implementation can be customized through macro

README.md

@@ -1,3 +1,41 @@
 # staticdot
 
-Rust library for general purpose fixed point arithmetic
+Rust library for general purpose fixed point arithmetic.
+
+This library exposes the functionality to implement custom fixed point arithmetic
+through the use of macros.
+
+The most important macro is `impl_fixed_point`. This macro requires a name for the new types name, a raw type which will store the actual fixed point data
+and the number of bits to use for the fraction.
+The raw type used to store the fixed point data should be a primitive type of either:
+* usize
+* isize
+* u8
+* u16
+* u32
+* u64
+* i8
+* i16
+* i32
+* i64
+
+Theoretically any type can be used if it implements the required traits.
+ 
+Quick start example::
+```rust
+impl_fixed_point!(Fixed64_32, i64, 32);
+
+fn main() {
+    let a = Fixed64_32::ZERO;
+    let b = Fixed64_32::from(3);
+
+    let c = a + b * Fixed64_32::from(4.5);
+
+    println!("{}", Into::<f32>::into(c));
+}
+```
+
+## TODO
+* add support for special functions such as sin(), sqrt(), ln()
+* add macro for converting between different formats
+* make precision retain shifts in operations customizable

src/lib.rs

@@ -1,84 +1,118 @@
-use std::ops;
-use std::ops::{Add, BitAnd, Div, Mul, Shl, Shr, Sub};
 
-const INTEGER_BITS: i32 = 8;
-const FRACTION_BITS: i32 = 24;
-/// in oder to create the fraction bits mask we first fill all bits with 1 by initializing it with -1
-/// then we reinterpret the -1 as unsigned and shift it to the left. We need to do this in order to
-/// avoid arithmetic shifts
-const FRACTION_MASK: i32 = (-1i32 as u32 >> INTEGER_BITS) as i32;
+macro_rules! __impl_from_into_for_rational {
+    ($impl_name:ident, $raw_type:ty, $frac_bits:expr, $from_type:ty) => {
+        impl From<$from_type> for $impl_name {
+            fn from(value: $from_type) -> Self {
+                let integral = (value as $raw_type).shl($frac_bits);
+                let fraction = (value.fract() * 1.shl($frac_bits) as $from_type) as $raw_type;
+                $impl_name(integral | fraction)
+            }
+        }
 
-#[derive(Copy, Clone)]
-pub struct Fixed32(i32);
+        impl Into<$from_type> for $impl_name {
+            fn into(self) -> $from_type {
 
-impl From<i32> for Fixed32 {
-    fn from(value: i32) -> Self {
-        Fixed32(value.shl(FRACTION_BITS))
+                let integral = self.0.shr($frac_bits);
+                let fraction = (self.0.bitand(FRAC_MASK)) as $from_type / (1 as $raw_type).shl($frac_bits) as $from_type;
+
+                integral as $from_type + fraction
+            }
+        }
     }
 }
 
-impl From<f32> for Fixed32 {
-    fn from(value: f32) -> Self {
-        let integral = (value as i32).shl(FRACTION_BITS);
-        let fraction = (value.fract() * 1.shl(FRACTION_BITS) as f32) as i32;
-        Fixed32(integral | fraction)
+macro_rules! impl_fixed_point {
+    ($impl_name:ident, $raw_type:ty, $frac_bits:expr) => {
+        mod $impl_name {
+            use std::ops;
+            use std::ops::{Add, BitAnd, Div, Mul, Shl, Shr, Sub};
+
+            #[derive(Copy, Clone, PartialOrd, PartialEq, Eq, Ord)]
+            pub struct $impl_name($raw_type);
+
+            pub const ZERO: $impl_name = $impl_name(0);
+
+            const FRAC_MASK: $raw_type = (-1) << (std::mem::size_of::<$raw_type>() * 8 - $frac_bits);
+
+            impl From<$raw_type> for $impl_name {
+                fn from(value: $raw_type) -> Self {
+                    $impl_name(value.shl($frac_bits))
                 }
-}
-
-impl Into<i32> for Fixed32 {
-    fn into(self) -> i32 {
-        self.0.shr(FRACTION_BITS)
             }
-}
 
