Struct FileScratch 

pub struct FileScratch { /* private fields */ }

A host Scratch over a temp file (milestone H): sequential appends go through a buffered writer; freeze flushes and memory-maps the file, so the staged pool is read (randomly and sequentially) straight from the map instead of RAM. Dropping it unmaps and deletes the temp file.

Implementations

impl FileScratch

pub fn create(path: impl Into<PathBuf>) -> Result<Self, HostError>

Creates (truncating) a staging file at path, ready for appends.

Errors

HostError::Io if the file cannot be created.

Trait Implementations

impl Drop for FileScratch

fn drop(&mut self)

Executes the destructor for this type.

fn pin_drop(self: Pin<&mut Self>)

🔬This is a nightly-only experimental API. (pin_ergonomics)

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.

impl Scratch for FileScratch

type Error = HostError

Implementation-specific failure (I/O error, host callback error…).

fn write(&mut self, bytes: &[u8]) -> Result<(), HostError>

Appends bytes to the staging area. Not to be called after freeze.

fn len(&self) -> u64

Bytes appended so far.

fn freeze(&mut self) -> Result<&[u8], HostError>

Ends the build and borrows everything written as one contiguous slice, for random and sequential reads (a file backing typically maps itself here). The borrow keeps the region alive, which is also what forbids a later write.

fn is_empty(&self) -> bool

Whether nothing has been written yet.