lib8: trig: rewrite sin8/cos8 to use traits, for easy modular math with usize

src/lib8/trig.rs

@@ -2,15 +2,21 @@ use num::PrimInt;
 
 const b_m16_interleave: [u8; 8] = [0, 49, 49, 41, 90, 27, 117, 10];
 
-pub fn sin8(theta: u8) -> u8 {
-    let mut offset: u8 = theta;
-    if theta & 0x40 != 0 {
+pub trait Trig8 {
+    fn sin8(self) -> u8;
+    fn cos8(self) -> u8;
+}
+
+impl Trig8 for u8 {
+    fn sin8(self) -> u8 {
+        let mut offset: u8 = self;
+        if self & 0x40 != 0 {
         offset = 255 - offset;
     }
     offset &= 0x3f;
 
     let mut secoffset: u8 = offset & 0x0f;
-    if theta & 0x40 != 0 {
+        if self & 0x40 != 0 {
         secoffset += 1;
     }
 
@@ -20,13 +26,32 @@ pub fn sin8(theta: u8) -> u8 {
     let m16: u8 = b_m16_interleave[s2 as usize + 1];
     let mx: u8 = m16.wrapping_mul(secoffset).unsigned_shr(4);
     let mut y: i8 = mx as i8 + b as i8;
-    if theta & 0x80 != 0 {
+        if self & 0x80 != 0 {
         y = -y;
     }
     y = y.wrapping_add(128u8 as i8);
     return y as u8;
 }
 
-pub fn cos8(theta: u8) -> u8 {
-    sin8(theta.wrapping_add(64))
+    fn cos8(self) -> u8 {
+        sin8(self.wrapping_add(64))
 }
+}
+
+impl Trig8 for usize {
+    fn sin8(self) -> u8 {
+        ((self % 255) as u8).sin8()
+    }
+
+    fn cos8(self) -> u8 {
+        ((self % 255) as u8).cos8()
+    }
+}
+
+pub fn sin8<T: Trig8>(theta: T) -> u8 {
+    theta.sin8()
+}
+
+pub fn cos8<T: Trig8>(theta: T) -> u8 {
+    theta.cos8()
+}