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Diffstat (limited to '')
-rw-r--r-- | tvix/store/src/blobservice/dumb_seeker.rs | 110 |
1 files changed, 0 insertions, 110 deletions
diff --git a/tvix/store/src/blobservice/dumb_seeker.rs b/tvix/store/src/blobservice/dumb_seeker.rs deleted file mode 100644 index 6df4eb57f5f1..000000000000 --- a/tvix/store/src/blobservice/dumb_seeker.rs +++ /dev/null @@ -1,110 +0,0 @@ -use std::io; - -use tracing::{debug, instrument}; - -use super::BlobReader; - -/// This implements [io::Seek] for and [io::Read] by simply skipping over some -/// bytes, keeping track of the position. -/// It fails whenever you try to seek backwards. -pub struct DumbSeeker<R: io::Read> { - r: R, - pos: u64, -} - -impl<R: io::Read> DumbSeeker<R> { - pub fn new(r: R) -> Self { - DumbSeeker { r, pos: 0 } - } -} - -impl<R: io::Read> io::Read for DumbSeeker<R> { - fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> { - let bytes_read = self.r.read(buf)?; - - self.pos += bytes_read as u64; - - Ok(bytes_read) - } -} - -impl<R: io::Read> io::Seek for DumbSeeker<R> { - #[instrument(skip(self))] - fn seek(&mut self, pos: io::SeekFrom) -> io::Result<u64> { - let absolute_offset: u64 = match pos { - io::SeekFrom::Start(start_offset) => { - if start_offset < self.pos { - return Err(io::Error::new( - io::ErrorKind::Unsupported, - format!("can't seek backwards ({} -> {})", self.pos, start_offset), - )); - } else { - start_offset - } - } - // we don't know the total size, can't support this. - io::SeekFrom::End(_end_offset) => { - return Err(io::Error::new( - io::ErrorKind::Unsupported, - "can't seek from end", - )); - } - io::SeekFrom::Current(relative_offset) => { - if relative_offset < 0 { - return Err(io::Error::new( - io::ErrorKind::Unsupported, - "can't seek backwards relative to current position", - )); - } else { - self.pos + relative_offset as u64 - } - } - }; - - debug!(absolute_offset=?absolute_offset, "seek"); - - // we already know absolute_offset is larger than self.pos - debug_assert!( - absolute_offset >= self.pos, - "absolute_offset {} is larger than self.pos {}", - absolute_offset, - self.pos - ); - - // calculate bytes to skip - let bytes_to_skip: u64 = absolute_offset - self.pos; - - // discard these bytes. We can't use take() as it requires ownership of - // self.r, but we only have &mut self. - let mut buf = [0; 1024]; - let mut bytes_skipped: u64 = 0; - while bytes_skipped < bytes_to_skip { - let len = std::cmp::min(bytes_to_skip - bytes_skipped, buf.len() as u64); - match self.r.read(&mut buf[..len as usize]) { - Ok(0) => break, - Ok(n) => bytes_skipped += n as u64, - Err(ref e) if e.kind() == std::io::ErrorKind::Interrupted => {} - Err(e) => return Err(e), - } - } - - // This will fail when seeking past the end of self.r - if bytes_to_skip != bytes_skipped { - return Err(std::io::Error::new( - std::io::ErrorKind::UnexpectedEof, - format!( - "tried to skip {} bytes, but only was able to skip {} until reaching EOF", - bytes_to_skip, bytes_skipped - ), - )); - } - - self.pos = absolute_offset; - - // return the new position from the start of the stream - Ok(absolute_offset) - } -} - -/// A Cursor<Vec<u8>> can be used as a BlobReader. -impl<R: io::Read + Send + 'static> BlobReader for DumbSeeker<R> {} |