feat(tvix/nar): init writer
Change-Id: I101f35840cb14c58af708c91e59f997f6d167f75 Reviewed-on: https://cl.tvl.fyi/c/depot/+/7505 Reviewed-by: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI Autosubmit: tazjin <tazjin@tvl.su>
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7
tvix/nar/Cargo.lock
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7
tvix/nar/Cargo.lock
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# This file is automatically @generated by Cargo.
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# It is not intended for manual editing.
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version = 3
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[[package]]
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name = "tvix_nar"
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version = "0.0.0"
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4
tvix/nar/Cargo.toml
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4
tvix/nar/Cargo.toml
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[package]
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name = "tvix_nar"
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version = "0.0.0"
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edition = "2021"
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157
tvix/nar/src/lib.rs
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157
tvix/nar/src/lib.rs
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use std::io::{self, BufRead, ErrorKind::UnexpectedEof, Write};
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mod wire;
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pub type Writer<'a> = dyn Write + 'a;
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pub fn open<'a, 'w: 'a>(writer: &'a mut Writer<'w>) -> io::Result<Node<'a, 'w>> {
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let mut node = Node { writer };
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node.write(&wire::TOK_NAR)?;
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Ok(node)
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}
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pub struct Node<'a, 'w: 'a> {
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writer: &'a mut Writer<'w>,
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}
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impl<'a, 'w> Node<'a, 'w> {
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fn write(&mut self, data: &[u8]) -> io::Result<()> {
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self.writer.write_all(data)
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}
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fn pad(&mut self, n: u64) -> io::Result<()> {
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match (n & 7) as usize {
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0 => Ok(()),
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n => self.write(&[0; 8][n..]),
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}
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}
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pub fn symlink(mut self, target: &str) -> io::Result<()> {
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debug_assert!(
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target.len() <= wire::MAX_TARGET_LEN,
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"target.len() > {}",
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wire::MAX_TARGET_LEN
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);
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debug_assert!(
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!target.contains('\0'),
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"invalid target characters: {target:?}"
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);
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debug_assert!(!target.is_empty(), "empty target");
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self.write(&wire::TOK_SYM)?;
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self.write(&target.len().to_le_bytes())?;
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self.write(target.as_bytes())?;
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self.pad(target.len() as u64)?;
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self.write(&wire::TOK_PAR)?;
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Ok(())
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}
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pub fn file(mut self, executable: bool, size: u64, reader: &mut dyn BufRead) -> io::Result<()> {
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self.write(if executable {
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&wire::TOK_EXE
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} else {
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&wire::TOK_REG
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})?;
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self.write(&size.to_le_bytes())?;
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let mut need = size;
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while need != 0 {
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let data = reader.fill_buf()?;
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if data.is_empty() {
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return Err(UnexpectedEof.into());
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}
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let n = need.min(data.len() as u64) as usize;
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self.write(&data[..n])?;
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need -= n as u64;
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reader.consume(n);
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}
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self.pad(size)?;
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self.write(&wire::TOK_PAR)?;
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Ok(())
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}
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pub fn directory(mut self) -> io::Result<Directory<'a, 'w>> {
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self.write(&wire::TOK_DIR)?;
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Ok(Directory::new(self))
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}
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}
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#[cfg(debug_assertions)]
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type Name = String;
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#[cfg(not(debug_assertions))]
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type Name = ();
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fn into_name(_name: &str) -> Name {
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#[cfg(debug_assertions)]
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_name.to_owned()
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}
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pub struct Directory<'a, 'w> {
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node: Node<'a, 'w>,
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prev_name: Option<Name>,
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}
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impl<'a, 'w> Directory<'a, 'w> {
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fn new(node: Node<'a, 'w>) -> Self {
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Self {
