seekable_iterator

Trait CursorPooledIterator

Source 
pub trait CursorPooledIterator: PooledIterator {
    // Required methods
    fn valid(&self) -> bool;
    fn current(&self) -> Option<Self::Item>;
    fn prev(&mut self) -> Option<Self::Item>;
    fn try_current(&self) -> Result<Option<Self::Item>, OutOfBuffers>;
    fn try_prev(&mut self) -> Result<Option<Self::Item>, OutOfBuffers>;
}
Expand description

A CursorPooledIterator provides access to the entries of some sorted collection, and can move its current position in either direction.

The iterator is similar to a lending iterator (which can lend one item at a time), but can make use of a buffer pool to lend out multiple items at a time.

Conceptually, it is circular, and its initial position is before the first entry and after the last entry. As such, it is not a FusedIterator, as continuing to call next() at the end of iteration wraps around to the start. (Note that if the collection is empty, then the iterator will remain at that phantom position.)

Implementations may or may not be threadsafe. Even if an implementation is threadsafe, newly-added entries may or may not be seen immediately by other threads.

Forwards iteration should be preferred over backwards iteration.

Required Methods§

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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.)

current() will be Some if and only if the iterator is valid.

Source

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

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

May need to wait for a buffer to become available.

§Potential Panics or Deadlocks

If self.buffer_pool_size() == 0, then this method may panic or deadlock.

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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.

May need to wait for a buffer to become available.

§Potential Panics or Deadlocks

If self.buffer_pool_size() == 0, then this method may panic or deadlock.

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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.

§Errors

Returns an error if no buffers were available.

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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.

§Errors

Returns an error if no buffers were available.

Implementors§