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//! Parser for implementing virtual terminal emulators
//!
//! [`Parser`] is implemented according to [Paul Williams' ANSI parser
//! state machine]. The state machine doesn't assign meaning to the parsed data
//! and is thus not itself sufficient for writing a terminal emulator. Instead,
//! it is expected that an implementation of [`Perform`] is provided which does
//! something useful with the parsed data. The [`Parser`] handles the book
//! keeping, and the [`Perform`] gets to simply handle actions.
//!
//! # Examples
//!
//! For an example of using the [`Parser`] please see the examples folder. The example included
//! there simply logs all the actions [`Perform`] does. One quick thing to see it in action is to
//! pipe `vim` into it
//!
//! ```sh
//! cargo build --release --example parselog
//! vim | target/release/examples/parselog
//! ```
//!
//! Just type `:q` to exit.
//!
//! # Differences from original state machine description
//!
//! * UTF-8 Support for Input
//! * OSC Strings can be terminated by 0x07
//! * Only supports 7-bit codes. Some 8-bit codes are still supported, but they no longer work in
//! all states.
//!
//! [Paul Williams' ANSI parser state machine]: https://vt100.net/emu/dec_ansi_parser
#![cfg_attr(not(test), no_std)]
#[cfg(not(feature = "core"))]
extern crate alloc;
use core::mem::MaybeUninit;
#[cfg(feature = "core")]
use arrayvec::ArrayVec;
#[cfg(feature = "utf8")]
use utf8parse as utf8;
mod params;
pub mod state;
pub use params::{Params, ParamsIter};
use state::{state_change, Action, State};
const MAX_INTERMEDIATES: usize = 2;
const MAX_OSC_PARAMS: usize = 16;
#[cfg(feature = "core")]
const MAX_OSC_RAW: usize = 1024;
/// Parser for raw _VTE_ protocol which delegates actions to a [`Perform`]
#[derive(Default, Clone, Debug, PartialEq, Eq)]
pub struct Parser<C = DefaultCharAccumulator> {
state: State,
intermediates: [u8; MAX_INTERMEDIATES],
intermediate_idx: usize,
params: Params,
param: u16,
#[cfg(feature = "core")]
osc_raw: ArrayVec<u8, MAX_OSC_RAW>,
#[cfg(not(feature = "core"))]
osc_raw: alloc::vec::Vec<u8>,
osc_params: [(usize, usize); MAX_OSC_PARAMS],
osc_num_params: usize,
ignoring: bool,
utf8_parser: C,
}
impl<C> Parser<C>
where
C: CharAccumulator,
{
/// Create a new Parser
pub fn new() -> Parser {
Parser::default()
}
#[inline]
fn params(&self) -> &Params {
&self.params
}
#[inline]
fn intermediates(&self) -> &[u8] {
&self.intermediates[..self.intermediate_idx]
}
/// Advance the parser state
///
/// Requires a [`Perform`] in case `byte` triggers an action
#[inline]
pub fn advance<P: Perform>(&mut self, performer: &mut P, byte: u8) {
// Utf8 characters are handled out-of-band.