-impl Into<f32> for Fixed32 {
-    fn into(self) -> f32 {
-        let integral = self.0.shr(FRACTION_BITS) as f32;
-        let fraction = self.0.bitand(FRACTION_MASK) as f32 / 1.shl(FRACTION_BITS) as f32;
-        integral + fraction
+            __impl_from_into_for_rational!($impl_name, $raw_type, $frac_bits, f32);
+            __impl_from_into_for_rational!($impl_name, $raw_type, $frac_bits, f64);
+
+            impl Into<$raw_type> for $impl_name {
+                fn into(self) -> $raw_type {
+                    self.0.shr($frac_bits)
                 }
-}
-
-impl Add<Fixed32> for Fixed32 {
-    type Output = Fixed32;
-
-    fn add(self, rhs: Fixed32) -> Self::Output {
-        Fixed32(self.0 + rhs.0)
             }
-}
 
-impl Sub<Fixed32> for Fixed32 {
-    type Output = Fixed32;
+            impl Add<$impl_name> for $impl_name {
+                type Output = $impl_name;
 
-    fn sub(self, rhs: Fixed32) -> Self::Output {
-        Fixed32(self.0 - rhs.0)
+                fn add(self, rhs: $impl_name) -> Self::Output {
+                    $impl_name(self.0 + rhs.0)
                 }
-}
-
-impl Mul<Fixed32> for Fixed32 {
-    type Output = Fixed32;
-
-    fn mul(self, rhs: Fixed32) -> Self::Output {
-        Fixed32(self.0.shr(FRACTION_BITS / 2) * rhs.0.shr(FRACTION_BITS / 2))
             }
-}
 
-impl Div<Fixed32> for Fixed32 {
-    type Output = Fixed32;
+            impl Sub<$impl_name> for $impl_name {
+                type Output = $impl_name;
 
-    fn div(self, rhs: Fixed32) -> Self::Output {
-        Fixed32((self.0 / rhs.0.shr(FRACTION_BITS / 2)).shl(FRACTION_BITS / 2))
+                fn sub(self, rhs: $impl_name) -> Self::Output {
+                    $impl_name(self.0 - rhs.0)
+                }
+            }
+
+            impl Mul<$impl_name> for $impl_name {
+                type Output = $impl_name;
+
+                fn mul(self, rhs: $impl_name) -> Self::Output {
+                    $impl_name(self.0.shr($frac_bits / 2) * rhs.0.shr($frac_bits / 2))
+                }
+            }
+
+            impl Div<$impl_name> for $impl_name {
+                type Output = $impl_name;
+
+                fn div(self, rhs: $impl_name) -> Self::Output {
+                    $impl_name((self.0 / rhs.0.shr($frac_bits / 2 as $raw_type)).shl($frac_bits / 2))
+                }
+            }
+
+            impl Default for $impl_name {
+                fn default() -> Self {
+                    ZERO
+                }
+            }
+
+            impl $impl_name {
+
+                pub fn integral(&self) -> $raw_type {
+                    self.0.shr($frac_bits)
+                }
+
+                pub fn fraction_bits(&self) -> $raw_type {
+                    self.0
+                }
+            }
+        }
     }
 }
 
 #[cfg(test)]
 mod tests {
+    use crate::tests::LowpFixed::LowpFixed;
     use super::*;
 
+    impl_fixed_point!(LowpFixed, i32, 16);
+    impl_fixed_point!(HighpFixed, i64, 32);
+
     #[test]
     fn test() {
-        let a = Fixed32::from(9);
-        let b = Fixed32::from(3);
+        let a = HighpFixed::ZERO;
+        let b =  HighpFixed::HighpFixed::from(3);
 
         let c = a * a / b;