectId);
    const int curCount = refs_->IncStrongRefCount(objectId);
    if (curCount == INITIAL_PRIMARY_VALUE) {
        OnFirstStrongRef(objectId);
    }
    if (refs_->IsAttemptAcquireSet()) {
        refs_->ClearAttemptAcquire();
        refs_->DecStrongRefCount(objectId);
        refs_->DecWeakRefCount(objectId);
    }
}

void RefBase::DecStrongRef(const void *objectId)
{
    if (refs_ == nullptr) {
        return;
    }

    RefCounter * const refs = refs_;
    const int curCount = refs->DecStrongRefCount(objectId);
    if (curCount == 1) {
        OnLastStrongRef(objectId);
        if (!refs->IsLifeTimeExtended()) {
            if (refs->callback_) {
                refs->callback_();
            }
        }
    }

    refs->DecWeakRefCount(objectId);
}

int RefBase::GetSptrRefCount()
{
    if (refs_ == nullptr) {
        return 0;
    }
    return refs_->GetStrongRefCount();
}

WeakRefCounter *RefBase::CreateWeakRef(void *cookie)
{
    if (refs_ != nullptr) {
        return new WeakRefCounter(refs_, cookie);
    }
    return nullptr;
}

void RefBase::IncWeakRef(const void *objectId)
{
    if (refs_ != nullptr) {
        refs_->IncWeakRefCount(objectId);
    }
}

RefCounter *RefBase::GetRefCounter() const
{
    return refs_;
}

void RefBase::DecWeakRef(const void *objectId)
{
    if (refs_ != nullptr) {
        refs_->DecWeakRefCount(objectId);
    }
}

int RefBase::GetWptrRefCount()
{
    if (refs_ == nullptr) {
        return 0;
    }
    return refs_->GetWeakRefCount();
}

bool RefBase::AttemptAcquire(const void *objectId)
{
    if (refs_ == nullptr) {
        return false;
    }

    int count = 0;
    if (refs_->AttemptIncStrongRef(objectId, count)) {
        refs_->SetAttemptAcquire();
        if (count == INITIAL_PRIMARY_VALUE) {
            OnFirstStrongRef(objectId);
        }

        return true;
    }
    return false;
}

bool RefBase::AttemptIncStrongRef(const void *objectId)
{
    if ((refs_ != nullptr) && (OnAttemptPromoted(objectId))) {
        int count = 0;
        bool ret = refs_->AttemptIncStrongRef(objectId, count);
        if (count == INITIAL_PRIMARY_VALUE) {
            OnFirstStrongRef(objectId);
        }
        return ret;
    }

    return false;
}

bool RefBase::AttemptIncStrong(const void *objectId)
{
    if (refs_ == nullptr) {
        return false;
    }
    if (refs_->AttemptIncStrong(objectId)) {
        refs_->SetAttemptAcquire();
        return true;
    }
    return false;
}

bool RefBase::IsAttemptAcquireSet()
{
    if (refs_ == nullptr) {
        return false;
    }
    return refs_->IsAttemptAcquireSet();
}

bool RefBase::IsExtendLifeTimeSet()
{
    if (refs_ == nullptr) {
        return false;
    }
    return refs_->IsLifeTimeExtended();
}

void RefBase::OnFirstStrongRef(const void*)
{}

void RefBase::OnLastStrongRef(const void*)
{}

void RefBase::OnLastWeakRef(const void*)
{}

bool RefBase::OnAttemptPromoted(const void*)
{
    return true;
}

#if ((defined DEBUG_REFBASE) && (!defined TRACK_ALL))
void RefBase::EnableTracker()
{
    refs_->EnableTracker();
}
#else
void RefBase::EnableTracker()
{
}
#endif

}  // namespace OHOS