ratio

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 +1,48 @@
+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);
+
+	// the idea: create exact float num/den ratio, and compute continued fraction if it doesn't fit
+
+
+	return Ok(())
+}