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use std::borrow::Cow;
use std::char;
use std::str;
/// A span, designating a range of bytes where a token is located.
#[derive(Eq, PartialEq, Debug, Clone, Copy)]
pub struct Span {
/// The start of the range.
pub start: usize,
/// The end of the range (exclusive).
pub end: usize,
}
impl From<Span> for (usize, usize) {
fn from(Span { start, end }: Span) -> (usize, usize) {
(start, end)
}
}
#[derive(Eq, PartialEq, Debug)]
pub enum Token<'a> {
Whitespace(&'a str),
Newline,
Comment(&'a str),
Equals,
Period,
Comma,
Colon,
Plus,
LeftBrace,
RightBrace,
LeftBracket,
RightBracket,
Keylike(&'a str),
String {
src: &'a str,
val: Cow<'a, str>,
multiline: bool,
},
}
#[derive(Eq, PartialEq, Debug)]
pub enum Error {
InvalidCharInString(usize, char),
InvalidEscape(usize, char),
InvalidHexEscape(usize, char),
InvalidEscapeValue(usize, u32),
NewlineInString(usize),
Unexpected(usize, char),
UnterminatedString(usize),
NewlineInTableKey(usize),
MultilineStringKey(usize),
Wanted {
at: usize,
expected: &'static str,
found: &'static str,
},
}
#[derive(Clone)]
pub struct Tokenizer<'a> {
input: &'a str,
chars: CrlfFold<'a>,
}
#[derive(Clone)]
struct CrlfFold<'a> {
chars: str::CharIndices<'a>,
}
#[derive(Debug)]
enum MaybeString {
NotEscaped(usize),
Owned(String),
}
impl<'a> Tokenizer<'a> {
pub fn new(input: &'a str) -> Tokenizer<'a> {
let mut t = Tokenizer {
input,
chars: CrlfFold {
chars: input.char_indices(),
},
};
// Eat utf-8 BOM
t.eatc('\u{feff}');
t
}
pub fn next(&mut self) -> Result<Option<(Span, Token<'a>)>, Error> {
let (start, token) = match self.one() {
Some((start, '\n')) => (start, Token::Newline),
Some((start, ' ' | '\t')) => (start, self.whitespace_token(start)),
Some((start, '#')) => (start, self.comment_token(start)),
Some((start, '=')) => (start, Token::Equals),
Some((start, '.')) => (start, Token::Period),
Some((start, ',')) => (start, Token::Comma),
Some((start, ':')) => (start, Token::Colon),
Some((start, '+')) => (start, Token::Plus),
Some((start, '{')) => (start, Token::LeftBrace),
Some((start, '}')) => (start, Token::RightBrace),
Some((start, '[')) => (start, Token::LeftBracket),
Some((start, ']')) => (start, Token::RightBracket),
Some((start, '\'')) => {
return self
.literal_string(start)
.map(|t| Some((self.step_span(start), t)))
}
Some((start, '"')) => {
return self
.basic_string(start)
.map(|t| Some((self.step_span(start), t)))
}
Some((start, ch)) if is_keylike(ch) => (start, self.keylike(start)),
Some((start, ch)) => return Err(Error::Unexpected(start, ch)),
None => return Ok(None),
};
let span = self.step_span(start);
Ok(Some((span, token)))
}
pub fn peek(&mut self) -> Result<Option<(Span, Token<'a>)>, Error> {
self.clone().next()
}
pub fn eat(&mut self, expected: Token<'a>) -> Result<bool, Error> {
self.eat_spanned(expected).map(|s| s.is_some())
}
/// Eat a value, returning it's span if it was consumed.
pub fn eat_spanned(&mut self, expected: Token<'a>) -> Result<Option<Span>, Error> {
let span = match self.peek()? {
Some((span, ref found)) if expected == *found => span,
Some(_) | None => return Ok(None),
};
drop(self.next());
Ok(Some(span))
}
pub fn expect(&mut self, expected: Token<'a>) -> Result<(), Error> {
// ignore span
let _ = self.expect_spanned(expected)?;
Ok(())
}
/// Expect the given token returning its span.
pub fn expect_spanned(&mut self, expected: Token<'a>) -> Result<Span, Error> {
let current = self.current();
match self.next()? {
Some((span, found)) => {
if expected == found {
Ok(span)
} else {
Err(Error::Wanted {
at: current,
expected: expected.describe(),
found: found.describe(),
})
}
}
None => Err(Error::Wanted {
at: self.input.len(),
expected: expected.describe(),
found: "eof",
}),
}
}
pub fn table_key(&mut self) -> Result<(Span, Cow<'a, str>), Error> {
let current = self.current();
match self.next()? {
Some((span, Token::Keylike(k))) => Ok((span, k.into())),
Some((
span,
Token::String {
src,
val,
multiline,
},
)) => {
let offset = self.substr_offset(src);
if multiline {
return Err(Error::MultilineStringKey(offset));
}
match src.find('\n') {
None => Ok((span, val)),
Some(i) => Err(Error::NewlineInTableKey(offset + i)),
}
}
Some((_, other)) => Err(Error::Wanted {
at: current,
expected: "a table key",
found: other.describe(),
}),
None => Err(Error::Wanted {
at: self.input.len(),
expected: "a table key",
found: "eof",
}),
}
}
pub fn eat_whitespace(&mut self) {
while self.eatc(' ') || self.eatc('\t') {
// ...
