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//! Functions for filling text.
use crate::{wrap, wrap_algorithms, Options, WordSeparator};
/// Fill a line of text at a given width.
///
/// The result is a [`String`], complete with newlines between each
/// line. Use [`wrap()`] if you need access to the individual lines.
///
/// The easiest way to use this function is to pass an integer for
/// `width_or_options`:
///
/// ```
/// use textwrap::fill;
///
/// assert_eq!(
/// fill("Memory safety without garbage collection.", 15),
/// "Memory safety\nwithout garbage\ncollection."
/// );
/// ```
///
/// If you need to customize the wrapping, you can pass an [`Options`]
/// instead of an `usize`:
///
/// ```
/// use textwrap::{fill, Options};
///
/// let options = Options::new(15)
/// .initial_indent("- ")
/// .subsequent_indent(" ");
/// assert_eq!(
/// fill("Memory safety without garbage collection.", &options),
/// "- Memory safety\n without\n garbage\n collection."
/// );
/// ```
pub fn fill<'a, Opt>(text: &str, width_or_options: Opt) -> String
where
Opt: Into<Options<'a>>,
{
let options = width_or_options.into();
if text.len() < options.width && !text.contains('\n') && options.initial_indent.is_empty() {
String::from(text.trim_end_matches(' '))
} else {
fill_slow_path(text, options)
}
}
/// Slow path for fill.
///
/// This is taken when `text` is longer than `options.width`.
pub(crate) fn fill_slow_path(text: &str, options: Options<'_>) -> String {
// This will avoid reallocation in simple cases (no
// indentation, no hyphenation).
let mut result = String::with_capacity(text.len());
let line_ending_str = options.line_ending.as_str();
for (i, line) in wrap(text, options).iter().enumerate() {
if i > 0 {
result.push_str(line_ending_str);
}
result.push_str(line);
}
result
}
/// Fill `text` in-place without reallocating the input string.
///
/// This function works by modifying the input string: some `' '`
/// characters will be replaced by `'\n'` characters. The rest of the
/// text remains untouched.
///
/// Since we can only replace existing whitespace in the input with
/// `'\n'` (there is no space for `"\r\n"`), we cannot do hyphenation
/// nor can we split words longer than the line width. We also need to
/// use `AsciiSpace` as the word separator since we need `' '`
/// characters between words in order to replace some of them with a
/// `'\n'`. Indentation is also ruled out. In other words,
/// `fill_inplace(width)` behaves as if you had called [`fill()`] with
/// these options:
///
/// ```
/// # use textwrap::{core, LineEnding, Options, WordSplitter, WordSeparator, WrapAlgorithm};
/// # let width = 80;
/// Options::new(width)
/// .break_words(false)
/// .line_ending(LineEnding::LF)
/// .word_separator(WordSeparator::AsciiSpace)
/// .wrap_algorithm(WrapAlgorithm::FirstFit)
/// .word_splitter(WordSplitter::NoHyphenation);
/// ```
///
/// The wrap algorithm is
/// [`WrapAlgorithm::FirstFit`](crate::WrapAlgorithm::FirstFit) since
/// this is the fastest algorithm — and the main reason to use
/// `fill_inplace` is to get the string broken into newlines as fast
/// as possible.
///
/// A last difference is that (unlike [`fill()`]) `fill_inplace` can
/// leave trailing whitespace on lines. This is because we wrap by
/// inserting a `'\n'` at the final whitespace in the input string:
///
/// ```
/// let mut text = String::from("Hello World!");
/// textwrap::fill_inplace(&mut text, 10);
/// assert_eq!(text, "Hello \nWorld!");
/// ```
///
/// If we didn't do this, the word `World!` would end up being
/// indented. You can avoid this if you make sure that your input text
/// has no double spaces.
///
/// # Performance
///
/// In benchmarks, `fill_inplace` is about twice as fast as
/// [`fill()`]. Please see the [`linear`
/// for details.
pub fn fill_inplace(text: &mut String, width: usize) {
let mut indices = Vec::new();
let mut offset = 0;
for line in text.split('\n') {
let words = WordSeparator::AsciiSpace
.find_words(line)
.collect::<Vec<_>>();
let wrapped_words = wrap_algorithms::wrap_first_fit(&words, &[width as f64]);
let mut line_offset = offset;
for words in &wrapped_words[..wrapped_words.len() - 1] {
let line_len = words
.iter()
.map(|word| word.len() + word.whitespace.len())
.sum::<usize>();
line_offset += line_len;
// We've advanced past all ' ' characters -- want to move
// one ' ' backwards and insert our '\n' there.
indices.push(line_offset - 1);
}
// Advance past entire line, plus the '\n' which was removed
// by the split call above.
