lib8: implement more fastled 8 bit math as lib8 submodules

src/lib8/trig.rs

@@ -0,0 +1,32 @@
+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 {
+        offset = 255 - offset;
+    }
+    offset &= 0x3f;
+
+    let mut secoffset: u8 = offset & 0x0f;
+    if theta & 0x40 != 0 {
+        secoffset += 1;
+    }
+
+    let section: u8 = offset.unsigned_shr(4);
+    let s2: u8 = section * 2;
+    let b: u8 = b_m16_interleave[s2 as usize];
+    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 {
+        y = -y;
+    }
+    y = y.wrapping_add(128u8 as i8);
+    return y as u8;
+}
+
+pub fn cos8(theta: u8) -> u8 {
+    sin8(theta.wrapping_add(64))
+}