From b207b9e909c05e10d770c7cabe27440cd176e8e7 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Fri, 22 Sep 2017 13:57:43 -0700
Subject: [PATCH] ircd: Rename ircd::scope to ircd::unwind.

---
 charybdis/console.cc      |  2 +-
 include/ircd/ctx/dock.h   | 12 +++---
 include/ircd/ctx/queue.h  |  6 +--
 include/ircd/ctx/view.h   |  2 +-
 include/ircd/js/context.h |  2 +-
 include/ircd/util.h       | 79 +++++++++++++++++++++++++--------------
 ircd/ctx.cc               |  8 ++--
 ircd/http.cc              |  4 +-
 ircd/ircd.cc              |  2 +-
 ircd/js.cc                |  4 +-
 ircd/logger.cc            |  2 +-
 ircd/mods.cc              |  2 +-
 12 files changed, 74 insertions(+), 51 deletions(-)

diff --git a/charybdis/console.cc b/charybdis/console.cc
index 44759b9ea..56996b3c6 100644
--- a/charybdis/console.cc
+++ b/charybdis/console.cc
@@ -135,7 +135,7 @@ try
 {
 	using namespace ircd;
 
-	const scope atexit([]
+	const unwind atexit([]
 	{
 		console_active = false;
 		console_in = nullptr;
diff --git a/include/ircd/ctx/dock.h b/include/ircd/ctx/dock.h
index f7547aa28..975777834 100644
--- a/include/ircd/ctx/dock.h
+++ b/include/ircd/ctx/dock.h
@@ -118,7 +118,7 @@ noexcept
 inline void
 ircd::ctx::dock::wait()
 {
-	const scope remove
+	const unwind remove
 	{
 		std::bind(&dock::remove_self, this)
 	};
@@ -134,7 +134,7 @@ ircd::ctx::dock::wait(predicate&& pred)
 	if(pred())
 		return;
 
-	const scope remove
+	const unwind remove
 	{
 		std::bind(&dock::remove_self, this)
 	};
@@ -152,7 +152,7 @@ ircd::ctx::dock::wait_for(const duration &dur)
 {
 	static const duration zero(0);
 
-	const scope remove
+	const unwind remove
 	{
 		std::bind(&dock::remove_self, this)
 	};
@@ -173,7 +173,7 @@ ircd::ctx::dock::wait_for(const duration &dur,
 	if(pred())
 		return true;
 
-	const scope remove
+	const unwind remove
 	{
 		std::bind(&dock::remove_self, this)
 	};
@@ -195,7 +195,7 @@ template<class time_point>
 ircd::ctx::cv_status
 ircd::ctx::dock::wait_until(time_point&& tp)
 {
-	const scope remove
+	const unwind remove
 	{
 		std::bind(&dock::remove_self, this)
 	};
@@ -214,7 +214,7 @@ ircd::ctx::dock::wait_until(time_point&& tp,
 	if(pred())
 		return true;
 
-	const scope remove
+	const unwind remove
 	{
 		std::bind(&dock::remove_self, this)
 	};
diff --git a/include/ircd/ctx/queue.h b/include/ircd/ctx/queue.h
index 870b23be6..476924373 100644
--- a/include/ircd/ctx/queue.h
+++ b/include/ircd/ctx/queue.h
@@ -93,7 +93,7 @@ ircd::ctx::queue<T>::pop()
 		return !q.empty();
 	});
 
-	const scope pop([this]
+	const unwind pop([this]
 	{
 		q.pop();
 	});
@@ -115,7 +115,7 @@ ircd::ctx::queue<T>::pop_for(const duration &dur)
 	if(status == cv_status::timeout)
 		throw timeout();
 
-	const scope pop([this]
+	const unwind pop([this]
 	{
 		q.pop();
 	});
@@ -137,7 +137,7 @@ ircd::ctx::queue<T>::pop_until(time_point&& tp)
 	if(status == cv_status::timeout)
 		throw timeout();
 
