Add barebones CPU structure

7 files changed, 355 insertions, 1 deletions

diff --git a/.gitignore b/.gitignore
index ea8c4bf..ff0915e 100644
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 /target
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diff --git a/Cargo.toml b/Cargo.toml
index e212b65..74f5753 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,3 +6,4 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+clap = { version = "4.4.12", features = ["derive"] }
diff --git a/src/cpu/chip.rs b/src/cpu/chip.rs
new file mode 100644
index 0000000..4866ff7
--- /dev/null
+++ b/src/cpu/chip.rs
@@ -0,0 +1,109 @@
+use std::fs::File;
+use std::io::Read;
+
+
+#[derive(Debug)]
+pub struct Flags {
+    pub zero: u8, //Zero flag
+    pub n: u8, //Subtraction flag (BCD)
+    pub h: u8, //Half carry flag (BCD)
+    pub carry: u8, //Carry flag
+}
+
+impl Flags {
+    fn new() -> Self {
+        Flags {
+            zero: 0,
+            n: 0,
+            h: 0,
+            carry: 0,
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct Chip {
+    pub a: u8, //Upper bits of AF, the Accumulator
+    pub b: u8,
+    pub c: u8,
+    pub d: u8,
+    pub e: u8,
+    pub h: u8,
+    pub l: u8,
+    pub instr: u8, //Current instruction
+    pub sp: u16, //Stack pointer
+    pub pc: u16, //Program counter
+    pub byte2: u8,
+    pub byte3: u8,
+    pub flags: Flags, //Lower bits of AF, Flags register
+    pub rom_bank_0: [u8; 16384],
+    pub rom_bank_n: [u8; 16384],
+    pub external_ram_bank_n: [u8; 8192],
+    pub wram_bank_0: [u8; 4096],
+    pub wram_bank_n: [u8; 4096],
+
+}
+
+impl Chip {
+    pub fn new() -> Self {
+        Chip {
+            a: 0,
+            b: 0,
+            c: 0,
+            d: 0,
+            e: 0,
+            h: 0,
+            l: 0,
+            instr: 0,
+            sp: 0,
+            pc: 0,
+            byte2: 0,
+            byte3: 0,
+            flags: Flags::new(),
+            rom_bank_0: [0; 16384],
+            rom_bank_n: [0; 16384],
+            external_ram_bank_n: [00; 8192],
+            wram_bank_0: [0; 4096],
+            wram_bank_n: [0; 4096],
+        }
+    }
+    pub fn load_rom(&mut self, rom_path: &str) {
+        let mut rom_buf = Vec::new();
+        let mut rom = File::open(rom_path).unwrap_or_else(|_err| panic!("Valid ROM needed!"));
+        rom.read_to_end(&mut rom_buf).unwrap_or_else(|_err| panic!("Error reading ROM"));
+
+	for i in 0..self.rom_bank_0.len() {
+            self.rom_bank_0[i] = rom_buf.get(i).unwrap().to_owned();
+        }
+    }
+    pub fn read_memory(&self, pc: usize) -> u8 {
+        let address = match pc {
+            0x0000..=0x3fff => { self.rom_bank_0[self.pc as usize]  }, //Fixed bank, rom_bank_0
+            0x4000..=0x7fff => { self.rom_bank_n[self.pc as usize - 0x4000] },
+            0x8000..=0x9fff => { 0x0 },
+            0xa000..=0xbfff => { 0x0 },
+            0xc000..=0xcfff => { 0x0 },
+            0xd000..=0xdfff => { 0x0 },
+            0xfe00..=0xfe9f => { 0x0 },
+            0xff00..=0xff7f => { 0x0 },
+            0xff80..=0xfffe => { 0x0 },
+            0xffff..=0xffff => { 0x0 },
+            _ => { 0xff }
+        };
+        address
+    }
+    pub fn fetch(&mut self) {
+        self.instr = self.read_memory(self.pc as usize);
+        let arg1 = self.read_memory(self.pc as usize + 1);
+        let arg2 = self.read_memory(self.pc as usize + 2);
+        self.byte2 = arg1;
+        self.byte3 = arg2;
+        self.pc += 1;
+    }
+    pub fn execute(&self) {
+
+        match self.instr {
+            _ => { panic!("Error: 0x{:02X} not implemented!", self.instr) }
+        }
+    }
+}
diff --git a/src/cpu/dassm.rs b/src/cpu/dassm.rs
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/src/cpu/dassm.rs
diff --git a/src/cpu/mod.rs b/src/cpu/mod.rs
new file mode 100644
index 0000000..ba87d03
--- /dev/null
+++ b/src/cpu/mod.rs
@@ -0,0 +1,2 @@
+pub mod chip;
+pub mod dassm;
diff --git a/src/main.rs b/src/main.rs
index e7a11a9..5a29737 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,21 @@
+use clap::Parser;
+mod cpu;
+
+#[derive(Parser, Debug)]
+#[command(author, version, about, long_about = None)]
+struct Args {
+    // Name of the ROM file
+    #[arg(short, long)]
+    name: String,
+}
+
+
 fn main() {
-    println!("Hello, world!");
+    let args = Args::parse();
+    let mut cpu = cpu::chip::Chip::new();
+    cpu.load_rom(&args.name);
+    loop {
+        cpu.fetch();
+        cpu.execute();
+    }
 }