Struct SparseCache 

pub struct SparseCache { /* private fields */ }

A tempfile-backed cache that tracks populated byte ranges.

Implementations

impl SparseCache

pub fn new(total_size: u64, spool_dir: &Path) -> Result<Self>

Create a new sparse cache for a file of the given total size.

Allocates an unlinked temp file in spool_dir (see crate::spool; the cache holds every byte read so far, so it must not land in a tmpfs) and sets its length so that sparse reads past the end don’t accidentally return 0 bytes before the caller has fetched them.

pub fn missing_ranges(&self, offset: u64, size: u64) -> Vec<Range<u64>>

Returns the byte ranges within [offset, offset+size) that are NOT yet populated.

The returned ranges are sorted and clipped to [0, total_size). If the entire requested range is already populated, returns an empty Vec.

pub fn write_at(&mut self, offset: u64, data: &[u8]) -> Result<()>

Write data at offset and mark [offset, offset+data.len()) as populated.

pub fn read_at(&mut self, offset: u64, size: u64) -> Result<Vec<u8>>

Read size bytes at offset from the tempfile.

Callers must ensure the requested range is fully populated (check with missing_ranges and fill gaps via write_at). Reads past total_size return a short slice.

Trait Implementations

impl Debug for SparseCache

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.