From 2fff8d2448de0e493614b7425240c35cb93a59f6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20L=C3=B6ffler?= <me@fatalerrorcoded.eu>
Date: Thu, 26 Jan 2023 06:02:11 +0100
Subject: [PATCH] accumulator transfer instructions

---
 src/emulator/instructions/transfer.rs | 16 +++++++++++++-
 src/emulator/main.rs                  | 31 +++++++++++++++------------
 src/emulator/structs.rs               | 17 +++++++++++++++
 3 files changed, 49 insertions(+), 15 deletions(-)

diff --git a/src/emulator/instructions/transfer.rs b/src/emulator/instructions/transfer.rs
index e39251c..9af545d 100644
--- a/src/emulator/instructions/transfer.rs
+++ b/src/emulator/instructions/transfer.rs
@@ -1,10 +1,24 @@
-use crate::{get_register, set_register, EmulatorState, Register};
+use crate::{get_register, set_register, structs::get_register_pair, EmulatorState, Register};
 
+/// Move (copy) value from source to destination register
 pub fn mov(src: Register, dest: Register, state: &mut EmulatorState) {
     let data = get_register(src, state);
     set_register(dest, data, state);
 }
 
+/// Move immediate into destination register
 pub fn mvi(byte: u8, dest: Register, state: &mut EmulatorState) {
     set_register(dest, byte, state);
 }
+
+/// Store accumulator using the BC or DE register pair
+pub fn stax(register: Register, state: &mut EmulatorState) {
+    let address = get_register_pair(register, state);
+    state.memory[address as usize] = state.a;
+}
+
+/// Load accumulator using the BC or DE register pair
+pub fn ldax(register: Register, state: &mut EmulatorState) {
+    let address = get_register_pair(register, state);
+    state.a = state.memory[address as usize];
+}
diff --git a/src/emulator/main.rs b/src/emulator/main.rs
index 6f6bf3c..abfe264 100644
--- a/src/emulator/main.rs
+++ b/src/emulator/main.rs
@@ -50,11 +50,6 @@ fn main() {
 fn tick(state: &mut EmulatorState) {
     let instruction = state.memory[state.pc as usize];
 
-    let mut next_byte = || {
-        state.pc += 1;
-        state.memory[state.pc as usize]
-    };
-
     match instruction {
         0x00 => {} // NOP
 
@@ -75,7 +70,7 @@ fn tick(state: &mut EmulatorState) {
         /* Data Transfer */
         // MVI
         0x06 | 0x0e | 0x16 | 0x1e | 0x26 | 0x2e | 0x36 | 0x3e => transfer::mvi(
-            next_byte(),
+            state.next_byte(),
             register_from_num((instruction & 0x38) >> 3),
             state,
         ),
@@ -87,6 +82,14 @@ fn tick(state: &mut EmulatorState) {
             state,
         ),
 
+        // Accumulator transfer instructions
+        0x02 => transfer::stax(Register::B, state), // STAX B
+        0x0a => transfer::ldax(Register::B, state), // LDAX B
+        0x12 => transfer::stax(Register::D, state), // STAX D
+        0x1a => transfer::ldax(Register::D, state), // LDAX D
+        0x32 => state.memory[state.next_word() as usize] = state.a, // STA
+        0x3a => state.a = state.memory[state.next_word() as usize], // LDA
+
         /* Maths */
         // INR
         0x04 => arithmetic::inr(Register::B, state),
@@ -140,22 +143,22 @@ fn tick(state: &mut EmulatorState) {
 
         0x80..=0x87 => arithmetic::add_reg(register_from_num(instruction & 0x7), false, state), // ADD
         0x88..=0x8f => arithmetic::add_reg(register_from_num(instruction & 0x7), state.cc.c, state), // ADC
-        0xc6 => arithmetic::add(next_byte(), false, state), // ADI
-        0xce => arithmetic::add(next_byte(), state.cc.c, state), // ACI
+        0xc6 => arithmetic::add(state.next_byte(), false, state), // ADI
+        0xce => arithmetic::add(state.next_byte(), state.cc.c, state), // ACI
 
         0x90..=0x97 => arithmetic::sub_reg(register_from_num(instruction & 0x7), false, state), // SUB
         0x98..=0x9f => arithmetic::sub_reg(register_from_num(instruction & 0x7), state.cc.c, state), // SBB
-        0xd6 => arithmetic::sub(next_byte(), false, state), // SUI
-        0xde => arithmetic::sub(next_byte(), state.cc.c, state), // SBI
+        0xd6 => arithmetic::sub(state.next_byte(), false, state), // SUI
+        0xde => arithmetic::sub(state.next_byte(), state.cc.c, state), // SBI
 
         0xa0..=0xa7 => arithmetic::and_reg(register_from_num(instruction & 0x7), state), // ANA
         0xa8..=0xaf => arithmetic::xor_reg(register_from_num(instruction & 0x7), state), // XRA
         0xb0..=0xb7 => arithmetic::or_reg(register_from_num(instruction & 0x7), state),  // ORA
         0xb8..=0xbf => arithmetic::cmp_reg(register_from_num(instruction & 0x7), state), // CMP
-        0xe6 => arithmetic::and(next_byte(), state),                                     // ANI
-        0xee => arithmetic::xor(next_byte(), state),                                     // XRI
-        0xf6 => arithmetic::or(next_byte(), state),                                      // ORI
-        0xfe => arithmetic::cmp(next_byte(), state),                                     // CPI
+        0xe6 => arithmetic::and(state.next_byte(), state),                               // ANI
+        0xee => arithmetic::xor(state.next_byte(), state),                               // XRI
+        0xf6 => arithmetic::or(state.next_byte(), state),                                // ORI
+        0xfe => arithmetic::cmp(state.next_byte(), state),                               // CPI
 
         _ => not_implemented(state),
     }
diff --git a/src/emulator/structs.rs b/src/emulator/structs.rs
index 7248023..df195c2 100644
--- a/src/emulator/structs.rs
+++ b/src/emulator/structs.rs
@@ -22,6 +22,23 @@ pub struct EmulatorState {
     pub memory: [u8; MEMORY_SIZE],
 }
 
+impl EmulatorState {
+    // Get the next byte from memory
+    pub fn next_byte(&mut self) -> u8 {
+        self.pc += 1;
+        self.memory[self.pc as usize]
+    }
+
+    // Get the next 16-bit word from memory, in little endian order
+    pub fn next_word(&mut self) -> u16 {
+        self.pc += 2;
+        u16::from_le_bytes([
+            self.memory[self.pc as usize - 1],
+            self.memory[self.pc as usize],
+        ])
+    }
+}
+
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
 pub struct ConditionCodes {
     /// Zero (Z), set if the result is zero.