std: Implement LineWriter::write_vectored
#67270
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This commit implements the `write_vectored` method of the `LineWriter` type. First discovered in bytecodealliance/wasmtime#629 the `write_vectored` method of `Stdout` bottoms out here but only ends up writing the first buffer due to the default implementation of `write_vectored`. Like `BufWriter`, however, `LineWriter` can have a non-default implementation of `write_vectored` which tries to preserve the vectored-ness as much as possible. Namely we can have a vectored write for everything before the newline and everything after the newline if all the stars align well. Also like `BufWriter`, though, special care is taken to ensure that whenever bytes are written we're sure to signal success since that represents a "commit" of writing bytes.
|
r? @cramertj (rust_highfive has picked a reviewer for you, use r? to override) |
rust-highfive
added
the
S-waiting-on-review
|
r? @sfackler |
sfackler
reviewed
Dec 13, 2019
| self.need_flush = true; | ||
| } | ||
| if n == prefix_amt { | ||
| match self.inner.write(&buf[..=j]) { |
There was a problem hiding this comment.
I'm not sure how I feel about one write_vectored call turning into up to write_vectored, write, flush, write, write_vectored. Maybe it makes sense for LineWriter, but IIRC in general we tend to want to keep write/write_vectored relative 1:1 with downstream calls.
There was a problem hiding this comment.
FWIW LineWriter::write is already a call to write, flush, then write. We could skip a few calls here by creating a local Vec<IoSlice>, but I figured that since it's all buffered here anyway a few more calls wouldn't matter too much.
The main thing is that we want to slice a &[IoSlice] as if it were &[u8] but we can't do that since we can't mutate IoSlice in place.
|
@bors r+ |
|
📌 Commit 2fee28e has been approved by |
|
🌲 The tree is currently closed for pull requests below priority 100, this pull request will be tested once the tree is reopened |
bors
added
S-waiting-on-bors
Centril
added a commit
to Centril/rust
that referenced
this pull request
Dec 19, 2019
…, r=sfackler std: Implement `LineWriter::write_vectored` This commit implements the `write_vectored` method of the `LineWriter` type. First discovered in bytecodealliance/wasmtime#629 the `write_vectored` method of `Stdout` bottoms out here but only ends up writing the first buffer due to the default implementation of `write_vectored`. Like `BufWriter`, however, `LineWriter` can have a non-default implementation of `write_vectored` which tries to preserve the vectored-ness as much as possible. Namely we can have a vectored write for everything before the newline and everything after the newline if all the stars align well. Also like `BufWriter`, though, special care is taken to ensure that whenever bytes are written we're sure to signal success since that represents a "commit" of writing bytes.
bors
added a commit
that referenced
this pull request
Dec 19, 2019
Rollup of 8 pull requests Successful merges: - #67189 (Unify binop wording) - #67270 (std: Implement `LineWriter::write_vectored`) - #67286 (Fix the configure.py TOML field for a couple LLVM options) - #67321 (make htons const fn) - #67382 (Remove some unnecessary `ATTR_*` constants.) - #67389 (Remove `SO_NOSIGPIPE` dummy variable on platforms that don't use it.) - #67394 (Remove outdated references to @t from comments) - #67406 (Suggest associated type when the specified one cannot be found) Failed merges: r? @ghost
# for free
to join this conversation on GitHub.
Already have an account?
# to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This commit implements the
write_vectoredmethod of theLineWritertype. First discovered in bytecodealliance/wasmtime#629 the
write_vectoredmethod ofStdoutbottoms out here but only ends upwriting the first buffer due to the default implementation of
write_vectored.Like
BufWriter, however,LineWritercan have a non-defaultimplementation of
write_vectoredwhich tries to preserve thevectored-ness as much as possible. Namely we can have a vectored write
for everything before the newline and everything after the newline if
all the stars align well.
Also like
BufWriter, though, special care is taken to ensure thatwhenever bytes are written we're sure to signal success since that
represents a "commit" of writing bytes.