offset += line.len() + 1;
}
let mut bytes = std::mem::take(text).into_bytes();
for idx in indices {
bytes[idx] = b'\n';
}
*text = String::from_utf8(bytes).unwrap();
}
#[cfg(test)]
mod tests {
use super::*;
use crate::WrapAlgorithm;
#[test]
fn fill_simple() {
assert_eq!(fill("foo bar baz", 10), "foo bar\nbaz");
}
#[test]
fn fill_unicode_boundary() {
fill("\u{1b}!Ͽ", 10);
}
#[test]
fn non_breaking_space() {
let options = Options::new(5).break_words(false);
assert_eq!(fill("foo bar baz", &options), "foo bar baz");
}
#[test]
fn non_breaking_hyphen() {
let options = Options::new(5).break_words(false);
assert_eq!(fill("foo‑bar‑baz", &options), "foo‑bar‑baz");
}
#[test]
fn fill_preserves_line_breaks_trims_whitespace() {
assert_eq!(fill(" ", 80), "");
assert_eq!(fill(" \n ", 80), "\n");
assert_eq!(fill(" \n \n \n ", 80), "\n\n\n");
}
#[test]
fn preserve_line_breaks() {
assert_eq!(fill("", 80), "");
assert_eq!(fill("\n", 80), "\n");
assert_eq!(fill("\n\n\n", 80), "\n\n\n");
assert_eq!(fill("test\n", 80), "test\n");
assert_eq!(fill("test\n\na\n\n", 80), "test\n\na\n\n");
assert_eq!(
fill(
"1 3 5 7\n1 3 5 7",
Options::new(7).wrap_algorithm(WrapAlgorithm::FirstFit)
),
"1 3 5 7\n1 3 5 7"
);
assert_eq!(
fill(
"1 3 5 7\n1 3 5 7",
Options::new(5).wrap_algorithm(WrapAlgorithm::FirstFit)
),
"1 3 5\n7\n1 3 5\n7"
);
}
#[test]
fn break_words_line_breaks() {
assert_eq!(fill("ab\ncdefghijkl", 5), "ab\ncdefg\nhijkl");
assert_eq!(fill("abcdefgh\nijkl", 5), "abcde\nfgh\nijkl");
}
#[test]
fn break_words_empty_lines() {
assert_eq!(
fill("foo\nbar", &Options::new(2).break_words(false)),
"foo\nbar"
);
}
#[test]
fn fill_inplace_empty() {
let mut text = String::from("");
fill_inplace(&mut text, 80);
assert_eq!(text, "");
}
#[test]
fn fill_inplace_simple() {
let mut text = String::from("foo bar baz");
fill_inplace(&mut text, 10);
assert_eq!(text, "foo bar\nbaz");
}
#[test]
fn fill_inplace_multiple_lines() {
let mut text = String::from("Some text to wrap over multiple lines");
fill_inplace(&mut text, 12);
assert_eq!(text, "Some text to\nwrap over\nmultiple\nlines");
}
#[test]
fn fill_inplace_long_word() {
let mut text = String::from("Internationalization is hard");
fill_inplace(&mut text, 10);
assert_eq!(text, "Internationalization\nis hard");
}
#[test]
fn fill_inplace_no_hyphen_splitting() {
let mut text = String::from("A well-chosen example");
fill_inplace(&mut text, 10);
assert_eq!(text, "A\nwell-chosen\nexample");
}
#[test]
fn fill_inplace_newlines() {
let mut text = String::from("foo bar\n\nbaz\n\n\n");
fill_inplace(&mut text, 10);
assert_eq!(text, "foo bar\n\nbaz\n\n\n");
}
#[test]
fn fill_inplace_newlines_reset_line_width() {
let mut text = String::from("1 3 5\n1 3 5 7 9\n1 3 5 7 9 1 3");
fill_inplace(&mut text, 10);
assert_eq!(text, "1 3 5\n1 3 5 7 9\n1 3 5 7 9\n1 3");
}
#[test]
fn fill_inplace_leading_whitespace() {
let mut text = String::from(" foo bar baz");
fill_inplace(&mut text, 10);
assert_eq!(text, " foo bar\nbaz");
}
#[test]
fn fill_inplace_trailing_whitespace() {
let mut text = String::from("foo bar baz ");
fill_inplace(&mut text, 10);
assert_eq!(text, "foo bar\nbaz ");
}
#[test]
fn fill_inplace_interior_whitespace() {
// To avoid an unwanted indentation of "baz", it is important
// to replace the final ' ' with '\n'.
let mut text = String::from("foo bar baz");
fill_inplace(&mut text, 10);
assert_eq!(text, "foo bar \nbaz");
}
}