more test

wasm-module/src/lib.rs

@@ -5,6 +5,8 @@ use strafesnet_roblox_bot_player::{bot,head,time,graphics};
 use strafesnet_graphics::setup;
 use strafesnet_common::physics::Time as PhysicsTime;
 
+mod ratio;
+
 // Hack to keep the code compiling,
 // SurfaceTarget::Canvas is not available in IDE for whatever reason.
 struct ToSurfaceTarget(web_sys::HtmlCanvasElement);
@@ -141,9 +143,10 @@ impl PlaybackHead{
 		self.head.set_paused(time,paused);
 	}
 	#[wasm_bindgen]
-	pub fn set_scale(&mut self,time:f64,scale_num:i64,scale_den:u64){
+	pub fn set_scale(&mut self,time:f64,scale:f64){
 		let time=time::from_float(time).unwrap();
-		self.head.set_scale(time,strafesnet_common::integer::Ratio64::new(scale_num,scale_den).unwrap());
+		let scale=crate::ratio::ratio_from_float(scale).unwrap();
+		self.head.set_scale(time,scale);
 	}
 	#[wasm_bindgen]
 	pub fn seek_to(&mut self,time:f64,new_time:f64){

wasm-module/src/ratio.rs

@@ -0,0 +1,130 @@
+use strafesnet_common::integer::Ratio64;
+
+#[derive(Debug)]
+pub enum RatioFromFloatError{
+	Nan,
+	Overflow,
+	Underflow,
+}
+
+fn f64_into_parts(f: f64) -> (u64, i16, i8) {
+	let bits: u64 = f.to_bits();
+	let sign: i8 = if bits >> 63 == 0 { 1 } else { -1 };
+	let mut exponent: i16 = ((bits >> 52) & 0x7ff) as i16;
+	let mantissa = if exponent == 0 {
+		(bits & 0xfffffffffffff) << 1
+	} else {
+		(bits & 0xfffffffffffff) | 0x10000000000000
+	};
+	// Exponent bias + mantissa shift
+	exponent -= 1023 + 52;
+	(mantissa, exponent, sign)
+}
+
+pub fn ratio_from_float(value:f64)->Result<Ratio64,RatioFromFloatError>{
+	// Handle special values first
+	match value.classify(){
+		core::num::FpCategory::Nan=>return Err(RatioFromFloatError::Nan),
+		core::num::FpCategory::Zero=>return Ok(Ratio64::ZERO),
+		core::num::FpCategory::Subnormal
+		|core::num::FpCategory::Normal
+		|core::num::FpCategory::Infinite=>{
+			if value<i64::MIN as f64{
+				return Err(RatioFromFloatError::Underflow);
+			}
+			if (i64::MAX as f64)<value{
+				return Err(RatioFromFloatError::Overflow);
+			}
+		}
+	}
+
+	// value = sign * mantissa * 2 ^ exponent
+	let (mantissa,exponent,sign)=f64_into_parts(value);
+
+	if 0<=exponent{
+		// we know value < i64::MIN, so it must just be an integer.
+		return Ok(Ratio64::new((sign as i64*mantissa as i64)<<exponent,1).unwrap());
+	}
+
+	if exponent< -62-52{
+		// very small number is not representable
+		return Ok(Ratio64::ZERO);
+	}
+
+	if -63<exponent{
+		// exactly representable
+		return Ok(Ratio64::new(sign as i64*mantissa as i64,1<<-exponent).unwrap());
+	}
+
+	// the denominator is necessarily bigger than the numerator at this point.
+
+	// create exact float num/den ratio
+	let mut in_num=mantissa as u128;
+	let mut in_den=1u128<<-exponent;
+
+	// a+b*c
+	fn ma(a:i64,b:i64,c:i64)->Option<i64>{
+		a.checked_add(b.checked_mul(c)?)
+	}
+
+	let mut p_prev=1i64;
+	let mut q_prev=0i64;
+	let mut p_cur=0i64;
+	let mut q_cur=1i64;
+
+	// compute continued fraction
+	loop{
+		let whole=in_den/in_num;
+
+		if whole==0{
+			// we have depleted the input fraction and created an exact representation
+			break;
+		}
+
+		if (i64::MAX as u128)<whole{
+			// cannot continue fraction
+			break;
+		}
+
+		let Some(p_next)=ma(p_prev,p_cur,whole as i64)else{
+			// overflow
+			break;
+		};
+		let Some(q_next)=ma(q_prev,q_cur,whole as i64)else{
+			// overflow
+			break;
+		};
+
+		p_prev=p_cur;
+		q_prev=q_cur;
+		p_cur=p_next;
+		q_cur=q_next;
+		(in_num,in_den)=(in_den-in_num*whole,in_num);
+	}
+
+	Ok(Ratio64::new(p_cur,q_cur as u64).unwrap())
+}
+
+#[cfg(test)]
+fn req(r0:Ratio64,r1:Ratio64){
+	println!("r0={r0:?} r1={r1:?}");
+	assert_eq!(r0.num(),r1.num(),"Nums not eq");
+	assert_eq!(r0.den(),r1.den(),"Dens not eq");
+}
+
+#[test]
+fn test(){
+	req(ratio_from_float(2.0).unwrap(),Ratio64::new(2,1).unwrap());
+	req(ratio_from_float(1.0).unwrap(),Ratio64::new(1,1).unwrap());
+	req(ratio_from_float(0.5).unwrap(),Ratio64::new(1,2).unwrap());
+	req(ratio_from_float(1.1).unwrap(),Ratio64::new(2476979795053773,2251799813685248).unwrap());
+	req(ratio_from_float(0.8).unwrap(),Ratio64::new(3602879701896397,4503599627370496).unwrap());
+	req(ratio_from_float(0.61).unwrap(),Ratio64::new(5494391545392005,9007199254740992).unwrap());
+	req(ratio_from_float(0.01).unwrap(),Ratio64::new(5764607523034235,576460752303423488).unwrap());
+	req(ratio_from_float(0.001).unwrap(),Ratio64::new(1152921504606847,1152921504606846976).unwrap());
+	req(ratio_from_float(0.00001).unwrap(),Ratio64::new(89605456633725,8960545663372499267).unwrap());
+	req(ratio_from_float(0.00000000001).unwrap(),Ratio64::new(35204848,3520484800000000213).unwrap());
+	req(ratio_from_float(0.000000000000000001).unwrap(),Ratio64::new(2,1999999999999999857).unwrap());
+	req(ratio_from_float(2222222222222.0).unwrap(),Ratio64::new(2222222222222,1).unwrap());
+	req(ratio_from_float(core::f64::consts::PI).unwrap(),Ratio64::new(884279719003555,281474976710656).unwrap());
+}

