http://www.xmailserver.org/diff2.pdf

It seems diff-rs allocates a big vector for diffing a small object resulting in out-of-memory

This was discussed in this issue as well
rust-pretty-assertions/rust-pretty-assertions#124

https://github.com/utkarshkukreti/diff.rs/blob/0.1.13/src/lib.rs?rgh-link-date=2024-01-31T21%3A37%3A48Z#L150

Since there are many variations of MIT license, Fedora requires license text to be present. Moreover, when you will relicense to ASL 2.0, that license itself requires text license to be present along with sources.

@utkarshkukreti I need a fast and functional diff-library. Does it make sense to improve this crate and do PRs? This crate looks like unmaintained.

Currently there is no way to receive the diff table indices. This is important, because without this functionality it is impossible to determine the line number of a Right(_) when used via diff::lines for example.

For line 71 here, although the right_skip has been defined in line 68 with the clone(), skip(), and take() functions, these three functions will be actually called in line 71 because of the lazy evaluation. Because the same functions keep being called on the same string inside the for loop, this causes a lot of redundant memory load operations. Based on my test with the rustfmt applications (https://github.com/rust-lang/rustfmt), this can be avoided if we change the right_skip to a vector and pass it by reference to the inside of the for loop. After this optimization, with my test input file, there is a 7.12x speedup and the execution time is reduced from 12.56 seconds to 1.54 seconds.

Here's the modified code

        let table: Vec<Vec<u32>> = {
        let mut table = vec![vec![0; right_diff_size + 1]; left_diff_size + 1];
        let mut left_skip = left.clone().skip(leading_equals).take(left_diff_size).enumerate();
        let mut right_skip = right.clone().skip(leading_equals).take(right_diff_size).enumerate().collect::<Vec<_>>();

        for (i, l) in left_skip {
            for (j, r) in &right_skip {
                table[i + 1][*j + 1] = if l == *r {
                    table[i][*j] + 1
                } else {
                    std::cmp::max(table[i][*j + 1], table[i + 1][*j])
                };
            }
        }

        table
    };

Why does Result::Both contain two values if they will always be the same?

This issue was automatically generated. Feel free to close without ceremony if
you do not agree with re-licensing or if it is not possible for other reasons.
Respond to @cmr with any questions or concerns, or pop over to
#rust-offtopic on IRC to discuss.

You're receiving this because someone (perhaps the project maintainer)
published a crates.io package with the license as "MIT" xor "Apache-2.0" and
the repository field pointing here.

TL;DR the Rust ecosystem is largely Apache-2.0. Being available under that
license is good for interoperation. The MIT license as an add-on can be nice
for GPLv2 projects to use your code.

Why?

The MIT license requires reproducing countless copies of the same copyright
header with different names in the copyright field, for every MIT library in
use. The Apache license does not have this drawback. However, this is not the
primary motivation for me creating these issues. The Apache license also has
protections from patent trolls and an explicit contribution licensing clause.
However, the Apache license is incompatible with GPLv2. This is why Rust is
dual-licensed as MIT/Apache (the "primary" license being Apache, MIT only for
GPLv2 compat), and doing so would be wise for this project. This also makes
this crate suitable for inclusion and unrestricted sharing in the Rust
standard distribution and other projects using dual MIT/Apache, such as my
personal ulterior motive, the Robigalia project.

Some ask, "Does this really apply to binary redistributions? Does MIT really
require reproducing the whole thing?" I'm not a lawyer, and I can't give legal
advice, but some Google Android apps include open source attributions using
this interpretation. Others also agree with
it.
But, again, the copyright notice redistribution is not the primary motivation
for the dual-licensing. It's stronger protections to licensees and better
interoperation with the wider Rust ecosystem.

How?

To do this, get explicit approval from each contributor of copyrightable work
(as not all contributions qualify for copyright) and then add the following to
your README:

## License

Licensed under either of
 * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
 * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
at your option.

### Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any
additional terms or conditions.

and in your license headers, use the following boilerplate (based on that used in Rust):

// Copyright (c) 2016 diff.rs developers
//
// Licensed under the Apache License, Version 2.0
// <LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0> or the MIT
// license <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. All files in the project carrying such notice may not be copied,
// modified, or distributed except according to those terms.

Be sure to add the relevant LICENSE-{MIT,APACHE} files. You can copy these
from the Rust repo for a plain-text
version.

And don't forget to update the license metadata in your Cargo.toml to:

license = "MIT/Apache-2.0"

I'll be going through projects which agree to be relicensed and have approval
by the necessary contributors and doing this changes, so feel free to leave
the heavy lifting to me!

Contributor checkoff

To agree to relicensing, comment with :

I license past and future contributions under the dual MIT/Apache-2.0 license, allowing licensees to chose either at their option

Or, if you're a contributor, you can check the box in this repo next to your
name. My scripts will pick this exact phrase up and check your checkbox, but
I'll come through and manually review this issue later as well.

• @utkarshkukreti
• @marcusklaas

These should pass:

test "#4" {
    assert_eq!(::diff::slice(&[1], &[2]), vec![::diff::Result::Left(&1),
                                               ::diff::Result::Right(&2)]);
    assert_eq!(::diff::lines("a", "b"), vec![::diff::Result::Left("a"),
                                             ::diff::Result::Right("b")]);
}

but they fail with:

thread 'speculate::_::bugs::#4' panicked at 'assertion failed: (left == right) (left: [Right(2), Left(1)], right: [Left(1), Right(2)])', tests/tests.rs:53

and

thread 'speculate::_::bugs::#4' panicked at 'assertion failed: (left == right) (left: [Right("b"), Left("a")], right: [Left("a"), Right("b")])', tests/tests.rs:53

This will probably fix rust-lang/rustfmt#606 too.

We are using this crate in rustfmt to make the diff.

Someone has reported an issue (rust-lang/rustfmt#1753), this is the digest of what is going on. Since you are using str.lines(), it doesn't include any empty line (i.e boo\n is just one line, which is not actually) so it causes some problems. What I'm trying to do is to change this crate so that it can detect and say that left has a trailing newline and right does not.

I can open a PR to patch but I just wanted to know if you have any suggestion for this? I was thinking about removing str.lines() and write a simple str.split and returns an empty iterator when the input is empty string.