Dekejit/src/lib.rs

use std::mem::transmute;

pub mod assembler;
pub mod cli;
pub mod cpu;
pub mod jit;
pub mod loader;
pub mod pretty_printers;

pub fn interpret_as_signed(x: u16) -> i16 {
    // the two types have the same size.
    unsafe {
        return transmute::<u16, i16>(x);
    }
}

pub fn interpret_as_unsigned(x: i16) -> u16 {
    // the two types have the same size.
    unsafe {
        return transmute::<i16, u16>(x);
    }
}

pub fn transmute_to_vecu16_as_is(x: Vec<u8>) -> Vec<u16> {
    let mut rb = x.iter();
    // raw_bytes must be converted to u16.
    //
    let bytes: Vec<u16> = {
        let mut res = vec![];
        // Depends on the order in which the arguments of a tuple are
        // evaluated. Rust guarantees to be left-to-right.
        while let (Some(word0), Some(word1)) = (rb.next(), rb.next()) {
            // println!("Pair: {}, {}, word: {:?}", word0, word1, raw_bytes);
            res.push(((*word0 as u16) << 8) + (*word1 as u16));
        }
        // if we branch into this else, either there's a single word left or zero.
        // since, in case a single word was left, the first rb.next() call in the line
        // above would've consumed it, we have to gather that last element again
        match x.len() {
            0 => res,
            n => {
                if n % 2 != 0 {
                    // if there's an uneven number of chunks of 8 bits,
                    // we introduce padding!
                    // println!("Adding last one too");
                    res.push((*x.last().unwrap() as u16) << 8);
                }
                res
            }
        }
    };

    return bytes;
}

pub fn transmute_to_vecu8_as_is(x: Vec<u16>) -> Vec<u8> {
    let mut bytes = vec![];

    for b in x.iter() {
        let x0 = (*b & 0xFF00) >> 8;
        let x1 = *b & 0x00FF;
        bytes.push(x0 as u8);
        bytes.push(x1 as u8);
    }

    return bytes;
}