}
}
pub fn eat_comment(&mut self) -> Result<bool, Error> {
if !self.eatc('#') {
return Ok(false);
}
drop(self.comment_token(0));
self.eat_newline_or_eof().map(|()| true)
}
pub fn eat_newline_or_eof(&mut self) -> Result<(), Error> {
let current = self.current();
match self.next()? {
None | Some((_, Token::Newline)) => Ok(()),
Some((_, other)) => Err(Error::Wanted {
at: current,
expected: "newline",
found: other.describe(),
}),
}
}
pub fn skip_to_newline(&mut self) {
loop {
match self.one() {
Some((_, '\n')) | None => break,
_ => {}
}
}
}
fn eatc(&mut self, ch: char) -> bool {
match self.chars.clone().next() {
Some((_, ch2)) if ch == ch2 => {
self.one();
true
}
_ => false,
}
}
pub fn current(&mut self) -> usize {
match self.chars.clone().next() {
Some(i) => i.0,
None => self.input.len(),
}
}
fn whitespace_token(&mut self, start: usize) -> Token<'a> {
while self.eatc(' ') || self.eatc('\t') {
// ...
}
Token::Whitespace(&self.input[start..self.current()])
}
fn comment_token(&mut self, start: usize) -> Token<'a> {
while let Some((_, ch)) = self.chars.clone().next() {
if ch != '\t' && (ch < '\u{20}' || ch > '\u{10ffff}') {
break;
}
self.one();
}
Token::Comment(&self.input[start..self.current()])
}
fn read_string(
&mut self,
delim: char,
start: usize,
new_ch: &mut dyn FnMut(
&mut Tokenizer,
&mut MaybeString,
bool,
usize,
char,
) -> Result<(), Error>,
) -> Result<Token<'a>, Error> {
let mut multiline = false;
if self.eatc(delim) {
if self.eatc(delim) {
multiline = true;
} else {
return Ok(Token::String {
src: &self.input[start..start + 2],
val: Cow::Borrowed(""),
multiline: false,
});
}
}
let mut val = MaybeString::NotEscaped(self.current());
let mut n = 0;
loop {
n += 1;
match self.one() {
Some((i, '\n')) => {
if multiline {
if self.input.as_bytes()[i] == b'\r' {
val.make_owned(&self.input[..i]);
}
if n == 1 {
val = MaybeString::NotEscaped(self.current());
} else {
val.push('\n');
}
} else {
return Err(Error::NewlineInString(i));
}
}
Some((mut i, ch)) if ch == delim => {
if multiline {
if !self.eatc(delim) {
val.push(delim);
continue;
}
if !self.eatc(delim) {
val.push(delim);
val.push(delim);
continue;
}
if self.eatc(delim) {
val.push(delim);
i += 1;
}
if self.eatc(delim) {
val.push(delim);
i += 1;
}
}
return Ok(Token::String {
src: &self.input[start..self.current()],
val: val.into_cow(&self.input[..i]),
multiline,
});
}
Some((i, c)) => new_ch(self, &mut val, multiline, i, c)?,
None => return Err(Error::UnterminatedString(start)),
}
}
}
fn literal_string(&mut self, start: usize) -> Result<Token<'a>, Error> {
self.read_string('\'', start, &mut |_me, val, _multi, i, ch| {
if ch == '\u{09}' || ('\u{20}' <= ch && ch <= '\u{10ffff}' && ch != '\u{7f}') {
val.push(ch);
Ok(())
} else {
Err(Error::InvalidCharInString(i, ch))
}
})
}
fn basic_string(&mut self, start: usize) -> Result<Token<'a>, Error> {
self.read_string('"', start, &mut |me, val, multi, i, ch| match ch {
'\\' => {
val.make_owned(&me.input[..i]);
match me.chars.next() {
Some((_, '"')) => val.push('"'),
Some((_, '\\')) => val.push('\\'),
Some((_, 'b')) => val.push('\u{8}'),
Some((_, 'f')) => val.push('\u{c}'),
Some((_, 'n')) => val.push('\n'),
Some((_, 'r')) => val.push('\r'),
Some((_, 't')) => val.push('\t'),
Some((i, c @ ('u' | 'U'))) => {
let len = if c == 'u' { 4 } else { 8 };
val.push(me.hex(start, i, len)?);
}
Some((i, c @ (' ' | '\t' | '\n'))) if multi => {
if c != '\n' {
