Struct PooledIter 

pub struct PooledIter<I, BorrowedItem: ToOwned> { /* private fields */ }

Available on crate feature anchored-pool only.

Convert a CursorLendingIterator into a CursorPooledIterator by storing recently accessed items in reusable buffers.

This effectively allows the iterator to lend out multiple items at once, unlike a lending iterator which can only lend out one. This comes primarily at the cost of extra copying into buffers, and in memory usage. The costs of allocating buffers is likely amortized by their reuse.

The user of a PooledIter is required not to attempt to get more PoolItems than there are buffers in the PooledIter; because PooledIter can only be used from a single thread, it is impossible for a buffer to be returned to the iterator while PooledIter::next is running, for example, unlike with the ThreadsafePooledIter type. Therefore, PooledIter panics in such a scenario.

Implementations

impl<I, BorrowedItem> PooledIter<I, BorrowedItem>

where BorrowedItem: ToOwned, BorrowedItem::Owned: Default,

pub fn new(iter: I, num_buffers: usize) -> Self

Create a PooledIter that can lend out up to num_buffers items at a time.

The user of a PooledIter is required not to attempt to get more than num_buffers PoolItems from this PooledIter at a time; because PooledIter can only be used from a single thread, it is impossible for a buffer to be returned to the iterator while PooledIter::next is running, for example, unlike with the ThreadsafePooledIter type. Therefore, PooledIter panics in such a scenario.

Trait Implementations

impl<I, BorrowedItem> CursorPooledIterator for PooledIter<I, BorrowedItem>

where I: CursorLendingIterator, BorrowedItem: ToOwned, for<'lend> LentItem<'lend, I>: Borrow<BorrowedItem>,

fn current(&self) -> Option<Self::Item>

Get the current value the iterator is at, if the iterator is valid.

Panics

Panics if there are no buffers available.

fn prev(&mut self) -> Option<Self::Item>

Move the iterator one position back, and return the entry at that position. Returns None if the iterator was at the first entry.

Some iterator implementations used as I may have worse performance for backwards iteration than forwards iteration, so prefer to not use prev.

Panics

Panics if there are no buffers available.

fn valid(&self) -> bool

Determine whether the iterator is currently at any value in the collection. If the iterator is invalid, then it is conceptually one position before the first entry and one position after the last entry. (Or, there may be no entries.)

fn try_current(&self) -> Result<Option<Self::Item>, OutOfBuffers>

If a buffer is available, get the current value the iterator is at, if the iterator is valid.

fn try_prev(&mut self) -> Result<Option<Self::Item>, OutOfBuffers>

If a buffer is available, move the iterator one position back, and return the entry at that position. Returns Ok(None) if the iterator was at the first entry.

impl<I: Debug, BorrowedItem: Debug + ToOwned> Debug for PooledIter<I, BorrowedItem>

where BorrowedItem::Owned: Debug,

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

Formats the value using the given formatter.

impl<I, BorrowedItem> PooledIterator for PooledIter<I, BorrowedItem>

where I: CursorLendingIterator, BorrowedItem: ToOwned, for<'lend> LentItem<'lend, I>: Borrow<BorrowedItem>,

fn next(&mut self) -> Option<Self::Item>

Move the iterator one position forwards, and return the entry at that position. Returns None if the iterator was at the last entry.

Panics

Panics if there are no buffers available.

type Item = PoolItem<<BorrowedItem as ToOwned>::Owned>

The item of this iterator, which likely has a nontrivial drop implementation that returns a buffer to the iterator’s buffer pool.

fn try_next(&mut self) -> Result<Option<Self::Item>, OutOfBuffers>

If a buffer is available, move the iterator one position forwards, and return the entry at that position. Returns Ok(None) if the iterator was at the last entry.

fn buffer_pool_size(&self) -> usize

Get the total number of buffers in the buffer pool, including buffers that are currently in use.

fn available_buffers(&self) -> usize

Get the number of buffers that are currently available.

fn into_lender(self) -> PooledLenderAdapter<Self>

where Self: Sized,

Available on crate feature lender only.

Convert the PooledIterator into a lender::Lender lending iterator which only uses one buffer at a time.

fn into_lending_iterator(self) -> PooledLendingIteratorAdapter<Self>

where Self: Sized,

Available on crate feature lending-iterator only.

Convert the PooledIterator into a lending_iterator::LendingIterator which only uses one buffer at a time.

impl<I, BorrowedItem, Key, Cmp> Seekable<Key, Cmp> for PooledIter<I, BorrowedItem>

where I: CursorLendingIterator + Seekable<Key, Cmp>, BorrowedItem: ToOwned, Key: ?Sized, Cmp: Comparator<Key>, for<'lend> LentItem<'lend, I>: Borrow<BorrowedItem>,

fn reset(&mut self)

Reset the iterator to its initial position, before the first entry and after the last entry (if there are any entries in the collection).

fn seek(&mut self, min_bound: &Key)

Move the iterator to the smallest key which is greater or equal than the provided min_bound.

fn seek_before(&mut self, strict_upper_bound: &Key)

Move the iterator to the greatest key which is strictly less than the provided strict_upper_bound.

fn seek_to_first(&mut self)

Move the iterator to the smallest key in the collection.

fn seek_to_last(&mut self)

Move the iterator to the greatest key in the collection.