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Implement default methods for `io::Empty` and `io::Sink`
Implements default methods of `io::Read`, `io::BufRead`, and `io::Write` for `io::Empty` and `io::Sink`. These implementations are equivalent to the defaults, except in doing less unnecessary work.
`Read::read_to_string` and `BufRead::read_line` both have a redundant call to `str::from_utf8` which can't be inlined from `core` and `Write::write_all_vectored` has slicing logic which can't be simplified (See on [Compiler Explorer](https://rust.godbolt.org/z/KK6xcrWr4)). The rest are optimized to the minimal with `-C opt-level=3`, but this PR gives that benefit to unoptimized builds.
This includes an implementation of `Write::write_fmt` which just ignores the `fmt::Arguments<'_>`. This could be problematic whenever a user formatting impl is impure, but the docs do not guarantee that the args will be expanded.
Tracked in https://github.com/rust-lang/rust/issues/136756.
r? `@m-ou-se`
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Eliminate any redundant, unobservable logic from the their default
method implementations.
The observable changes are that `Write::write_fmt` for both types now
ignores the formatting arguments, so a user fmt impl which has side
effects is not invoked, and `Write::write_all_vectored` for both types
does not advance the borrowed buffers. Neither behavior is guaranteed by
the docs and the latter is documented as unspecified.
`Empty` is not marked as vectored, so that `Chain<Empty, _>` and
`Chain<_, Empty>` are not forced to be vectored.
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Use the existing `fill` methods on slices instead of manually
writing the fill loop.
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cc #136756
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This also keeps the old `advance` method under `advance_unchecked` name.
This makes pattern like `std::io::default_read_buf` safe to write.
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Related to #117925
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Signed-off-by: Nick Cameron <nrc@ncameron.org>
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Signed-off-by: Nick Cameron <nrc@ncameron.org>
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Signed-off-by: Nick Cameron <nrc@ncameron.org>
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Fix spacing for links inside code blocks, and improve link tooltips in alloc::fmt
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Fix spacing for links inside code blocks, and improve link tooltips in alloc::{rc, sync}
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Fix spacing for links inside code blocks, and improve link tooltips in alloc::string
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Fix spacing for links inside code blocks in alloc::vec
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Fix spacing for links inside code blocks in core::option
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Fix spacing for links inside code blocks, and improve a few link tooltips in core::result
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Fix spacing for links inside code blocks in core::{iter::{self, iterator}, stream::stream, poll}
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Fix spacing for links inside code blocks, and improve a few link tooltips in std::{fs, path}
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Fix spacing for links inside code blocks in std::{collections, time}
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Fix spacing for links inside code blocks in and make formatting of `&str`-like types consistent in std::ffi::{c_str, os_str}
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Fix spacing for links inside code blocks, and improve link tooltips in std::ffi
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Fix spacing for links inside code blocks, and improve a few link tooltips
in std::{io::{self, buffered::{bufreader, bufwriter}, cursor, util}, net::{self, addr}}
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Fix typo in link to `into` for `OsString` docs
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Remove tooltips that will probably become redundant in the future
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Apply suggestions from code review
Replacing `…std/primitive.reference.html` paths with just `reference`
Co-authored-by: Joshua Nelson <github@jyn.dev>
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Also replace `…std/primitive.reference.html` paths with just `reference` in `core::pin`
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The omission of Sink: Default is causing me a slight inconvenience in
a test harness. There seems little reason for this and Empty not to
be Clone and Copy too.
I have made all three of these insta-stable, because:
AIUI Copycan only be derived, and I was not able to find any
examples of how to unstably derive it. I think it is probably not
possible.
I hunted through the git history for precedent and found
79b8ad84c84481a43704213cd0948d2ba0ea63b4
Implement `Copy` for `IoSlice`
https://github.com/rust-lang/rust/pull/69403
which was also insta-stable.
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
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Due to the std/alloc split, it is not possible to make
`alloc::collections::TryReserveError::AllocError` non-exhaustive without
having an unstable, doc-hidden method to construct (which negates the
benefits from `#[non_exhaustive]`.
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Fix #78029
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specialize io::copy to use copy_file_range, splice or sendfile
Fixes #74426.
Also covers #60689 but only as an optimization instead of an official API.
The specialization only covers std-owned structs so it should avoid the problems with #71091
Currently linux-only but it should be generalizable to other unix systems that have sendfile/sosplice and similar.
There is a bit of optimization potential around the syscall count. Right now it may end up doing more syscalls than the naive copy loop when doing short (<8KiB) copies between file descriptors.
The test case executes the following:
```
[pid 103776] statx(3, "", AT_STATX_SYNC_AS_STAT|AT_EMPTY_PATH, STATX_ALL, {stx_mask=STATX_ALL|STATX_MNT_ID, stx_attributes=0, stx_mode=S_IFREG|0644, stx_size=17, ...}) = 0
[pid 103776] write(4, "wxyz", 4) = 4
[pid 103776] write(4, "iklmn", 5) = 5
[pid 103776] copy_file_range(3, NULL, 4, NULL, 5, 0) = 5
```
0-1 `stat` calls to identify the source file type. 0 if the type can be inferred from the struct from which the FD was extracted
𝖬 `write` to drain the `BufReader`/`BufWriter` wrappers. only happen when buffers are present. 𝖬 ≾ number of wrappers present. If there is a write buffer it may absorb the read buffer contents first so only result in a single write. Vectored writes would also be an option but that would require more invasive changes to `BufWriter`.
𝖭 `copy_file_range`/`splice`/`sendfile` until file size, EOF or the byte limit from `Take` is reached. This should generally be *much* more efficient than the read-write loop and also have other benefits such as DMA offload or extent sharing.
## Benchmarks
```
OLD
test io::tests::bench_file_to_file_copy ... bench: 21,002 ns/iter (+/- 750) = 6240 MB/s [ext4]
test io::tests::bench_file_to_file_copy ... bench: 35,704 ns/iter (+/- 1,108) = 3671 MB/s [btrfs]
test io::tests::bench_file_to_socket_copy ... bench: 57,002 ns/iter (+/- 4,205) = 2299 MB/s
test io::tests::bench_socket_pipe_socket_copy ... bench: 142,640 ns/iter (+/- 77,851) = 918 MB/s
NEW
test io::tests::bench_file_to_file_copy ... bench: 14,745 ns/iter (+/- 519) = 8889 MB/s [ext4]
test io::tests::bench_file_to_file_copy ... bench: 6,128 ns/iter (+/- 227) = 21389 MB/s [btrfs]
test io::tests::bench_file_to_socket_copy ... bench: 13,767 ns/iter (+/- 3,767) = 9520 MB/s
test io::tests::bench_socket_pipe_socket_copy ... bench: 26,471 ns/iter (+/- 6,412) = 4951 MB/s
```
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Currently it only applies to linux systems. It can be extended to make use
of similar syscalls on other unix systems.
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Includes:
- io::Cursor::new
- io::Cursor::get_ref
- io::Cursor::position
- io::empty
- io::repeat
- io::sink
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Implementation of Write for some immutable ref structs
Fixes #73836
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Fixes #73836
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rename get_{ref, mut} to assume_init_{ref,mut} in Maybeuninit
References #63568
Rework with comments addressed from #66174
Have replaced most of the occurrences I've found, hopefully didn't miss out anything
r? @RalfJung
(thanks @danielhenrymantilla for the initial work on this)
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Also doing fmt inplace as requested.
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