From eacc01c2c81f106d89ee08afb32887e281998373 Mon Sep 17 00:00:00 2001
From: Greg Burri <greg.burri@gmail.com>
Date: Sat, 10 Sep 2022 12:35:15 +0200
Subject: [PATCH] CHIP-8 WIP

---
 ch5-data-in-depth/src/chip8.rs | 54 ++++++++++++++++++++++++++++++++--
 ch5-data-in-depth/src/main.rs  |  4 +--
 2 files changed, 54 insertions(+), 4 deletions(-)

diff --git a/ch5-data-in-depth/src/chip8.rs b/ch5-data-in-depth/src/chip8.rs
index 0a36044..2b6d1a4 100644
--- a/ch5-data-in-depth/src/chip8.rs
+++ b/ch5-data-in-depth/src/chip8.rs
@@ -1,7 +1,57 @@
 
+/// Operations are coded on 16 bits (Four nibbles, a nibble = half-byte):
+/// 1) Opcode group (c).
+/// 2) First register (x).                                       / Memory address (nnn).
+/// 3) Second register (y).                       / Integer (kk) / Memory address (nnn).
+/// 4) Opcode subgroup (d) / Number of bytes (n). / Integer (kk) / Memory address (nnn).
 
 struct CPU {
-    current_operation: u16,
-    registers: [u8; 2],
+    registers: [u8; 16],
+    position_in_memory: usize,
+    memory: [u8; 0x1000], // 4 KB of memory.
 }
 
+impl CPU {
+    fn read_opcode(&self) -> u16 {
+        self.current_operation
+    }
+
+    fn run(&mut self) {
+        // loop {
+            let opcode = self.read_opcode();
+            let c = ((opcode & 0xF000) >> 12) as u8;
+            let x = ((opcode & 0x0F00) >>  8) as u8;
+            let y = ((opcode & 0x00F0) >>  4) as u8;
+            let d = ((opcode & 0x000F) >>  0) as u8;
+
+            match (c, x, y, d) {
+                (0x8, _, _, 0x4) => self.add_xy(x, y),
+                _ => todo!("opcode: {:04x}", opcode),
+            }
+        //}
+    }
+
+    fn add_xy(&mut self, x: u8, y: u8) {
+        self.registers[x as usize] += self.registers[y as usize];
+    }
+}
+
+mod tests {
+    use super::*;
+
+    #[test]
+    fn addition() {
+        let mut cpu = CPU {
+            current_operation: 0,
+            registers: [0; 2]
+        };
+
+        cpu.current_operation = 0x8014;
+        cpu.registers[0] = 5;
+        cpu.registers[1] = 10;
+
+        cpu.run();
+
+        assert_eq!(cpu.registers[0], 15);
+    }
+}
\ No newline at end of file
diff --git a/ch5-data-in-depth/src/main.rs b/ch5-data-in-depth/src/main.rs
index 7f26aeb..ba04717 100644
--- a/ch5-data-in-depth/src/main.rs
+++ b/ch5-data-in-depth/src/main.rs
@@ -20,7 +20,7 @@ fn test_chip() {
 }
 
 fn main() {
-    // test_decode_f32();
-    // test_q7();
+    test_decode_f32();
+    test_q7();
     test_chip();
 }
-- 
2.45.2