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use std::convert::Infallible;
use std::io::{self, BufRead, BufReader, Read};
/// An object that provides characters to the tokenizer.
///
/// Patches are welcome for providing an efficient implementation over async streams,
/// iterators, files, etc, as long as any dependencies come behind featureflags.
pub trait Reader {
/// The error returned by this reader.
type Error: std::error::Error;
/// Return a new character from the input stream.
///
/// The input stream does **not** have to be preprocessed in any way, it can contain standalone
/// surrogates and have inconsistent newlines.
fn read_char(&mut self) -> Result<Option<char>, Self::Error>;
/// Attempt to read an entire string at once, either case-insensitively or not.
///
/// `case_sensitive=false` means that characters of the input stream should be compared while
/// ignoring ASCII-casing.
///
/// It can be assumed that this function is never called with a string that contains `\r` or
/// `\n`.
///
/// If the next characters equal to `s`, this function consumes the respective characters from
/// the input stream and returns `true`. If not, it does nothing and returns `false`.
fn try_read_string(&mut self, s: &str, case_sensitive: bool) -> Result<bool, Self::Error>;
}
/// An object that can be converted into a [`crate::Reader`].
///
/// For example, any utf8-string can be converted into a `StringReader`, such that
/// `Tokenizer::new("mystring")` and `Tokenizer::new(&String::new("foo"))` work.
pub trait IntoReader<'a> {
/// The reader type into which this type should be converted.
type Reader: Reader + 'a;
/// Convert self into some sort of reader.
fn into_reader(self) -> Self::Reader;
}
impl<'a, R: 'a + Reader> IntoReader<'a> for R {
type Reader = Self;
fn into_reader(self) -> Self::Reader {
self
}
}
/// A helper struct to seek forwards and backwards in strings. Used by the tokenizer to read HTML
/// from strings.
pub struct StringReader<'a> {
input: &'a str,
cursor: std::str::Chars<'a>,
pos: usize,
}
impl<'a> StringReader<'a> {
fn new(input: &'a str) -> Self {
let cursor = input.chars();
StringReader {
input,
cursor,
pos: 0,
}
}
}
impl<'a> Reader for StringReader<'a> {
type Error = Infallible;
fn read_char(&mut self) -> Result<Option<char>, Self::Error> {
let c = match self.cursor.next() {
Some(c) => c,
None => return Ok(None),
};
self.pos += c.len_utf8();
Ok(Some(c))
}
fn try_read_string(&mut self, s1: &str, case_sensitive: bool) -> Result<bool, Self::Error> {
// we do not need to call validate_char here because `s` hopefully does not contain invalid
// characters
if let Some(s2) = self.input.get(self.pos..self.pos + s1.len()) {
if s1 == s2 || (!case_sensitive && s1.eq_ignore_ascii_case(s2)) {
self.pos += s1.len();
self.cursor = self.input[self.pos..].chars();
return Ok(true);
}
}
Ok(false)
}
}
impl<'a> IntoReader<'a> for &'a str {
type Reader = StringReader<'a>;
fn into_reader(self) -> Self::Reader {
StringReader::new(self)
}
}
impl<'a> IntoReader<'a> for &'a String {
type Reader = StringReader<'a>;
fn into_reader(self) -> Self::Reader {
StringReader::new(self.as_str())
}
}
/// A [`BufReadReader`] can be used to construct a tokenizer from any type that implements
/// `BufRead`.
pub struct BufReadReader<R: BufRead> {
line: String,
line_pos: usize,
reader: R,
}
impl<R: BufRead> BufReadReader<R> {
/// Construct a new `BufReadReader` from any type that implements `BufRead`.
pub fn new(reader: R) -> Self {
BufReadReader {
line: String::new(),
line_pos: 0,
reader,
}
}
#[inline]
fn get_remaining_line(&mut self) -> Result<&str, io::Error> {
if self.line_pos < self.line.len() {
return Ok(&self.line[self.line_pos..]);
}
self.line.clear();
self.line_pos = 0;
self.reader.read_line(&mut self.line)?;
Ok(&self.line)
}
}
impl<R: BufRead> Reader for BufReadReader<R> {
type Error = io::Error;
fn read_char(&mut self) -> Result<Option<char>, Self::Error> {
let rv = self.get_remaining_line()?.chars().next();
self.line_pos += rv.map(char::len_utf8).unwrap_or(1);
Ok(rv)
}
fn try_read_string(&mut self, s1: &str, case_sensitive: bool) -> Result<bool, Self::Error> {
debug_assert!(!s1.contains('\r'));
debug_assert!(!s1.contains('\n'));
if let Some(s2) = self.get_remaining_line()?.get(..s1.len()) {
if s1 == s2 || (!case_sensitive && s1.eq_ignore_ascii_case(s2)) {
self.line_pos += s1.len();
return Ok(true);
}
}
Ok(false)
}
}
impl<'a, R: Read + 'a> IntoReader<'a> for BufReader<R> {
type Reader = BufReadReader<BufReader<R>>;
fn into_reader(self) -> Self::Reader {
BufReadReader::new(self)
}
}
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