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authorAdam Carpenter <gitlab@53hor.net>2019-07-09 15:14:04 -0400
committerAdam Carpenter <gitlab@53hor.net>2019-07-09 15:14:04 -0400
commit7e8ee5ed9cad6484e9f13f81731b102ced58402e (patch)
tree5395402ab07bbb5a659dbd68c701e22a1227202f /meap/meap-code/ch5/ch5-cpu2/src
downloadlearning-rust-7e8ee5ed9cad6484e9f13f81731b102ced58402e.tar.xz
learning-rust-7e8ee5ed9cad6484e9f13f81731b102ced58402e.zip
Init.
Diffstat (limited to 'meap/meap-code/ch5/ch5-cpu2/src')
-rwxr-xr-xmeap/meap-code/ch5/ch5-cpu2/src/main.rs60
1 files changed, 60 insertions, 0 deletions
diff --git a/meap/meap-code/ch5/ch5-cpu2/src/main.rs b/meap/meap-code/ch5/ch5-cpu2/src/main.rs
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+++ b/meap/meap-code/ch5/ch5-cpu2/src/main.rs
@@ -0,0 +1,60 @@
+const HALT: u8 = 0x0;
+const ARITHMETIC_AND_LOGIC: u8 = 0x8;
+const ADD_XY: u8 = 0x4;
+
+struct CPU {
+ // current_operation: u16, // no longer needed
+ registers: [u8; 16], // increase number of registers to 16 (0..F), as per CHIP-8
+ position_in_memory: usize, // add a program counter.. using a usize to simplify array indexing
+ memory: [u8; 4096], // give the system 4kb memory
+}
+
+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;
+
+ self.position_in_memory += 2;
+
+ 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;
+
+ match (op_major, op_minor) {
+ (HALT, HALT) => { return; },
+ (ARITHMETIC_AND_LOGIC, ADD_XY) => self.add_xy(x, y),
+ _ => unimplemented!("opcode {:04x}", raw_op), // this macro is useful when you are debugging, as it will promptly indicate that you have made a typo
+ }
+ }
+ }
+
+ 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; // initialise a few more registers
+ cpu.registers[3] = 10; //
+
+ cpu.memory[0] = 0x80; cpu.memory[1] = 0x14; // 0x8014 -> ADD register 1 to register 0
+ cpu.memory[2] = 0x80; cpu.memory[3] = 0x24; // 0x8014 -> ADD register 2 to register 0
+ cpu.memory[4] = 0x80; cpu.memory[5] = 0x34; // 0x8014 -> ADD register 3 to register 0
+
+ cpu.run();
+
+ assert_eq!(cpu.registers[0], 35);
+
+ println!("5 + 10 + 10 + 10 = {}", cpu.registers[0]);
+}