web-demo/player.js

@@ -44,20 +44,11 @@ function elapsed() {
 const control_speed = document.getElementById("control_speed");
 
 var paused = false;
-var speed = 0;
+var scale = 1;
-function set_speed(new_speed) {
+function set_scale(new_scale) {
-	speed = new_speed;
+	scale = new_scale;
-	var speed_num = null;
+	playback.set_scale(elapsed(), scale);
-	var speed_den = null;
+	control_speed.value = `${scale.toPrecision(3)}x`;
-	if (new_speed < 0) {
-		speed_num = BigInt(4) ** BigInt(-new_speed);
-		speed_den = BigInt(5) ** BigInt(-new_speed);
-	} else {
-		speed_num = BigInt(5) ** BigInt(new_speed);
-		speed_den = BigInt(4) ** BigInt(new_speed);
-	}
-	playback.set_scale(elapsed(), speed_num, speed_den);
-	control_speed.value = `${((5 / 4) ** new_speed).toPrecision(3)}x`;
 }
 
 // Controls
@@ -75,25 +66,24 @@ document.getElementById("control_backward").addEventListener("click", (e) => {
 	playback.seek_backward(2.0);
 });
 document.getElementById("control_slower").addEventListener("click", (e) => {
-	set_speed(Math.max(speed - 1, -27));
+	set_scale((scale * 4) / 5);
 });
 const regex = new RegExp("^([^x]*)x?$");
 control_speed.addEventListener("change", (e) => {
 	const parsed = regex.exec(e.target.value);
 	if (!parsed) {
-		set_speed(0);
+		set_scale(1);
 		return;
 	}
 	const input = Number(parsed.at(1));
 	if (Number.isNaN(input)) {
-		set_speed(0);
+		set_scale(1);
 		return;
 	}
-	const rounded = Math.round(Math.log(input) / Math.log(5 / 4));
+	set_scale(input);
-	set_speed(Math.max(-27, Math.min(27, rounded)));
 });
 document.getElementById("control_faster").addEventListener("click", (e) => {
-	set_speed(Math.min(speed + 1, 27));
+	set_scale((scale * 5) / 4);
 });
 
 // Rendering