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Clarify EOF handling for `BufRead::skip_until`
This aligns `BufRead::skip_until`'s description more with `BufRead::read_until` in terms of how it handles EOF and extends the doctest to include this behavior.
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r=tgross35
bufreader::Buffer::backshift: don't move the uninit bytes
previous code was perfectly sound because of MaybeUninit, but it did waste cycles on copying memory that is known to be uninitialized.
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previous code was perfectly sound because of MaybeUninit,
but it did waste cycles on copying memory that is
known to be uninitialized.
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Migrate the standard library from using the external `cfg_if` crate to
using the now-built-in `cfg_select` macro.
This does not yet eliminate the dependency from
`library/std/Cargo.toml`, because while the standard library itself no
longer uses `cfg_if`, it also incorporates the `backtrace` crate, which
does.
Migration assisted by the following vim command (after selecting the
full `cfg_if!` invocation):
```
'<,'>s/\(cfg_if::\)\?cfg_if/cfg_select/ | '<,'>s/^\( *\)} else {/\1}\r\1_ => {/c | '<,'>s/^\( *\)} else if #\[cfg(\(.*\))\] /\1}\r\1\2 => /e | '<,'>s/if #\[cfg(\(.*\))\] {/\1 => {/e
```
This is imperfect, but substantially accelerated the process. This
prompts for confirmation on the `} else {` since that can also appear
inside one of the arms. This also requires manual intervention to handle
any multi-line conditions.
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This method was not really useful: at no point one would only need to
read the initialized part of the cursor without mutating it.
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docs: Small clarification on the usage of read_to_string and read_to_end trait methods
Small clarification on the usage of read_to_string and read_to_end trait methods. The goal is to make it clear that these trait methods will become locked up if attempting to read to the end of stdin (which is a bit non-sensical unless the other end closes the pipe).
Fixes: rust-lang/rust#141714
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trait methods
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It can only describe the inner workings of the default implementation,
other implementations might not be implemented using seeks at all.
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It uses the file metadata on Unix with a fallback for files incorrectly
reported as zero-sized. It uses `GetFileSizeEx` on Windows.
This reduces the number of syscalls needed for determining the file size
of an open file from 3 to 1.
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discuss deadlocks in the std::io::pipe() example
I think it's important to discuss deadlocks in examples of how to use pipes. The current example does include an explicit `drop()`, but it also implicitly relies on the fact that the `Command` object is temporary, so that it drops its copy of `pong_tx`. This sort of thing tends to trip people up when they use pipes for the first time. I might've gone overboard with the comments in this version, but I'm curious what folks think.
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The inline documentation for all other free functions in the `std::io`
module use the phrase "creates a" instead of "create a", except for the
currently nightly-only `std::io::pipe()` function. This commit updates
the text to align with the predominant wording in the `std::io` module.
I recognize this PR is quite a minuscule nitpick, so feel free to ignore
and close if you disagree and/or there are bigger fish to fry. :smile:
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in core/alloc/std only for now, and ignoring test files
Co-authored-by: Pavel Grigorenko <GrigorenkoPV@ya.ru>
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The methods `Take::get_mut` and `Chain::get_mut` include comments
warning about modifying the I/O state of the underlying reader. However,
many readers (e.g. `File`) allow I/O using a shared reference (e.g.
`&File`). So, add the same caveat to the `get_ref` methods.
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Fixes #139665
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Provide optional `Read`/`Write` methods for stdio
Override more of the default methods for `io::Read` and `io::Write` for stdio types, when efficient to do so, and deduplicate unsupported types.
Tracked in https://github.com/rust-lang/rust/issues/136756.
try-job: x86_64-msvc-1
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Optimize `io::Write::write_fmt` for constant strings
When the formatting args to `fmt::Write::write_fmt` are a statically known string, it simplifies to only calling `write_str` without a runtime branch. Do the same in `io::Write::write_fmt` with `write_all`.
Also, match the convention of `fmt::Write` for the name of `args`.
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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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`MaybeUninit` inherent slice methods part 2
These were moved out of #129259 since they require additional libs-api approval. Tracking issue: #117428.
New API surface:
```rust
impl<T> [MaybeUninit<T>] {
// replacing fill; renamed to avoid conflict
pub fn write_filled(&mut self, value: T) -> &mut [T] where T: Clone;
// replacing fill_with; renamed to avoid conflict
pub fn write_with<F>(&mut self, value: F) -> &mut [T] where F: FnMut() -> T;
// renamed to remove "fill" terminology, since this is closer to the write_*_of_slice methods
pub fn write_iter<I>(&mut self, iter: I) -> (&mut [T], &mut Self) where I: Iterator<Item = T>;
}
```
Relevant motivation for these methods; see #129259 for earlier methods' motiviations.
* I chose `write_filled` since `filled` is being used as an object here, whereas it's being used as an action in `fill`.
* I chose `write_with` instead of `write_filled_with` since it's shorter and still matches well.