-	const scope pop([this]
+	const unwind pop([this]
 	{
 		q.pop();
 	});
diff --git a/include/ircd/ctx/view.h b/include/ircd/ctx/view.h
index 4a9f3df02..db94039a2 100644
--- a/include/ircd/ctx/view.h
+++ b/include/ircd/ctx/view.h
@@ -80,7 +80,7 @@ template<class T>
 void
 ircd::ctx::view<T>::notify(T &t)
 {
-	const scope afterward{[this]
+	const unwind afterward{[this]
 	{
 		assert(a.empty());
 		this->t = nullptr;
diff --git a/include/ircd/js/context.h b/include/ircd/js/context.h
index 2aa8c7b8b..6c762d15c 100644
--- a/include/ircd/js/context.h
+++ b/include/ircd/js/context.h
@@ -184,7 +184,7 @@ run(F&& function)
 	assert(!pending_exception(*cx));
 
 	enter(*cx);
-	const scope out([]
+	const unwind out([]
 	{
 		leave(*cx);
 	});
diff --git a/include/ircd/util.h b/include/ircd/util.h
index 99d6ccbb9..38c81a410 100644
--- a/include/ircd/util.h
+++ b/include/ircd/util.h
@@ -79,7 +79,14 @@ enum class init_priority
 #define IRCD_INIT_PRIORITY(name) \
     __attribute__((init_priority(int(ircd::init_priority::name))))
 
-struct scope
+
+///
+/// Fundamental scope-unwind utilities establishing actions during destruction
+///
+
+/// Unconditionally executes the provided code when the object goes out of scope.
+///
+struct unwind
 {
 	struct nominal;
 	struct exceptional;
@@ -87,48 +94,64 @@ struct scope
 	const std::function<void ()> func;
 
 	template<class F>
-	scope(F &&func): func(std::forward<F>(func)) {}
-	scope() = default;
-	scope(const scope &) = delete;
-	scope &operator=(const scope &) = delete;
-	~scope() noexcept
+	unwind(F &&func)
+	:func{std::forward<F>(func)}
+	{}
+
+	unwind(const unwind &) = delete;
+	unwind &operator=(const unwind &) = delete;
+	~unwind() noexcept
 	{
 		func();
 	}
 };
 
-struct scope::nominal
-:scope
+/// Executes function only if the unwind takes place without active exception
+///
+/// The function is expected to be executed and the likely() should pipeline
+/// that branch and make this device cheaper to use under normal circumstances.
+///
+struct unwind::nominal
 {
+	const std::function<void ()> func;
+
 	template<class F>
 	nominal(F &&func)
-	:scope
-	{
-		[func(std::forward<F>(func))]
-		{
-			if(likely(!std::uncaught_exception()))
-				func();
-		}
-	}{}
+	:func{std::forward<F>(func)}
+	{}
 
-	nominal() = default;
+	~nominal() noexcept
+	{
+		if(likely(!std::uncaught_exception()))
+			func();
+	}
+
+	nominal(const nominal &) = delete;
 };
 
-struct scope::exceptional
-:scope
+/// Executes function only if unwind is taking place because exception thrown
+///
+/// The unlikely() intends for the cost of a branch misprediction to be paid
+/// for fetching and executing this function. This is because we strive to
+/// optimize the pipeline for the nominal path, making this device as cheap
+/// as possible to use.
+///
+struct unwind::exceptional
 {
+	const std::function<void ()> func;
+
 	template<class F>
 	exceptional(F &&func)
-	:scope
-	{
-		[func(std::forward<F>(func))]
-		{
-			if(unlikely(std::uncaught_exception()))
-				func();
-		}
-	}{}
+	:func{std::forward<F>(func)}
+	{}
 
-	exceptional() = default;
+	~exceptional() noexcept
+	{
+		if(unlikely(std::uncaught_exception()))
+			func();
+	}
+
+	exceptional(const exceptional &) = delete;
 };
 
 
diff --git a/ircd/ctx.cc b/ircd/ctx.cc
index 4016c6994..177c9224f 100644
--- a/ircd/ctx.cc
+++ b/ircd/ctx.cc
@@ -101,7 +101,7 @@ noexcept
 	ircd::ctx::current = this;
 	mark(prof::event::CUR_ENTER);
 
-	const scope atexit([this]
+	const unwind atexit([this]
 	{
 		mark(prof::event::CUR_LEAVE);
 
