ft(interpreter): impl SAR

src/operands.rs

@@ -9,7 +9,7 @@ use crate::{disasm::DisasmError, register::Register};
 use core::fmt;
 use std::{
     cmp::Ordering,
-    ops::{Add, BitAnd, BitOr, BitXor, Div, Mul, Not, Shl, Shr, Sub},
+    ops::{Add, BitAnd, BitOr, BitXor, Div, Not, Shl, Shr, Sub},
 };
 
 pub type Byte = u8; // b
@@ -72,6 +72,20 @@ impl ImmediateOperand {
         }
     }
 
+    /// Sets or removes sign.
+    pub fn set_sign(self, sign: bool) -> Self {
+        match self {
+            Self::Byte(b) => {
+                let msb = 1 << 7;
+                Self::Byte(if sign { b | msb } else { b & !msb })
+            }
+            Self::Word(w) => {
+                let msb = 1 << 15;
+                Self::Word(if sign { w | msb } else { w & !msb })
+            }
+        }
+    }
+
     /// Check if inner value is zero.
     pub fn zero(&self) -> bool {
         match self {
@@ -92,7 +106,7 @@ impl ImmediateOperand {
     }
 
     /// Check if least significant bit is set.
-    pub fn _lsb(&self) -> bool {
+    pub fn lsb(&self) -> bool {
         match self {
             Self::Byte(byte) => return byte & 1 == 1,
             Self::Word(word) => return word & 1 == 1,