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Implement BufRead for VecDeque<u8> #110604

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merged 1 commit into from
Oct 15, 2023
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@a1phyr a1phyr commented Apr 20, 2023

Note: it would become insta-stable

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rustbot commented Apr 20, 2023

r? @Mark-Simulacrum

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@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Apr 20, 2023
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rustbot commented Apr 20, 2023

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

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  • Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
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  • Changing public documentation in ways that create new stability guarantees
  • Changing observable runtime behavior of library APIs

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r? @joshtriplett for libs-api FCP

@workingjubilee workingjubilee added the T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. label Jul 26, 2023
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r? libs-api

Need FCP for impl BufRead on VecDeque<u8>. It's needed for VecDeque<u8> instead of using the one for &[u8] because unlike Vec<u8>, the VecDeque can't simply deref to &[u8] (due to being internally disjoint).

@rustbot rustbot assigned BurntSushi and unassigned joshtriplett Jul 31, 2023
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dtolnay commented Sep 7, 2023

r? dtolnay

@rustbot rustbot assigned dtolnay and unassigned BurntSushi Sep 7, 2023
@dtolnay dtolnay removed the T-libs Relevant to the library team, which will review and decide on the PR/issue. label Sep 7, 2023
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This is great!

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dtolnay commented Sep 7, 2023

@rust-lang/libs-api:
@rfcbot fcp merge

Note that there is no impl BufRead for Vec<u8>. It wouldn't make sense -- .consume(n) could not be implemented efficiently. But for VecDeque<u8> it can!

For Vec<u8>, one must use a Cursor instead. That impl looks like this:

impl<T> BufRead for Cursor<T>
where
    T: AsRef<[u8]>

With or without the impl proposed by this PR, a Cursor does not work for VecDeque<u8> because it cannot be viewed as a single contiguous &[u8].

An alternative worth considering instead of this PR would be how to generalize that Cursor impl so that it works regardless of whether the &[u8] covers the whole buffer, or only a prefix of it.

pub trait PrefixBytes {
    fn prefix_bytes(&self) -> &[u8];
}

impl PrefixBytes for VecDeque<u8> {
    fn prefix_bytes(&self) -> &[u8] {
        let (front, _) = self.as_slices();
        front
    }
}

impl<T> PrefixBytes for T
where
    T: AsRef<[u8]>,
{
    fn prefix_bytes(&self) -> &[u8] {
        self.as_ref()
    }
}

impl<T> BufRead for Cursor<T>
where
    T: PrefixBytes  // instead of AsRef<[u8]>
...

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rfcbot commented Sep 7, 2023

Team member @dtolnay has proposed to merge this. The next step is review by the rest of the tagged team members:

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

@rfcbot rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Sep 7, 2023
@rfcbot rfcbot added final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. and removed proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. labels Oct 5, 2023
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rfcbot commented Oct 5, 2023

🔔 This is now entering its final comment period, as per the review above. 🔔

@rfcbot rfcbot added finished-final-comment-period The final comment period is finished for this PR / Issue. to-announce Announce this issue on triage meeting and removed final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. labels Oct 15, 2023
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rfcbot commented Oct 15, 2023

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

This will be merged soon.

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Thank you!

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dtolnay commented Oct 15, 2023

@bors r+

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bors commented Oct 15, 2023

📌 Commit a9ece12 has been approved by dtolnay

It is now in the queue for this repository.

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 15, 2023
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bors commented Oct 15, 2023

⌛ Testing commit a9ece12 with merge f70779b...

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bors commented Oct 15, 2023

☀️ Test successful - checks-actions
Approved by: dtolnay
Pushing f70779b to master...

@bors bors added the merged-by-bors This PR was explicitly merged by bors. label Oct 15, 2023
@bors bors merged commit f70779b into rust-lang:master Oct 15, 2023
1 check passed
@rustbot rustbot added this to the 1.75.0 milestone Oct 15, 2023
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Finished benchmarking commit (f70779b): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

This benchmark run did not return any relevant results for this metric.

