simplify eat_digits

[klensy]

Simplify eat_digits by checking values in iterator, plus decrease function size, by returning unchecked slices.

https://godbolt.org/z/cxjav4

[rust-highfive]

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[tesuji]

I'd prefer to fix the LLVM optimizing issue to using unsafe code for this.

[klensy]

Also works that:

#![feature(core_intrinsics)]
use std::intrinsics::assume;

pub fn eat_digits(s: &[u8]) -> (&[u8], &[u8]) {
    let sep = s.iter().take_while(|x| (b'0'..=b'9').contains(x)).count();

    unsafe{ assume(sep <= s.len()); };

    (&s[..sep], &s[sep..])
}

[klensy]

Or that without bound check, but looks ugly:

pub fn eat_digits(s: &[u8]) -> (&[u8], &[u8]) {
    for i in 0..s.len(){
        if !s[i].is_ascii_digit(){
            return s.split_at(i);
        }
    }
    s.split_at(s.len())
}

https://godbolt.org/z/nxqz4n

[camsteffen]

How about

pub fn eat_digits(s: &[u8]) -> (&[u8], &[u8]) {
    let pos = s.iter().position(|c| !c.is_ascii_digit()).unwrap_or(s.len());
    s.split_at(pos)
}

[LingMan]

@camsteffen's version looks nice. It compiles to the exact same assembly as the versions with get_unchecked/assume and is the easiest to read if you ask me.

[klensy]

@camsteffen Yes, this looks nice, can i PR this version?

[camsteffen]

Yes you can use it 🙂

[klensy]

This removes bound checks, and as this function get inlined, few more.

@rustbot label -S-waiting-on-author +S-waiting-on-review

[m-ou-se]

@bors r+

[bors]

📌 Commit ec09d7f has been approved by m-ou-se

[bors]

⌛ Testing commit ec09d7f with merge da5f7f1...

[bors]

☀️ Test successful - checks-actions
Approved by: m-ou-se
Pushing da5f7f1 to master...

[rust-log-analyzer]

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  git switch -

Turn off this advice by setting config variable advice.detachedHead to false

HEAD is now at da5f7f109 Auto merge of #81427 - klensy:eat-digits, r=m-ou-se
##[group]Run src/ci/publish_toolstate.sh
src/ci/publish_toolstate.sh
env:
  SCCACHE_BUCKET: rust-lang-ci-sccache2
  DEPLOY_BUCKET: rust-lang-ci2
  TOOLSTATE_REPO: https://github.com/rust-lang-nursery/rust-toolstate
---
  CACHE_DOMAIN: ci-caches.rust-lang.org
  TOOLSTATE_REPO_ACCESS_TOKEN: ***
##[endgroup]
Cloning into 'rust-toolstate'...
/home/runner/work/rust/rust/src/tools/publish_toolstate.py:121: DeprecationWarning: 'U' mode is deprecated
📣 Toolstate changed by rust-lang/rust#81427!
  with open(path, 'rU') as f:

Tested on commit rust-lang/rust@da5f7f10936198bad22c370118bad1ac332d2f46.
Direct link to PR: <https://github.com/rust-lang/rust/pull/81427>

💔 miri on windows: test-fail → build-fail (cc @eddyb @RalfJung @oli-obk).
💔 miri on linux: test-fail → build-fail (cc @eddyb @RalfJung @oli-obk).
Traceback (most recent call last):
Traceback (most recent call last):
  File "/home/runner/work/rust/rust/src/tools/publish_toolstate.py", line 338, in <module>
    response = urllib2.urlopen(urllib2.Request(
  File "/usr/lib/python3.8/urllib/request.py", line 222, in urlopen
    return opener.open(url, data, timeout)
  File "/usr/lib/python3.8/urllib/request.py", line 522, in open
    req = meth(req)
  File "/usr/lib/python3.8/urllib/request.py", line 1281, in do_request_
    raise TypeError(msg)
TypeError: POST data should be bytes, an iterable of bytes, or a file object. It cannot be of type str.
##[error]Process completed with exit code 1.