if let State::Utf8 = self.state {
self.process_utf8(performer, byte);
return;
}
let (state, action) = state_change(self.state, byte);
self.perform_state_change(performer, state, action, byte);
}
#[inline]
fn process_utf8<P>(&mut self, performer: &mut P, byte: u8)
where
P: Perform,
{
if let Some(c) = self.utf8_parser.add(byte) {
performer.print(c);
self.state = State::Ground;
}
}
#[inline]
fn perform_state_change<P>(&mut self, performer: &mut P, state: State, action: Action, byte: u8)
where
P: Perform,
{
match state {
State::Anywhere => {
// Just run the action
self.perform_action(performer, action, byte);
}
state => {
match self.state {
State::DcsPassthrough => {
self.perform_action(performer, Action::Unhook, byte);
}
State::OscString => {
self.perform_action(performer, Action::OscEnd, byte);
}
_ => (),
}
match action {
Action::Nop => (),
action => {
self.perform_action(performer, action, byte);
}
}
match state {
State::CsiEntry | State::DcsEntry | State::Escape => {
self.perform_action(performer, Action::Clear, byte);
}
State::DcsPassthrough => {
self.perform_action(performer, Action::Hook, byte);
}
State::OscString => {
self.perform_action(performer, Action::OscStart, byte);
}
_ => (),
}
// Assume the new state
self.state = state;
}
}
}
/// Separate method for osc_dispatch that borrows self as read-only
///
/// The aliasing is needed here for multiple slices into self.osc_raw
#[inline]
fn osc_dispatch<P: Perform>(&self, performer: &mut P, byte: u8) {
let mut slices: [MaybeUninit<&[u8]>; MAX_OSC_PARAMS] =
unsafe { MaybeUninit::uninit().assume_init() };
for (i, slice) in slices.iter_mut().enumerate().take(self.osc_num_params) {
let indices = self.osc_params[i];
*slice = MaybeUninit::new(&self.osc_raw[indices.0..indices.1]);
}
unsafe {
let num_params = self.osc_num_params;
let params = &slices[..num_params] as *const [MaybeUninit<&[u8]>] as *const [&[u8]];
performer.osc_dispatch(&*params, byte == 0x07);
}
}
#[inline]
fn perform_action<P: Perform>(&mut self, performer: &mut P, action: Action, byte: u8) {
match action {
Action::Print => performer.print(byte as char),
Action::Execute => performer.execute(byte),
Action::Hook => {
if self.params.is_full() {
self.ignoring = true;
} else {
self.params.push(self.param);
}
performer.hook(self.params(), self.intermediates(), self.ignoring, byte);
}
Action::Put => performer.put(byte),
Action::OscStart => {
self.osc_raw.clear();
self.osc_num_params = 0;
}
Action::OscPut => {
#[cfg(feature = "core")]
{
if self.osc_raw.is_full() {
return;
}
}
let idx = self.osc_raw.len();
// Param separator
if byte == b';' {
let param_idx = self.osc_num_params;
match param_idx {
// Only process up to MAX_OSC_PARAMS
MAX_OSC_PARAMS => return,
// First param is special - 0 to current byte index
0 => {
self.osc_params[param_idx] = (0, idx);
}
// All other params depend on previous indexing
_ => {
let prev = self.osc_params[param_idx - 1];
let begin = prev.1;
self.osc_params[param_idx] = (begin, idx);
}
}
self.osc_num_params += 1;
} else {
self.osc_raw.push(byte);
}
}
Action::OscEnd => {
let param_idx = self.osc_num_params;
let idx = self.osc_raw.len();
match param_idx {
// Finish last parameter if not already maxed
MAX_OSC_PARAMS => (),
// First param is special - 0 to current byte index
0 => {
self.osc_params[param_idx] = (0, idx);
self.osc_num_params += 1;
}
// All other params depend on previous indexing
_ => {
let prev = self.osc_params[param_idx - 1];
let begin = prev.1;
self.osc_params[param_idx] = (begin, idx);
self.osc_num_params += 1;
}
}
self.osc_dispatch(performer, byte);
}
Action::Unhook => performer.unhook(),
Action::CsiDispatch => {
if self.params.is_full() {
self.ignoring = true;
} else {
self.params.push(self.param);
}
performer.csi_dispatch(self.params(), self.intermediates(), self.ignoring, byte);
}
Action::EscDispatch => {
performer.esc_dispatch(self.intermediates(), self.ignoring, byte);
}
Action::Collect => {
if self.intermediate_idx == MAX_INTERMEDIATES {
self.ignoring = true;
} else {
self.intermediates[self.intermediate_idx] = byte;
self.intermediate_idx += 1;
}
}
Action::Param => {
if self.params.is_full() {
self.ignoring = true;
return;
}
if byte == b';' {