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 625.359s -> 625.093s (-0.04%)
Artifact size: 305.52 MiB -> 305.52 MiB (-0.00%)

estebank pushed a commit to estebank/rust that referenced this pull request Oct 16, 2023
Implement `BufRead` for `VecDeque<u8>`

Note: it would become insta-stable
bors-ferrocene bot added a commit to ferrocene/ferrocene that referenced this pull request Oct 17, 2023
54: Pull upstream master 2023 10 17 r=pietroalbini a=Veykril

* rust-lang/rust#116196
* rust-lang/rust#116824
* rust-lang/rust#116822
* rust-lang/rust#116477
* rust-lang/rust#116826
* rust-lang/rust#116820
  * rust-lang/rust#116811
  * rust-lang/rust#116808
  * rust-lang/rust#116805
  * rust-lang/rust#116800
  * rust-lang/rust#116798
  * rust-lang/rust#116754
* rust-lang/rust#114370
* rust-lang/rust#116804
  * rust-lang/rust#116802
  * rust-lang/rust#116790
  * rust-lang/rust#116786
  * rust-lang/rust#116709
  * rust-lang/rust#116430
  * rust-lang/rust#116257
  * rust-lang/rust#114157
* rust-lang/rust#116731
* rust-lang/rust#116550
* rust-lang/rust#114330
* rust-lang/rust#116724
* rust-lang/rust#116782
  * rust-lang/rust#116776
  * rust-lang/rust#115955
  * rust-lang/rust#115196
* rust-lang/rust#116775
* rust-lang/rust#114589
* rust-lang/rust#113747
* rust-lang/rust#116772
  * rust-lang/rust#116771
  * rust-lang/rust#116760
  * rust-lang/rust#116755
  * rust-lang/rust#116732
  * rust-lang/rust#116522
  * rust-lang/rust#116341
  * rust-lang/rust#116172
* rust-lang/rust#110604
* rust-lang/rust#110729
* rust-lang/rust#116527
* rust-lang/rust#116688
* rust-lang/rust#116757
  * rust-lang/rust#116753
  * rust-lang/rust#116748
  * rust-lang/rust#116741
  * rust-lang/rust#116594
* rust-lang/rust#116691
* rust-lang/rust#116643
* rust-lang/rust#116683
* rust-lang/rust#116635
* rust-lang/rust#115515
* rust-lang/rust#116742
  * rust-lang/rust#116661
  * rust-lang/rust#116576
  * rust-lang/rust#116540
* rust-lang/rust#116352
* rust-lang/rust#116737
  * rust-lang/rust#116730
  * rust-lang/rust#116723
  * rust-lang/rust#116715
  * rust-lang/rust#116603
  * rust-lang/rust#116591
  * rust-lang/rust#115439
* rust-lang/rust#116264
* rust-lang/rust#116727
  * rust-lang/rust#116704
  * rust-lang/rust#116696
  * rust-lang/rust#116695
  * rust-lang/rust#116644
  * rust-lang/rust#116630
* rust-lang/rust#116728
  * rust-lang/rust#116689
  * rust-lang/rust#116679
  * rust-lang/rust#116618
  * rust-lang/rust#116577
  * rust-lang/rust#115653
* rust-lang/rust#116702
* rust-lang/rust#116015
* rust-lang/rust#115822
* rust-lang/rust#116407
* rust-lang/rust#115719
* rust-lang/rust#115524
* rust-lang/rust#116705
* rust-lang/rust#116645
* rust-lang/rust#116233
* rust-lang/rust#115108
* rust-lang/rust#116670
* rust-lang/rust#116676
* rust-lang/rust#116666



Co-authored-by: Benoît du Garreau <bdgdlm@outlook.com>
Co-authored-by: Colin Finck <colin@reactos.org>
Co-authored-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
Co-authored-by: Joshua Liebow-Feeser <joshlf@users.noreply.github.com>
Co-authored-by: León Orell Valerian Liehr <me@fmease.dev>
Co-authored-by: Trevor Gross <tmgross@umich.edu>
Co-authored-by: Evan Merlock <evan@merlock.dev>
Co-authored-by: joboet <jonasboettiger@icloud.com>
Co-authored-by: Ralf Jung <post@ralfj.de>
Co-authored-by: DaniPopes <57450786+DaniPopes@users.noreply.github.com>
Co-authored-by: Mark Rousskov <mark.simulacrum@gmail.com>
Co-authored-by: onur-ozkan <work@onurozkan.dev>
Co-authored-by: Nicholas Nethercote <n.nethercote@gmail.com>
Co-authored-by: The 8472 <git@infinite-source.de>
Co-authored-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Co-authored-by: reez12g <reez12g@gmail.com>
Co-authored-by: Jakub Beránek <berykubik@gmail.com>
@apiraino apiraino removed the to-announce Announce this issue on triage meeting label Oct 19, 2023
@wiseaidev
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wiseaidev commented Jan 11, 2024

