deduplicate calculation

fixed_wide/src/fixed.rs

@@ -197,34 +197,6 @@ macro_rules! impl_into_float {
 impl_into_float!(f32,u32,8,24);
 impl_into_float!(f64,u64,11,53);
 
-#[inline]
-fn integer_decode_f32(f: f32) -> (u64, i16, bool) {
-	let bits: u32 = f.to_bits();
-	let sign: bool = bits & (1<<31) != 0;
-	let mut exponent: i16 = ((bits >> 23) & 0xff) as i16;
-	let mantissa = if exponent == 0 {
-		(bits & 0x7fffff) << 1
-	} else {
-		(bits & 0x7fffff) | 0x800000
-	};
-	// Exponent bias + mantissa shift
-	exponent -= 127 + 23;
-	(mantissa as u64, exponent, sign)
-}
-#[inline]
-fn integer_decode_f64(f: f64) -> (u64, i16, bool) {
-	let bits: u64 = f.to_bits();
-	let sign: bool = bits & (1u64<<63) != 0;
-	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)
-}
 #[derive(Debug,Eq,PartialEq)]
 pub enum FixedFromFloatError{
 	Nan,
@@ -240,13 +212,19 @@ impl FixedFromFloatError{
 		}
 	}
 }
+
+struct FloatInfo{
+	sign:bool,
+	digit_index:usize,
+	bits:[u64;2],
+}
+
 macro_rules! impl_from_float {
-	( $decode:ident, $input: ty, $mantissa_bits:expr ) => {
+	( $input: ty, $unsigned: ty, $exponent_bits:expr, $mantissa_bits:expr, $exp_bias:expr ) => {
 		impl<const N:usize,const F:usize> TryFrom<$input> for Fixed<N,F>{
 			type Error=FixedFromFloatError;
 			#[inline]
 			fn try_from(value:$input)->Result<Self,Self::Error>{
-				const DIGIT_SHIFT:u32=6;
 				match value.classify(){
 					std::num::FpCategory::Nan=>Err(FixedFromFloatError::Nan),
 					std::num::FpCategory::Infinite=>Err(FixedFromFloatError::Infinite),
@@ -254,27 +232,54 @@ macro_rules! impl_from_float {
 					std::num::FpCategory::Subnormal
 					|std::num::FpCategory::Normal
 					=>{
-						let (m,e,s)=$decode(value);
+						fn to_float_info<const F:usize>(f:$input)->Option<FloatInfo>{
+							const DIGIT_SHIFT:u32=6;
+							let bits=f.to_bits();
+							//extract exponent, add fractional offset
+							//usize is used to calculate digit_index. exp_cycle must be at least 8 bits so 32 bits is fine
+							let exp=((bits>>($mantissa_bits-1)) as usize&((1<<$exponent_bits)-1))+F;
+							//if it's less than zero, that's a conversion underflow.
+							let exp_bias=exp.checked_sub($exp_bias)?;
+							//cycle the exponent to keep the top bit of the mantissa within the hi digit
+							let exp_cycle=exp_bias.rem_euclid(64).overflowing_add($exp_bias+64).0;
+							let out_bits=
+								bits
+								//remove (mask) sign bit and exponent
+								&((1 as $unsigned<<($mantissa_bits-1))-1)
+								//write exponent
+								|((exp_cycle as $unsigned)<<($mantissa_bits-1));
+							//ready to convert
+							let _128=<$input>::from_bits(out_bits) as u128;
+							Some(FloatInfo{
+								sign:f.is_sign_negative(),
+								//digit_index is where the hi digit should end up in a fixed point number
+								digit_index:exp_bias>>DIGIT_SHIFT,
+								bits:[_128 as u64,(_128>>64) as u64],
+							})
+						}
+
+						let FloatInfo{
+							sign,
+							digit_index,
+							bits:[lo,hi],
+						}=to_float_info::<F>(value)
+							.ok_or(FixedFromFloatError::Underflow)?;
+
 						let mut digits=[0u64;N];
-						let most_significant_bit=e as i32+$mantissa_bits as i32+F as i32;
-						if most_significant_bit<0{
-							return Err(FixedFromFloatError::Underflow);
-						}
-						let digit_index=most_significant_bit>>DIGIT_SHIFT;
-						let digit=digits.get_mut(digit_index as usize).ok_or(FixedFromFloatError::Overflow)?;
-						let take_bits=most_significant_bit-(digit_index<<DIGIT_SHIFT);
-						let rest_of_mantissa=-($mantissa_bits as i32-(take_bits as i32));
-						*digit=signed_shift(m,rest_of_mantissa);
-						if rest_of_mantissa<0&&digit_index!=0{
-							//we don't care if some float bits are partially truncated
-							if let Some(digit)=digits.get_mut((digit_index-1) as usize){
-								let take_bits=most_significant_bit-((digit_index-1)<<DIGIT_SHIFT);
-								let rest_of_mantissa=-($mantissa_bits as i32-(take_bits as i32));
-								*digit=signed_shift(m,rest_of_mantissa);
-							}
+						let digit=digits.get_mut(digit_index)
+							.ok_or(FixedFromFloatError::Overflow)?;
+						*digit=hi;
+
+						if digit_index!=0{
+							//if digit_index exists, so does digit_index-1
+							digits[digit_index-1]=lo;
 						}
+
 						let bits=BInt::from_bits(bnum::BUint::from_digits(digits));
-						Ok(if s{
+						if bits.is_negative()&&!(sign&&bits==BInt::MIN){
+							return Err(FixedFromFloatError::Overflow);
+						}
+						Ok(if sign{
 							Self::from_bits(bits.overflowing_neg().0)
 						}else{
 							Self::from_bits(bits)
@@ -285,8 +290,8 @@ macro_rules! impl_from_float {
 		}
 	}
 }
-impl_from_float!(integer_decode_f32,f32,24);
-impl_from_float!(integer_decode_f64,f64,53);
+impl_from_float!(f32,u32,8,24,127);
+impl_from_float!(f64,u64,11,53,1023);
 
