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extern crate alloc;
use alloc::boxed::Box;
use core::cmp::Ordering;
use core::slice;
use core::ptr;
use crate::ops::*;
/// Common re-indexing logic used internally by the `SortOps` trait.
fn build_swap_trace(ordering : &mut [(usize,usize)]) -> &mut [(usize,usize)]
{
let len = ordering.len();
// Create a reverse lookup
for idx in 0..len {
unsafe {
// We know 0 <= idx < ordering.len(), so we don't need to check the indexing.
let v = ordering.get_unchecked(idx).0;
// It's less trivial to figure out that 0 <= v <= ordering.len() - the input
// array is created by sorted_box_to_ordering()
ordering.get_unchecked_mut(v).1 = idx;
}
}
let mut swap_count = 0;
// Build a swap trace that will shuffle everything into the right position.
for i in 0..len {
// Used get_unchecked for the same reason as above
unsafe {
let (other, inv_i) = *ordering.get_unchecked(i);
if i != other {
// we re-use the ordering slice to store the swap trace
*ordering.get_unchecked_mut(swap_count) = (i, other);
swap_count += 1;
if inv_i > i {
ordering.get_unchecked_mut(inv_i).0 = other;
ordering.get_unchecked_mut(other).1 = inv_i;
}
}
}
}
// Only return the portion of the slice containing the swap trace.
&mut ordering[..swap_count]
}
/// Use some unsafeness to coerce a [(usize, &T)] into a [(usize, usize)]. The `Box` is consumed,
/// meaning that we "unborrow" the &T values.
fn sorted_box_to_ordering<T>(sorted: Box<[(usize, &T)]>) -> Box<[(usize,usize)]> {
debug_assert_eq!(core::mem::size_of::<&T>(), core::mem::size_of::<usize>());
let len = sorted.len();
let p = Box::into_raw(sorted);
unsafe {
let p2 = slice::from_raw_parts_mut(p as *mut (usize, usize), len);
Box::from_raw(p2)
}
}
/// Provides sorting capabilities to two-dimensional arrays. Sorting of the rows and columns
/// is performed in-place, and care is taken to minimise row/col swaps. This is achieved by
/// sorting the row/col and original index pair, then repositioning the rows/columns once the
/// new ordering has been determined.
pub trait SortOps<T> : TooDeeOpsMut<T> {
/// Sort the entire two-dimensional array by comparing elements on a specific row, using the natural ordering.
/// This sort is stable.
fn sort_row_ord<F>(&mut self, row: usize) where T : Ord {
self.sort_by_row(row, T::cmp);
}
/// Sort the entire two-dimensional array by comparing elements on a specific row, using the natural ordering.
/// This sort is unstable.
fn sort_unstable_row_ord<F>(&mut self, row: usize) where T : Ord {
self.sort_unstable_by_row(row, T::cmp);
}
/// Sort the entire two-dimensional array by comparing elements on a specific row using the provided compare function.
/// This sort is stable.
fn sort_by_row<F>(&mut self, row: usize, mut compare: F)
where
F: FnMut(&T, &T) -> Ordering,
{
assert!(row < self.num_rows());
let mut sort_data : Box<[(usize, &T)]> = self[row].iter().enumerate().map(|(i, v)| (i, v)).collect();
sort_data.sort_by(|i, j| compare(i.1, j.1));
// Build up a "trace" of column swaps to apply
let mut ordering = sorted_box_to_ordering(sort_data);
let swap_trace = build_swap_trace(&mut ordering);
// Apply the swap trace to each row. For larger arrays, this approach is faster than applying swap_cols() directly.
for r in self.rows_mut() {
for i in swap_trace.iter() {
// The swap indices will definitely be within the expected range,
// so we can use `get_unchecked_mut` here
unsafe {
let pa: *mut T = r.get_unchecked_mut(i.0);
let pb: *mut T = r.get_unchecked_mut(i.1);
ptr::swap(pa, pb);
}
// r.swap(i.0, i.1);
}
}
}
/// Sort the entire two-dimensional array by comparing elements on a specific row using the provided compare function.
