From d186950e99f4ea3d18722a8a5887f505deb9dd08 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20L=C3=B6ffler?= <me@fatalerrorcoded.eu>
Date: Wed, 25 Jan 2023 23:44:10 +0100
Subject: [PATCH] 16-bit increment and decrement

---
 src/emulator/instructions/arithmetic.rs | 12 ++++++++++++
 src/emulator/main.rs                    | 14 +++++++++++++-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/src/emulator/instructions/arithmetic.rs b/src/emulator/instructions/arithmetic.rs
index 517c3c3..58bde33 100644
--- a/src/emulator/instructions/arithmetic.rs
+++ b/src/emulator/instructions/arithmetic.rs
@@ -68,3 +68,15 @@ pub fn dcr(register: Register, state: &mut EmulatorState) {
     set_cc(state, result as u16, 0b1101);
     set_register(register, result, state);
 }
+
+/// Increase register pair
+pub fn inx(register: Register, state: &mut EmulatorState) {
+    let (result, _) = get_register_pair(register, state).overflowing_add(1);
+    set_register_pair(register, result, state);
+}
+
+/// Decrease register pair
+pub fn dcx(register: Register, state: &mut EmulatorState) {
+    let (result, _) = get_register_pair(register, state).overflowing_sub(1);
+    set_register_pair(register, result, state);
+}
diff --git a/src/emulator/main.rs b/src/emulator/main.rs
index 8863c78..277ec20 100644
--- a/src/emulator/main.rs
+++ b/src/emulator/main.rs
@@ -62,10 +62,10 @@ fn tick(state: &mut EmulatorState) {
         0xfb => state.ei = true,  // EI
         0xf3 => state.ei = false, // DI
         0x76 => {
+            // HLT
             if state.ei {
                 todo!()
             } else {
-                // HLT
                 println!("HLT called after DI; exiting.");
                 print_state(state);
                 std::process::exit(0);
@@ -99,6 +99,18 @@ fn tick(state: &mut EmulatorState) {
         0x29 => arithmetic::dad(Register::H, state),
         0x39 => arithmetic::dad(Register::SP, state),
 
+        // INX
+        0x03 => arithmetic::inx(Register::B, state),
+        0x13 => arithmetic::inx(Register::D, state),
+        0x23 => arithmetic::inx(Register::H, state),
+        0x33 => arithmetic::inx(Register::SP, state),
+
+        // DCX
+        0x0b => arithmetic::dcx(Register::B, state),
+        0x1b => arithmetic::dcx(Register::D, state),
+        0x2b => arithmetic::dcx(Register::H, state),
+        0x3b => arithmetic::dcx(Register::SP, state),
+
         0x80..=0x87 => arithmetic::add(register_from_num(instruction & 0xf), state), // ADD
         0x88..=0x8f => arithmetic::adc(register_from_num(instruction & 0xf), state), // ADC
         0xc6 => arithmetic::adi(next_byte(), state),                                 // ADI