 impl<const N:usize,const F:usize> core::fmt::Display for Fixed<N,F>{
 	#[inline]
@@ -412,7 +417,7 @@ macro_rules! impl_multiply_operator_not_const_generic {
 			type Output=Self;
 			#[inline]
 			fn divide(self, other: i64)->Self::Output{
-				Self::from_bits(self.bits.div_euclid(BInt::from(other)))
+				Self::from_bits(self.bits/BInt::from(other))
 			}
 		}
 	}
@@ -422,11 +427,11 @@ macro_rules! impl_divide_operator_not_const_generic {
 		impl<const F:usize> $struct<$width,F>{
 			paste::item!{
 			#[inline]
-			pub fn [<fixed_ $method>](self,other:Self)->Self{
+			pub fn [<fixed_ $method>](self, other: Self) -> Self {
 				//this only needs to be $width+F as u32/64+1 but MUH CONST GENERICS!!!!!
 				let lhs=self.bits.as_::<BInt::<{$width*2}>>().shl(F as u32);
 				let rhs=other.bits.as_::<BInt::<{$width*2}>>();
-				Self::from_bits(lhs.div_euclid(rhs).as_())
+				Self::from_bits(lhs.div(rhs).as_())
 			}
 			}
 		}
@@ -446,28 +451,28 @@ macro_rules! impl_divide_operator_not_const_generic {
 }
 
 macro_rules! impl_multiplicative_operator {
-	( $struct: ident, $trait: ident, $method: ident, $inner_method: ident, $output: ty ) => {
+	( $struct: ident, $trait: ident, $method: ident, $output: ty ) => {
 		impl<const N:usize,const F:usize,U> core::ops::$trait<U> for $struct<N,F>
 			where
 				BInt::<N>:From<U>+core::ops::$trait,
 		{
 			type Output = $output;
 			#[inline]
-			fn $method(self,other:U)->Self::Output{
-				Self::from_bits(self.bits.$inner_method(BInt::<N>::from(other)))
+			fn $method(self, other: U) -> Self::Output {
+				Self::from_bits(self.bits.$method(BInt::<N>::from(other)))
 			}
 		}
 	};
 }
 macro_rules! impl_multiplicative_assign_operator {
-	( $struct: ident, $trait: ident, $method: ident, $not_assign_method: ident ) => {
+	( $struct: ident, $trait: ident, $method: ident ) => {
 		impl<const N:usize,const F:usize,U> core::ops::$trait<U> for $struct<N,F>
 			where
 				BInt::<N>:From<U>+core::ops::$trait,
 		{
 			#[inline]
-			fn $method(&mut self,other:U){
-				self.bits=self.bits.$not_assign_method(BInt::<N>::from(other));
+			fn $method(&mut self, other: U) {
+				self.bits.$method(BInt::<N>::from(other));
 			}
 		}
 	};
@@ -495,10 +500,10 @@ macro_16!( impl_multiplicative_assign_operator_not_const_generic, (Fixed, MulAss
 macro_16!( impl_multiply_operator_not_const_generic, (Fixed, Mul, mul, Self) );
 macro_16!( impl_multiplicative_assign_operator_not_const_generic, (Fixed, DivAssign, div_assign, div) );
 macro_16!( impl_divide_operator_not_const_generic, (Fixed, Div, div, Self) );
-impl_multiplicative_assign_operator!( Fixed, MulAssign, mul_assign, mul );
-impl_multiplicative_operator!( Fixed, Mul, mul, mul, Self );
-impl_multiplicative_assign_operator!( Fixed, DivAssign, div_assign, div_euclid );
-impl_multiplicative_operator!( Fixed, Div, div, div_euclid, Self );
+impl_multiplicative_assign_operator!( Fixed, MulAssign, mul_assign );
+impl_multiplicative_operator!( Fixed, Mul, mul, Self );
+impl_multiplicative_assign_operator!( Fixed, DivAssign, div_assign );
+impl_multiplicative_operator!( Fixed, Div, div, Self );
 #[cfg(feature="deferred-division")]
 impl<const LHS_N:usize,const LHS_F:usize,const RHS_N:usize,const RHS_F:usize> core::ops::Div<Fixed<RHS_N,RHS_F>> for Fixed<LHS_N,LHS_F>{
 	type Output=ratio_ops::ratio::Ratio<Fixed<LHS_N,LHS_F>,Fixed<RHS_N,RHS_F>>;

