chipmunk-backend 1.0.0

Shared, platform agnostic, backend for the chipmunk emulator
Documentation 
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#[derive(Copy, Clone, Debug)]
pub enum Reg {
    V0,
    V1,
    V2,
    V3,
    V4,
    V5,
    V6,
    V7,
    V8,
    V9,
    VA,
    VB,
    VC,
    VD,
    VE,
    VF,
    DelayTimer,
    SoundTimer,
}

impl From<Reg> for usize {
    fn from(reg: Reg) -> usize {
        match reg {
            Reg::V0 => 0x0,
            Reg::V1 => 0x1,
            Reg::V2 => 0x2,
            Reg::V3 => 0x3,
            Reg::V4 => 0x4,
            Reg::V5 => 0x5,
            Reg::V6 => 0x6,
            Reg::V7 => 0x7,
            Reg::V8 => 0x8,
            Reg::V9 => 0x9,
            Reg::VA => 0xA,
            Reg::VB => 0xB,
            Reg::VC => 0xC,
            Reg::VD => 0xD,
            Reg::VE => 0xE,
            Reg::VF => 0xF,
            Reg::DelayTimer => 0x10,
            Reg::SoundTimer => 0x11,
        }
    }
}

impl From<u8> for Reg {
    fn from(v: u8) -> Reg {
        match v {
            0x0 => Reg::V0,
            0x1 => Reg::V1,
            0x2 => Reg::V2,
            0x3 => Reg::V3,
            0x4 => Reg::V4,
            0x5 => Reg::V5,
            0x6 => Reg::V6,
            0x7 => Reg::V7,
            0x8 => Reg::V8,
            0x9 => Reg::V9,
            0xA => Reg::VA,
            0xB => Reg::VB,
            0xC => Reg::VC,
            0xD => Reg::VD,
            0xE => Reg::VE,
            0xF => Reg::VF,
            0x10 => panic!("Should never convert u8 to Reg::DelayTimer"),
            0x11 => panic!("Should never convert u8 to Reg::SoundTimer"),
            _ => panic!("Unknown register V{:x}", v),
        }
    }
}

impl From<usize> for Reg {
    fn from(v: usize) -> Reg {
        match v {
            0x0 => Reg::V0,
            0x1 => Reg::V1,
            0x2 => Reg::V2,
            0x3 => Reg::V3,
            0x4 => Reg::V4,
            0x5 => Reg::V5,
            0x6 => Reg::V6,
            0x7 => Reg::V7,
            0x8 => Reg::V8,
            0x9 => Reg::V9,
            0xA => Reg::VA,
            0xB => Reg::VB,
            0xC => Reg::VC,
            0xD => Reg::VD,
            0xE => Reg::VE,
            0xF => Reg::VF,
            0x10 => panic!("Should never convert u8 to Reg::DelayTimer"),
            0x11 => panic!("Should never convert u8 to Reg::SoundTimer"),
            _ => panic!("Unknown register V{:x}", v),
        }
    }
}

const TIMER_COUNT: usize = 2;
const REG_COUNT: usize = 16 + TIMER_COUNT;

#[derive(Debug)]
pub struct Registers {
    inner: [u8; REG_COUNT],
    // default: used as carry flag
    // subtraction mode: no borrow flag
    // drawing: used for collision detection

    // program counter
    pc: u16,
    // index  register - 12 bits wide
    i: u16,
}

impl Registers {
    pub fn new() -> Self {
        let inner = [0; REG_COUNT];
        Self {
            inner,
            pc: 0x200,
            i: 0,
        }
    }

    pub fn pc(&self) -> u16 {
        self.pc
    }

    // move pc forward 2 bytes
    pub fn advance_pc(&mut self) {
        self.pc += 0x2;
    }

    pub fn goto(&mut self, address: u16) {
        self.pc = address;
    }

    pub fn get_i(&self) -> u16 {
        self.i
    }

    pub fn set_i(&mut self, value: u16) {
        self.i = value;
    }

    pub fn get(&self, reg: Reg) -> u8 {
        let i: usize = reg.into();
        *self.inner.get(i).expect("Reg doesnt exist")
    }

    pub fn set(&mut self, reg: Reg, value: u8) {
        let i: usize = reg.into();
        *self.inner.get_mut(i).expect("Reg doesnt exist") = value;
    }
}