provide From<Fixed*> for {f32,f64} when lossless

src/display.rs

@@ -21,7 +21,6 @@ use core::mem;
 use core::str;
 use frac::Unsigned;
 use FixedHelper;
-
 use {
     FixedI128, FixedI16, FixedI32, FixedI64, FixedI8, FixedU128, FixedU16, FixedU32, FixedU64,
     FixedU8,
@@ -74,11 +73,11 @@ trait FmtRadix2Helper {
 }
 
 macro_rules! fmt_radix2_helper {
-    ($($Inner:ty)*) => { $(
-        impl FmtRadix2Helper for $Inner {
+    ($($UInner:ty)*) => { $(
+        impl FmtRadix2Helper for $UInner {
             #[inline]
             fn int_frac_bits() -> u32 {
-                mem::size_of::<$Inner>() as u32 * 8
+                mem::size_of::<$UInner>() as u32 * 8
             }
 
             #[inline]
@@ -96,7 +95,7 @@ macro_rules! fmt_radix2_helper {
 
             #[inline]
             fn take_frac_digit(&mut self, digit_bits: u32) -> u8 {
-                let int_frac_bits = <$Inner as FmtRadix2Helper>::int_frac_bits();
+                let int_frac_bits = <$UInner as FmtRadix2Helper>::int_frac_bits();
                 let rem_bits = int_frac_bits - digit_bits;
                 let mask = !0 << rem_bits;
                 let ret = ((*self & mask) >> rem_bits) as u8;
@@ -158,14 +157,14 @@ where
 }
 
 #[inline]
-fn fmt_radix2<Frac: Unsigned, F, Inner>(
+fn fmt_radix2<Frac: Unsigned, F, UInner>(
     num: F,
     radix: &dyn Radix2,
     fmt: &mut Formatter,
 ) -> FmtResult
 where
-    F: FixedHelper<Frac, Inner = Inner>,
-    Inner: FmtRadix2Helper,
+    F: FixedHelper<Frac, UInner = UInner>,
+    UInner: FmtRadix2Helper,
 {
     fmt_radix2_helper(Frac::to_u32(), num.parts(), radix, fmt)
 }
@@ -272,11 +271,11 @@ trait FmtDecHelper {
 }
 
 macro_rules! fmt_dec_helper {
-    ($($Inner:ty)*) => { $(
-        impl FmtDecHelper for $Inner {
+    ($($UInner:ty)*) => { $(
+        impl FmtDecHelper for $UInner {
             #[inline]
             fn int_frac_bits() -> u32 {
-                mem::size_of::<$Inner>() as u32 * 8
+                mem::size_of::<$UInner>() as u32 * 8
             }
 
             #[inline]
@@ -398,10 +397,10 @@ where
 }
 
 #[inline]
-fn fmt_dec<Frac: Unsigned, F, Inner>(num: F, fmt: &mut Formatter) -> FmtResult
+fn fmt_dec<Frac: Unsigned, F, UInner>(num: F, fmt: &mut Formatter) -> FmtResult
 where
-    F: FixedHelper<Frac, Inner = Inner>,
-    Inner: FmtDecHelper,
+    F: FixedHelper<Frac, UInner = UInner>,
+    UInner: FmtDecHelper,
 {
     fmt_dec_helper(Frac::to_u32(), num.parts(), fmt)
 }

src/flt.rs

@@ -14,7 +14,9 @@
 // <https://opensource.org/licenses/MIT>.
 
 use core::mem;
+use frac::Unsigned;
 use helper::FloatHelper;
+use {FixedI16, FixedI32, FixedI8, FixedU16, FixedU32, FixedU8};
 
 macro_rules! to_f {
     (fn $method:ident($Uns:ty) -> $Flt:ty) => {
@@ -99,3 +101,25 @@ macro_rules! flt_conv {
     )* };
 }
 flt_conv! { u8 u16 u32 u64 u128 }
+
+macro_rules! lossless {
+    ($Fixed:ident:: $method:ident -> $Flt:ident) => {
+        impl<Frac: Unsigned> From<$Fixed<Frac>> for $Flt {
+            #[inline]
+            fn from(src: $Fixed<Frac>) -> $Flt {
+                src.$method()
+            }
+        }
+    };
+}
+
+lossless! { FixedI8::to_f32 -> f32 }
+lossless! { FixedI16::to_f32 -> f32 }
+lossless! { FixedU8::to_f32 -> f32 }
+lossless! { FixedU16::to_f32 -> f32 }
+lossless! { FixedI8::to_f64 -> f64 }
+lossless! { FixedI16::to_f64 -> f64 }
+lossless! { FixedI32::to_f64 -> f64 }
+lossless! { FixedU8::to_f64 -> f64 }
+lossless! { FixedU16::to_f64 -> f64 }
+lossless! { FixedU32::to_f64 -> f64 }

src/helper.rs

@@ -114,22 +114,23 @@ float_helper! { f32(u32, 24) }
 float_helper! { f64(u64, 53) }
 
 pub(crate) trait FixedHelper<Frac: Unsigned>: Sized {
-    type Inner;
+    type UInner;
 
