diff options
Diffstat (limited to 'tvix/glue/src')
| -rw-r--r-- | tvix/glue/src/refscan.rs | 265 |
1 files changed, 243 insertions, 22 deletions
diff --git a/tvix/glue/src/refscan.rs b/tvix/glue/src/refscan.rs index 0e0bb6c77828..4393c98614e5 100644 --- a/tvix/glue/src/refscan.rs +++ b/tvix/glue/src/refscan.rs @@ -6,62 +6,247 @@ //! //! The scanner itself is using the Wu-Manber string-matching algorithm, using //! our fork of the `wu-mamber` crate. - +use pin_project::pin_project; use std::collections::BTreeSet; +use std::pin::Pin; +use std::sync::Arc; +use std::task::{ready, Poll}; +use tokio::io::{AsyncBufRead, AsyncRead, ReadBuf}; use wu_manber::TwoByteWM; -pub const STORE_PATH_LEN: usize = "/nix/store/00000000000000000000000000000000".len(); - -/// Represents a "primed" reference scanner with an automaton that knows the set -/// of store paths to scan for. -pub struct ReferenceScanner<P: Ord + AsRef<[u8]>> { +/// A searcher that incapsulates the candidates and the Wu-Manber searcher. +/// This is separate from the scanner because we need to look for the same +/// pattern in multiple outputs and don't want to pay the price of constructing +/// the searcher for each build output. +pub struct ReferencePatternInner<P> { candidates: Vec<P>, + longest_candidate: usize, + // FUTUREWORK: Support overlapping patterns to be compatible with cpp Nix searcher: Option<TwoByteWM>, - matches: Vec<usize>, } -impl<P: Clone + Ord + AsRef<[u8]>> ReferenceScanner<P> { - /// Construct a new `ReferenceScanner` that knows how to scan for the given - /// candidate store paths. +#[derive(Clone)] +pub struct ReferencePattern<P> { + inner: Arc<ReferencePatternInner<P>>, +} + +impl<P> ReferencePattern<P> { + pub fn candidates(&self) -> &[P] { + &self.inner.candidates + } + + pub fn longest_candidate(&self) -> usize { + self.inner.longest_candidate + } +} + +impl<P: AsRef<[u8]>> ReferencePattern<P> { + /// Construct a new `ReferencePattern` that knows how to scan for the given + /// candidates. pub fn new(candidates: Vec<P>) -> Self { let searcher = if candidates.is_empty() { None } else { Some(TwoByteWM::new(&candidates)) }; + let longest_candidate = candidates.iter().fold(0, |v, c| v.max(c.as_ref().len())); - ReferenceScanner { - searcher, - candidates, - matches: Default::default(), + ReferencePattern { + inner: Arc::new(ReferencePatternInner { + searcher, + candidates, + longest_candidate, + }), } } +} + +impl<P> From<Vec<P>> for ReferencePattern<P> +where + P: AsRef<[u8]>, +{ + fn from(candidates: Vec<P>) -> Self { + Self::new(candidates) + } +} + +/// Represents a "primed" reference scanner with an automaton that knows the set +/// of bytes patterns to scan for. +pub struct ReferenceScanner<P> { + pattern: ReferencePattern<P>, + matches: Vec<bool>, +} - /// Scan the given str for all non-overlapping matches and collect them +impl<P: AsRef<[u8]>> ReferenceScanner<P> { + /// Construct a new `ReferenceScanner` that knows how to scan for the given + /// candidate bytes patterns. + pub fn new<IP: Into<ReferencePattern<P>>>(pattern: IP) -> Self { + let pattern = pattern.into(); + let matches = vec![false; pattern.candidates().len()]; + ReferenceScanner { pattern, matches } + } + + /// Scan the given buffer for all non-overlapping matches and collect them /// in the scanner. pub fn scan<S: AsRef<[u8]>>(&mut self, haystack: S) { - if haystack.as_ref().len() < STORE_PATH_LEN { + if haystack.as_ref().len() < self.pattern.longest_candidate() { return; } - if let Some(searcher) = &self.searcher { + if let Some(searcher) = &self.pattern.inner.searcher { for m in searcher.find(haystack) { - self.matches.push(m.pat_idx); + self.matches[m.pat_idx] = true; } } } + pub fn pattern(&self) -> &ReferencePattern<P> { + &self.pattern + } + + pub fn matches(&self) -> &[bool] { + &self.matches + } + + pub fn candidate_matches(&self) -> impl Iterator<Item = &P> { + let candidates = self.pattern.candidates(); + self.matches.iter().enumerate().filter_map(|(idx, found)| { + if *found { + Some(&candidates[idx]) + } else { + None + } + }) + } +} + +impl<P: Clone + Ord + AsRef<[u8]>> ReferenceScanner<P> { /// Finalise the reference scanner and return the resulting matches. pub fn finalise(self) -> BTreeSet<P> { - self.matches - .into_iter() - .map(|idx| self.candidates[idx].clone()) - .collect() + self.candidate_matches().cloned().collect() + } +} + +const DEFAULT_BUF_SIZE: usize = 8 * 1024; + +#[pin_project] +pub struct ReferenceReader<P, R> { + scanner: ReferenceScanner<P>, + buffer: Vec<u8>, + consumed: usize, + #[pin] + reader: R, +} + +impl<P, R> ReferenceReader<P, R> +where + P: AsRef<[u8]>, +{ + pub fn new(pattern: ReferencePattern<P>, reader: R) -> ReferenceReader<P, R> { + Self::with_capacity(DEFAULT_BUF_SIZE, pattern, reader) + } + + pub fn with_capacity( + capacity: usize, + pattern: ReferencePattern<P>, + reader: R, + ) -> ReferenceReader<P, R> { + // If capacity is not at least as long as longest_candidate we can't do a scan + let capacity = capacity.max(pattern.longest_candidate()); + ReferenceReader { + scanner: ReferenceScanner::new(pattern), + buffer: Vec::with_capacity(capacity), + consumed: 0, + reader, + } + } + + pub fn scanner(&self) -> &ReferenceScanner<P> { + &self.scanner + } +} + +impl<P, R> ReferenceReader<P, R> +where + P: Clone + Ord + AsRef<[u8]>, +{ + pub fn finalise(self) -> BTreeSet<P> { + self.scanner.finalise() + } +} + +impl<P, R> AsyncRead for ReferenceReader<P, R> +where + R: AsyncRead, + P: AsRef<[u8]>, +{ + fn poll_read( + mut self: Pin<&mut Self>, + cx: &mut std::task::Context<'_>, + buf: &mut tokio::io::ReadBuf<'_>, + ) -> Poll<std::io::Result<()>> { + let internal_buf = ready!(self.as_mut().poll_fill_buf(cx))?; + let amt = buf.remaining().min(internal_buf.len()); + buf.put_slice(&internal_buf[..amt]); + self.consume(amt); + Poll::Ready(Ok(())) + } +} + +impl<P, R> AsyncBufRead for ReferenceReader<P, R> +where + R: AsyncRead, + P: AsRef<[u8]>, +{ + fn poll_fill_buf( + self: Pin<&mut Self>, + cx: &mut std::task::Context<'_>, + ) -> Poll<std::io::Result<&[u8]>> { + let overlap = self.scanner.pattern.longest_candidate() - 1; + let mut this = self.project(); + // Still data in buffer + if *this.consumed < this.buffer.len() { + return Poll::Ready(Ok(&this.buffer[*this.consumed..])); + } + // We need to copy last `overlap` bytes to front to deal with references that overlap reads + if *this.consumed > overlap { + let start = this.buffer.len() - overlap; + this.buffer.copy_within(start.., 0); + this.buffer.truncate(overlap); + *this.consumed = overlap; + } + // Read at least until self.buffer.len() > overlap so we can do one scan + loop { + let filled = { + let mut buf = ReadBuf::uninit(this.buffer.spare_capacity_mut()); + ready!(this.reader.as_mut().poll_read(cx, &mut buf))?; + buf.filled().len() + }; + // SAFETY: We just read `filled` amount of data above + unsafe { + this.buffer.set_len(filled + this.buffer.len()); + } + if filled == 0 || this.buffer.len() > overlap { + break; + } + } + this.scanner.scan(&this.buffer); + Poll::Ready(Ok(&this.buffer[*this.consumed..])) + } + + fn consume(self: Pin<&mut Self>, amt: usize) { + debug_assert!(self.consumed + amt <= self.buffer.len()); + let this = self.project(); + *this.consumed += amt; } } #[cfg(test)] mod tests { + use rstest::rstest; + use tokio::io::AsyncReadExt as _; + use tokio_test::io::Builder; + use super::*; // The actual derivation of `nixpkgs.hello`. @@ -112,4 +297,40 @@ mod tests { assert!(result.contains(c)); } } + + #[rstest] + #[case::normal(8096, 8096)] + #[case::small_capacity(8096, 1)] + #[case::small_read(1, 8096)] + #[case::all_small(1, 1)] + #[tokio::test] + async fn test_reference_reader(#[case] chunk_size: usize, #[case] capacity: usize) { + let candidates = vec![ + // these exist in the drv: + "33l4p0pn0mybmqzaxfkpppyh7vx1c74p", + "pf80kikyxr63wrw56k00i1kw6ba76qik", + "cp65c8nk29qq5cl1wyy5qyw103cwmax7", + // this doesn't: + "fn7zvafq26f0c8b17brs7s95s10ibfzs", + ]; + let pattern = ReferencePattern::new(candidates.clone()); + let mut mock = Builder::new(); + for c in HELLO_DRV.as_bytes().chunks(chunk_size) { + mock.read(c); + } + let mock = mock.build(); + let mut reader = ReferenceReader::with_capacity(capacity, pattern, mock); + let mut s = String::new(); + reader.read_to_string(&mut s).await.unwrap(); + assert_eq!(s, HELLO_DRV); + + let result = reader.finalise(); + assert_eq!(result.len(), 3); + + for c in candidates[..3].iter() { + assert!(result.contains(c)); + } + } + + // FUTUREWORK: Test with large file } |