Hello friends. While reviewing this feature, I realized that we can the accomplish the same using the as_slices. Here is an example using as_slices:

use std::collections::VecDeque;

fn main() {
    let mut vec_deque: VecDeque<u8> = VecDeque::new();
    vec_deque.push_back(1);
    vec_deque.push_back(2);
    vec_deque.push_back(3);

    let (buffer, _) = vec_deque.as_slices();
    println!("Buffer: {:?}", buffer);

    vec_deque.drain(..2);

    let (new_buffer, _) = vec_deque.as_slices();
    println!("New Buffer: {:?}", new_buffer);
}

This would accomplish the same as BufRead:

use std::collections::VecDeque;
use std::io::BufRead;

fn main() {
    let mut vec_deque: VecDeque<u8> = VecDeque::new();

    vec_deque.push_back(1);
    vec_deque.push_back(2);
    vec_deque.push_back(3);

    let buf_reader: &mut dyn BufRead = &mut vec_deque;

    let buffer = buf_reader.fill_buf().expect("Error reading buffer");

    println!("Buffer: {:?}", buffer);

    buf_reader.consume(2);

    let new_buffer = buf_reader.fill_buf().expect("Error reading buffer after consume");

    println!("New Buffer: {:?}", new_buffer);
}

So, I am wondering when this feature could be useful. Thanks!

Edit: I just read the documentation:

    /// Returns the contents of the "front" slice as returned by
    /// [`as_slices`][`VecDeque::as_slices`]. If the contained byte slices of the `VecDeque` are
    /// discontiguous, multiple calls to `fill_buf` will be needed to read the entire content.

Now I see what's the difference. Thanks

netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Mar 3, 2024
Pkgsrc changes:
 * Adjust patches and cargo checksums to new versions.
 * For an external LLVM, set dependency of llvm >= 16, in accordance
   with the upstream changes.
 * Mark that on NetBSD we now need >= 9.0, so 8.x is no longer supported.
 * On NetBSD/sparc64 10.x, we now need GCC 12 to build the embedded
   LLVM, which is version 17; apparently GCC 10.4 or 10.5 mis-compiles it,
   resulting in an illegal instruction fault during the build.
   Ref. rust-lang/rust#117231

Upstream changes:

Version 1.75.0 (2023-12-28)
==========================

- [Stabilize `async fn` and return-position `impl Trait` in traits.]
  (rust-lang/rust#115822)
- [Allow function pointer signatures containing `&mut T` in `const` contexts.]
  (rust-lang/rust#116015)
- [Match `usize`/`isize` exhaustively with half-open ranges.]
  (rust-lang/rust#116692)
- [Guarantee that `char` has the same size and alignment as `u32`.]
  (rust-lang/rust#116894)
- [Document that the null pointer has the 0 address.]
  (rust-lang/rust#116988)
- [Allow partially moved values in `match`.]
  (rust-lang/rust#103208)
- [Add notes about non-compliant FP behavior on 32bit x86 targets.]
  (rust-lang/rust#113053)
- [Stabilize ratified RISC-V target features.]
  (rust-lang/rust#116485)

Compiler
--------

- [Rework negative coherence to properly consider impls that only
  partly overlap.] (rust-lang/rust#112875)
- [Bump `COINDUCTIVE_OVERLAP_IN_COHERENCE` to deny, and warn in dependencies.]
  (rust-lang/rust#116493)
- [Consider alias bounds when computing liveness in NLL.]
  (rust-lang/rust#116733)
- [Add the V (vector) extension to the `riscv64-linux-android` target spec.]
  (rust-lang/rust#116618)
- [Automatically enable cross-crate inlining for small functions]
  (rust-lang/rust#116505)
- Add several new tier 3 targets:
    - [`csky-unknown-linux-gnuabiv2hf`]
      (rust-lang/rust#117049)
    - [`i586-unknown-netbsd`]
      (rust-lang/rust#117170)
    - [`mipsel-unknown-netbsd`]
      (rust-lang/rust#117356)

Refer to Rust's [platform support page][platform-support-doc]
for more information on Rust's tiered platform support.