self.params.push(self.param);
self.param = 0;
} else if byte == b':' {
self.params.extend(self.param);
self.param = 0;
} else {
// Continue collecting bytes into param
self.param = self.param.saturating_mul(10);
self.param = self.param.saturating_add((byte - b'0') as u16);
}
}
Action::Clear => {
// Reset everything on ESC/CSI/DCS entry
self.intermediate_idx = 0;
self.ignoring = false;
self.param = 0;
self.params.clear();
}
Action::BeginUtf8 => self.process_utf8(performer, byte),
Action::Ignore => (),
Action::Nop => (),
}
}
}
/// Build a `char` out of bytes
pub trait CharAccumulator: Default {
/// Build a `char` out of bytes
///
/// Return `None` when more data is needed
fn add(&mut self, byte: u8) -> Option<char>;
}
#[cfg(feature = "utf8")]
pub type DefaultCharAccumulator = Utf8Parser;
#[cfg(not(feature = "utf8"))]
pub type DefaultCharAccumulator = AsciiParser;
/// Only allow parsing 7-bit ASCII
#[derive(Default, Clone, Debug, PartialEq, Eq)]
pub struct AsciiParser;
impl CharAccumulator for AsciiParser {
fn add(&mut self, _byte: u8) -> Option<char> {
unreachable!("multi-byte UTF8 characters are unsupported")
}
}
/// Allow parsing UTF-8
#[cfg(feature = "utf8")]
#[derive(Default, Clone, Debug, PartialEq, Eq)]
pub struct Utf8Parser {
utf8_parser: utf8::Parser,
}
#[cfg(feature = "utf8")]
impl CharAccumulator for Utf8Parser {
fn add(&mut self, byte: u8) -> Option<char> {
let mut c = None;
let mut receiver = VtUtf8Receiver(&mut c);
self.utf8_parser.advance(&mut receiver, byte);
c
}
}
#[cfg(feature = "utf8")]
struct VtUtf8Receiver<'a>(&'a mut Option<char>);
#[cfg(feature = "utf8")]
impl<'a> utf8::Receiver for VtUtf8Receiver<'a> {
fn codepoint(&mut self, c: char) {
*self.0 = Some(c);
}
fn invalid_sequence(&mut self) {
*self.0 = Some('�');
}
}
/// Performs actions requested by the [`Parser`]
///
/// Actions in this case mean, for example, handling a CSI escape sequence describing cursor
/// movement, or simply printing characters to the screen.
///
/// The methods on this type correspond to actions described in
/// <http://vt100.net/emu/dec_ansi_parser>. I've done my best to describe them in
/// a useful way in my own words for completeness, but the site should be
/// referenced if something isn't clear. If the site disappears at some point in
/// the future, consider checking archive.org.
pub trait Perform {
/// Draw a character to the screen and update states.
fn print(&mut self, _c: char) {}
/// Execute a C0 or C1 control function.
fn execute(&mut self, _byte: u8) {}
/// Invoked when a final character arrives in first part of device control string.
///
/// The control function should be determined from the private marker, final character, and
/// execute with a parameter list. A handler should be selected for remaining characters in the
/// string; the handler function should subsequently be called by `put` for every character in
/// the control string.
///
/// The `ignore` flag indicates that more than two intermediates arrived and
/// subsequent characters were ignored.
fn hook(&mut self, _params: &Params, _intermediates: &[u8], _ignore: bool, _action: u8) {}
/// Pass bytes as part of a device control string to the handle chosen in `hook`. C0 controls
/// will also be passed to the handler.
fn put(&mut self, _byte: u8) {}
/// Called when a device control string is terminated.
///
/// The previously selected handler should be notified that the DCS has
/// terminated.
fn unhook(&mut self) {}
/// Dispatch an operating system command.
fn osc_dispatch(&mut self, _params: &[&[u8]], _bell_terminated: bool) {}
/// A final character has arrived for a CSI sequence
///
/// The `ignore` flag indicates that either more than two intermediates arrived
/// or the number of parameters exceeded the maximum supported length,
/// and subsequent characters were ignored.
fn csi_dispatch(
&mut self,
_params: &Params,
_intermediates: &[u8],
_ignore: bool,
_action: u8,
) {
}
/// The final character of an escape sequence has arrived.
///
/// The `ignore` flag indicates that more than two intermediates arrived and
/// subsequent characters were ignored.
fn esc_dispatch(&mut self, _intermediates: &[u8], _ignore: bool, _byte: u8) {}
}