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read_buf_exact: on error, all read bytes are appended to the buffer #109022

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Merged
merged 1 commit into from
Mar 19, 2023
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read_buf_exact: on error, all read bytes are appended to the buffer #109022

merged 1 commit into from
Mar 19, 2023

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tmiasko
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@tmiasko tmiasko commented Mar 11, 2023

Guarantee that when read_buf_exact returns, all bytes read will be
appended to the buffer. Including the case when the operations fails.

The motivating use case are operations on a non-blocking reader. When
read_buf_exact fails with ErrorKind::WouldBlock error, the operation
can be resumed at a later time.

@tmiasko
read_buf_exact: on error, all read bytes are appended to the buffer
c21f1d0 
Guarantee that when `read_buf_exact` returns, all bytes read will be
appended to the buffer. Including the case when the operations fails.

The motivating use case are operations on a non-blocking reader. When
`read_buf_exact` fails with `ErrorKind::WouldBlock` error, the operation
can be resumed at a later time.
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rustbot commented Mar 11, 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 Mar 11, 2023
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rustbot commented Mar 11, 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:

  • Stabilizing library features
  • Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
  • Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
  • Changing public documentation in ways that create new stability guarantees
  • Changing observable runtime behavior of library APIs

@tmiasko tmiasko added T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. and removed T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Mar 11, 2023
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r? dtolnay for T-libs-api FCP

@rustbot rustbot assigned dtolnay and unassigned Mark-Simulacrum Mar 18, 2023
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Looks good. Hopefully my understanding is correct: the reason this is different than read_exact (which makes ∅ guarantee about what's put in buf in the error case) is that read_exact has no way to convey to the caller the number of bytes that got written in the error case, whereas in read_buf_exact the BorrowedCursor keeps track of that and can let the caller soundly access the written part after an error if they want.

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dtolnay commented Mar 18, 2023

@bors r+ rollup

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bors commented Mar 18, 2023

📌 Commit c21f1d0 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 Mar 18, 2023
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dtolnay commented Mar 18, 2023

(The method is unstable; no T-libs-api FCP until later.)

@Dylan-DPC Dylan-DPC mentioned this pull request Mar 19, 2023
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bors added a commit to rust-lang-ci/rust that referenced this pull request Mar 19, 2023
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Auto merge of rust-lang#109346 - Dylan-DPC:rollup-vszi5bn, r=Dylan-DPC
8826b68 
Rollup of 10 pull requests

Successful merges:

 - rust-lang#104100 (Allow using `Range` as an `Iterator` in const contexts. )
 - rust-lang#105793 (Add note for mismatched types because of circular dependencies)
 - rust-lang#108798 (move default backtrace setting to sys)
 - rust-lang#108829 (Use Edition 2021 :pat in matches macro)
 - rust-lang#108973 (Beautify pin! docs)
 - rust-lang#109003 (Add `useless_anonymous_reexport` lint)
 - rust-lang#109022 (read_buf_exact: on error, all read bytes are appended to the buffer)
 - rust-lang#109212 (fix: don't suggest similar method when unstable)
 - rust-lang#109243 (The name of NativeLib will be presented)
 - rust-lang#109324 (Implement FixedSizeEncoding for UnusedGenericParams.)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 654204f into rust-lang:master Mar 19, 2023
@rustbot rustbot added this to the 1.70.0 milestone Mar 19, 2023
@tmiasko tmiasko deleted the read-buf-exact branch March 27, 2023 14:45
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