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node,
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prev_name: None,
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}
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}
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pub fn entry(&mut self, name: &str) -> io::Result<Node<'_, 'w>> {
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debug_assert!(
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name.len() <= wire::MAX_NAME_LEN,
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"name.len() > {}",
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wire::MAX_NAME_LEN
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);
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debug_assert!(!["", ".", ".."].contains(&name), "invalid name: {name:?}");
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debug_assert!(
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!name.contains(['/', '\0']),
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"invalid name characters: {name:?}"
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);
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match self.prev_name {
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None => {
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self.prev_name = Some(into_name(name));
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}
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Some(ref mut _prev_name) => {
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#[cfg(debug_assertions)]
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{
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assert!(
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&**_prev_name < name,
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"misordered names: {_prev_name:?} >= {name:?}"
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);
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_prev_name.clear();
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_prev_name.push_str(name);
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}
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self.node.write(&wire::TOK_PAR)?;
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}
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}
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self.node.write(&wire::TOK_ENT)?;
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self.node.write(&name.len().to_le_bytes())?;
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self.node.write(name.as_bytes())?;
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self.node.pad(name.len() as u64)?;
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self.node.write(&wire::TOK_NOD)?;
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Ok(Node {
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writer: &mut *self.node.writer,
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})
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}
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pub fn close(mut self) -> io::Result<()> {
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if self.prev_name.is_some() {
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self.node.write(&wire::TOK_PAR)?;
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}
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self.node.write(&wire::TOK_PAR)?;
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Ok(())
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}
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}
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46
tvix/nar/src/wire.rs
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46
tvix/nar/src/wire.rs
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pub const MAX_NAME_LEN: usize = 255;
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pub const MAX_TARGET_LEN: usize = 4095;
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#[cfg(test)]
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fn token(xs: &[&str]) -> Vec<u8> {
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let mut out = vec![];
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for x in xs {
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let len = x.len() as u64;
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out.extend_from_slice(&len.to_le_bytes());
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out.extend_from_slice(x.as_bytes());
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let n = x.len() & 7;
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if n != 0 {
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const ZERO: [u8; 8] = [0; 8];
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out.extend_from_slice(&ZERO[n..]);
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}
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}
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out
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}
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pub const TOK_NAR: [u8; 56] = *b"\x0d\0\0\0\0\0\0\0nix-archive-1\0\0\0\x01\0\0\0\0\0\0\0(\0\0\0\0\0\0\0\x04\0\0\0\0\0\0\0type\0\0\0\0";
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pub const TOK_REG: [u8; 32] = *b"\x07\0\0\0\0\0\0\0regular\0\x08\0\0\0\0\0\0\0contents";
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pub const TOK_EXE: [u8; 64] = *b"\x07\0\0\0\0\0\0\0regular\0\x0a\0\0\0\0\0\0\0executable\0\0\0\0\0\0\0\0\0\0\0\0\0\0\x08\0\0\0\0\0\0\0contents";
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pub const TOK_SYM: [u8; 32] = *b"\x07\0\0\0\0\0\0\0symlink\0\x06\0\0\0\0\0\0\0target\0\0";
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pub const TOK_DIR: [u8; 24] = *b"\x09\0\0\0\0\0\0\0directory\0\0\0\0\0\0\0";
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pub const TOK_ENT: [u8; 48] = *b"\x05\0\0\0\0\0\0\0entry\0\0\0\x01\0\0\0\0\0\0\0(\0\0\0\0\0\0\0\x04\0\0\0\0\0\0\0name\0\0\0\0";
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pub const TOK_NOD: [u8; 48] = *b"\x04\0\0\0\0\0\0\0node\0\0\0\0\x01\0\0\0\0\0\0\0(\0\0\0\0\0\0\0\x04\0\0\0\0\0\0\0type\0\0\0\0";
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pub const TOK_PAR: [u8; 16] = *b"\x01\0\0\0\0\0\0\0)\0\0\0\0\0\0\0";
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#[test]
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fn tokens() {
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let cases: &[(&[u8], &[&str])] = &[
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(&TOK_NAR, &["nix-archive-1", "(", "type"]),
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(&TOK_REG, &["regular", "contents"]),
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(&TOK_EXE, &["regular", "executable", "", "contents"]),
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(&TOK_SYM, &["symlink", "target"]),
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(&TOK_DIR, &["directory"]),
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(&TOK_ENT, &["entry", "(", "name"]),
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(&TOK_NOD, &["node", "(", "type"]),
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(&TOK_PAR, &[")"]),
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];
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for &(tok, xs) in cases {
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assert_eq!(tok, token(xs));
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}
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}
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