#!/usr/bin/python

# proc_run will run the given function in another process
# A real process!  Like, one with it's own memory space and such.
# The function cannot take any arguments (use lambda) and will be able to return a bit of text (use pickle)
# The result will appear in result_return[1].  result_return[0] indicates whether the function is done or not.

from sys import exit
from os import pipe, waitpid, fork, close, fdopen
from thread import start_new_thread
from time import sleep

def wait_for_client(r,result_return,pid):
	result = r.read()
	result_return.append(result)
	waitpid(pid,0)
	result_return[0] = 1

# Function must be made using lambda
def proc_run(function, result_return):
	if len(result_return) < 1:
		result_return.append(0)
	else:
		result_return[0] = 0
	r, w = pipe() 
	pid = fork()
	if pid: # parent
		close(w) 
		r = fdopen(r) # r becomes a file object
		# We must start a pthread to wait for the client, and return 
		start_new_thread(wait_for_client, (r,result_return,pid))
	else:
		close(r)
		w = fdopen(w, 'w')
		sleep(0.01)
		w.write(function())
		w.close()
		exit(0)
	return 

def exec_list(cmd, params, nthreads, delay=0):
	if nthreads <= 1:
		return [cmd(p) for p in params]
	results = [[0] for i in range(len(params))]
	for i,p in enumerate(params):
		proc_run(lambda : cmd(p), results[i])
		if delay:
			sleep(delay)
		running_count = (i+1) - sum(r[0] for r in results[:i+1])
		while running_count >= nthreads:
			sleep(0.1)
			running_count = (i+1) - sum(r[0] for r in results[:i+1])
	done = False
	while not done:
		sleep(0.1)
		done = True
		for r in results:
			if not r[0]:
				done = False
	return [r[1] for r in results]