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View Code? Open in Web Editor NEWRust package for owned iterators over the the chars of a string
Home Page: https://crates.io/crates/owned-chars
License: Other
Rust package for owned iterators over the the chars of a string
Home Page: https://crates.io/crates/owned-chars
License: Other
Using rental we should be able to directly store Chars
/CharIndices
and remove the slicing and arithmetic.
Assigned to @doomrobo.
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.
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.
To do this, get explicit approval from each contributor of copyrightable work
(as not all contributions qualify for copyright, due to not being a "creative
work", e.g. a typo fix) 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, if you have them, use the following boilerplate
(based on that used in Rust):
// Copyright 2016 owned-chars Developers
//
// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
// http://opensource.org/licenses/MIT>, at your option. This file may not be
// copied, modified, or distributed except according to those terms.
It's commonly asked whether license headers are required. I'm not comfortable
making an official recommendation either way, but the Apache license
recommends it in their appendix on how to use the license.
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 OR 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!
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.
I noticed that structs in this crate doesn't fully implement the things supported by Chars
and CharIndices
, such as DoubleEndedIterator
and FusedIterator
(relatively recent addition). It is also missing the optional methods in Iterator
(such as count
and size_hint
) which results in suboptimal performance.
I also noticed that this crate somewhat re-implements the logic of Chars
and CharIndices
. Notably, I believe the implementation of as_str
is wrong, since it's supposed to return the remaining substring rather than the whole string (demo).
Would you be interested in switching to an implementation strategy that delegates to the built-in implementations? That was, we "more or less" don't have to worry about testing for correctness (other than the methods exists and takes the same arguments) since they are just forwarding to the underlying stdlib code.
Concretely, it would look something like this:
use std::str::{Chars, CharIndices};
use std::mem::{transmute, uninitialized};
use std::iter::{Iterator, DoubleEndedIterator, FusedIterator};
#[derive(Clone, Debug)]
struct OwnedChars {
// This is needed to keep the actual buffer alive, but this should be
// treated as opaque/read-only. Mutating this will invalidate the
// iteratior and cause safety issues.
storage: String,
// Store and delegate all methods to this underlying iterator.
// 'static is a lie, it really is 'self, but this is a private field and
// we are exposing only safe APIs with the correct lifetime.
delegate: Chars<'static>
}
pub trait IntoChars {
fn into_chars(self) -> OwnedChars;
}
impl IntoChars for String {
fn into_chars(self) -> OwnedChars {
// First, move ourself into the owner
let mut owner = OwnedChars {
storage: self,
delegate: unsafe { uninitialized() }
};
// Then, we can call .chars, which with have the same lifetime
// of the owner. We need the transmute to "widen" the lifetime
// into 'static which would allow us to store it in the owner.
owner.delegate = unsafe { transmute(owner.storage.chars()) };
owner
}
}
// Now, we can just delegate everything to the underlying iterator...
impl OwnedChars {
#[inline]
fn as_str(&self) -> &str {
self.delegate.as_str()
}
}
impl Iterator for OwnedChars {
type Item = char;
#[inline]
fn next(&mut self) -> Option<char> {
self.delegate.next()
}
#[inline]
fn count(self) -> usize {
self.delegate.count()
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.delegate.size_hint()
}
#[inline]
fn last(self) -> Option<char> {
self.delegate.last()
}
}
impl DoubleEndedIterator for OwnedChars {
#[inline]
fn next_back(&mut self) -> Option<char> {
self.delegate.next_back()
}
}
impl FusedIterator for OwnedChars {}
Here is a working version. (I got tired of writing the delegating code so I turned it into a macro, but that we can extract and maintain as a separate crate, with its own test.)
Thoughts?
This crate has been throwing warnings for a while and finally stopped compiling on nightly because of the usage of std::mem::uninitialized
.
At some point this should be an RFC to include in Rust proper. Maybe with different names for the structs?
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