Crate operational_transform

A library for Operational Transformation

Operational transformation (OT) is a technology for supporting a range of collaboration functionalities in advanced collaborative software systems. [1]

When working on the same document over the internet concurrent operations from multiple users might be in conflict. Operational Transform can help to resolve conflicts in such a way that documents stay in sync.

The basic operations that are supported are:

• Retain(n): Move the cursor n positions forward
• Delete(n): Delete n characters at the current position
• Insert(s): Insert the string s at the current position

This library can be used to…

… compose sequences of operations:

use operational_transform::OperationSeq;

let mut a = OperationSeq::default();
a.insert("abc");
let mut b = OperationSeq::default();
b.retain(3);
b.insert("def");
let after_a = a.apply("").unwrap();
let after_b = b.apply(&after_a).unwrap();
let c = a.compose(&b).unwrap();
let after_ab = a.compose(&b).unwrap().apply("").unwrap();
assert_eq!(after_ab, after_b);

… transform sequences of operations

use operational_transform::OperationSeq;

let s = "abc";
let mut a = OperationSeq::default();
a.retain(3);
a.insert("def");
let mut b = OperationSeq::default();
b.retain(3);
b.insert("ghi");
let (a_prime, b_prime) = a.transform(&b).unwrap();
let ab_prime = a.compose(&b_prime).unwrap();
let ba_prime = b.compose(&a_prime).unwrap();
let after_ab_prime = ab_prime.apply(s).unwrap();
let after_ba_prime = ba_prime.apply(s).unwrap();
assert_eq!(ab_prime, ba_prime);
assert_eq!(after_ab_prime, after_ba_prime);

… invert sequences of operations

use operational_transform::OperationSeq;

let s = "abc";
let mut o = OperationSeq::default();
o.retain(3);
o.insert("def");
let p = o.invert(s);
assert_eq!(p.apply(&o.apply(s).unwrap()).unwrap(), s);

Features

Serialization is supported by using the serde feature.

• Delete(n) will be serialized to -n
• Insert(s) will be serialized to “{s}”
• Retain(n) will be serialized to n

use operational_transform::OperationSeq;
use serde_json;

let o: OperationSeq = serde_json::from_str("[1,-1,\"abc\"]").unwrap();
let mut o_exp = OperationSeq::default();
o_exp.retain(1);
o_exp.delete(1);
o_exp.insert("abc");
assert_eq!(o, o_exp);

Acknowledgement

In the current state the code is ported from here. It might change in the future as there is much room for optimisation and also usability.

Structs

OTError

Error for failed operational transform operations.

OperationSeq

A sequence of Operations on text.

Enums

Operation

A single operation to be executed at the cursor’s current position.