memfdbufferimpl.h

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#pragma once
 
#include <promeki/namespace.h>
#include <promeki/config.h>
#include <promeki/hostbufferimpl.h>
#include <promeki/memfdregion.h>
#include <promeki/mutex.h>
#include <promeki/sharedptr.h>
 
PROMEKI_NAMESPACE_BEGIN
 
#if PROMEKI_ENABLE_MEMFD
class MemfdBufferImpl : public HostMappedBufferImpl {
        public:
                MemfdBufferImpl(const MemSpace &ms, size_t bytes, size_t align);
 
                ~MemfdBufferImpl() override;
 
                bool   canClone() const override;
                bool   isCowBacked() const override { return true; }
                Error  seal() const override;
                size_t residentBytes() const override;
 
                MemfdBufferImpl *_promeki_clone() const override;
 
        private:
                MemfdBufferImpl(const MemfdBufferImpl &source, void *cloneView);
 
                using RegionPtr = SharedPtr<MemfdRegion, false>;
 
                RegionPtr      _region;
                mutable Mutex  _sealMutex;
                mutable bool   _sealed = false;
                mutable bool   _dead   = false;
                // Set to true at sibling-clone construction time.
                // ensureExclusive() implies the caller intends to
                // write through the new clone; subsequent detaches
                // from this clone must therefore preserve any
                // such writes (the kernel's MAP_PRIVATE-from-file
                // semantics would silently drop them).  The post-
                // seal source (and the producer-phase impl) stay
                // _dirty=false so the first detach from a clean
                // cached payload still uses the cheap kernel-CoW
                // path — the SystemCow optimisation hinges on
                // exactly that case.
                bool           _dirty  = false;
};
 
#endif // PROMEKI_ENABLE_MEMFD
PROMEKI_NAMESPACE_END