while let Some((_, ch)) = me.chars.clone().next() {
match ch {
' ' | '\t' => {
me.chars.next();
continue;
}
'\n' => {
me.chars.next();
break;
}
_ => return Err(Error::InvalidEscape(i, c)),
}
}
}
while let Some((_, ch)) = me.chars.clone().next() {
match ch {
' ' | '\t' | '\n' => {
me.chars.next();
}
_ => break,
}
}
}
Some((i, c)) => return Err(Error::InvalidEscape(i, c)),
None => return Err(Error::UnterminatedString(start)),
}
Ok(())
}
ch if ch == '\u{09}' || ('\u{20}' <= ch && ch <= '\u{10ffff}' && ch != '\u{7f}') => {
val.push(ch);
Ok(())
}
_ => Err(Error::InvalidCharInString(i, ch)),
})
}
fn hex(&mut self, start: usize, i: usize, len: usize) -> Result<char, Error> {
let mut buf = String::with_capacity(len);
for _ in 0..len {
match self.one() {
Some((_, ch)) if ch as u32 <= 0x7F && ch.is_ascii_hexdigit() => buf.push(ch),
Some((i, ch)) => return Err(Error::InvalidHexEscape(i, ch)),
None => return Err(Error::UnterminatedString(start)),
}
}
let val = u32::from_str_radix(&buf, 16).unwrap();
match char::from_u32(val) {
Some(ch) => Ok(ch),
None => Err(Error::InvalidEscapeValue(i, val)),
}
}
fn keylike(&mut self, start: usize) -> Token<'a> {
while let Some((_, ch)) = self.peek_one() {
if !is_keylike(ch) {
break;
}
self.one();
}
Token::Keylike(&self.input[start..self.current()])
}
pub fn substr_offset(&self, s: &'a str) -> usize {
assert!(s.len() <= self.input.len());
let a = self.input.as_ptr() as usize;
let b = s.as_ptr() as usize;
assert!(a <= b);
b - a
}
/// Calculate the span of a single character.
fn step_span(&mut self, start: usize) -> Span {
let end = match self.peek_one() {
Some(t) => t.0,
None => self.input.len(),
};
Span { start, end }
}
/// Peek one char without consuming it.
fn peek_one(&mut self) -> Option<(usize, char)> {
self.chars.clone().next()
}
/// Take one char.
pub fn one(&mut self) -> Option<(usize, char)> {
self.chars.next()
}
}
impl<'a> Iterator for CrlfFold<'a> {
type Item = (usize, char);
fn next(&mut self) -> Option<(usize, char)> {
self.chars.next().map(|(i, c)| {
if c == '\r' {
let mut attempt = self.chars.clone();
if let Some((_, '\n')) = attempt.next() {
self.chars = attempt;
return (i, '\n');
}
}
(i, c)
})
}
}
impl MaybeString {
fn push(&mut self, ch: char) {
match *self {
MaybeString::NotEscaped(..) => {}
MaybeString::Owned(ref mut s) => s.push(ch),
}
}
fn make_owned(&mut self, input: &str) {
match *self {
MaybeString::NotEscaped(start) => {
*self = MaybeString::Owned(input[start..].to_owned());
}
MaybeString::Owned(..) => {}
}
}
fn into_cow(self, input: &str) -> Cow<str> {
match self {
MaybeString::NotEscaped(start) => Cow::Borrowed(&input[start..]),
MaybeString::Owned(s) => Cow::Owned(s),
}
}
}
fn is_keylike(ch: char) -> bool {
('A' <= ch && ch <= 'Z')
|| ('a' <= ch && ch <= 'z')
|| ('0' <= ch && ch <= '9')
|| ch == '-'
|| ch == '_'
}
impl<'a> Token<'a> {
pub fn describe(&self) -> &'static str {
match *self {
Token::Keylike(_) => "an identifier",
Token::Equals => "an equals",
Token::Period => "a period",
Token::Comment(_) => "a comment",
Token::Newline => "a newline",
Token::Whitespace(_) => "whitespace",
Token::Comma => "a comma",
Token::RightBrace => "a right brace",
Token::LeftBrace => "a left brace",
Token::RightBracket => "a right bracket",
Token::LeftBracket => "a left bracket",
Token::String { multiline, .. } => {
if multiline {
"a multiline string"
} else {
"a string"
}
}
Token::Colon => "a colon",
Token::Plus => "a plus",
}
}
}