     #[inline]
     fn int_frac_bits() -> u32 {
-        mem::size_of::<Self::Inner>() as u32 * 8
+        mem::size_of::<Self::UInner>() as u32 * 8
     }
 
     fn one() -> Option<Self>;
     fn minus_one() -> Option<Self>;
-    fn parts(self) -> (bool, Self::Inner, Self::Inner);
+    fn from_parts(neg: bool, int_abs: Self::UInner, frac_abs: Self::UInner) -> Self;
+    fn parts(self) -> (bool, Self::UInner, Self::UInner);
 }
 
 macro_rules! fixed_num_unsigned {
-    ($Fixed:ident($Inner:ty)) => {
+    ($Fixed:ident($UInner:ty)) => {
         impl<Frac: Unsigned> FixedHelper<Frac> for $Fixed<Frac> {
-            type Inner = $Inner;
+            type UInner = $UInner;
 
             #[inline]
             fn one() -> Option<Self> {
@@ -148,10 +149,33 @@ macro_rules! fixed_num_unsigned {
             }
 
             #[inline]
-            fn parts(self) -> (bool, $Inner, $Inner) {
-                let bits = self.to_bits();
+            fn from_parts(
+                neg: bool,
+                int_abs: Self::UInner,
+                frac_abs: Self::UInner,
+            ) -> $Fixed<Frac> {
                 let int_bits = <$Fixed<Frac>>::int_bits();
                 let frac_bits = <$Fixed<Frac>>::frac_bits();
+
+                let _ = neg;
+                debug_assert!(!neg);
+
+                let int_frac = if int_bits == 0 {
+                    frac_abs
+                } else if frac_bits == 0 {
+                    int_abs
+                } else {
+                    (int_abs << frac_bits) | (frac_abs >> int_bits)
+                };
+                $Fixed::from_bits(int_frac)
+            }
+
+            #[inline]
+            fn parts(self) -> (bool, $UInner, $UInner) {
+                let int_bits = <$Fixed<Frac>>::int_bits();
+                let frac_bits = <$Fixed<Frac>>::frac_bits();
+
+                let bits = self.to_bits();
                 let int_part = if int_bits == 0 { 0 } else { bits >> frac_bits };
                 let frac_part = if frac_bits == 0 { 0 } else { bits << int_bits };
                 (false, int_part, frac_part)
@@ -161,9 +185,9 @@ macro_rules! fixed_num_unsigned {
 }
 
 macro_rules! fixed_num_signed {
-    ($Fixed:ident($Inner:ty)) => {
+    ($Fixed:ident($UInner:ty)) => {
         impl<Frac: Unsigned> FixedHelper<Frac> for $Fixed<Frac> {
-            type Inner = $Inner;
+            type UInner = $UInner;
 
             #[inline]
             fn one() -> Option<Self> {
@@ -188,13 +212,47 @@ macro_rules! fixed_num_signed {
             }
 
             #[inline]
-            fn parts(self) -> (bool, $Inner, $Inner) {
-                let bits = self.to_bits().wrapping_abs() as $Inner;
+            fn from_parts(
+                neg: bool,
+                int_abs: Self::UInner,
+                frac_abs: Self::UInner,
+            ) -> $Fixed<Frac> {
                 let int_bits = <$Fixed<Frac>>::int_bits();
                 let frac_bits = <$Fixed<Frac>>::frac_bits();
-                let int_part = if int_bits == 0 { 0 } else { bits >> frac_bits };
-                let frac_part = if frac_bits == 0 { 0 } else { bits << int_bits };
-                (self.to_bits() < 0, int_part, frac_part)
+
+                let int_frac_abs = if int_bits == 0 {
+                    frac_abs
+                } else if frac_bits == 0 {
+                    int_abs
+                } else {
+                    (int_abs << frac_bits) | (frac_abs >> int_bits)
+                };
+                let int_frac = if neg {
+                    int_frac_abs.wrapping_neg()
+                } else {
+                    int_frac_abs
+                };
+                $Fixed::from_bits(int_frac as _)
+            }
+
+            #[inline]
+            fn parts(self) -> (bool, $UInner, $UInner) {
+                let int_bits = <$Fixed<Frac>>::int_bits();
+                let frac_bits = <$Fixed<Frac>>::frac_bits();
+
+                let (neg, abs) = if self.to_bits() < 0 {
+                    (true, self.to_bits().wrapping_neg() as $UInner)
+                } else {
+                    (false, self.to_bits() as $UInner)
+                };
+                let (int_abs, frac_abs) = if int_bits == 0 {
+                    (0, abs)
+                } else if frac_bits == 0 {
+                    (abs, 0)
+                } else {
+                    ((abs >> frac_bits), (abs << int_bits))
+                };
+                (neg, int_abs, frac_abs)
             }
         }
     };