149983 – [new port] devel/lua-alien: Lua -> C FFI

no flags

Unlike alien rock[1] the port uses system libffi. And I've changed
install paths a bit to prevent possible filename collisions with games,
other FFIs or if someone ports it to a different version of lua.

The only rock that depends on alien seems to be fbclient. And I'm not
interested in firebird client so the port'll likely remain a leaf.

[1] http://luarocks.org/repositories/rocks/alien-0.5.0-1.rockspec

---
Alien lets a Lua application call load dynamic libraries and call C
functions in a portable way, using libffi.

WWW: http://alien.luaforge.net/

How-To-Repeat: Example of a propeller using nanosleep(2):
%%
require 'alien'

local timespec = alien.defstruct {
   { 'sec',  'long' },
   { 'nsec', 'long' },
}

local def = alien.default
def.nanosleep:types('int', 'pointer', 'pointer')

function nanosleep(seconds, nanoseconds)
   local t = timespec:new()
   t.sec, t.nsec = seconds, nanoseconds
   return def.nanosleep(t(), nil)
end

function propeller()
   local prop_sym = { '/', '-', '\\', '|' }
   local function prop_iter(a, i)
      i = i < #a and i + 1 or 1
      return i, a[i]
   end

   return prop_iter, prop_sym, 1
end

io.write('waiting...')
for i,v in propeller() do
   io.write(v .. '\b')
   io.flush()
   nanosleep(0, 1)
end
%%

There are a few more examples in EXAMPLESDIR and one test in DATADIR/tests.