Trait Blob

Source

pub trait Blob:
    Clone
    + Send
    + Sync
    + 'static {
    // Required methods
    fn read_at_buf(
        &self,
        offset: u64,
        len: usize,
        bufs: impl Into<IoBufsMut> + Send,
        options: ReadOptions,
    ) -> impl Future<Output = Result<IoBufsMut, Error>> + Send;
    fn read_at(
        &self,
        offset: u64,
        len: usize,
        options: ReadOptions,
    ) -> impl Future<Output = Result<IoBufsMut, Error>> + Send;
    fn write_at(
        &self,
        offset: u64,
        bufs: impl Into<IoBufs> + Send,
        options: WriteOptions,
    ) -> impl Future<Output = Result<(), Error>> + Send;
    fn resize(&self, len: u64) -> impl Future<Output = Result<(), Error>> + Send;
    fn sync(&self) -> impl Future<Output = Result<(), Error>> + Send;
    fn start_sync(&self) -> impl Future<Output = Handle<()>> + Send;
}

Expand description

Interface to read and write to a blob.

To support blob implementations that enable concurrent reads and writes, blobs are responsible for maintaining synchronization.

Cloning a blob is similar to wrapping a single file descriptor in a lock whereas opening a new blob (of the same name) is similar to opening a new file descriptor. If multiple blobs are opened with the same name, they are not expected to coordinate access to underlying storage and writing to both is undefined behavior.

When a blob is dropped, any unsynced changes may be discarded. Implementations may attempt to sync during drop but errors will go unhandled. Call sync before dropping to ensure all changes are durably persisted.

§Durability

After a crash, a write not covered by a completed Blob::sync may be torn: any subset of its bytes may be durable. Bytes outside the written range remain unchanged.

Required Methods§

Source

fn read_at_buf( &self, offset: u64, len: usize, bufs: impl Into<IoBufsMut> + Send, options: ReadOptions, ) -> impl Future<Output = Result<IoBufsMut, Error>> + Send

Read exactly len bytes at offset into caller-provided buffers.

Returns the same buffers with their chunk layout preserved.

§Panics

Panics if len exceeds the total capacity of bufs.

Source

fn read_at( &self, offset: u64, len: usize, options: ReadOptions, ) -> impl Future<Output = Result<IoBufsMut, Error>> + Send

Read exactly len bytes at offset.

To reuse a buffer(s), use Blob::read_at_buf.

Source

fn write_at( &self, offset: u64, bufs: impl Into<IoBufs> + Send, options: WriteOptions, ) -> impl Future<Output = Result<(), Error>> + Send

Write every remaining byte in bufs to the blob at offset.

The buffers are treated as one logical byte sequence in chunk order.

Source

fn resize(&self, len: u64) -> impl Future<Output = Result<(), Error>> + Send

Resize the blob to the given length.

If the length is greater than the current length, the blob is extended with zeros. If the length is less than the current length, the blob is resized.

Source