From e03f17d40415fb1bac6f9167c34073bed49fb231 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sun, 17 Apr 2022 12:50:08 +0100
Subject: Simplified constexpr operations map

---
 netfs/fuse/fuseApp.cpp       |   3 --
 netfs/fuse/fuseAppBase.h     | 105 ++++++++++++++++++++++---------------------
 netfs/unittests/testCore.cpp |   3 ++
 3 files changed, 58 insertions(+), 53 deletions(-)

diff --git a/netfs/fuse/fuseApp.cpp b/netfs/fuse/fuseApp.cpp
index f9b6884..cfd9689 100644
--- a/netfs/fuse/fuseApp.cpp
+++ b/netfs/fuse/fuseApp.cpp
@@ -20,9 +20,6 @@ namespace AdHoc {
 	template class CallCacheable<struct stat, std::string>;
 }
 
-static_assert(NetFS::FuseApp::operations.access);
-static_assert(!NetFS::FuseApp::operations.destroy);
-
 NetFS::FuseApp::FuseApp(Ice::StringSeq && a) : iceArgs(std::move(a)) { }
 
 NetFS::FuseApp::~FuseApp()
diff --git a/netfs/fuse/fuseAppBase.h b/netfs/fuse/fuseAppBase.h
index e4c1c62..7d8edce 100644
--- a/netfs/fuse/fuseAppBase.h
+++ b/netfs/fuse/fuseAppBase.h
@@ -74,15 +74,67 @@ public:
 
 protected:
 	static FuseAppBase * fuseApp;
+
+	template<bool Implemented, auto bfunc>
+	constexpr static auto
+	getInternalHelper()
+	{
+		if constexpr (Implemented) {
+			return [](auto... a) {
+				SharedLock(fuseApp->_lock);
+				return (fuseApp->*bfunc)(a...);
+			};
+		}
+		else {
+			return nullptr;
+		}
+	}
+
+	template<bool Implemented, auto bfunc>
+	constexpr static auto
+	getHelper()
+	{
+		if constexpr (Implemented) {
+			return [](auto... a) -> decltype((fuseApp->*bfunc)(a...)) {
+				for (int t = 0;; ++t) {
+					try {
+						fuseApp->beforeOperation();
+						SharedLock(fuseApp->_lock);
+						return (fuseApp->*bfunc)(a...);
+					}
+					catch (const std::exception & ex) {
+						if (t < 10) {
+							if (int rtn = fuseApp->onError(ex)) {
+								return rtn;
+							}
+						}
+						else {
+							fuseApp->logf(
+									LOG_ERR, "Retries expired with %s calling %s", ex.what(), typeid(bfunc).name());
+							return -EIO;
+						}
+					}
+					catch (...) {
+						fuseApp->logf(LOG_ERR, "Unknown exception calling %s", typeid(bfunc).name());
+						return -EIO;
+					}
+				}
+			};
+		}
+		else {
+			return nullptr;
+		}
+	}
 };
 
 template<typename FuseApp> class FuseAppBaseT : public FuseAppBase {
+private:
 public:
 #define GetIntHelper(func) \
-	getInternalHelper<decltype(&FuseAppBase::func), decltype(&FuseApp::func), &FuseAppBase::func>(&FuseAppBase::func)
+	getInternalHelper<!std::is_same_v<decltype(&FuseAppBase::func), decltype(&FuseApp::func)>, &FuseAppBase::func>()
 #define GetHelper(func) \
-	getHelper<decltype(&FuseAppBase::func), decltype(&FuseApp::func), &FuseAppBase::func>(&FuseAppBase::func)
-	constexpr static fuse_operations operations {
+	getHelper<!std::is_same_v<decltype(&FuseAppBase::func), decltype(&FuseApp::func)>, &FuseAppBase::func>()
+	constexpr const static fuse_operations operations {
 			GetHelper(getattr),
 			GetHelper(readlink),
 			GetHelper(mknod),
@@ -129,53 +181,6 @@ public:
 #undef GetHelper
 #undef GetIntHelper
 
-private:
-	template<typename BFunc, typename IFunc, BFunc bfunc, typename Rtn, typename... Args>
-	constexpr static auto
-	getInternalHelper(Rtn (FuseAppBase::*)(Args...)) -> Rtn (*)(Args...)
-	{
-		if constexpr (!std::is_same<BFunc, IFunc>::value) {
-			return [](Args... a) {
-				SharedLock(fuseApp->_lock);
-				return (fuseApp->*bfunc)(a...);
-			};
-		}
-		return nullptr;
-	}
-	template<typename BFunc, typename IFunc, BFunc bfunc, typename Rtn, typename... Args>
-	constexpr static auto
-	getHelper(Rtn (FuseAppBase::*)(Args...)) -> Rtn (*)(Args...)
-	{
-		if constexpr (!std::is_same<BFunc, IFunc>::value) {
-			return [](Args... a) -> Rtn {
-				for (int t = 0;; ++t) {
-					try {
-						fuseApp->beforeOperation();
-						SharedLock(fuseApp->_lock);
-						return (fuseApp->*bfunc)(a...);
-					}
-					catch (const std::exception & ex) {
-						if (t < 10) {
-							if (int rtn = fuseApp->onError(ex)) {
-								return rtn;
-							}
-						}
-						else {
-							fuseApp->logf(
-									LOG_ERR, "Retries expired with %s calling %s", ex.what(), typeid(bfunc).name());
-							return -EIO;
-						}
-					}
-					catch (...) {
-						fuseApp->logf(LOG_ERR, "Unknown exception calling %s", typeid(bfunc).name());
-						return -EIO;
-					}
-				}
-			};
-		}
-		return nullptr;
-	}
-
 protected:
 	template<typename Func, Func f, typename... Args>
 	static int
diff --git a/netfs/unittests/testCore.cpp b/netfs/unittests/testCore.cpp
index 717cc16..385b826 100644
--- a/netfs/unittests/testCore.cpp
+++ b/netfs/unittests/testCore.cpp
@@ -86,6 +86,9 @@ BOOST_FIXTURE_TEST_SUITE(NetfsCore, Core);
 
 BOOST_AUTO_TEST_CASE(fuse_operations_correct)
 {
+	BOOST_CHECK(NetFS::FuseApp::operations.access);
+	BOOST_CHECK(!NetFS::FuseApp::operations.destroy);
+
 	// open should be defined
 	BOOST_REQUIRE(fuse->open);
 	// bmap should not be defined (Not supported)
-- 
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