fixed_wide/src/tests.rs

@@ -47,6 +47,8 @@ fn from_f32(){
 	assert_eq!(b,Ok(a));
 	let a=I256F256::from(0);
 	let b:Result<I256F256,_>=0.try_into();
+	//test float mantissa spread across digit boundary
+	//16 is within the 24 bits of float precision
 	assert_eq!(b,Ok(a));
 	let a=I256F256::from(0b101011110101001010101010000000000000000000000000000i64)<<16;
 	let b:Result<I256F256,_>=(0b101011110101001010101010000000000000000000000000000u64 as f32*2.0f32.powi(16)).try_into();
@@ -56,11 +58,11 @@ fn from_f32(){
 	let b:Result<I32F32,_>=Into::<f32>::into(I32F32::MAX).try_into();
 	assert_eq!(b,Ok(a));
 	//I32F32::MIN hits a special case since it's not representable as a positive signed integer
-	//TODO: don't return an overflow because this is technically possible
 	let a=I32F32::MIN;
 	let b:Result<I32F32,_>=Into::<f32>::into(I32F32::MIN).try_into();
+	assert_eq!(b,Ok(a));
+	let b:Result<I32F32,_>=Into::<f32>::into(I32F32::MIN.fix_2()+(I32F32::MIN>>1).fix_2()).try_into();
 	assert_eq!(b,Err(crate::fixed::FixedFromFloatError::Overflow));
-	//16 is within the 24 bits of float precision
 	let b:Result<I32F32,_>=Into::<f32>::into(-I32F32::MIN.fix_2()).try_into();
 	assert_eq!(b,Err(crate::fixed::FixedFromFloatError::Overflow));
 	let b:Result<I32F32,_>=f32::MIN_POSITIVE.try_into();

ratio_ops/src/ratio.rs

@@ -251,35 +251,32 @@ impl_ratio_assign_operator!(RemAssign,rem_assign);
 // Only implement PartialEq<Self>
 // Rust's operators aren't actually that good
 
-impl<LhsNum,LhsDen,RhsNum,RhsDen,T,U> PartialEq<Ratio<RhsNum,RhsDen>> for Ratio<LhsNum,LhsDen>
+impl<Num,Den,T> PartialEq for Ratio<Num,Den>
 	where
-		LhsNum:Copy,
-		LhsDen:Copy,
-		RhsNum:Copy,
-		RhsDen:Copy,
-		LhsNum:core::ops::Mul<RhsDen,Output=T>,
-		RhsNum:core::ops::Mul<LhsDen,Output=U>,
-		T:PartialEq<U>,
+		Num:Copy,
+		Den:Copy,
+		Num:core::ops::Mul<Den,Output=T>,
+		T:PartialEq,
 {
 	#[inline]
-	fn eq(&self,other:&Ratio<RhsNum,RhsDen>)->bool{
+	fn eq(&self,&other:&Self)->bool{
 		(self.num*other.den).eq(&(other.num*self.den))
 	}
 }
-impl<Num,Den> Eq for Ratio<Num,Den> where Self:PartialEq{}
-
-impl<LhsNum,LhsDen,RhsNum,RhsDen,T,U> PartialOrd<Ratio<RhsNum,RhsDen>> for Ratio<LhsNum,LhsDen>
+impl<Num,Den> Eq for Ratio<Num,Den>
 	where
-		LhsNum:Copy,
-		LhsDen:Copy,
-		RhsNum:Copy,
-		RhsDen:Copy,
-		LhsNum:core::ops::Mul<RhsDen,Output=T>,
-		RhsNum:core::ops::Mul<LhsDen,Output=U>,
-		T:PartialOrd<U>,
+		Ratio<Num,Den>:PartialEq,
+{}
+
+impl<Num,Den,T> PartialOrd for Ratio<Num,Den>
+	where
+		Num:Copy,
+		Den:Copy,
+		Num:core::ops::Mul<Den,Output=T>,
+		T:PartialOrd,
 {
 	#[inline]
-	fn partial_cmp(&self,other:&Ratio<RhsNum,RhsDen>)->Option<core::cmp::Ordering>{
+	fn partial_cmp(&self,&other:&Self)->Option<core::cmp::Ordering>{
 		(self.num*other.den).partial_cmp(&(other.num*self.den))
 	}
 }