register pair manipulation functions

src/emulator/instructions/arithmetic.rs

@@ -1,4 +1,5 @@
-use crate::{get_register, structs::set_register, EmulatorState, Register};
+use crate::structs::{get_register_pair, set_register, set_register_pair};
+use crate::{get_register, EmulatorState, Register};
 
 /// Sets the condition code flags according to `result`. `flags` parameter
 /// indicates which flags will be set, 0b1111 will set all (Z, S, C, P)
@@ -20,7 +21,7 @@ fn set_cc(state: &mut EmulatorState, result: u16, flags: u8) {
 
 /// Add values of `register` and `A`
 pub fn add(register: Register, state: &mut EmulatorState) {
-    let result = get_register(&register, state) as u16 + state.a as u16;
+    let result = get_register(register, state) as u16 + state.a as u16;
     set_cc(state, result, 0b1111);
     state.a = (result & 0xff) as u8;
 }
@@ -34,7 +35,7 @@ pub fn adi(byte: u8, state: &mut EmulatorState) {
 
 /// Add values of `register` and `A` and add +1 if carry bit is set
 pub fn adc(register: Register, state: &mut EmulatorState) {
-    let result = get_register(&register, state) as u16 + state.a as u16 + u16::from(state.cc.c);
+    let result = get_register(register, state) as u16 + state.a as u16 + u16::from(state.cc.c);
     set_cc(state, result, 0b1111);
     state.a = (result & 0xff) as u8;
 }
@@ -48,30 +49,22 @@ pub fn aci(byte: u8, state: &mut EmulatorState) {
 
 /// Double precision add - Add B&C, D&E or H&L to H&L
 pub fn dad(register: Register, state: &mut EmulatorState) {
-    let num = match register {
+    let num = get_register_pair(register, state);
-        Register::B => u16::from_le_bytes([state.c, state.b]),
-        Register::D => u16::from_le_bytes([state.e, state.d]),
-        Register::H => u16::from_le_bytes([state.l, state.h]),
-        Register::SP => state.sp,
-        _ => panic!("Cannot perform DAD on register {:?}", register),
-    };
-
     let (result, overflow) = num.overflowing_add(u16::from_le_bytes([state.l, state.h]));
     state.cc.c = overflow;
-    state.h = (result >> 8) as u8;
+    set_register_pair(register, result, state);
-    state.l = result as u8;
 }
 
 /// Increase register
 pub fn inr(register: Register, state: &mut EmulatorState) {
-    let (result, _) = get_register(&register, state).overflowing_add(1);
+    let (result, _) = get_register(register, state).overflowing_add(1);
     set_cc(state, result as u16, 0b1101);
-    set_register(&register, result, state);
+    set_register(register, result, state);
 }
 
 /// Decrease register
 pub fn dcr(register: Register, state: &mut EmulatorState) {
-    let (result, _) = get_register(&register, state).overflowing_sub(1);
+    let (result, _) = get_register(register, state).overflowing_sub(1);
     set_cc(state, result as u16, 0b1101);
-    set_register(&register, result, state);
+    set_register(register, result, state);
 }

src/emulator/main.rs

@@ -58,6 +58,20 @@ fn tick(state: &mut EmulatorState) {
     match instruction {
         0x00 => {} // NOP
 
+        /* Special */
+        0xfb => state.ei = true,  // EI
+        0xf3 => state.ei = false, // DI
+        0x76 => {
+            if state.ei {
+                todo!()
+            } else {
+                // HLT
+                println!("HLT called after DI; exiting.");
+                print_state(state);
+                std::process::exit(0);
+            }
+        }
+
         /* Maths */
         // INR
         0x04 => arithmetic::inr(Register::B, state),
@@ -90,20 +104,6 @@ fn tick(state: &mut EmulatorState) {
         0xc6 => arithmetic::adi(next_byte(), state),                                 // ADI
         0xce => arithmetic::aci(next_byte(), state),                                 // ACI
 
