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Added support for specifying a tape size limit

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tdark 2021-05-15 18:39:49 +02:00
parent 7b5ae34bfd
commit 1b195dc955
1 changed files with 61 additions and 16 deletions
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77
src/brian.rs
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@ -2,7 +2,8 @@
//!
//! If you just want to execute some simple brainfuck, check the [`interpret_with_io`] function.
//!
//! To construct the interpreter, use the [`from_ascii`] or [`from_ascii_with_input_buffer`] methods. The latter grants access to
//! To construct the interpreter, use the [`from_ascii`] or [`from_ascii_with_input_buffer`] methods
//! (or their variants that take a maximum tape size). The latter grants access to
//! the method [`add_input`], which allows for the addition of input while the interpreter is running.
//!
//! [`from_ascii`]: Interpreter::from_ascii
@ -24,6 +25,9 @@ use std::{
// NOTE(Able): This is the brain fuck interface
/// The default limit for the tape size. This is the value used by methods that don't take it as a parameter
pub const DEFAULT_TAPE_SIZE_LIMIT: usize = 30_000;
#[derive(Debug, Clone, PartialEq, Eq)]
/// A brainfuck interpreter. Read the [module level documentation](self) for more
pub struct Interpreter<'a, I> {
@ -31,17 +35,29 @@ pub struct Interpreter<'a, I> {
instr_ptr: usize,
tape: Vec<i8>,
data_ptr: usize,
tape_size_limit: usize,
input: I,
}
impl<'a> Interpreter<'a, InputBuffer> {
/// Construct an `Interpreter` from an ASCII string of code with an empty input buffer
/// This methods sets the tape size limit to [its default value](DEFAULT_TAPE_SIZE_LIMIT)
pub fn from_ascii_with_input_buffer(code: &'a [u8]) -> Self {
Self::from_ascii_with_input_buffer_and_tape_limit(code, DEFAULT_TAPE_SIZE_LIMIT)
}
/// Construct an `Interpreter` from an ASCII string of code with an empty input buffer,
/// setting the tape size limit to the specified value
pub fn from_ascii_with_input_buffer_and_tape_limit(
code: &'a [u8],
tape_size_limit: usize,
) -> Self {
Self {
code,
instr_ptr: 0,
tape: Vec::new(),
data_ptr: 0,
tape_size_limit,
input: InputBuffer(VecDeque::new()),
}
}
@ -53,17 +69,23 @@ impl<'a> Interpreter<'a, InputBuffer> {
}
impl<'a, I: BootlegRead> Interpreter<'a, I> {
/// Construct an interpreter from an ASCII string of code and an source of input bytes
pub fn from_ascii(code: &'a [u8], input: I) -> Self {
/// Construct an interpreter from an ASCII string of code, a source of input bytes, and a tape size limit
pub fn from_ascii_with_tape_limit(code: &'a [u8], input: I, tape_size_limit: usize) -> Self {
Self {
code,
instr_ptr: 0,
tape: Vec::new(),
data_ptr: 0,
tape_size_limit,
input,
}
}
/// Constructs an interpreter from an ASCII string of code, a source of input bytes, and [the default tape size limit](DEFAULT_TAPE_SIZE_LIMIT)
pub fn from_ascii(code: &'a [u8], input: I) -> Self {
Self::from_ascii_with_tape_limit(code, input, DEFAULT_TAPE_SIZE_LIMIT)
}
/// Advance the interpreter by one instruction.
/// A return value of Ok(None) indicates succesful termination of the interpreter
pub fn advance(&mut self) -> Result<Option<Status>, ProgramError> {
@ -83,12 +105,16 @@ impl<'a, I: BootlegRead> Interpreter<'a, I> {
}
b'+' => {
let val = self.get_or_resize_tape_mut();
let val = self
.get_or_resize_tape_mut()
.ok_or(ProgramError::TapeSizeExceededLimit)?;
*val = val.checked_add(1).ok_or(ProgramError::IntegerOverflow)?;
}
b'-' => {
let val = self.get_or_resize_tape_mut();
let val = self
.get_or_resize_tape_mut()
.ok_or(ProgramError::TapeSizeExceededLimit)?;
*val = val.checked_sub(1).ok_or(ProgramError::IntegerUnderflow)?;
}
@ -98,7 +124,12 @@ impl<'a, I: BootlegRead> Interpreter<'a, I> {
}
b',' => match self.input.bootleg_read() {
Ok(Some(num)) => *self.get_or_resize_tape_mut() = num,
Ok(Some(num)) => {
let cell = self
.get_or_resize_tape_mut()
.ok_or(ProgramError::TapeSizeExceededLimit)?;
*cell = num;
}
Ok(None) => return Ok(Some(Status::NeedsInput)),
Err(_) => return Err(ProgramError::InputReadError),
},
@ -157,11 +188,14 @@ impl<'a, I: BootlegRead> Interpreter<'a, I> {
Ok(())
}
fn get_or_resize_tape_mut(&mut self) -> &mut i8 {
fn get_or_resize_tape_mut(&mut self) -> Option<&mut i8> {
if self.data_ptr > self.tape_size_limit {
return None;
}
if self.data_ptr >= self.tape.len() {
self.tape.resize(self.data_ptr + 1, 0);
}
&mut self.tape[self.data_ptr]
Some(&mut self.tape[self.data_ptr])
}
fn get_at_data_ptr(&self) -> i8 {
@ -251,6 +285,7 @@ pub enum ProgramError {
InputReadError,
UnmatchedOpeningBracket,
UnmatchedClosingBracket,
TapeSizeExceededLimit,
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
@ -308,6 +343,7 @@ mod tests {
instr_ptr: 0,
tape: vec![10, 5],
data_ptr: 0,
tape_size_limit: DEFAULT_TAPE_SIZE_LIMIT,
input: std::io::empty(),
};
@ -323,14 +359,10 @@ mod tests {
#[test]
fn hello_world() {
let mut interpreter = Interpreter {
//Source: https://en.wikipedia.org/wiki/Brainfuck
code: b"++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++.",
instr_ptr: 0,
tape: vec![],
data_ptr: 0,
input: std::io::empty(),
};
let mut interpreter = Interpreter::from_ascii(
b"++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++.",
std::io::empty(),
);
let mut string = Vec::new();
interpreter
@ -364,4 +396,17 @@ mod tests {
);
assert_eq!(interpreter.advance_until_io(), Ok(None));
}
#[test]
fn hit_tape_size_limit() {
let mut interpreter =
Interpreter::from_ascii_with_tape_limit(b"+>+>+>+>+>", std::io::empty(), 1);
let result = interpreter.interpret_with_output(std::io::sink());
assert_eq!(
result,
Err(InterpretError::ProgramError(
ProgramError::TapeSizeExceededLimit
))
);
}
}