Enum Steps 

pub enum Steps {
    Stride {
        start: usize,
        len: usize,
        step: isize,
    },
    Padded {
        start: i128,
        len: usize,
        size: usize,
        stride: usize,
        edge: Edge,
    },
    Rotated {
        shift: usize,
        len: usize,
        stride: usize,
    },
    Table(Table),
}

The source offsets of one result axis. Regular patterns need no position table; a missing offset reads fill.

Variants

Stride

Consecutive offsets with a signed step.

Fields

start: usize

len: usize

step: isize

Padded

Positions along one source axis, reading past its ends under the edge mode.

Fields

start: i128

len: usize

size: usize

stride: usize

edge: Edge

Rotated

A whole source axis beginning at the shift and wrapping to the start.

Fields

shift: usize

len: usize

stride: usize

Table(Table)

Explicit source offsets.

Implementations

impl Steps

pub const FILL: usize = usize::MAX

The table entry that marks a fill.

pub fn along(len: usize, stride: usize) -> Self

Every position of an axis of len items with stride, in order.

pub fn row_major( lens: &[usize], scale: usize, start: usize, ) -> impl Iterator<Item = Self> + '_

One entry for each of lens, reading an array of those lengths in row-major order from position start, with every stride multiplied by scale.

pub fn table(offsets: Vec<usize>) -> Self

A table of offsets, with Steps::FILL where a fill goes.

pub fn scaled(self, k: usize) -> Self

This entry with its offsets k times as far apart, as where each position it reads is a cell of k items.

pub fn padded( start: i128, len: usize, size: usize, stride: usize, edge: Edge, ) -> Self

len positions from start along an axis of size items with stride, read past the axis’s ends by edge: a Padded entry where a position falls outside the axis, the Rotated entry for a wrapped stretch as long as the axis, a Stride of step 0 for an axis of one item that an edge other than Fill reads, and otherwise the Stride that reads the same offsets.

pub fn clipped(start: i128, len: usize, size: usize, stride: usize) -> Self

padded with a fill past the axis’s ends.

pub fn rotated(shift: usize, len: usize, stride: usize) -> Self

All len positions of an axis with stride, from position shift, wrapping round: a Rotated entry, or the Stride that reads the same offsets where the shift is a whole turn.

pub fn len(&self) -> usize

The number of offsets.

pub fn footprint(&self) -> usize

The bytes this entry takes: itself, and a table’s listed offsets.

pub fn get(&self, j: usize) -> Option<usize>

Offset j, or None for a fill.

pub fn offsets(&self) -> impl ExactSizeIterator<Item = Option<usize>> + '_

Every offset, in order, None for a fill.

pub fn for_each(&self, each: impl FnMut(usize, Option<usize>))

Calls each with each position along this axis and its offset, or None where it gives a fill. It matches the kind of step once, before its loop. A loop through Steps::offsets or Steps::get matches it at every position, and makes a call there wherever LLVM keeps get out of line, as it can despite #[inline].

pub fn count(steps: &[impl Borrow<Self>]) -> usize

How many positions steps reach: the product of their lengths.

pub fn combined(base: usize, steps: &[impl Borrow<Self>]) -> Vec<usize>

The offset of every position that steps reach from base, in the order that walk visits them, with Steps::FILL where a fill goes. Steps::reach gives one of them.

pub fn reach( base: usize, steps: &[impl Borrow<Self>], i: usize, ) -> Option<usize>

The offset that steps, one entry for each axis, outermost first, reach from base for item i of their frame, or None for a fill.

pub fn furthest(base: usize, steps: &[impl Borrow<Self>]) -> Option<usize>

An offset that no item of steps passes from base: base plus each entry’s furthest offset, where a fill reaches none and a padded entry stops at the end of its axis. Only a table’s entry reads its offsets to find it. None where an entry has no items, so the walk reads nothing.

pub fn run( base: usize, steps: &[impl Borrow<Self>], start: usize, n: usize, ) -> Option<(usize, isize)>

The first source offset and stride of items start..start + n, where they form one regular run. Singleton axes disappear and neighbouring strides can form one run. Padded and rotated reads must stay within their valid, unwrapped part.

pub fn regular(steps: &[Self]) -> (usize, isize)

The innermost stretch of the frame whose items read at one regular stride, as its length and that stride: the product of the lengths of the innermost axes, outward, while each axis steps on from the ones inside it. Edges of padded and rotated axes don’t count, because only the runs that cross them copy. A run reads through run only where it lies inside one such stretch.

pub fn contiguous(steps: &[Self]) -> usize

How many consecutive items of the frame read adjacent offsets: the stretch that regular gives where its stride is 1. A run reads in place only inside one such stretch, so a frame whose stretches are shorter than its blocks copies every block.

pub fn skips(&self) -> bool

Whether this entry reads items that aren’t adjacent: a step or stride of more than 1, as a transpose’s innermost axis has.

pub fn fills(&self) -> bool

Whether this entry gives a fill at some position: a Padded entry does where its edge mode is fill, and a table does where it holds Steps::FILL.

pub fn affine(&self) -> Option<(usize, isize)>

This entry’s first offset and step, where it reads its whole axis as one regular run with no fill: a Stride, or a Rotated entry that doesn’t rotate.

pub fn in_order(tables: &[Self]) -> bool

Whether a walk through tables reads offsets 0, 1, 2 and so on, in order. A copy through such tables of a source with as many items as the walk reads is the source unchanged. Only Stride entries that start at 0 qualify, and tables whose offsets run 0, 1, 2 and so on at their axis’s stride.

pub fn spreads(&self) -> bool

Whether this entry repeats an offset or gives a fill. Applying an element-wise function to the items it reads, in place of reading the function’s results, would then compute an item more than once, or apply the function to a fill.

pub fn per_axis(tables: &[Self], shape: &[usize]) -> Option<(usize, Vec<Self>)>

tables, a walk’s entries for a result of shape, as one entry for each axis of shape, with the offset of each entry of one item moved into the base. Neighbouring entries that step as one axis merge first (simplify), so that one axis of shape can read several of them, as a view that merges axes does. An entry over several axes splits into one Stride for each. None where an entry that isn’t a Stride covers several axes, or where one axis of shape reads entries that don’t merge.

pub fn with_base(base: usize, steps: Vec<Self>) -> Vec<Self>

The tables of a walk from base whose entries are steps: steps, after an entry of one item at base where base isn’t 0. per_axis splits such tables back into base and steps.

pub fn through( outer: &[Self], shape: &[usize], base: usize, inner: &[Self], ) -> Option<(usize, Vec<Self>)>

outer’s reads of an array of shape, composed with inner, which maps the positions along each axis of shape to offsets from base, with the new base. Walking the result reads what walking inner and then outer reads. Where an entry of outer walks several whole axes of shape, as a reshape of a view reads them, the walk splits it into one entry for each of those axes (by_axes), and the result holds one entry for each. None where outer’s entries don’t each walk one axis of shape even so (Walk::new), where two entries walk one axis that inner doesn’t map by a Stride, or where an entry reads part of an axis that inner rotates or clips. Callers then force the copy that inner describes, in one walk.

pub fn rereads(outer: &[Self], shape: &[usize]) -> bool

Whether two of outer’s entries walk one axis of shape, as overlapping windows do. Applying an element-wise function to the items they read, in place of reading its results, would then compute each item once for every window that holds it.

Trait Implementations

impl Clone for Steps

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Steps

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

Formats the value using the given formatter.

impl Eq for Steps

impl PartialEq for Steps

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Steps