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#![no_std]
pub trait DiffInPlace<T, const N: usize>
where
T: PartialEq,
{
/// Fallible version of `diff_in_place` for propagating errors.
/// Perform an in-place diff between two const-size arrays, invoking the given function
/// for each run of different elements, with the index into the array and
/// the slice of different elements from the other array.
///
///
/// # Arguments
/// * `other` - The other array to compare against.
/// * `func` - The function to call for each run of different elements.
///
/// # Example
/// ```
/// use diff_in_place::DiffInPlace;
/// let a = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
/// let mut b = [0, 0, 1, 2, 0, 0, 0, 3, 4, 5];
///
/// a.try_diff_in_place(&b, |idx, diff| -> Result<(), ()> {
/// // println!("{}: {:?}", idx, diff);
/// // Prints:
/// // 2: [1, 2]
/// // 7: [3, 4, 5]
/// Ok(())
/// }).unwrap();
/// ```
fn try_diff_in_place<F, R>(&self, other: &[T; N], func: F) -> Result<(), R>
where
F: FnMut(usize, &[T]) -> Result<(), R>;
/// Perform an in-place diff between two const-size arrays, invoking the given function
/// for each run of different elements, with the index into the array and
/// the slice of different elements from the other array.
///
/// # Arguments
/// * `other` - The other array to compare against.
/// * `func` - The function to call for each run of different elements.
///
/// # Example
/// ```
/// use diff_in_place::DiffInPlace;
/// let a = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
/// let mut b = [0, 0, 1, 2, 0, 0, 0, 3, 4, 5];
///
/// a.diff_in_place(&b, |idx, diff| {
/// // println!("{}: {:?}", idx, diff);
/// // Prints:
/// // 2: [1, 2]
/// // 7: [3, 4, 5]
/// });
/// ```
fn diff_in_place<F>(&self, other: &[T; N], mut func: F)
where
F: FnMut(usize, &[T]),
{
self.try_diff_in_place(other, |idx, diff| -> Result<(), ()> {
func(idx, diff);
Ok(())
})
.unwrap();
}
}
#[derive(Copy, Clone)]
enum DiffState {
Same,
Different(usize),
}
impl<T, const N: usize> DiffInPlace<T, N> for [T; N]
where
T: PartialEq + Copy,
{
fn try_diff_in_place<F, R>(&self, other: &[T; N], mut func: F) -> Result<(), R>
where
F: FnMut(usize, &[T]) -> Result<(), R>,
{
// Go over the bytes in both arrays, comparing them.
// For all different runs within the two buffers, call the diff function
// with the index into the buffers and the bytes that need to be changed.
let byte_for_byte = self.iter().zip(other.iter());
let mut run_state = DiffState::Same;
for (current, (left, right)) in byte_for_byte.enumerate() {
match (run_state, left == right) {
(DiffState::Same, false) => {
// We are starting an unequal run, preserve the current index
run_state = DiffState::Different(current);
}
(DiffState::Different(run_start), true) => {
// We are ending an unequal run, call the diff function
func(run_start, &other[run_start..current])?;
run_state = DiffState::Same;
}
_ => {
// Run state is unchanged
}
}
}
// If we are still in a different run, call the diff function
if let DiffState::Different(run_start) = run_state {
func(run_start, &other[run_start..])?;
}
Ok(())
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_fully_same() {
let a = [0u8; 40];
let b = [0u8; 40];
a.diff_in_place(&b, |_, _| panic!("Should not be called"))
}
#[test]
fn test_fully_different() {
let a = [0u8; 40];
let b = [1u8; 40];
let mut called = false;
a.diff_in_place(&b, |idx, diff| {
assert_eq!(idx, 0);
assert_eq!(diff, &[1u8; 40]);
called = true;
});
assert!(called);
}
#[test]
fn test_start_different() {
let a = [0u8; 40];
let mut b = [0u8; 40];
b[..10].copy_from_slice(&[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
const EXPECTED_CALLS: [(usize, &[u8]); 1] = [(0usize, &[1, 2, 3, 4, 5, 6, 7, 8, 9, 10])];
let mut called = false;
a.diff_in_place(&b, |idx, diff| {
let (expected_idx, expected_diff) = EXPECTED_CALLS[0];
assert_eq!(idx, expected_idx);
assert_eq!(diff, expected_diff);
called = true;
});
assert!(called);
}
#[test]
fn test_middle_different() {
let a = [0u8; 40];
let mut b = [0u8; 40];
b[10..20].copy_from_slice(&[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
const EXPECTED_CALLS: [(usize, &[u8]); 1] = [(10usize, &[1, 2, 3, 4, 5, 6, 7, 8, 9, 10])];
let mut called = false;
a.diff_in_place(&b, |idx, diff| {
let (expected_idx, expected_diff) = EXPECTED_CALLS[0];
assert_eq!(idx, expected_idx);
assert_eq!(diff, expected_diff);
called = true;
});
assert!(called);
}
#[test]
fn test_end_different() {
let a = [0u8; 40];
let mut b = [0u8; 40];
b[30..].copy_from_slice(&[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
const EXPECTED_CALLS: [(usize, &[u8]); 1] = [(30usize, &[1, 2, 3, 4, 5, 6, 7, 8, 9, 10])];
let mut called = false;
a.diff_in_place(&b, |idx, diff| {
let (expected_idx, expected_diff) = EXPECTED_CALLS[0];
assert_eq!(idx, expected_idx);
assert_eq!(diff, expected_diff);
called = true;
});
assert!(called);
}
#[test]
fn test_multiple_different() {
let a = [0u8; 40];
let mut b = [0u8; 40];
b[..10].copy_from_slice(&[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
b[20..25].copy_from_slice(&[11, 12, 13, 14, 15]);
b[39] = 20;
const EXPECTED_CALLS: [(usize, &[u8]); 3] = [
(0usize, &[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]),
(20usize, &[11, 12, 13, 14, 15]),
(39usize, &[20]),
];
let mut call_idx = 0;
let mut called = false;
a.diff_in_place(&b, |idx, diff| {
let (expected_idx, expected_diff) = EXPECTED_CALLS[call_idx];
assert_eq!(idx, expected_idx);
assert_eq!(diff, expected_diff);
call_idx += 1;
called = true;
});
assert!(called);
}
#[test]
fn test_other_types() {
let a = [0.0f32; 40];
let mut b = [0.0f32; 40];
b[..10].copy_from_slice(&[1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7., 8., 9., 10.]);
const EXPECTED_CALLS: [(usize, &[f32]); 1] =
[(0usize, &[1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7., 8., 9., 10.])];
let mut called = false;
a.diff_in_place(&b, |idx, diff| {
let (expected_idx, expected_diff) = EXPECTED_CALLS[0];
assert_eq!(idx, expected_idx);
assert_eq!(diff, expected_diff);
called = true;
});
assert!(called);
}
#[test]
#[should_panic]
fn test_fallible_diff() {
let a = [0u8; 40];
let mut b = [0u8; 40];
b[..10].copy_from_slice(&[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);
a.try_diff_in_place(&b, |_idx, _diff| -> Result<(), ()> { Err(()) })
.unwrap();
}
}