Libraries
---------

- [Override `Waker::clone_from` to avoid cloning `Waker`s unnecessarily.]
  (rust-lang/rust#96979)
- [Implement `BufRead` for `VecDeque<u8>`.]
  (rust-lang/rust#110604)
- [Implement `FusedIterator` for `DecodeUtf16` when the inner iterator does.]
  (rust-lang/rust#110729)
- [Implement `Not, Bit{And,Or}{,Assign}` for IP addresses.]
  (rust-lang/rust#113747)
- [Implement `Default` for `ExitCode`.]
  (rust-lang/rust#114589)
- [Guarantee representation of None in NPO]
  (rust-lang/rust#115333)
- [Document when atomic loads are guaranteed read-only.]
  (rust-lang/rust#115577)
- [Broaden the consequences of recursive TLS initialization.]
  (rust-lang/rust#116172)
- [Windows: Support sub-millisecond sleep.]
  (rust-lang/rust#116461)
- [Fix generic bound of `str::SplitInclusive`'s `DoubleEndedIterator` impl]
  (rust-lang/rust#100806)
- [Fix exit status / wait status on non-Unix `cfg(unix)` platforms.]
  (rust-lang/rust#115108)

Stabilized APIs
---------------

- [`Atomic*::from_ptr`]
  (https://doc.rust-lang.org/stable/core/sync/atomic/struct.AtomicUsize.html#method.from_ptr)
- [`FileTimes`]
  (https://doc.rust-lang.org/stable/std/fs/struct.FileTimes.html)
- [`FileTimesExt`]
  (https://doc.rust-lang.org/stable/std/os/windows/fs/trait.FileTimesExt.html)
- [`File::set_modified`]
  (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.set_modified)
- [`File::set_times`]
  (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.set_times)
- [`IpAddr::to_canonical`]
  (https://doc.rust-lang.org/stable/core/net/enum.IpAddr.html#method.to_canonical)
- [`Ipv6Addr::to_canonical`]
  (https://doc.rust-lang.org/stable/core/net/struct.Ipv6Addr.html#method.to_canonical)
- [`Option::as_slice`]
  (https://doc.rust-lang.org/stable/core/option/enum.Option.html#method.as_slice)
- [`Option::as_mut_slice`]
  (https://doc.rust-lang.org/stable/core/option/enum.Option.html#method.as_mut_slice)
- [`pointer::byte_add`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.byte_add)
- [`pointer::byte_offset`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.byte_offset)
- [`pointer::byte_offset_from`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.byte_offset_from)
- [`pointer::byte_sub`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.byte_sub)
- [`pointer::wrapping_byte_add`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.wrapping_byte_add)
- [`pointer::wrapping_byte_offset`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.wrapping_byte_offset)
- [`pointer::wrapping_byte_sub`]
  (https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.wrapping_byte_sub)

These APIs are now stable in const contexts:

- [`Ipv6Addr::to_ipv4_mapped`]
  (https://doc.rust-lang.org/stable/core/net/struct.Ipv6Addr.html#method.to_ipv4_mapped)
- [`MaybeUninit::assume_init_read`]
  (https://doc.rust-lang.org/stable/core/mem/union.MaybeUninit.html#method.assume_init_read)
- [`MaybeUninit::zeroed`]
  (https://doc.rust-lang.org/stable/core/mem/union.MaybeUninit.html#method.zeroed)
- [`mem::discriminant`]
  (https://doc.rust-lang.org/stable/core/mem/fn.discriminant.html)
- [`mem::zeroed`]
  (https://doc.rust-lang.org/stable/core/mem/fn.zeroed.html)

Cargo
-----

- [Add new packages to `[workspace.members]` automatically.]
  (rust-lang/cargo#12779)
- [Allow version-less `Cargo.toml` manifests.]
  (rust-lang/cargo#12786)
- [Make browser links out of HTML file paths.]
  (rust-lang/cargo#12889)

Rustdoc
-------

- [Accept less invalid Rust in rustdoc.]
  (rust-lang/rust#117450)
- [Document lack of object safety on affected traits.]
  (rust-lang/rust#113241)
- [Hide `#[repr(transparent)]` if it isn't part of the public ABI.]
  (rust-lang/rust#115439)
- [Show enum discriminant if it is a C-like variant.]
  (rust-lang/rust#116142)

Compatibility Notes
-------------------

- [FreeBSD targets now require at least version 12.]
  (rust-lang/rust#114521)
- [Formally demote tier 2 MIPS targets to tier 3.]
  (rust-lang/rust#115238)
- [Make misalignment a hard error in `const` contexts.]
  (rust-lang/rust#115524)
- [Fix detecting references to packed unsized fields.]
  (rust-lang/rust#115583)
- [Remove support for compiler plugins.]
  (rust-lang/rust#116412)
@a1phyr a1phyr deleted the vecdeque_buf_read branch March 12, 2024 17:12
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