tempest-kv 0.0.2

Key-Value storage layer for TempestDB
Documentation 
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use std::marker::PhantomData;

use bytes::Bytes;
use tempest_io::Io;

use crate::{
    StorageError,
    base::{Comparer, InternalKey, SeqNum},
    iterator::StorageIterator,
};

pub(crate) struct SnapshotIterator<I, C, S>
where
    I: Io,
    C: Comparer,
    S: StorageIterator<I, C>,
{
    inner: S,
    snapshot: SeqNum,
    _marker: PhantomData<(I, C)>,
}

impl<I, C, S> SnapshotIterator<I, C, S>
where
    I: Io,
    C: Comparer,
    S: StorageIterator<I, C>,
{
    pub fn new(inner: S, snapshot: SeqNum) -> Self {
        Self {
            inner,
            snapshot,
            _marker: PhantomData,
        }
    }
}

impl<I, C, S> StorageIterator<I, C> for SnapshotIterator<I, C, S>
where
    I: Io,
    C: Comparer,
    S: StorageIterator<I, C>,
{
    async fn next(&mut self) -> Result<Option<(InternalKey<C, Bytes>, Bytes)>, StorageError> {
        while let Some((key, value)) = self.inner.next().await? {
            if key.trailer().seqnum() <= self.snapshot {
                return Ok(Some((key, value)));
            }
            trace!(
                key.len = key.key().len(),
                entry_seqnum = key.trailer().seqnum().get(),
                snapshot = self.snapshot.get(),
                "snapshot_iter: skipping entry above snapshot"
            );
        }
        Ok(None)
    }

    async fn seek(&mut self, key: InternalKey<C, Bytes>) -> Result<(), StorageError> {
        self.inner.seek(key).await
    }
}