Rotate left/right impl (#9)

* Remove don'tpanic idea, not needed

* Add rotate left/right

Author: kaidokert

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "fixed-bigint"
-version = "0.1.4"
+version = "0.1.5"
 authors = ["kaidokert <[email protected]>"]
 documentation = "https://docs.rs/fixed-bigint"
 edition = "2018"

README.md

@@ -21,7 +21,6 @@ _TODO list_:
  * Implement experimental `unchecked_math` operands, unchecked_mul, unchecked_div etc.
  * Probably needs its own error structs instead of reusing core::fmt::Error and core::num::ParseIntError
  * Decimal string to/from conversion, currently only binary and hex strings are supported.
- * Implement a `dontpanic` feature, changing arithmetic ops to behave like wrapping versions, i.e. a non-standard C-like way.
  * Comprehensive testing fixture, fully validate all ops up to 32-bit against native types
  * Some test code relies on 64-bit ToPrimitive/FromPrimitive conversions, clean this up
  * Lots of test code can be written cleaner

src/fixeduint.rs

@@ -1095,7 +1095,6 @@ enum PanicReason {
     RemByZero,
 }
 
-// todo: Add a "don't panic" option
 fn maybe_panic(r: PanicReason) {
     match r {
         PanicReason::Add => panic!("attempt to add with overflow"),
@@ -1205,11 +1204,15 @@ impl<T: MachineWord, const N: usize> num_traits::PrimInt for FixedUInt<T, N> {
         }
         ret
     }
-    fn rotate_left(self, _: u32) -> Self {
-        todo!()
+    fn rotate_left(self, bits: u32) -> Self {
+        let a = self << bits;
+        let b = self >> (Self::BIT_SIZE - bits as usize);
+        a | b
     }
-    fn rotate_right(self, _: u32) -> Self {
-        todo!()
+    fn rotate_right(self, bits: u32) -> Self {
+        let a = self >> bits;
+        let b = self << (Self::BIT_SIZE - bits as usize);
+        a | b
     }
     fn signed_shl(self, _: u32) -> Self {
         todo!()

tests/bit_shift.rs

@@ -225,3 +225,39 @@ fn test_sh_variants() {
     test_shifts::<u32, Bn<u16, 2>>(8, &left_ops, 0x20000000, &right_ops);
     test_shifts::<u32, Bn<u8, 4>>(8, &left_ops, 0x20000000, &right_ops);
 }
+
+#[test]
+fn test_rotate() {
+    fn test_rotate<
+        T: num_traits::PrimInt,
+        INT: num_traits::PrimInt + core::fmt::Debug + core::convert::From<T>,
+    >(
+        (a_ref, b_ref, c_ref): (T, T, T),
+        half_shift: u32,
+        full_shift: u32,
+    ) {
+        let a: INT = a_ref.into();
+        let b: INT = b_ref.into();
+        let c: INT = c_ref.into();
+        assert_eq!(a.rotate_left(1), b);
+        assert_eq!(a.rotate_left(half_shift), c);
+        assert_eq!(a.rotate_right(half_shift), c);
+        assert_eq!(a.rotate_left(full_shift), a);
+        assert_eq!(b.rotate_right(1), a);
+        assert_eq!(b.rotate_right(full_shift), b);
+    }
+    let test_8bit = (0xc1, 0x83, 0x1C);
+    test_rotate::<u8, u8>(test_8bit, 4, 8);
+    test_rotate::<u8, Bn<u8, 1>>(test_8bit, 4, 8);
+
+    let test_16bit = (0xc001, 0x8003, 0x01C0);
+    test_rotate::<u16, u16>(test_16bit, 8, 16);
+    test_rotate::<u16, Bn<u8, 2>>(test_16bit, 8, 16);
+    test_rotate::<u16, Bn<u16, 1>>(test_16bit, 8, 16);
+
+    let test_32bit = (0xc0000001u32, 0x80000003u32, 0x0001C000u32);
+    test_rotate::<u32, u32>(test_32bit, 16, 32);
+    test_rotate::<u32, Bn<u8, 4>>(test_32bit, 16, 32);
+    test_rotate::<u32, Bn<u16, 2>>(test_32bit, 16, 32);
+    test_rotate::<u32, Bn<u32, 1>>(test_32bit, 16, 32);
+}