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#![deny(missing_docs)]
use std::io::Read;
use std::fmt::{Display,Formatter};
use smallvec::SmallVec;
#[derive(Debug)]
pub enum Error {
NotAnUtf8(Vec<u8>),
Io(std::io::Error),
EOF,
}
impl Display for Error {
fn fmt(&self, f: &mut Formatter) -> std::fmt::Result {
match self {
Error::EOF => write!(f, "end of file"),
Error::NotAnUtf8(b) => write!(f, "invalid utf-8 sequence: {:?}", b),
Error::Io(e) => write!(f, "i/o error: {}", e),
}
}
}
impl std::error::Error for Error {
fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
match self {
Error::Io(e) => Some(e),
_ => None,
}
}
}
const MAX_UNICODE_LEN : usize = 6;
#[inline]
pub fn read_next_char<R: Read>(r: &mut R) -> Result<char, Error> {
let mut offset = 0;
let mut buf = SmallVec::<[u8; MAX_UNICODE_LEN+1]>::new();
buf.push(0);
loop {
debug_assert!(!buf.spilled());
if buf.len() > MAX_UNICODE_LEN {
return Err(Error::NotAnUtf8(buf.to_vec()));
}
match r.read(&mut buf[offset..offset+1]) {
Err(e) => return Err(Error::Io(e)),
Ok(0) => return Err(Error::EOF),
Ok(_) => {},
};
match std::str::from_utf8(&buf) {
Ok(s) => {
return Ok(s.chars().next().unwrap());
},
Err(_) => {
buf.push(0);
offset += 1;
}
}
}
}
pub struct ReadIter<R: Read> {
r: R
}
impl<R: Read> ReadIter<R> {
pub fn new(r: R) -> Self {
ReadIter{r}
}
}
impl<R: Read> Iterator for ReadIter<R> {
type Item = Result<char, Error>;
fn next(&mut self) -> Option<Self::Item> {
match read_next_char(&mut self.r) {
Err(Error::EOF) => None,
e @ Err(_) => Some(e),
c @ Ok(_) => Some(c),
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::io::Cursor;
use proptest::prelude::*;
#[test]
fn char_iter() {
let input = "foo bar baz";
let iter = ReadIter::new(Cursor::new(&input));
let output : Result<String,_> = iter.collect();
assert_eq!(input, output.unwrap());
}
#[test]
fn char_iter_unicode() {
let input = "ążł¥アあ𝓐";
let iter = ReadIter::new(Cursor::new(&input));
let output : Result<String,_> = iter.collect();
assert_eq!(input, output.unwrap());
}
#[test]
fn incorrect_input() {
let input = vec![195, 195, 195, 195, 195, 195, 0];
let iter = ReadIter::new(Cursor::new(&input));
let output : Result<Vec<_>,_> = iter.collect();
assert!(output.is_err());
if let Err(Error::NotAnUtf8(b)) = output {
assert_eq!(input, b);
} else {
panic!("invalid error: {:?}", output)
}
}
proptest! {
#[test]
fn any_correct_string(input in ".*") {
let iter = ReadIter::new(Cursor::new(&input));
let output : Result<String,_> = iter.collect();
assert_eq!(input, output.unwrap());
}
#[test]
fn incorrect_suffix_doesnt_prevent_prefix_decoding(prefix in ".*") {
let mut input : Vec<u8> = prefix.clone().into();
input.append(&mut vec![195, 195, 195, 195, 195, 195, 0]);
let iter = ReadIter::new(Cursor::new(&input));
let output : Result<String, _> = iter.take(prefix.chars().count()).collect();
assert_eq!(prefix, output.unwrap());
}
#[test]
fn incorrect_suffix_breaks_collect(prefix in ".*") {
let mut input : Vec<u8> = prefix.clone().into();
input.append(&mut vec![195, 195, 195, 195, 195, 195, 0]);
let iter = ReadIter::new(Cursor::new(&input));
let output : Result<String,_> = iter.collect();
if let Err(Error::NotAnUtf8(_)) = output {
} else {
panic!("invalid error: {:?}", output)
}
}
}
}