ircd:Ⓜ️:room: Add preliminary interface specific to event content.

include/ircd/m/room/content.h

@@ -0,0 +1,41 @@
+// The Construct
+//
+// Copyright (C) The Construct Developers, Authors & Contributors
+// Copyright (C) 2016-2020 Jason Volk <jason@zemos.net>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice is present in all copies. The
+// full license for this software is available in the LICENSE file.
+
+#pragma once
+#define HAVE_IRCD_M_ROOM_CONTENT_H
+
+/// Interfaced optimized for iterating the `content` of room events.
+///
+struct ircd::m::room::content
+{
+	using closure = std::function
+	<
+		bool (const json::object &, const uint64_t &, const event::idx &)
+	>;
+
+	static const size_t prefetch_max;
+	static conf::item<size_t> prefetch;
+
+	m::room room;
+	std::pair<uint64_t, int64_t> range; // highest (inclusive) to lowest (exclusive)
+
+  public:
+	bool for_each(const closure &) const;
+
+	content(const m::room &,
+	        const decltype(range) &  = { -1UL, -1L });
+};
+
+inline
+ircd::m::room::content::content(const m::room &room,
+                                const decltype(range) &range)
+:room{room}
+,range{range}
+{}

include/ircd/m/room/room.h

@@ -124,6 +124,7 @@ struct ircd::m::room
 	struct server_acl;
 	struct message;
 	struct bootstrap;
+	struct content;
 
 	using id = m::id::room;
 	using alias = m::id::room_alias;
@@ -194,6 +195,7 @@ struct ircd::m::room
 #include "members.h"
 #include "origins.h"
 #include "type.h"
+#include "content.h"
 #include "head.h"
 #include "auth.h"
 #include "power.h"

matrix/Makefile.am

@@ -113,6 +113,7 @@ libircd_matrix_la_SOURCES += room_visible.cc
 libircd_matrix_la_SOURCES += room_members.cc
 libircd_matrix_la_SOURCES += room_origins.cc
 libircd_matrix_la_SOURCES += room_type.cc
+libircd_matrix_la_SOURCES += room_content.cc
 libircd_matrix_la_SOURCES += room_power.cc
 libircd_matrix_la_SOURCES += room_state.cc
 libircd_matrix_la_SOURCES += room_state_history.cc

matrix/room_content.cc

@@ -0,0 +1,77 @@
+// The Construct
+//
+// Copyright (C) The Construct Developers, Authors & Contributors
+// Copyright (C) 2016-2020 Jason Volk <jason@zemos.net>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice is present in all copies. The
+// full license for this software is available in the LICENSE file.
+
+decltype(ircd::m::room::content::prefetch_max)
+ircd::m::room::content::prefetch_max
+{
+	32
+};
+
+decltype(ircd::m::room::content::prefetch)
+ircd::m::room::content::prefetch
+{
+	{ "name",     "ircd.m.room.content.prefetch" },
+	{ "default",  16L                            },
+};
+
+bool
+ircd::m::room::content::for_each(const closure &closure)
+const
+{
+	// ring queue buffer
+	using entry = pair<uint64_t, m::event::idx>;
+	entry queue[prefetch_max];
+
+	// ring queue state
+	size_t i{0};           // monotonic
+	size_t pos{0};         // modulated index of the current ring head.
+	const size_t queue_max
+	{
+		std::min(size_t(prefetch), size_t(prefetch_max))
+	};
+
+	bool ret{true};
+	const auto call_user
+	{
+		[&closure, &queue, &pos, &ret](const json::object &content)
+		{
+			ret = closure(content, queue[pos].first, queue[pos].second);
+		}
+	};
+
+	m::room::events it{room};
+	for(; it && ret; --it, ++i, pos = i % queue_max)
+	{
+		// Entry at the current ring head. A prefetch has been for this entry
+		// during the last iteration and the fetch will be made this iteration.
+		auto &[depth, event_idx]
+		{
+			queue[pos]
+		};
+
+		// Fetch the content for the event at the current queue pos; this will
+		// be a no-op on the first iteration when the entries are all zero.
+		m::get(std::nothrow, event_idx, "content", call_user);
+
+		// After the user consumed the fetched entry, overwrite it with the
+		// next prefetch and continue the iteration.
+		depth = it.depth();
+		event_idx = it.event_idx();
+		m::prefetch(event_idx, "content");
+	}
+
+	// The primary loop completes when there's no more events left to
+	// prefetch, but another loop around the queue needs to be made for
+	// any fetches still in flight.
+	for(size_t j(i); ret && i < j + queue_max; ++i, pos = i % queue_max)
+		m::get(std::nothrow, queue[pos].second, "content", call_user);
+
+	return ret;
+}