improve nf7::Mutex

common/mutex.hh

@@ -5,32 +5,37 @@
 #include <memory>
 #include <utility>
 
+#include "common/life.hh"
 #include "common/future.hh"
 
 
 namespace nf7 {
 
-// nf7::Mutex is not thread-safe.
+// nf7::Mutex is not thread-safe except Mutex::Lock's destructor.
 class Mutex final {
  public:
+  class Sync;
   class Lock;
+  template <typename T> class Resource;
 
-  Mutex() noexcept {
+  Mutex() noexcept : life_(*this) {
   }
-  ~Mutex() noexcept;
 
-  nf7::Future<std::shared_ptr<Lock>> AcquireLock(bool ex = false) noexcept {
-    if (auto ret = TryAcquireLock(ex)) {
+  // It's guaranteed that the promise is finalized in a sub task or is done immediately.
+  nf7::Future<std::shared_ptr<Lock>> AcquireLock(
+      const std::shared_ptr<nf7::Context>& ctx, bool ex = false) noexcept {
+    if (auto ret = TryAcquireLock(ctx, ex)) {
       return {ret};
     } else {
       if (ex || pends_.size() == 0 || pends_.back().ex) {
-        pends_.push_back({.pro = {}, .ex = ex});
+        pends_.push_back({.pro = {ctx}, .ctx = ctx, .ex = ex});
       }
       return pends_.back().pro.future();
     }
   }
-  std::shared_ptr<Lock> TryAcquireLock(bool ex = false) noexcept {
-    auto k = TryAcquireLock_(ex);
+  std::shared_ptr<Lock> TryAcquireLock(
+      const std::shared_ptr<nf7::Context>& ctx, bool ex = false) noexcept {
+    auto k = TryAcquireLock_(ctx, ex);
     if (k) {
       onLock();
     }
@@ -41,53 +46,55 @@ class Mutex final {
   std::function<void()> onUnlock = [](){};
 
  private:
+  nf7::Life<Mutex> life_;
+
   bool ex_ = false;
-  std::weak_ptr<Lock> k_;
+  std::weak_ptr<Sync> sync_;
 
   struct Item final {
     nf7::Future<std::shared_ptr<Lock>>::Promise pro;
+    std::shared_ptr<nf7::Context> ctx;
     bool ex;
   };
   std::deque<Item> pends_;
 
 
-  std::shared_ptr<Lock> TryAcquireLock_(bool ex) noexcept {
-    if (auto k = k_.lock()) {
-      if (!ex_ && !ex) {
-        return k;
-      }
+  std::shared_ptr<Lock> TryAcquireLock_(
+      const std::shared_ptr<nf7::Context>& ctx, bool ex) noexcept {
+    auto sync = sync_.lock();
+    if (sync) {
+      if (ex_ || ex) return nullptr;
     } else {
-      k   = std::make_shared<Lock>(*this);
-      ex_ = ex;
-      k_  = k;
-      return k;
+      sync  = std::make_shared<Sync>(*this);
+      ex_   = ex;
+      sync_ = sync;
     }
-    return nullptr;
+    return std::make_shared<Mutex::Lock>(ctx, sync);
   }
 };
 
-class Mutex::Lock final {
+class Mutex::Sync {
  public:
   friend nf7::Mutex;
 
-  Lock() = delete;
-  Lock(nf7::Mutex& mtx) noexcept : mtx_(&mtx) {
+  Sync() = delete;
+  Sync(nf7::Mutex& mtx) noexcept : mtx_(mtx.life_) {
   }
-  Lock(const Lock&) = delete;
-  Lock(Lock&&) = delete;
-  Lock& operator=(const Lock&) = delete;
-  Lock& operator=(Lock&&) = delete;
+  Sync(const Sync&) = delete;
+  Sync(Sync&&) = delete;
+  Sync& operator=(const Sync&) = delete;
+  Sync& operator=(Sync&&) = delete;
 
-  ~Lock() noexcept {
+  ~Sync() noexcept {
     if (mtx_) {
       auto& pends = mtx_->pends_;
       if (pends.size() > 0) {
         auto item = std::move(pends.front());
         pends.pop_front();
-        mtx_->ex_ = false;
-        mtx_->k_  = {};
+        mtx_->ex_   = false;
+        mtx_->sync_ = {};
 
-        auto k = mtx_->TryAcquireLock_(item.ex);
+        auto k = mtx_->TryAcquireLock_(item.ctx, item.ex);
         assert(k);
         item.pro.Return(std::move(k));
       } else {
@@ -97,13 +104,58 @@ class Mutex::Lock final {
   }
 
  private:
-  nf7::Mutex* mtx_;
+  nf7::Life<nf7::Mutex>::Ref mtx_;
 };
-Mutex::~Mutex() noexcept {
-  pends_.clear();
-  if (auto k = k_.lock()) {
-    k->mtx_ = nullptr;
+
+class Mutex::Lock {
+ public:
+  Lock(const std::shared_ptr<nf7::Context>& ctx,
+       const std::shared_ptr<Mutex::Sync>&  sync) noexcept :
+      ctx_(ctx), sync_(sync) {
   }
-}
+  Lock(const Lock&) = default;
+  Lock(Lock&&) = default;
+  Lock& operator=(const Lock&) = default;
+  Lock& operator=(Lock&&) = default;
+
+  ~Lock() noexcept {
+    // Ensure that the Sync's destructor is called on worker thread.
+    ctx_->env().ExecSub(ctx_, [sync = sync_](){});
+  }
+
+ private:
+  std::shared_ptr<nf7::Context> ctx_;
+  std::shared_ptr<Mutex::Sync> sync_;
+};
+
+
+template <typename T>
+class Mutex::Resource {
+ public:
+  Resource() = delete;
+  Resource(const std::shared_ptr<Mutex::Lock>& k, T&& v) noexcept :
+      lock_(k), value_(std::move(v)) {
+  }
+  Resource(const std::shared_ptr<Mutex::Lock>& k, const T& v) noexcept :
+      Resource(k, T {v}) {
+  }
+  Resource(const Resource&) = default;
+  Resource(Resource&&) = default;
+  Resource& operator=(const Resource&) = default;
+  Resource& operator=(Resource&&) = default;
+
+  T& operator*() noexcept { return value_; }
+  const T& operator*() const noexcept { return value_; }
+
+  T* operator->() noexcept { return &value_; }
+  const T* operator->() const noexcept { return &value_; }
+
+  const std::shared_ptr<Mutex::Lock>& lock() const noexcept { return lock_; }
+  const T& value() const noexcept { return value_; }
+
+ private:
+  std::shared_ptr<Mutex::Lock> lock_;
+  T value_;
+};
 
 }  // namespace nf7