From 067263bb5049d3a5fde10af7eda685b9a0aa7593 Mon Sep 17 00:00:00 2001
From: Emil Renner Berthing <esmil@mailme.dk>
Date: Sat, 9 Feb 2013 11:24:39 +0100
Subject: queue: add blocking multiple producer/consumer queue

---
 Makefile.in    |  3 +-
 lem/queue.lua  | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 test/queue.lua | 85 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 175 insertions(+), 1 deletion(-)
 create mode 100644 lem/queue.lua
 create mode 100755 test/queue.lua

diff --git a/Makefile.in b/Makefile.in
index 5c7e8a5..f4b58e2 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -29,7 +29,8 @@ llibs = \
 	lem/lfs.lua \
 	lem/http.lua \
 	lem/http/server.lua \
-	lem/hathaway.lua
+	lem/queue.lua \
+	lem/hathaway.lua 
 
 clibs = \
 	lem/utils.so \
diff --git a/lem/queue.lua b/lem/queue.lua
new file mode 100644
index 0000000..c3e5e42
--- /dev/null
+++ b/lem/queue.lua
@@ -0,0 +1,88 @@
+--
+-- This file is part of LEM, a Lua Event Machine.
+-- Copyright 2013 Emil Renner Berthing
+--
+-- LEM is free software: you can redistribute it and/or modify it
+-- under the terms of the GNU Lesser General Public License as
+-- published by the Free Software Foundation, either version 3 of
+-- the License, or (at your option) any later version.
+--
+-- LEM is distributed in the hope that it will be useful, but
+-- WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU Lesser General Public License for more details.
+--
+-- You should have received a copy of the GNU Lesser General Public
+-- License along with LEM.  If not, see <http://www.gnu.org/licenses/>.
+--
+
+local utils = require 'lem.utils'
+
+local M = {}
+
+local Queue = {}
+Queue.__index = Queue
+M.Queue = Queue
+
+local remove = table.remove
+local thisthread, suspend, resume =
+	utils.thisthread, utils.suspend, utils.resume
+
+function Queue:put(v)
+	local n = self.n + 1
+	self.n = n
+
+	if n >= 1 then
+		self[n] = v
+	else
+		resume(remove(self, 1), v)
+	end
+end
+
+function Queue:signal(...)
+	local n = self.n
+	if n < 0 then
+		for i = 1, -n do
+			resume(self[i], ...)
+			self[i] = nil
+		end
+		self.n = 0
+	end
+end
+
+function Queue:get()
+	local n = self.n - 1
+	self.n = n
+
+	if n >= 0 then
+		return remove(self, 1)
+	end
+
+	self[-n] = thisthread()
+	return suspend()
+end
+
+function Queue:reset()
+	self:signal(nil, 'reset')
+	for i = self.n, 1, -1 do
+		self[i] = nil
+	end
+	self.n = 0
+end
+
+local get = Queue.get
+function Queue:consume()
+	return get, self
+end
+
+function Queue:empty()
+	return self.n <= 0
+end
+
+function M.new()
+	return setmetatable({ n = 0 }, Queue)
+end
+
+return M
+
+-- vim: ts=2 sw=2 noet:
diff --git a/test/queue.lua b/test/queue.lua
new file mode 100755
index 0000000..54f025b
--- /dev/null
+++ b/test/queue.lua
@@ -0,0 +1,85 @@
+#!bin/lem
+--
+-- This file is part of LEM, a Lua Event Machine.
+-- Copyright 2011-2012 Emil Renner Berthing
+--
+-- LEM is free software: you can redistribute it and/or modify it
+-- under the terms of the GNU Lesser General Public License as
+-- published by the Free Software Foundation, either version 3 of
+-- the License, or (at your option) any later version.
+--
+-- LEM is distributed in the hope that it will be useful, but
+-- WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU Lesser General Public License for more details.
+--
+-- You should have received a copy of the GNU Lesser General Public
+-- License along with LEM.  If not, see <http://www.gnu.org/licenses/>.
+--
+
+package.path = '?.lua'
+package.cpath = '?.so'
+
+local utils = require 'lem.utils'
+local queue = require 'lem.queue'
+
+local consumers = 0
+local function consumer(q, id)
+	consumers = consumers + 1
+	local sleeper = utils.newsleeper()
+	for v in q:consume() do
+		print(string.format('thread %d, n = %2d, received "%s"',
+			id, q.n, tostring(v)))
+		sleeper:sleep(0.04)
+	end
+	consumers = consumers - 1
+end
+
+local q, sleeper = queue.new(), utils.newsleeper()
+
+print "One consumer:\n"
+for i = 1, 5 do
+	q:put(i)
+end
+
+utils.spawn(consumer, q, 1)
+utils.yield()
+assert(consumers == 1)
+
+for i = 6, 10 do
+	q:put(i)
+	sleeper:sleep(0.1)
+end
+
+assert(q:empty())
+
+assert(consumers == 1)
+q:reset()
+utils.yield()
+assert(consumers == 0)
+
+print "\nFive consumers:\n"
+
+for i = 1, 10 do
+	q:put(i)
+end
+
+for i = 1, 5 do
+	utils.spawn(consumer, q, i)
+end
+utils.yield()
+assert(consumers == 5)
+
+for i = 11, 20 do
+	q:put(i)
+	sleeper:sleep(0.1)
+end
+
+assert(q:empty())
+assert(consumers == 5)
+
+q:signal(nil)
+utils.yield()
+assert(consumers == 0)
+
+-- vim: syntax=lua ts=2 sw=2 noet:
-- 
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