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//! Some usefull functions
use std::io;
use std::os::fd::{AsFd, AsRawFd};
use serde::Deserialize;
use serde_json::{Deserializer, Error as JsonError};
/// Read from a raw file descriptor to the vector.
///
/// Appends data at the end of the buffer. Resizes vector as needed.
#[allow(clippy::needless_pass_by_ref_mut)]
pub fn read_to_vec(fd: &mut impl AsFd, buf: &mut Vec<u8>) -> io::Result<usize> {
if buf.capacity() - buf.len() < 1024 {
buf.reserve(buf.capacity().max(1024));
}
let res = unsafe {
libc::read(
fd.as_fd().as_raw_fd(),
buf.as_mut_ptr().add(buf.len()) as *mut libc::c_void,
(buf.capacity() - buf.len()) as libc::size_t,
)
};
if res == -1 {
return Err(io::Error::last_os_error());
}
let read = res as usize;
unsafe { buf.set_len(buf.len() + read) };
Ok(read)
}
/// Retuns (`last_line`, `remaining`). See tests for examples.
pub fn last_line(s: &[u8]) -> Option<(&[u8], &[u8])> {
let mut it = memchr::memrchr_iter(b'\n', s);
let last = it.next()?;
let rem = &s[(last + 1)..];
if let Some(pre_last) = it.next() {
Some((&s[(pre_last + 1)..last], rem))
} else {
Some((&s[..last], rem))
}
}
/// Deserialize the last complete object. Returns (`object`, `remaining`). See tests for examples.
pub fn de_last_json<'a, T: Deserialize<'a>>(
mut s: &'a [u8],
) -> Result<(Option<T>, &'a [u8]), JsonError> {
let mut last = None;
let mut tmp;
loop {
(tmp, s) = de_first_json(s)?;
last = match tmp {
Some(obj) => Some(obj),
None => return Ok((last, s)),
};
}
}
/// Deserialize the first complete object. Returns (`object`, `remaining`). See tests for examples.
pub fn de_first_json<'a, T: Deserialize<'a>>(
mut s: &'a [u8],
) -> Result<(Option<T>, &'a [u8]), JsonError> {
while s
.first()
.map_or(false, |&x| x == b' ' || x == b',' || x == b'\n')
{
s = &s[1..];
}
let mut de = Deserializer::from_slice(s).into_iter();
match de.next() {
Some(Ok(obj)) => Ok((Some(obj), &s[de.byte_offset()..])),
Some(Err(e)) if e.is_eof() => Ok((None, &s[de.byte_offset()..])),
Some(Err(e)) => Err(e),
None => Ok((None, &s[de.byte_offset()..])),
}
}
/// Returns a byte slice with leading ASCII whitespace bytes removed.
///
/// TODO: remove if/when slice::trim_ascii_start is stabilized.
pub fn trim_ascii_start(mut bytes: &[u8]) -> &[u8] {
while let [first, rest @ ..] = bytes {
if first.is_ascii_whitespace() {
bytes = rest;
} else {
break;
}
}
bytes
}
#[cfg(test)]
mod tests {
use super::*;
macro_rules! str {
($str:expr) => {
&$str.as_bytes()[..]
};
}
#[test]
fn streaming_json() {
let s = b",[2]\n, [3], [4, 3],[32][3] ";
assert_eq!(
de_first_json::<Vec<u8>>(s).unwrap(),
(Some(vec![2]), str!("\n, [3], [4, 3],[32][3] "))
);
assert_eq!(
de_last_json::<Vec<u8>>(s).unwrap(),
(Some(vec![3]), str!(""))
);
let s = b",[2]\n, [3], [4, 3],[32][3] [2, 4";
assert_eq!(
de_last_json::<Vec<u8>>(s).unwrap(),
(Some(vec![3]), str!("[2, 4"))
);
let s = b",[2]\n, [3], [4, 3],[32] invalid";
assert_eq!(
de_first_json::<Vec<u8>>(s).unwrap(),
(Some(vec![2]), str!("\n, [3], [4, 3],[32] invalid"))
);
assert!(de_last_json::<Vec<u8>>(s).is_err());
}
#[test]
fn test_last_line() {
let s = b"hello";
assert_eq!(last_line(s), None);
let s = b"hello\n";
assert_eq!(last_line(s), Some((str!("hello"), str!(""))));
let s = b"hello\nworld";
assert_eq!(last_line(s), Some((str!("hello"), str!("world"))));
let s = b"hello\nworld\n";
assert_eq!(last_line(s), Some((str!("world"), str!(""))));
let s = b"hello\nworld\n...";
assert_eq!(last_line(s), Some((str!("world"), str!("..."))));
}
#[test]
fn test_trim_start() {
let s = b" ";
assert_eq!(trim_ascii_start(s), b"");
let s = b"hello";
assert_eq!(trim_ascii_start(s), b"hello");
let s = b"\t \nhello";
assert_eq!(trim_ascii_start(s), b"hello");
let s = b" \t \nhello\n";
assert_eq!(trim_ascii_start(s), b"hello\n");
}
}
|
