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split_string_by_width: return &str to avoid allocations 

since we're returning padding numbers, we no longer allocate for new Strings any more.
pull/301/head
lilydjwg 2022-07-04 11:49:06 +07:00
parent 526b24d00d
commit 5d2fdf65b9
1 changed files with 33 additions and 37 deletions
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70
src/display/style.rs
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@ -40,10 +40,10 @@ fn substring_by_width(s: &str, start: usize, end: usize) -> &str {
})
.skip_while(|(_, before, _)| *before < start);
let byte_start = idx_width_iter
.nth(0)
.next()
.expect("Expected a width index inside `s`.")
.0;
match idx_width_iter.skip_while(|(_, _, after)| *after <= end).nth(0) {
match idx_width_iter.skip_while(|(_, _, after)| *after <= end).next() {
Some(byte_end) => &s[byte_start..byte_end.0],
None => &s[byte_start..],
}
@ -53,43 +53,38 @@ fn substring_by_byte(s: &str, start: usize, end: usize) -> &str {
&s[start..end]
}
/// Split a string into equal length parts, padding if necessary.
/// Split a string into equal length parts and how many spaces should be padded.
///
/// Return splitted strings and how many spaces each has been padded with.
/// Return splitted strings and how many spaces each should be padded with.
///
/// ```
/// split_string_by_width("fooba", 3, true) // vec![("foo", 0), ("ba ", 1)]
/// split_string_by_width("fooba", 3, true) // vec![("foo", 0), ("ba", 1)]
/// split_string_by_width("一个汉字两列宽", 8, false) // vec![("一个汉字", 0), ("两列宽", 0)]
/// ```
fn split_string_by_width(s: &str, max_width: usize, pad: bool) -> Vec<(String, usize)> {
fn split_string_by_width(s: &str, max_width: usize, pad: bool) -> Vec<(&str, usize)> {
let mut res = vec![];
let mut s = s;
while s.width() > max_width {
let mut l = substring_by_width(s, 0, max_width).to_owned();
let l = substring_by_width(s, 0, max_width);
let used = l.width();
let padded;
if pad && used < max_width {
let padding = if pad && used < max_width {
// a fullwidth char is followed
l.push(' ');
padded = 1;
1
} else {
padded = 0;
}
res.push((l, padded));
0
};
res.push((l, padding));
s = substring_by_width(s, used, s.width());
}
if res.is_empty() || !s.is_empty() {
let mut string = s.to_string();
let padded;
if pad {
padded = max_width - s.width();
string.push_str(&" ".repeat(padded));
let padding = if pad {
max_width - s.width()
} else {
padded = 0;
}
res.push((string, padded));
0
};
res.push((s, padding));
}
res
@ -115,9 +110,9 @@ pub fn split_and_apply(
.into_iter()
.map(|(part, _)| {
if use_color {
highlight_missing_style_bug(&part)
highlight_missing_style_bug(part)
} else {
part
part.to_owned()
}
})
.collect();
@ -126,8 +121,8 @@ pub fn split_and_apply(
let mut styled_parts = vec![];
let mut part_start = 0;
for (part, padded) in split_string_by_width(line, max_len, matches!(side, Side::Left)) {
let mut res = String::with_capacity(part.len());
for (part, pad) in split_string_by_width(line, max_len, matches!(side, Side::Left)) {
let mut res = String::with_capacity(part.len() + pad);
let mut prev_style_end = 0;
for (span, style) in styles {
let start_col = span.start_col as usize;
@ -143,7 +138,7 @@ pub fn split_and_apply(
// Then append that text without styling.
let unstyled_start = max(prev_style_end, part_start);
res.push_str(substring_by_byte(
&part,
part,
unstyled_start - part_start,
start_col - part_start,
));
@ -152,9 +147,9 @@ pub fn split_and_apply(
// Apply style to the substring in this span.
if end_col > part_start {
let span_s = substring_by_byte(
&part,
part,
max(0, span.start_col as isize - part_start as isize) as usize,
min(byte_len(&part), end_col - part_start),
min(byte_len(part), end_col - part_start),
);
res.push_str(&span_s.style(*style).to_string());
}
@ -168,13 +163,14 @@ pub fn split_and_apply(
}
// Unstyled text after the last span.
if prev_style_end < part_start + byte_len(&part) {
let span_s = substring_by_byte(&part, prev_style_end - part_start, byte_len(&part));
if prev_style_end < part_start + byte_len(part) {
let span_s = substring_by_byte(part, prev_style_end - part_start, byte_len(part));
res.push_str(span_s);
}
res.push_str(&" ".repeat(pad));
styled_parts.push(res);
part_start += byte_len(&part) - padded;
part_start += byte_len(part);
}
styled_parts
@ -409,7 +405,7 @@ mod tests {
fn split_string_simple() {
assert_eq!(
split_string_by_width("fooba", 3, true),
vec![(String::from("foo"), 0), (String::from("ba "), 1)]
vec![("foo", 0), ("ba", 1)]
);
}
@ -417,7 +413,7 @@ mod tests {
fn split_string_simple_no_pad() {
assert_eq!(
split_string_by_width("fooba", 3, false),
vec![(String::from("foo"), 0), (String::from("ba"), 0)]
vec![("foo", 0), ("ba", 0)]
);
}
@ -425,7 +421,7 @@ mod tests {
fn split_string_unicode() {
assert_eq!(
split_string_by_width("ab📦def", 4, true),
vec![(String::from("ab📦"), 0), (String::from("def "), 1)]
vec![("ab📦", 0), ("def", 1)]
);
}
@ -433,7 +429,7 @@ mod tests {
fn split_string_cjk() {
assert_eq!(
split_string_by_width("一个汉字两列宽", 8, false),
vec![(String::from("一个汉字"), 0), (String::from("两列宽"), 0)]
vec![("一个汉字", 0), ("两列宽", 0)]
);
}
@ -441,7 +437,7 @@ mod tests {
fn split_string_cjk2() {
assert_eq!(
split_string_by_width("你好啊", 5, true),
vec![(String::from("你好 "), 1), (String::from("啊 "), 3)]
vec![("你好", 1), ("啊", 3)]
);
}