Re: Any tips on 2 process vinyl to file converter?

[Michal Kolodziejczyk <miko@...>]

On 27.01.2011 00:30, Steve Litt wrote:

> Notice that the digitizer process polls the queue. I'd like the input process 
> notify it every time a new file is pushed on the queue, but it was tough using 
> shellscripts.

I would use pipes (assuming you are using linux/unix). It is easy then.

> I'm thinking of redoing this in Lua. Can coroutines be run in two different 
> xterms? Can coroutines signal each other? Would you even recommend coroutines? 

No. Yes. No.
Coroutines are like a functions called at some point in your code. Can
you see the output from two different functions in different xterms? (I
mean without "hacking").

> Does Lua have facilities to send Linux signals? Might they communicate via 
> sockets? Any other words of wisdom?

Do you want to build a cross-platform solution, or just a short script
for your environment? It it is for yourself, and you want it to "just
work", i would use 2 processes using unix pipes (or tcp sockets with
luasocket).
I am attaching sample solution using named pipes. (run "lua vinyl.lua"
for the first process and "lua vinyl.lua something" for the second one).

Regards,
	miko

function pop_queue()
  if not INPIPE then
    INPIPE=io.open('/tmp/pipe','r')
  end
  local filename=INPIPE:read('*l')
  return filename
end

function push_queue(filename)
  if not OUTPIPE then
    OUTPIPE=io.open('/tmp/pipe','w')
    OUTPIPE:setvbuf ('line')
  end
  OUTPIPE:write(filename.."\n")
end

function meta()
  print('METADATA INPUT LOOP PROCESS')
  os.execute('mkfifo /tmp/pipe')
  local ID=0
  for line in io.lines() do
    ID=ID+1
    print('Line=', line)
    outfilename="/tmp/file"..ID
    fp=io.open(outfilename,'w')
    fp:write('Meta: '..line)
    fp:close()
    push_queue(outfilename)
  end
  print('EXIT')
  push_queue('QUIT')
end

function digitizer()
  print('DIGITIZER/CONVERTER LOOP PROCESS')
  local filename=pop_queue()
  while filename~='QUIT' do
    print('Got file:', filename)
    print('Got meta:', io.open(filename,'r'):read('*a'))
    filename=pop_queue()
  end
  print('FINISHED')
end

if arg[1] then
  digitizer()
else
  meta()
end