Limit main loop and packet send rates

LED data packets are now sent with at most 60 updates per second. The
main loop tries to uniformly distribute calculation updates over time.

src/main.rs

@@ -17,6 +17,9 @@ use crate::udpproto::UdpProto;
 use std::rc::Rc;
 use std::cell::RefCell;
 
+use std::thread::sleep;
+use std::time::{Duration, Instant};
+
 fn main()
 {
 	let mut stdin = std::io::stdin();
@@ -41,7 +44,7 @@ fn main()
 
 	println!("Loading user script...");
 
-	let mut script = match UserScript::new(sigproc.clone(), "test.lua") {
+	let mut script = match UserScript::new(sigproc.clone(), "particles.lua") {
 		Ok(script) => script,
 		Err(e) => {
 			println!("=== Lua Error ===\n{}\n====> Terminating.", e);
@@ -61,6 +64,14 @@ fn main()
 
 	println!("Done! Starting main loop…");
 
+	// Timing setup
+
+	let block_period = Duration::from_nanos((0.95 * (config::SAMPLES_PER_UPDATE as f32) * 1e9 / config::SAMP_RATE) as u64);
+	let send_period = Duration::from_nanos(1000000000 / 60);
+
+	let mut next_block_instant = Instant::now() + block_period;
+	let mut next_send_instant = Instant::now() + send_period;
+
 	// array for samples directly read from stream
 	let mut samples: VecDeque<i16> = VecDeque::with_capacity(config::BLOCK_LEN);
 
@@ -111,16 +122,27 @@ fn main()
 
 		// FIXME: only send with 60 FPS!
 
-		for i in 0..script.colorlists[0].len() {
-			udpproto.set_color((i / config::NUM_LEDS_PER_STRIP) as u8,
-							   (i % config::NUM_LEDS_PER_STRIP) as u8,
-							   (script.colorlists[0][i] * 255.0) as u8,
-							   (script.colorlists[1][i] * 255.0) as u8,
-							   (script.colorlists[2][i] * 255.0) as u8,
-							   (script.colorlists[3][i] * 255.0) as u8).unwrap();
+		if Instant::now() > next_send_instant {
+			for i in 0..script.colorlists[0].len() {
+				udpproto.set_color((i / config::NUM_LEDS_PER_STRIP) as u8,
+								   (i % config::NUM_LEDS_PER_STRIP) as u8,
+								   (script.colorlists[0][i] * 255.0) as u8,
+								   (script.colorlists[1][i] * 255.0) as u8,
+								   (script.colorlists[2][i] * 255.0) as u8,
+								   (script.colorlists[3][i] * 255.0) as u8).unwrap();
+			}
+
+			udpproto.commit().unwrap();
+
+			next_send_instant += send_period;
+		}
+
+		let now = Instant::now();
+		if now < next_block_instant {
+			sleep(next_block_instant - now);
 		}
 
-		udpproto.commit().unwrap();
+		next_block_instant = Instant::now() + block_period;
 	}
 
 }