From 9693a932a30adbea59bee65041bd3e9eae32df6c Mon Sep 17 00:00:00 2001
From: Lars Immisch <lars@ibp.de>
Date: Fri, 16 Feb 2024 14:14:37 +0100
Subject: [PATCH] Add echo (seed for loopback.py)

---
 echo.py | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 echo.py

diff --git a/echo.py b/echo.py
new file mode 100644
index 0000000..72c39f7
--- /dev/null
+++ b/echo.py
@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+# -*- mode: python; indent-tabs-mode: t; c-basic-offset: 4; tab-width: 4 -*-
+
+import alsaaudio
+import select
+
+def echo(inpcm, outpcm):
+	q = list()
+
+	# setup the synchronous event loop
+	# See https://docs.python.org/3/library/select.html#poll-objects for background
+	reactor = select.poll()
+
+	infd, inmask = inpcm.polldecriptors()
+	outfd, outmask = outpcm.polldescriptors()
+
+	write_started = False
+
+	def write():
+		data = q.pop()
+		written = outpcm.write(data)
+		if written < len(data):
+			q.insert(0, data[written:])
+
+	reactor.register(infd, inmask)
+	reactor.register(outfd, outmask)
+
+	while True:
+		events = reactor.poll()
+		for fd, event in events:
+			if event == select.POLLIN and fd == infd:
+				data = inpcm.read()
+				q.append(data)
+				if not write_started:
+					write()
+					write_started = True
+			elif event == select.POLLOUT and fd == outfd:
+				if not q:
+					return
+				write()
\ No newline at end of file