-        /* Special */
-        0xfb => state.ei = true,  // EI
-        0xf3 => state.ei = false, // DI
-        0x76 => {
-            if state.ei {
-                todo!()
-            } else {
-                // HLT
-                println!("HLT called after DI; exiting.");
-                print_state(state);
-                std::process::exit(0);
-            }
-        }
-
         _ => not_implemented(state),
     }
 

src/emulator/structs.rs

@@ -1,5 +1,6 @@
 use crate::MEMORY_SIZE;
 
+#[derive(Clone, PartialEq, Eq, Debug)]
 pub struct EmulatorState {
     pub a: u8,
     pub b: u8,
@@ -21,6 +22,7 @@ pub struct EmulatorState {
     pub memory: [u8; MEMORY_SIZE],
 }
 
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
 pub struct ConditionCodes {
     /// Zero (Z), set if the result is zero.
     pub z: bool,
@@ -35,7 +37,7 @@ pub struct ConditionCodes {
     // ac: bool,
 }
 
-#[derive(PartialEq, Debug)]
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
 pub enum Register {
     B,
     C,
@@ -63,7 +65,7 @@ pub fn register_from_num(b: u8) -> Register {
     }
 }
 
-pub fn get_register(register: &Register, state: &EmulatorState) -> u8 {
+pub fn get_register(register: Register, state: &EmulatorState) -> u8 {
     match register {
         Register::B => state.b,
         Register::C => state.c,
@@ -77,7 +79,7 @@ pub fn get_register(register: &Register, state: &EmulatorState) -> u8 {
     }
 }
 
-pub fn set_register(register: &Register, value: u8, state: &mut EmulatorState) {
+pub fn set_register(register: Register, value: u8, state: &mut EmulatorState) {
     match register {
         Register::B => state.b = value,
         Register::C => state.c = value,
@@ -91,6 +93,61 @@ pub fn set_register(register: &Register, value: u8, state: &mut EmulatorState) {
     };
 }
 
+pub fn get_register_pair(register: Register, state: &mut EmulatorState) -> u16 {
+    match register {
+        Register::B => u16::from_le_bytes([state.c, state.b]),
+        Register::D => u16::from_le_bytes([state.e, state.d]),
+        Register::H => u16::from_le_bytes([state.l, state.h]),
+        Register::A => {
+            // the PSW looks like this: SZ0A0P1C
+            let flags: u8 = u8::from(state.cc.s) << 7 // bit 7
+                | u8::from(state.cc.z) << 6 // bit 6
+                //| u8::from(state.cc.a) << 4 // bit 4
+                | u8::from(state.cc.p) << 2 // bit 2
+                | 0x02 // bit 1
+                | u8::from(state.cc.c); // bit 0
+
+            u16::from_le_bytes([flags, state.a])
+        }
+        Register::SP => state.sp,
+        _ => unreachable!(),
+    }
+}
+
+pub fn set_register_pair(register: Register, value: u16, state: &mut EmulatorState) {
+    let arr = value.to_le_bytes();
+    let high = arr[1];
+    let low = arr[0];
+    match register {
+        Register::B => {
+            state.b = high;
+            state.c = low;
+        }
+        Register::D => {
+            state.d = high;
+            state.e = low;
+        }
+        Register::H => {
+            state.h = high;
+            state.l = low;
+        }
+        Register::A => {
+            state.a = high;
+            // the PSW looks like this: SZ0A0P1C
+            state.cc.s = low & 0b1000_0000 > 0;
+            state.cc.z = low & 0b0100_0000 > 0;
+            debug_assert!(low & 0b0010_0000 == 0, "malformed PSW");
+            //state.cc.a = low & 0b0001_0000 > 0;
+            debug_assert!(low & 0b0000_1000 == 0, "malformed PSW");
+            state.cc.p = low & 0b0000_0100 > 0;
+            debug_assert!(low & 0b0000_0010 > 0, "malformed PSW");
+            state.cc.c = low & 0b0000_0001 > 0;
+        }
+        Register::SP => state.sp = value,
+        _ => unreachable!(),
+    }
+}
+
 /// Print values of registers and flags to stdout
 pub fn print_state(state: &EmulatorState) {
     // State