* I chose `write_iter` because it feels completely different from the fill methods, and still has the intent clear.
In all of the methods, it felt appropriate to ensure that they contained `write` to clarify that they are effectively just special ways of doing `MaybeUninit::write` for each element of a slice.
Tracking issue: https://github.com/rust-lang/rust/issues/117428
r? libs-api
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clarify BufRead::{fill_buf, consume} docs
Fixes #85394
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Co-authored-by: Ibraheem Ahmed <ibraheem@ibraheem.ca>
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When the formatting args to `fmt::Write::write_fmt` are a statically
known string, it simplifies to only calling `write_str` without a
runtime branch. Do the same in `io::Write::write_fmt` with `write_all`.
Also, match the convention of `fmt::Write` for the name of `args`.
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Stablize anonymous pipe
Since #135822 is staled, I create this PR to stablise anonymous pipe
Closes #127154
try-job: test-various
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r=Mark-Simulacrum
doc: clarify that consume can be called after BufReader::peek
tracking issue #128405
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Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>
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Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>
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Simulate OOM for the `try_oom_error` test
We can create the expected error manually, rather than trying to produce
a real one, so the error conversion test can run on all targets. Before,
it was only running on 64-bit and not miri.
In Fedora, we also found that s390x was not getting the expected error,
"successfully" allocating the huge size because it was optimizing the
real `malloc` call away. It's possible to counter that by looking at the
pointer in any way, like a debug print, but it's more robust to just
deal with errors directly, since this test is only about conversion.
Related: #133806
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We can create the expected error manually, rather than trying to produce
a real one, so the error conversion test can run on all targets. Before,
it was only running on 64-bit and not miri.
In Fedora, we also found that s390x was not getting the expected error,
"successfully" allocating the huge size because it was optimizing the
real `malloc` call away. It's possible to counter that by looking at the
pointer in any way, like a debug print, but it's more robust to just
deal with errors directly, since this test is only about conversion.
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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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Rollup of 6 pull requests
Successful merges:
- #137674 (Enable `f16` for LoongArch)
- #138034 (library: Use `size_of` from the prelude instead of imported)
- #138060 (Revert #138019 after further discussion about how hir-pretty printing should work)
- #138073 (Break critical edges in inline asm before code generation)
- #138107 (`librustdoc`: clippy fixes)
- #138111 (Use `default_field_values` for `rustc_errors::Context`, `rustc_session::config::NextSolverConfig` and `rustc_session::config::ErrorOutputType`)
r? `@ghost`
`@rustbot` modify labels: rollup
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library: Use `size_of` from the prelude instead of imported
Use `std::mem::{size_of, size_of_val, align_of, align_of_val}` from the prelude instead of importing or qualifying them.
These functions were added to all preludes in Rust 1.80.
try-job: test-various
try-job: x86_64-gnu
try-job: x86_64-msvc-1
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Fix crash in BufReader::peek()
`bufreader_peek` tracking issue: #128405
This fixes a logic error in `Buffer::read_more()` that would make `BufReader::peek()` expose uninitialized data and/or segfault if `read_more()` was called with a partially-full buffer and a non-empty inner reader.
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Override default `Write` methods for cursor-like types
Override the default `io::Write` methods for cursor-like types to provide more efficient versions.
Writes to resizable containers already write everything, so implement `write_all` and `write_all_vectored` in terms of those. For fixed-sized containers, cut out unnecessary error checking and looping for those same methods.
| `impl Write for T` | `vectored` | `all` | `all_vectored` | `fmt` |
| ------------------------------- | ---------- | ----- | -------------- | ------- |
| `&mut [u8]` | Y | Y | new | |
| `Vec<u8>` | Y | Y | new | #137762 |
| `VecDeque<u8>` | Y | Y | new | #137762 |
| `std::io::Cursor<&mut [u8]>` | Y | new | new | |
| `std::io::Cursor<&mut Vec<u8>>` | Y | new | new | #137762 |
| `std::io::Cursor<Vec<u8>>` | Y | new | new | #137762 |
| `std::io::Cursor<Box<[u8]>>` | Y | new | new | |
| `std::io::Cursor<[u8; N]>` | Y | new | new | |
| `core::io::BorrowedCursor<'_>` | new | new | new | |
Tracked in https://github.com/rust-lang/rust/issues/136756.
# Open questions
Is it guaranteed by `Write::write_all` that the maximal write is performed when not everything can be written? Its documentation describes the behavior of the default implementation, which writes until a 0-length write is encountered, thus implying that a maximal write is expected. In contrast, `Read::read_exact` declares that the contents of the buffer are unspecified for short reads. If it were allowed, these cursor-like types could bail on the write altogether if it has insufficient capacity.
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Use `std::mem::{size_of, size_of_val, align_of, align_of_val}` from the
prelude instead of importing or qualifying them.
These functions were added to all preludes in Rust 1.80.
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Added documentation for flushing per #74348
Resolves #74348
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