Make and use a (simple) atomic unique_ptr

3 files changed, 69 insertions, 3 deletions

diff --git a/common/atomic.h b/common/atomic.h
index a579dcab..51ddaa5d 100644
--- a/common/atomic.h
+++ b/common/atomic.h
@@ -2,7 +2,9 @@
 #define AL_ATOMIC_H
 
 #include <atomic>
+#include <memory>
 
+#include "almalloc.h"
 
 template<typename T>
 auto IncrementRef(std::atomic<T> &ref) noexcept
@@ -27,4 +29,68 @@ inline void AtomicReplaceHead(std::atomic<T> &head, T newhead)
             std::memory_order_acq_rel, std::memory_order_acquire));
 }
 
+namespace al {
+
+template<typename T, typename D=std::default_delete<T>>
+class atomic_unique_ptr {
+    std::atomic<gsl::owner<T*>> mPointer{};
+
+public:
+    atomic_unique_ptr() = default;
+    atomic_unique_ptr(const atomic_unique_ptr&) = delete;
+    explicit atomic_unique_ptr(std::nullptr_t) noexcept { }
+    explicit atomic_unique_ptr(gsl::owner<T*> ptr) noexcept : mPointer{ptr} { }
+    explicit atomic_unique_ptr(std::unique_ptr<T>&& rhs) noexcept : mPointer{rhs.release()} { }
+    ~atomic_unique_ptr() { if(auto ptr = mPointer.load(std::memory_order_relaxed)) D{}(ptr); }
+
+    atomic_unique_ptr& operator=(const atomic_unique_ptr&) = delete;
+    atomic_unique_ptr& operator=(std::nullptr_t) noexcept
+    {
+        if(auto ptr = mPointer.exchange(nullptr))
+            D{}(ptr);
+        return *this;
+    }
+    atomic_unique_ptr& operator=(std::unique_ptr<T>&& rhs) noexcept
+    {
+        if(auto ptr = mPointer.exchange(rhs.release()))
+            D{}(ptr);
+        return *this;
+    }
+
+    [[nodiscard]]
+    T* load(std::memory_order m=std::memory_order_seq_cst) const { return mPointer.load(m); }
+    void store(std::nullptr_t, std::memory_order m=std::memory_order_seq_cst) noexcept
+    {
+        if(auto oldptr = mPointer.exchange(nullptr, m))
+            D{}(oldptr);
+    }
+    void store(gsl::owner<T*> ptr, std::memory_order m=std::memory_order_seq_cst) noexcept
+    {
+        if(auto oldptr = mPointer.exchange(ptr, m))
+            D{}(oldptr);
+    }
+    void store(std::unique_ptr<T>&& ptr, std::memory_order m=std::memory_order_seq_cst) noexcept
+    {
+        if(auto oldptr = mPointer.exchange(ptr.release(), m))
+            D{}(oldptr);
+    }
+
+    [[nodiscard]]
+    std::unique_ptr<T> exchange(std::nullptr_t, std::memory_order m=std::memory_order_seq_cst) noexcept
+    { return std::unique_ptr<T>{mPointer.exchange(nullptr, m)}; }
+    [[nodiscard]]
+    std::unique_ptr<T> exchange(gsl::owner<T*> ptr, std::memory_order m=std::memory_order_seq_cst) noexcept
+    { return std::unique_ptr<T>{mPointer.exchange(ptr, m)}; }
+    [[nodiscard]]
+    std::unique_ptr<T> exchange(std::unique_ptr<T>&& ptr, std::memory_order m=std::memory_order_seq_cst) noexcept
+    { return std::unique_ptr<T>{mPointer.exchange(ptr.release(), m)}; }
+
+    [[nodiscard]]
+    bool is_lock_free() const noexcept { mPointer.is_lock_free(); }
+
+    static constexpr auto is_always_lock_free = std::atomic<gsl::owner<T*>>::is_always_lock_free;
+};
+
+} // namespace al
+
 #endif /* AL_ATOMIC_H */
diff --git a/core/context.cpp b/core/context.cpp
index b969583b..cb00ae70 100644
--- a/core/context.cpp
+++ b/core/context.cpp
@@ -52,7 +52,7 @@ ContextBase::~ContextBase()
     if(std::unique_ptr<EffectSlotArray> curarray{mActiveAuxSlots.exchange(nullptr, std::memory_order_relaxed)})
         std::destroy_n(curarray->end(), curarray->size());
 
-    std::unique_ptr<ContextBase::VoiceArray>{mVoices.exchange(nullptr, std::memory_order_relaxed)};
+    mVoices.store(nullptr, std::memory_order_relaxed);
 
     if(mAsyncEvents)
     {
@@ -142,7 +142,7 @@ void ContextBase::allocVoices(size_t addcount)
         voice_iter = std::transform(cluster->begin(), cluster->end(), voice_iter,
             [](Voice &voice) noexcept -> Voice* { return &voice; });
 
-    if(std::unique_ptr<ContextBase::VoiceArray> oldvoices{mVoices.exchange(newarray.release(), std::memory_order_acq_rel)})
+    if(auto oldvoices = mVoices.exchange(std::move(newarray), std::memory_order_acq_rel))
         std::ignore = mDevice->waitForMix();
 }
 
diff --git a/core/context.h b/core/context.h
index 0b830205..6fc1ed5d 100644
--- a/core/context.h
+++ b/core/context.h
@@ -112,7 +112,7 @@ struct ContextBase {
     ContextParams mParams;
 
     using VoiceArray = al::FlexArray<Voice*>;
-    std::atomic<VoiceArray*> mVoices{};
+    al::atomic_unique_ptr<VoiceArray> mVoices{};
     std::atomic<size_t> mActiveVoiceCount{};
 
     void allocVoices(size_t addcount);