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expand: replace while loop with constant time algorithm

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Sebastian Bentmar Holgersson 2023-01-03 21:27:20 +00:00 committed by Sylvestre Ledru
parent ddc6fabca0
commit 69d8729598
2 changed files with 33 additions and 20 deletions
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19
src/uu/expand/src/expand.rs
View file

@ -338,11 +338,6 @@ fn open(path: &str) -> BufReader<Box<dyn Read + 'static>> {
/// in the `tabstops` slice is interpreted as a relative number of
/// spaces, which this function will return for every input value of
/// `col` beyond the end of the second-to-last element of `tabstops`.
///
/// If `remaining_mode` is [`RemainingMode::Plus`], then the last entry
/// in the `tabstops` slice is interpreted as a relative number of
/// spaces, which this function will return for every input value of
/// `col` beyond the end of the second-to-last element of `tabstops`.
fn next_tabstop(tabstops: &[usize], col: usize, remaining_mode: &RemainingMode) -> usize {
let num_tabstops = tabstops.len();
match remaining_mode {
@ -350,13 +345,11 @@ fn next_tabstop(tabstops: &[usize], col: usize, remaining_mode: &RemainingMode)
Some(t) => t - col,
None => {
let step_size = tabstops[num_tabstops - 1];
let last_before_repeating = tabstops[num_tabstops-2];
let mut r = last_before_repeating+step_size;
let last_fixed_tabstop = tabstops[num_tabstops-2];
let characters_since_last_tabstop = col-last_fixed_tabstop;
while col >= r {
r += step_size;
}
r - col
let steps_required = 1 + characters_since_last_tabstop/step_size;
steps_required*step_size-characters_since_last_tabstop
}
},
RemainingMode::Slash => match tabstops[0..num_tabstops - 1].iter().find(|&&t| t > col) {
@ -498,8 +491,8 @@ mod tests {
#[test]
fn test_next_tabstop_remaining_mode_plus() {
assert_eq!(next_tabstop(&[1, 5], 0, &RemainingMode::Plus), 1);
assert_eq!(next_tabstop(&[1, 5], 3, &RemainingMode::Plus), 4);
assert_eq!(next_tabstop(&[1, 5], 6, &RemainingMode::Plus), 4);
assert_eq!(next_tabstop(&[1, 5], 3, &RemainingMode::Plus), 3);
assert_eq!(next_tabstop(&[1, 5], 6, &RemainingMode::Plus), 5);
}
#[test]

34
tests/by-util/test_expand.rs
View file

@ -350,21 +350,41 @@ fn test_ignore_initial_plus_slash_combination() {
}
#[test]
fn test_comma_with_plus_and_multi_character_values() {
fn test_comma_with_plus_1() {
new_ucmd!()
.args(&["--tabs=3,+6"])
.pipe_in("\taaa\tbbb\tccc")
.pipe_in("\t111\t222\t333")
.succeeds()
// 01234567890
.stdout_is(" aaa bbb ccc");
.stdout_is(" 111 222 333");
}
#[test]
fn test_comma_with_plus_and_multi_character_values() {
fn test_comma_with_plus_2() {
new_ucmd!()
.args(&["--tabs=3,+6"])
.pipe_in("\taaa\tbbb\tccc")
.args(&["--tabs=1,+5"])
.pipe_in("\ta\tb\tc")
.succeeds()
// 01234567890
.stdout_is(" aaa bbb ccc");
.stdout_is(" a b c");
}
#[test]
fn test_comma_with_plus_3() {
new_ucmd!()
.args(&["--tabs=2,+5"])
.pipe_in("a\tb\tc")
.succeeds()
// 01234567890
.stdout_is("a b c");
}
#[test]
fn test_comma_with_plus_4() {
new_ucmd!()
.args(&["--tabs=1,3,+5"])
.pipe_in("a\tb\tc")
.succeeds()
// 01234567890
.stdout_is("a b c");
}