#!/usr/bin/env python
# Provide copies of fifos with fixed-size buffers, and periodically print a
# report of how much space has been used. I wrote this to try and improve
# mythtranscode's performance a bit, but it didn't turn out to be useful -- it
# should have other applications, though.

import sys, os, select, errno, time

def main(args):
	fifos = []
	limit = {}
	bufs = {}
	used = {}
	ifds = {}
	ifds_b = {}
	ofds = {}
	ofds_b = {}
	for i in range(0, len(args), 2):
		f = args[i + 1]
		fifos.append(f)
		limit[f] = 1024 * 1024 * int(args[i])
		bufs[f] = []
		used[f] = 0
		oname = f + ".buf"
		ifds[f] = os.open(f, os.O_RDONLY | os.O_NONBLOCK)
		ifds_b[ifds[f]] = f
		try:
			os.unlink(oname)
		except OSError:
			pass
		os.mkfifo(oname)
		ofds[f] = os.open(oname, os.O_RDWR | os.O_NONBLOCK)
		ofds_b[ofds[f]] = f

	last = time.time()
	while fifos != []:
		rs = [ifds[f] for f in fifos if used[f] < limit[f]]
		ws = [ofds[f] for f in fifos if bufs[f] != []]
		(rs, ws, xs) = select.select(rs, ws, [], 1.0)

		now = time.time()
		if (now - last) > 10:
			last = now
			print "Buffer usage:"
			for f in fifos:
				print "  %-20s %d" % (f, used[f])

		for fd in rs:
			f = ifds_b[fd]
			try:
				data = os.read(fd, 65536)
			except OSError, e:
				if e.errno == errno.EWOULDBLOCK:
					continue
			bufs[f].append(data)
			used[f] += len(data)

		for fd in ws:
			f = ofds_b[fd]
			buf = bufs[f]
			if buf[0] == "":
				os.close(ifds[f])
				os.close(ofds[f])
				fifos.remove(f)
			else:
				try:
					count = os.write(fd, buf[0])
				except OSError, e:
					if e.errno == errno.EWOULDBLOCK:
						continue
				if count == len(buf[0]):
					buf.pop(0)
				else:
					buf[0] = buf[0][count:]
				used[f] -= count

if __name__ == "__main__":
	main(sys.argv[1:])