Add new Spinscale C++ Coroutine support

include/spinscale/co/promiseChainLink.h

@@ -0,0 +1,72 @@
+#ifndef PROMISE_CHAIN_LINK_H
+#define PROMISE_CHAIN_LINK_H
+
+#include <functional>
+#include <list>
+
+namespace sscl::co {
+
+class CoQutex;
+
+/**
+ * Non-template base for coroutine promises participating in a logical
+ * promise chain (analogous to libspinscale AsynchronousContinuationChainLink).
+ * A future deadlock detector can walk callerPromiseChainLink() without
+ * knowing concrete promise_type.
+ */
+class PromiseChainLink
+{
+public:
+	virtual ~PromiseChainLink() = default;
+
+	/** Reserved for deadlock detection: link toward the caller / outer coroutine. */
+	virtual const PromiseChainLink *callerPromiseChainLink() const noexcept
+		{ return nullptr; }
+	virtual PromiseChainLink *callerPromiseChainLink() noexcept
+		{ return nullptr; }
+
+	void addAcquiredLock(CoQutex &coQutex) noexcept
+		{ acquiredLocks.emplace_back(std::ref(coQutex)); }
+
+	bool holdsAcquiredLock(const CoQutex &coQutex) const noexcept
+		{ return findMatchingAcquiredLock(coQutex) != acquiredLocks.end(); }
+
+	virtual void removeAcquiredLock(CoQutex &coQutex) noexcept = 0;
+
+protected:
+	using AcquiredLockList = std::list<std::reference_wrapper<CoQutex>>;
+
+	AcquiredLockList::iterator findMatchingAcquiredLock(CoQutex &coQutex) noexcept
+	{
+		for (auto it = acquiredLocks.begin(); it != acquiredLocks.end(); ++it) {
+			if (&it->get() == &coQutex) {
+				return it;
+			}
+		}
+		return acquiredLocks.end();
+	}
+
+	AcquiredLockList::const_iterator findMatchingAcquiredLock(const CoQutex &coQutex) const noexcept
+	{
+		for (auto it = acquiredLocks.begin(); it != acquiredLocks.end(); ++it) {
+			if (&it->get() == &coQutex) {
+				return it;
+			}
+		}
+		return acquiredLocks.end();
+	}
+
+	void eraseFirstMatchingAcquiredLock(CoQutex &coQutex) noexcept
+	{
+		auto match = findMatchingAcquiredLock(coQutex);
+		if (match != acquiredLocks.end()) {
+			acquiredLocks.erase(match);
+		}
+	}
+
+	AcquiredLockList acquiredLocks;
+};
+
+} // namespace sscl::co
+
+#endif // PROMISE_CHAIN_LINK_H