/// This sort is unstable.
fn sort_unstable_by_row<F>(&mut self, row: usize, mut compare: F)
where
F: FnMut(&T, &T) -> Ordering,
{
assert!(row < self.num_rows());
let mut sort_data : Box<[(usize, &T)]> = self[row].iter().enumerate().map(|(i, v)| (i, v)).collect();
sort_data.sort_unstable_by(|i, j| compare(i.1, j.1));
// Build up a "trace" of column swaps to apply
let mut ordering = sorted_box_to_ordering(sort_data);
let swap_trace = build_swap_trace(&mut ordering);
// Apply the swap trace to each row. For larger arrays, this approach is faster than applying swap_cols() directly.
for r in self.rows_mut() {
for i in swap_trace.iter() {
// The swap indices will definitely be within the expected range,
// so we can use `get_unchecked_mut` here
unsafe {
let pa: *mut T = r.get_unchecked_mut(i.0);
let pb: *mut T = r.get_unchecked_mut(i.1);
ptr::swap(pa, pb);
}
// r.swap(i.0, i.1);
}
}
}
/// Sort the entire two-dimensional array by comparing elements on a specific row using a key
/// extraction function.
/// This sort is stable.
fn sort_by_row_key<B, F>(&mut self, row: usize, mut f: F)
where
B: Ord,
F: FnMut(&T) -> B,
{
self.sort_by_row(row, |a, b| f(a).cmp(&f(b)));
}
/// Sort the entire two-dimensional array by comparing elements on a specific row using a key
/// extraction function.
/// This sort is unstable.
fn sort_unstable_by_row_key<B, F>(&mut self, row: usize, mut f: F)
where
B: Ord,
F: FnMut(&T) -> B,
{
self.sort_unstable_by_row(row, |a, b| f(a).cmp(&f(b)));
}
/// Sort the entire two-dimensional array by comparing elements on a specific column using the natural ordering.
/// This sort is stable.
fn sort_col_ord<F>(&mut self, col: usize) where T : Ord {
self.sort_by_col(col, T::cmp);
}
/// Sort the entire two-dimensional array by comparing elements on in a specific column.
/// This sort is stable.
fn sort_by_col<F>(&mut self, col: usize, mut compare: F)
where
F: FnMut(&T, &T) -> Ordering,
{
assert!(col < self.num_cols());
let mut sort_data : Box<[(usize, &T)]> = self.col(col).enumerate().map(|(i, v)| (i, v)).collect();
sort_data.sort_by(|i, j| compare(i.1, j.1));
let mut ordering = sorted_box_to_ordering(sort_data);
let swap_trace = build_swap_trace(&mut ordering);
for i in swap_trace.iter() {
self.swap_rows(i.0, i.1);
}
}
/// Sort the entire two-dimensional array by comparing elements on in a specific column.
/// This sort is unstable.
fn sort_unstable_by_col<F>(&mut self, col: usize, mut compare: F)
where
F: FnMut(&T, &T) -> Ordering,
{
assert!(col < self.num_cols());
let mut sort_data : Box<[(usize, &T)]> = self.col(col).enumerate().map(|(i, v)| (i, v)).collect();
sort_data.sort_unstable_by(|i, j| compare(i.1, j.1));
let mut ordering = sorted_box_to_ordering(sort_data);
let swap_trace = build_swap_trace(&mut ordering);
for i in swap_trace.iter() {
self.swap_rows(i.0, i.1);
}
}
/// Sort the entire two-dimensional array by comparing elements on a specific column using a key
/// extraction function.
/// This sort is stable.
fn sort_by_col_key<B, F>(&mut self, col: usize, mut f: F)
where
B: Ord,
F: FnMut(&T) -> B,
{
self.sort_by_row(col, |a, b| f(a).cmp(&f(b)));
}
/// Sort the entire two-dimensional array by comparing elements on a specific column using a key
/// extraction function.
/// This sort is unstable.
fn sort_unstable_by_col_key<B, F>(&mut self, col: usize, mut f: F)
where
B: Ord,
F: FnMut(&T) -> B,
{
self.sort_unstable_by_row(col, |a, b| f(a).cmp(&f(b)));
}
}
impl<T, O> SortOps<T> for O where O : TooDeeOpsMut<T> {}