[cpu_openbsd] Add a CPU usage widget for OpenBSD (#95)

* [cpu_openbsd] Add a CPU usage widget for OpenBSD

* Remove filename from the header and fix the license name

* Reindent file to get rid of tabs

* Re-add file header and add space after year in copyright line

* Remove space before parens

* Make `ticks` local to the module

README.md

@@ -170,12 +170,15 @@ Provides CPU usage for all available CPUs/cores. Since this widget type give
 CPU utilization between two consecutive calls, it is recommended to enable
 caching if it is used to register multiple widgets (#71).
 
-Supported platforms: GNU/Linux, FreeBSD.
+Supported platforms: GNU/Linux, FreeBSD, OpenBSD.
 
-Returns an array containing:
+On FreeBSD and Linux returns an array containing:
 * `$1`: usage of all CPUs/cores
 * `$2`, `$3`, etc. are respectively the usage of 1st, 2nd, etc. CPU/core
 
+On OpenBSD returns an array containing:
+* `$1`: usage of all CPUs/cores
+
 ### vicious.widgets.cpufreq
 
 Provides freq, voltage and governor info for a requested CPU.

widgets/cpu_openbsd.lua

@@ -0,0 +1,60 @@
+-- CPU usage widget type for OpenBSD
+-- Copyright (C) 2019  Enric Morales
+--
+-- This file is part of Vicious.
+--
+-- Vicious is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU General Public License as
+-- published by the Free Software Foundation, either version 2 of the
+-- License, or (at your option) any later version.
+--
+-- Vicious 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 General Public License for more details.
+--
+-- You should have received a copy of the GNU General Public License
+-- along with Vicious.  If not, see <https://www.gnu.org/licenses/>.
+
+local math = { ceil = math.ceil }
+local string = { gmatch = string.gmatch }
+local table = { insert = table.insert }
+local tonumber = tonumber
+
+local helpers = require("vicious.helpers")
+
+
+-- cpu_openbsd: provides both a helper function that allows reading
+-- the CPU usage on OpenBSD systems.
+local cpu_openbsd = {}
+
+-- Initialize the table that will contain the ticks spent in each subsystem
+-- values: user, nice, system, spin, interrupts, idle
+local ticks = { 0, 0, 0, 0, 0, 0 }
+
+function cpu_openbsd.async(format, warg, callback)
+    helpers.sysctl_async({ "kern.cp_time" },
+        function (ret)
+            local current_ticks = {}
+            for match in string.gmatch(ret["kern.cp_time"], "(%d+)") do
+                table.insert(current_ticks, tonumber(match))
+            end
+
+            local period_ticks = {}
+            for i = 1, 6 do
+                table.insert(period_ticks,
+                             current_ticks[i] - ticks[i])
+            end
+
+            local cpu_total, cpu_busy = 0, 0
+            for i = 1, 6 do cpu_total = cpu_total + period_ticks[i] end
+            for i = 1, 5 do cpu_busy = cpu_busy + period_ticks[i] end
+
+            local cpu_usage = math.ceil((cpu_busy / cpu_total) * 100)
+
+            ticks = current_ticks
+            return callback({ cpu_usage })
+        end)
+end
+
+return helpers.setasyncall(cpu_openbsd)