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|
use std::{
mem::MaybeUninit,
pin::Pin,
task::{self, Poll},
};
use tokio::io::{self, AsyncBufRead, AsyncRead, ErrorKind::InvalidData};
// Required reading for understanding this module.
use crate::{
nar::{self, wire::PadPar},
wire::{self, BytesReader},
};
mod read;
#[cfg(test)]
mod test;
pub type Reader<'a> = dyn AsyncBufRead + Unpin + Send + 'a;
/// Start reading a NAR file from `reader`.
pub async fn open<'a, 'r>(reader: &'a mut Reader<'r>) -> io::Result<Node<'a, 'r>> {
read::token(reader, &nar::wire::TOK_NAR).await?;
Node::new(reader).await
}
pub enum Node<'a, 'r: 'a> {
Symlink {
target: Vec<u8>,
},
File {
executable: bool,
reader: FileReader<'a, 'r>,
},
Directory(DirReader<'a, 'r>),
}
impl<'a, 'r: 'a> Node<'a, 'r> {
/// Start reading a [Node], matching the next [wire::Node].
///
/// Reading the terminating [wire::TOK_PAR] is done immediately for [Node::Symlink],
/// but is otherwise left to [DirReader] or [BytesReader].
async fn new(reader: &'a mut Reader<'r>) -> io::Result<Self> {
Ok(match read::tag(reader).await? {
nar::wire::Node::Sym => {
let target = wire::read_bytes(reader, 1..=nar::wire::MAX_TARGET_LEN).await?;
if target.contains(&0) {
return Err(InvalidData.into());
}
read::token(reader, &nar::wire::TOK_PAR).await?;
Node::Symlink { target }
}
tag @ (nar::wire::Node::Reg | nar::wire::Node::Exe) => Node::File {
executable: tag == nar::wire::Node::Exe,
reader: FileReader {
inner: BytesReader::new_internal(reader, ..).await?,
},
},
nar::wire::Node::Dir => Node::Directory(DirReader::new(reader)),
})
}
}
/// File contents, readable through the [AsyncRead] trait.
///
/// It comes with some caveats:
/// * You must always read the entire file, unless you intend to abandon the entire archive reader.
/// * You must abandon the entire archive reader upon the first error.
///
/// It's fine to read exactly `reader.len()` bytes without ever seeing an explicit EOF.
pub struct FileReader<'a, 'r> {
inner: BytesReader<&'a mut Reader<'r>, PadPar>,
}
impl<'a, 'r> FileReader<'a, 'r> {
pub fn is_empty(&self) -> bool {
self.len() == 0
}
pub fn len(&self) -> u64 {
self.inner.len()
}
}
impl<'a, 'r> AsyncRead for FileReader<'a, 'r> {
fn poll_read(
self: Pin<&mut Self>,
cx: &mut task::Context,
buf: &mut io::ReadBuf,
) -> Poll<io::Result<()>> {
Pin::new(&mut self.get_mut().inner).poll_read(cx, buf)
}
}
impl<'a, 'r> AsyncBufRead for FileReader<'a, 'r> {
fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut task::Context) -> Poll<io::Result<&[u8]>> {
Pin::new(&mut self.get_mut().inner).poll_fill_buf(cx)
}
fn consume(self: Pin<&mut Self>, amt: usize) {
Pin::new(&mut self.get_mut().inner).consume(amt)
}
}
/// A directory iterator, yielding a sequence of [Node]s.
/// It must be fully consumed before reading further from the [DirReader] that produced it, if any.
pub struct DirReader<'a, 'r> {
reader: &'a mut Reader<'r>,
/// Previous directory entry name.
/// We have to hang onto this to enforce name monotonicity.
prev_name: Vec<u8>,
}
pub struct Entry<'a, 'r> {
pub name: &'a [u8],
pub node: Node<'a, 'r>,
}
impl<'a, 'r> DirReader<'a, 'r> {
fn new(reader: &'a mut Reader<'r>) -> Self {
Self {
reader,
prev_name: vec![],
}
}
/// Read the next [Entry] from the directory.
///
/// We explicitly don't implement [Iterator], since treating this as
/// a regular Rust iterator will surely lead you astray.
///
/// * You must always consume the entire iterator, unless you abandon the entire archive reader.
/// * You must abandon the entire archive reader on the first error.
/// * You must abandon the directory reader upon the first [None].
/// * Even if you know the amount of elements up front, you must keep reading until you encounter [None].
pub async fn next(&mut self) -> io::Result<Option<Entry<'_, 'r>>> {
// COME FROM the previous iteration: if we've already read an entry,
// read its terminating TOK_PAR here.
if !self.prev_name.is_empty() {
read::token(self.reader, &nar::wire::TOK_PAR).await?;
}
if let nar::wire::Entry::None = read::tag(self.reader).await? {
return Ok(None);
}
let mut name = [MaybeUninit::uninit(); nar::wire::MAX_NAME_LEN + 1];
let name =
wire::read_bytes_buf(self.reader, &mut name, 1..=nar::wire::MAX_NAME_LEN).await?;
if name.contains(&0) || name.contains(&b'/') || name == b"." || name == b".." {
return Err(InvalidData.into());
}
// Enforce strict monotonicity of directory entry names.
if &self.prev_name[..] >= name {
return Err(InvalidData.into());
}
self.prev_name.clear();
self.prev_name.extend_from_slice(name);
read::token(self.reader, &nar::wire::TOK_NOD).await?;
Ok(Some(Entry {
name: &self.prev_name,
node: Node::new(self.reader).await?,
}))
}
}
|
