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//! Executor engine implementation for Brainfuck interpreter.
//!
//! This predominantly allows implementation of a [`u16`] executor.
#[cfg(feature = "bigint-engine")]
use std::io::Cursor;
use std::io::Read;
#[cfg(feature = "bigint-engine")]
use byteorder::{BigEndian, ReadBytesExt};
use num_traits::{One, Unsigned, WrappingAdd, WrappingSub, Zero};
use thiserror::Error;
use crate::executor;
/// Error type for engine errors
#[derive(Debug, Error)]
pub enum Error {
/// Engine ran into an io Error
#[error(transparent)]
Io(#[from] std::io::Error),
/// Utf16 error from widestring
#[error("could not convert byte to Utf16Str")]
Utf16,
/// Utf32 error from widestring
#[error("could not convert byte to Utf32Str")]
Utf32,
}
/// Generic engine implementation for the Brainfuck interpreter.
pub trait Engine {
/// Inner type of the Tape.
type TapeInner: Clone + Copy + Unsigned + WrappingAdd + WrappingSub + One + Zero;
/// Read one byte from stdin.
///
/// # Errors
///
/// This function will return an error if it is unable to read from stdin,
/// or if it indexes out of bounds.
fn read_byte() -> Result<Self::TapeInner, Error>;
/// Write the provided byte to stdout.
///
/// # Errors
///
/// This function will return an error if it is unable to write a byte to
/// stdout.
fn write_byte(byte: Self::TapeInner) -> Result<(), Error>;
}
impl Engine for executor::U8 {
type TapeInner = u8;
fn read_byte() -> Result<u8, Error> {
let mut input: [u8; 1] = [0; 1];
std::io::stdin().read_exact(&mut input)?;
Ok(input[0])
}
fn write_byte(byte: u8) -> Result<(), Error> {
print!("{}", char::from(byte));
Ok(())
}
}
#[cfg(feature = "engine-u16")]
impl Engine for executor::U16 {
type TapeInner = u16;
fn read_byte() -> Result<u16, Error> {
let mut input: [u8; 2] = [0; 2];
std::io::stdin().read_exact(&mut input)?;
let mut reader = Cursor::new(input);
Ok(reader.read_u16::<BigEndian>()?)
}
fn write_byte(byte: u16) -> Result<(), Error> {
print!(
"{}",
widestring::Utf16Str::from_slice(&[byte]).map_err(|_err| Error::Utf16)?
);
Ok(())
}
}
#[cfg(feature = "engine-u32")]
impl Engine for executor::U32 {
type TapeInner = u32;
fn read_byte() -> Result<u32, Error> {
let mut input: [u8; 4] = [0; 4];
std::io::stdin().read_exact(&mut input)?;
let mut reader = Cursor::new(input);
Ok(reader.read_u32::<BigEndian>()?)
}
fn write_byte(byte: u32) -> Result<(), Error> {
print!(
"{}",
widestring::Utf32Str::from_slice(&[byte]).map_err(|_err| Error::Utf32)?
);
Ok(())
}
}
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