From 02b835eb2bb524887e75c2cd73850a9917870ea2 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Thu, 18 Apr 2019 21:23:00 -0700
Subject: [PATCH] ircd::m::feds: Add additional options; document options.

---
 include/ircd/m/feds.h | 30 +++++++++++++++++++++++++++++
 modules/s_feds.cc     | 45 +++++++++++++++++++++++++++++++++++++++----
 2 files changed, 71 insertions(+), 4 deletions(-)

diff --git a/include/ircd/m/feds.h b/include/ircd/m/feds.h
index 8311bc1f6..ceb5bd946 100644
--- a/include/ircd/m/feds.h
+++ b/include/ircd/m/feds.h
@@ -50,13 +50,43 @@ struct ircd::m::feds::result
 
 struct ircd::m::feds::opts
 {
+	/// Operation type
 	enum op op {(enum op)0};
+
+	/// Timeout for this operation. For a batch of operations, this system
+	/// may attempt -- but does not guarantee -- to cancel timed-out requests
+	/// before the highest timeout value in the batch.
 	milliseconds timeout {20000L};
+
+	/// Apropos room_id: this is almost always required for this interface
+	/// because the servers in the room is used for the request target set.
 	m::room::id room_id;
+
+	/// Apropos event_id for several operations.
 	m::event::id event_id;
+
+	/// Apropos user_id for several operations.
 	m::user::id user_id;
+
+	/// Misc string argument registers. These convey values for special
+	/// features in individual operations.
 	string_view arg[4];  // misc argv
+
+	/// Misc integer argument registers. These convey values for special
+	/// features in individual operations.
 	uint64_t argi[4];    // misc integer argv
+
+	/// Whether exceptions from the supplied result closure are propagated.
+	bool nothrow_closure {false};
+
+	/// When nothrow_closure is true, this determines whether or not to
+	/// continue receiving results or to break and return. True to continue.
+	bool nothrow_closure_retval {true};
+
+	/// Whether to call the user's result closure for error results, which
+	/// would have the eptr set. When this is false, the closure is never
+	/// invoked with eptr set and nothrow_closure_retval is used to continue.
+	bool closure_errors {true};
 };
 
 enum class ircd::m::feds::op
diff --git a/modules/s_feds.cc b/modules/s_feds.cc
index d0a6a1824..5b9ad0ec6 100644
--- a/modules/s_feds.cc
+++ b/modules/s_feds.cc
@@ -24,6 +24,8 @@ namespace ircd::m::feds
 	template<class T> using create_closure = std::function<T (request<T> &, const string_view &origin)>;
 
 	template<class T> static request_list creator(const opts &, const create_closure<T> &);
+
+	static bool call_user(const closure &closure, const result &result);
 	static bool handler(request_list &, const milliseconds &, const closure &);
 
 	static request_list head(const opts &, const closure &);
@@ -351,6 +353,10 @@ ircd::m::feds::handler(request_list &reqs,
 		};
 
 		assert(it != end(reqs));
+		const unwind remove{[&reqs, &it]
+		{
+			reqs.erase(it);
+		}};
 
 		request_base &req(**it);
 		server::request &sreq(dynamic_cast<server::request &>(req)); try
@@ -358,23 +364,54 @@ ircd::m::feds::handler(request_list &reqs,
 			const auto code{sreq.get()};
 			const json::array &array{sreq.in.content};
 			const json::object &object{sreq.in.content};
-			if(!closure({req.opts, req.origin, {}, object, array}))
+			const result result
+			{
+				req.opts, req.origin, {}, object, array
+			};
+
+			if(!call_user(closure, result))
 				return false;
 		}
 		catch(const std::exception &)
 		{
+			if(!req.opts->closure_errors && !req.opts->nothrow_closure_retval)
+				return false;
+
+			if(!req.opts->closure_errors)
+				continue;
+
 			const ctx::exception_handler eptr;
 			const std::exception_ptr &eptr_(eptr);
-			if(!closure({req.opts, req.origin, eptr_}))
+			const result result
+			{
+				req.opts, req.origin, eptr_
+			};
+
+			if(!call_user(closure, result))
 				return false;
 		}
-
-		reqs.erase(it);
 	}
 
 	return true;
 }
 
+bool
+ircd::m::feds::call_user(const closure &closure,
+                         const result &result)
+try
+{
+	return closure(result);
+}
+catch(const std::exception &)
+{
+	assert(result.request);
+	if(result.request->nothrow_closure)
+		return result.request->nothrow_closure_retval;
+
+	throw;
+}
+
+
 template<class T>
 ircd::m::feds::request_list
 ircd::m::feds::creator(const opts &opts,