From 7e8ee5ed9cad6484e9f13f81731b102ced58402e Mon Sep 17 00:00:00 2001
From: Adam Carpenter <gitlab@53hor.net>
Date: Tue, 9 Jul 2019 15:14:04 -0400
Subject: Init.

---
 meap/cpu/src/main.rs | 199 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 199 insertions(+)
 create mode 100755 meap/cpu/src/main.rs

(limited to 'meap/cpu/src')

diff --git a/meap/cpu/src/main.rs b/meap/cpu/src/main.rs
new file mode 100755
index 0000000..2feb29d
--- /dev/null
+++ b/meap/cpu/src/main.rs
@@ -0,0 +1,199 @@
+//const ADD_XY: u8 = 0x8;
+//
+//struct CPU {
+//    current_operation: u16,
+//    registers: [u8; 2],
+//}
+//
+//impl CPU {
+//    fn run(&mut self) {
+//        let encoded_op = self.current_operation;
+//        let op = ((encoded_op & 0xf000) >> 12) as u8;
+//        let x = ((encoded_op & 0x0f00) >> 8) as u8;
+//        let y = ((encoded_op & 0x00f0) >> 4) as u8;
+//
+//        match op {
+//            ADD_XY => {
+//                self.add_xy(x, y);
+//            },
+//            _ => unimplemented!(),
+//        }
+//    }
+//
+//    fn add_xy(&mut self, x: u8, y: u8) {
+//        self.registers[x as usize] += self.registers[y as usize];
+//    }
+//}
+//
+//
+//fn main() {
+//    let mut cpu = CPU {
+//        current_operation: 0x8014,
+//        registers: [0; 2],
+//    };
+//
+//    cpu.registers[0] = 5;
+//    cpu.registers[1] = 10;
+//    cpu.run();
+//
+//    assert_eq!(cpu.registers[0], 15);
+//    println!("5 + 10 = {}", cpu.registers[0]);
+//}
+
+//const ARITHMETIC_AND_LOGIC: u8 = 0x8;
+//const HALT: u8 = 0x0;
+//const ADD_XY: u8 = 0x4;
+//
+//struct CPU {
+//    // current_operation: u16
+//    registers: [u8; 16],
+//    position_in_memory: usize,
+//    memory: [u8; 4096],
+//}
+//
+//impl CPU {
+//    fn run(&mut self) {
+//        loop {
+//            let op_byte1 = self.memory[self.position_in_memory] as u16;
+//            let op_byte2 = self.memory[self.position_in_memory + 1] as u16;
+//            let raw_op = op_byte1 << 8 | op_byte2;
+//
+//            let op_major = ((raw_op & 0xf000) >> 12) as u8;
+//            let x = ((raw_op & 0x0f00) >> 8) as u8;
+//            let y = ((raw_op & 0x00f0) >> 4) as u8;
+//            let op_minor = (raw_op & 0x000f) as u8;
+//
+//            self.position_in_memory += 2;
+//
+//            match (op_major, op_minor) {
+//                (HALT, HALT) => { return; },
+//                (ARITHMETIC_AND_LOGIC, ADD_XY) => self.add_xy(x, y),
+//                _ => unimplemented!("opcode: {:04x}", raw_op),
+//            }
+//        }
+//    }
+//
+//    fn add_xy(&mut self, x: u8, y: u8) {
+//        self.registers[x as usize] += self.registers[y as usize];
+//    }
+//}
+//
+//fn main() {
+//    let mut cpu = CPU {
+//        registers: [0; 16],
+//        memory: [0; 4096],
+//        position_in_memory: 0,
+//    };
+//
+//    cpu.registers[0] = 5;
+//    cpu.registers[1] = 10;
+//    cpu.registers[2] = 10;
+//    cpu.registers[3] = 10;
+//
+//    cpu.memory[0] = 0x80;
+//    cpu.memory[1] = 0x14;
+//    cpu.memory[2] = 0x80;
+//    cpu.memory[3] = 0x24;
+//    cpu.memory[4] = 0x80;
+//    cpu.memory[5] = 0x34;
+//
+//    cpu.run();
+//
+//    assert_eq!(cpu.registers[0], 35);
+//    println!("5 + 10 + 10 + 10 = {}", cpu.registers[0]);
+//
+//}
+
+struct CPU {
+    registers: [u8; 16],
+    position_in_memory: usize,
+    memory: [u8; 4096],
+    stack: [u16; 16],
+    stack_pointer: usize,
+}
+
+impl CPU {
+    fn run(&mut self) {
+        loop {
+            let op_byte1 = self.memory[self.position_in_memory] as u16;
+            let op_byte2 = self.memory[self.position_in_memory + 1] as u16;
+            let opcode = op_byte1 << 8 | op_byte2;
+
+            let x = ((opcode & 0x0f00) >> 8) as u8;
+            let y = ((opcode & 0x00f0) >> 4) as u8;
+            let op_minor = (opcode & 0x000f) as u8;
+            let addr = opcode & 0x0fff;
+
+            self.position_in_memory += 2;
+
+            match opcode {
+                0x0000 => { return; },
+                0x00ee => { self.ret(); },
+                0x2000...0x2fff => { self.call(addr); },
+                0x8000...0x8fff => {
+                    match op_minor {
+                        4 => { self.add_xy(x, y); }
+                        _ => { unimplemented!("opcode: {:04x}", opcode); },
+                    }
+                },
+                _ => unimplemented!("opcode {:04x}", opcode),
+            }
+        }
+    }
+
+    fn call(&mut self, addr: u16) {
+        let sp = self.stack_pointer;
+        let stack = &mut self.stack;
+
+        if sp > stack.len() {
+            panic!("stack overflow!");
+        }
+
+        stack[sp] = self.position_in_memory as u16;
+        self.stack_pointer += 1;
+        self.position_in_memory = addr as usize;
+
+    }
+
+    fn ret(&mut self) {
+        if self.stack_pointer == 0 {
+            panic!("stack underflow!");
+        }
+
+        self.stack_pointer -= 1;
+        self.position_in_memory = self.stack[self.stack_pointer] as usize;
+    }
+
+    fn add_xy(&mut self, x: u8, y: u8) {
+        self.registers[x as usize] += self.registers[y as usize];
+    }
+}
+
+fn main() {
+    let mut cpu = CPU {
+        registers: [0; 16],
+        memory: [0; 4096],
+        position_in_memory: 0,
+        stack: [0; 16],
+        stack_pointer: 0,
+    };
+
+    cpu.registers[0] = 5;
+    cpu.registers[1] = 10;
+
+    cpu.memory[0x000] = 0x21;
+    cpu.memory[0x001] = 0x00;
+    cpu.memory[0x002] = 0x21;
+    cpu.memory[0x003] = 0x00;
+    cpu.memory[0x100] = 0x80;
+    cpu.memory[0x101] = 0x14;
+    cpu.memory[0x102] = 0x80;
+    cpu.memory[0x103] = 0x14;
+    cpu.memory[0x104] = 0x00;
+    cpu.memory[0x105] = 0xee;
+
+    cpu.run();
+
+    assert_eq!(cpu.registers[0], 45);
+    dbg!(cpu.registers[0]);
+}
-- 
cgit v1.2.3