Crate ropey [] [src]

Ropey is a utf8 text rope library, designed to be the backing text buffer for applications such as text editors. Ropey is fast, Unicode-safe, has low memory overhead, and can handle huge texts and memory-incoherent edits without trouble.

The library is made up of four main components:

  • Rope: the main editable text buffer type.
  • RopeSlice: an immutable view into part of a Rope.
  • RopeBuilder: an efficient incremental Rope builder.
  • iter: iterators over a Rope's/RopeSlice's data.

A Contrived Example

Let's say we want to open up a file, replace the 516th line (the writing was terrible!), and save it back to disk. It's contrived, but will give a good sampling of the APIs and how they work together.

use std::fs::File;
use std::io::{Write, BufReader, BufWriter};
use ropey::Rope;

// Load the file into a Rope.
let mut text = Rope::from_reader(

// Make sure there are at least 516 lines.
if text.len_lines() >= 516 {
    // Let's print the line first, to embarrass ourselves with our
    // terrible writing!  Note that lines are zero-indexed, so the
    // 516th line is at index 515.
    println!("{}", text.line(515));

    // Get the char indices of the start/end of the line.
    let start_idx = text.line_to_char(515);
    let end_idx = text.line_to_char(516);

    // Remove that terrible writing!

    // ...and replace it with something better.
    text.insert(start_idx, "The flowers are... so... dunno.\n");

    // Let's print our changes, along with the previous few lines
    // for context.  Gotta make sure the writing works!
    let start_idx = text.line_to_char(511);
    let end_idx = text.line_to_char(516);
    println!("{}", text.slice(start_idx..end_idx));

// Write the file back out to disk.  We use the `Chunks` iterator
// here to be maximally efficient.
let mut file = BufWriter::new(File::create("my_great_book.txt")?);
for chunk in text.chunks() {



Iterators over a Rope's data.


Facilities for customizing grapheme cluster segmentation.



A utf8 text rope.


An efficient incremental Rope builder.


An immutable view into part of a Rope.