snabbco · eugeneia · Oct 7, 2016 · Mar 2, 2016 · Mar 2, 2016 · Mar 2, 2016
diff --git a/src/apps/rate_limiter/rate_limiter.lua b/src/apps/rate_limiter/rate_limiter.lua
@@ -7,6 +7,7 @@ local link = require("core.link")
 local config = require("core.config")
 local packet = require("core.packet")
 local timer = require("core.timer")
+local parameters = require("lib.parameters")
 local basic_apps = require("apps.basic.basic_apps")
 local ffi = require("ffi")
 local C = ffi.C
@@ -25,10 +26,12 @@ RateLimiter = {}
 -- Source produces synthetic packets of such size
 local PACKET_SIZE = 60
 
+local required = {'rate', 'bucket_capacity'}
+local optional = {initial_capacity=false}
+
 function RateLimiter:new (arg)
-   local conf = arg and config.parse_app_arg(arg) or {}
-   assert(conf.rate)
-   assert(conf.bucket_capacity)
+   local conf = parameters.parse(config.parse_app_arg(arg or {}),
+                                 required, optional)
    conf.initial_capacity = conf.initial_capacity or conf.bucket_capacity
    local o =
    {

diff --git a/src/lib/parameters.lua b/src/lib/parameters.lua
@@ -0,0 +1,72 @@
+-- Use of this source code is governed by the Apache 2.0 license; see COPYING.
+
+module(..., package.seeall)
+
+local function values(t)
+   local ret = {}
+   for k, v in pairs(t) do ret[v] = true end
+   return ret
+end
+
+-- Given PARAMETERS, a table of parameters, assert that all of the
+-- REQUIRED keys are present, fill in any missing values from OPTIONAL,
+-- and error if any unknown keys are found.
+--
+-- parameters := { k=v, ... }
+-- required := { k, ... }
+-- optional := { k=v, ... }
+-- k, v := not nil
+function parse(parameters, required, optional)
+   local ret = {}
+   if parameters == nil then parameters = {} end
+   required = values(required)
+   if optional == nil then optional = {} end
+   for k, _ in pairs(required) do
+      if parameters[k] == nil then error('missing required option ' .. k) end
+   end
+   for k, v in pairs(parameters) do
+      if not required[k] and optional[k] == nil then
+         error('unrecognized option ' .. k)
+      end
+      ret[k] = v
+   end
+   for k, v in pairs(optional) do
+      if ret[k] == nil then ret[k] = v end
+   end
+   return ret
+end
+
+function selftest ()
+   print('selftest: lib.parameters')
+   local equal = require('core.lib').equal
+   local function assert_equal(parameters, required, optional, expected)
+      assert(equal(parse(parameters, required, optional), expected))
+   end
+   local function assert_error(parameters, required, optional)
+      assert(not pcall(parse, parameters, required, optional))
+   end
+
+   local req = {'a', 'b'}
+   local opt = {c=42, d=43}
+
+   assert_equal({a=1, b=2}, req, opt, {a=1, b=2, c=42, d=43})
+   assert_equal({a=1, b=2}, req, {}, {a=1, b=2})
+   assert_equal({a=1, b=2, c=30}, req, opt, {a=1, b=2, c=30, d=43})
+   assert_equal({a=1, b=2, d=10}, req, opt, {a=1, b=2, c=42, d=10})
+   assert_equal({d=10}, {}, opt, {c=42, d=10})
+   assert_equal({}, {}, opt, {c=42, d=43})
+   assert_equal({d=false}, {}, opt, {c=42, d=false})
+   assert_equal({d=nil}, {}, opt, {c=42, d=43})
+   assert_equal({a=false, b=2}, req, {}, {a=false, b=2})
+
+   assert_error({}, req, opt)
+   assert_error({d=30}, req, opt)
+   assert_error({a=1}, req, opt)
+   assert_error({b=1}, req, opt)
+   assert_error({a=nil, b=2}, req, opt)
+   assert_error({a=1, b=nil}, req, opt)
+   assert_error({a=1, b=2, d=10, e=100}, req, opt)
+   assert_error({a=1, b=2, c=4}, req, {})
+   assert_error({a=1, b=2}, {}, {})
+   print('selftest: ok')
+end