Struct Cursor 

pub struct Cursor<'a, K, A, N, T>
where
    K: DataTrait + ?Sized,
    A: DataTrait + ?Sized,
{ /* private fields */ }

A cursor for a layer file.

A cursor traverses a RowGroup. It can be positioned on a particular row or before or after the row group. (If the row group is empty, then the cursor can only be before or after the row group.)

Implementations

impl<'a, K, A, N, T> Cursor<'a, K, A, N, T>

where K: DataTrait + ?Sized, A: DataTrait + ?Sized, T: ColumnSpec,

pub unsafe fn move_next(&mut self) -> Result<(), Error>

Moves to the next row in the row group. If the cursor was previously before the row group, it moves to the first row; if it was on the last row, it moves after the row group.

Safety

Unsafe because rkyv deserialization is unsafe.

pub unsafe fn move_prev(&mut self) -> Result<(), Error>

Moves to the previous row in the row group. If the cursor was previously after the row group, it moves to the last row; if it was on the first row, it moves before the row group.

Safety

Unsafe because rkyv deserialization is unsafe.

pub unsafe fn move_first(&mut self) -> Result<(), Error>

Moves to the first row in the row group. If the row group is empty, this has no effect.

Safety

Unsafe because rkyv deserialization is unsafe.

pub unsafe fn move_last(&mut self) -> Result<(), Error>

Moves to the last row in the row group. If the row group is empty, this has no effect.

Safety

Unsafe because rkyv deserialization is unsafe.

pub unsafe fn move_to_row(&mut self, row: u64) -> Result<(), Error>

Moves to row row. If row >= self.len(), moves after the row group.

Safety

Unsafe because rkyv deserialization is unsafe.

pub fn key(&self) -> Option<&K>

Returns the key in the current row, or None if the cursor is before or after the row group.

pub unsafe fn aux<'b>(&self, aux: &'b mut A) -> Option<&'b mut A>

Returns the auxiliary data in the current row, or None if the cursor is before or after the row group.

Safety

Unsafe because rkyv deserialization is unsafe.

pub unsafe fn item<'b>( &self, item: (&'b mut K, &'b mut A), ) -> Option<(&'b mut K, &'b mut A)>

Returns the key and auxiliary data in the current row, or None if the cursor is before or after the row group.

Safety

Unsafe because rkyv deserialization is unsafe.

pub unsafe fn archived_item(&self) -> Option<&dyn ArchivedItem<'_, K, A>>

Returns archived representation of the key and auxiliary data in the current row, or None if the cursor is before or after the row group.

Safety

Unsafe because rkyv deserialization is unsafe.

pub fn has_value(&self) -> bool

Returns true if the cursor is on a row.

pub fn len(&self) -> u64

Returns the number of rows in the cursor’s row group.

pub fn is_empty(&self) -> bool

Returns true if this cursor’s row group has no rows.

pub fn absolute_position(&self) -> u64

Returns the row number of the current row, as an absolute number relative to the top of the column rather than the top of the row group. If the cursor is before the row group or on the first row, returns the row number of the first row in the row group; if the cursor is after the row group, returns the row number of the row just after the row group.

pub fn remaining_rows(&self) -> u64

Returns the number of times move_next may be called before the cursor is after the row group.

pub unsafe fn seek_forward_until<P>( &mut self, predicate: P, ) -> Result<(), Error>

where P: Fn(&K) -> bool + Clone,

Moves the cursor forward past rows for which predicate returns false, where predicate is a function such that if it is true for a given key, it is also true for all larger keys.

This function does not move the cursor if predicate is true for the current row or a previous row.

Safety

Unsafe because rkyv deserialization is unsafe.

pub unsafe fn advance_to_value_or_larger( &mut self, target: &K, ) -> Result<(), Error>

Moves the cursor forward past rows whose keys are less than target. This function does not move the cursor if the current row’s key is greater than or equal to target.

Safety

Unsafe because rkyv deserialization is unsafe.

pub unsafe fn advance_to_first_ge<C>( &mut self, compare: &C, ) -> Result<(), Error>

where C: Fn(&K) -> Ordering,

Moves the cursor forward past rows for which compare returns Less, where compare is a function such that if it returns Equal or Greater for a given key, it returns Greater for all larger keys.

This function does not move the cursor if compare returns Equal or Greater for the current row or a previous row.

Error handling

If this returns an error, then the cursor’s position might be lost. If so, then its position is advanced past the end of the row group.

Safety

Unsafe because rkyv deserialization is unsafe.

pub unsafe fn seek_backward_until<P>( &mut self, predicate: P, ) -> Result<(), Error>

where P: Fn(&K) -> bool + Clone,

Moves the cursor backward past rows for which predicate returns false, where predicate is a function such that if it is true for a given key, it is also true for all lesser keys.

This function does not move the cursor if predicate is true for the current row or a previous row.

Safety

Unsafe because rkyv deserialization is unsafe.

pub unsafe fn rewind_to_value_or_smaller( &mut self, target: &K, ) -> Result<(), Error>

where K: Ord,

Moves the cursor backward past rows whose keys are greater than target. This function does not move the cursor if the current row’s key is less than or equal to target.

Safety

Unsafe because rkyv deserialization is unsafe.

pub unsafe fn rewind_to_last_le<C>(&mut self, compare: &C) -> Result<(), Error>

where C: Fn(&K) -> Ordering,

Moves the cursor backward past rows for which compare returns Greater, where compare is a function such that if it returns Equal or Less for a given key, it returns Less for all lesser keys.

This function does not move the cursor if compare returns Equal or Less for the current row or a previous row.

Safety

Unsafe because rkyv deserialization is unsafe.

impl<'a, K, A, NK, NA, NN, T> Cursor<'a, K, A, (&'static NK, &'static NA, NN), T>

where K: DataTrait + ?Sized, A: DataTrait + ?Sized, NK: DataTrait + ?Sized, NA: DataTrait + ?Sized, T: ColumnSpec,

pub fn next_column<'b>(&'b self) -> Result<RowGroup<'a, NK, NA, NN, T>, Error>

Obtains the row group in the next column associated with the current row. If the cursor is on a row, the returned row group will contain at least one row. If the cursor is before or after the row group, the returned row group will be empty.

This method does not do I/O, but it can report Error::Corruption.

Trait Implementations

impl<K, A, N, T> Clone for Cursor<'_, K, A, N, T>

where K: DataTrait + ?Sized, A: DataTrait + ?Sized,

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<K, A, N, T> Debug for Cursor<'_, K, A, N, T>

where K: DataTrait + ?Sized, A: DataTrait + ?Sized,

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

Formats the value using the given formatter.