@@ -428,7 +428,7 @@ ircd::ctx::context::context(const char *const &name,
 	});
 
 	// The current context must be reasserted if spawn returns here
-	const scope recurrent([current(ircd::ctx::current)]
+	const unwind recurrent([current(ircd::ctx::current)]
 	{
 		ircd::ctx::current = current;
 	});
@@ -584,7 +584,7 @@ ircd::ctx::pool::main()
 try
 {
 	++available;
-	const scope avail([this]
+	const unwind avail([this]
 	{
 		--available;
 	});
@@ -610,7 +610,7 @@ try
 	});
 
 	--available;
-	const scope avail([this]
+	const unwind avail([this]
 	{
 		++available;
 	});
diff --git a/ircd/http.cc b/ircd/http.cc
index d03cdbb88..a8c2c58ec 100644
--- a/ircd/http.cc
+++ b/ircd/http.cc
@@ -260,7 +260,7 @@ try
 {
 	const head h{pc, headers_closure};
 	const char *const content_mark(pc.parsed);
-	const scope discard_unused_content{[&pc, &h, &content_mark]
+	const unwind discard_unused_content{[&pc, &h, &content_mark]
 	{
 		const size_t consumed(pc.parsed - content_mark);
 		const size_t remain(h.content_length - consumed);
@@ -369,7 +369,7 @@ ircd::http::response::response(parse::capstan &pc,
 {
 	const head h{pc, headers_closure};
 	const char *const content_mark(pc.parsed);
-	const scope discard_unused_content{[&pc, &h, &content_mark]
+	const unwind discard_unused_content{[&pc, &h, &content_mark]
 	{
 		const size_t consumed(pc.parsed - content_mark);
 		const size_t remain(h.content_length - consumed);
diff --git a/ircd/ircd.cc b/ircd/ircd.cc
index 4ef45ab90..c1336a4b9 100644
--- a/ircd/ircd.cc
+++ b/ircd/ircd.cc
@@ -99,7 +99,7 @@ ircd::main()
 try
 {
 	log::debug("IRCd entered main context.");
-	const scope main_exit(&main_exiting);   // The user is notified when this function ends
+	const unwind main_exit(&main_exiting);   // The user is notified when this function ends
 
 	// These objects are the init()'s and fini()'s for each subsystem. Appearing here ties their life
 	// to the main context. Initialization can also occur in ircd::init() or static initialization
diff --git a/ircd/js.cc b/ircd/js.cc
index cb928ae01..18e3e3b7f 100644
--- a/ircd/js.cc
+++ b/ircd/js.cc
@@ -72,7 +72,7 @@ ircd::js::init::init()
 	         "SpiderMonkey",
 	         version(ver::IMPLEMENTATION));
 
-	const scope exit([this]
+	const unwind exit([this]
 	{
 		// Ensure ~init() is always safe to call at any intermediate state
 		if(std::current_exception())
@@ -3348,7 +3348,7 @@ noexcept
 
 	// After the interrupt is handled the phase indicates entry back to JS,
 	// IRQ is left indicating JS in case we don't trigger the next interrupt.
-	const scope interrupt_return([&c, &state]
+	const unwind interrupt_return([&c, &state]
 	{
 		state.phase = phase::ENTER;
 		state.irq = irq::JS;
diff --git a/ircd/logger.cc b/ircd/logger.cc
index 9c1770f9f..02a80028b 100644
--- a/ircd/logger.cc
+++ b/ircd/logger.cc
@@ -274,7 +274,7 @@ ircd::log::slog(const facility &fac,
 	if(!file[fac].is_open() && !console_out[fac] && !console_err[fac])
 		return;
 
-	const scope always_newline([&fac]
+	const unwind always_newline([&fac]
 	{
 		suffix(fac);
 	});
diff --git a/ircd/mods.cc b/ircd/mods.cc
index 7e1878476..c822b5e6d 100644
--- a/ircd/mods.cc
+++ b/ircd/mods.cc
@@ -650,7 +650,7 @@ try
 		}
 	});
 
-	const scope reset{[this, &theirs]
+	const unwind reset{[this, &theirs]
 	{
 		assert(loading.top() == this);
 		loading.pop();