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.
Minor internal comments fix for `BufRead::read_line`
Just a little fix that came up while I was reading through this source code, and had to search for a few minutes to find out what was actually *meant* here.
Error messages are supposed to start with lowercase letters, but a lot
of `io::const_error` messages did not. This fixes them to start with a
lowercase letter.
I did consider adding a const check for this to the macro, but some of
them start with proper nouns that make sense to uppercase them.
See https://doc.rust-lang.org/1.85.0/std/error/trait.Error.html
Use `const_error!` when possible
Replace usages of `io::Error::new(io::ErrorKind::Variant, "constant string")` with `io::const_error!(io::ErrorKind::Variant, "constant string")` to avoid allocations when possible. Additionally, fix `&&str` error messages in SGX and missing/misplaced trailing commas in `const_error!`.
Update bootstrap compiler and rustfmt
The rustfmt version we previously used formats things differently from what the latest nightly rustfmt does. This causes issues for subtrees that get formatted both in-tree and in their own repo. Updating the rustfmt used in-tree solves those issues. Also bumped the bootstrap compiler as the stage0 update command always updates both at the same
time.
std: move `io` module out of `pal`, get rid of `sys_common::io`
Part of #117276.
This does two related things:
1. It moves the platform-specific definitions for `IoSlice`, `IoSliceMut` and `is_terminal` out of `pal` and into `sys` and unifies some of them.
2. It gets rid of `sys_common::io`, moving the non-platform-specific test helpers into `std::test_helpers` and the buffer size definition to the new `sys::io` module.
Update emscripten std tests
This disables a bunch of emscripten tests that test things emscripten doesn't support and re-enables a whole bunch of tests which now work just fine on emscripten.
Tested with `EMCC_CFLAGS="-s MAXIMUM_MEMORY=2GB" ./x.py test library/ --target wasm32-unknown-emscripten`.
- Simplify some of the language
- Minor grammar fixes
- Don't imply that pipes *only* work across multiple processes; instead,
*suggest* that they're typically used across two or more separate
processes.
- Specify that portable applications cannot use multiple readers or
multiple writers for messages larger than a byte, due to potential
interleaving.
- Remove no-longer-referenced footnote URLs.
Stabilize `std::io::ErrorKind::CrossesDevices`
FCP in #130191
cc #86442
See #130191 for more info and a recap of what has happened up until now.
TLDR: This had been FCP'd in December 2022 with some other `ErrorKind`s, but the stabilization got postponed due to some concerns voiced about several of the variants. However, the only concern ever voiced for this variant in particular was a wish to rename this to `NotSameDevice` analogous to Windows's `ERROR_NOT_SAME_DEVICE` (as opposed to Unix's `EXDEV`). This suggestion did not receive any support. So let's try to FCP this as is.
r? libs-api
Mark `get_mut` and `set_position` in `std::io::Cursor` as const.
Relevant tracking issue: #130801
The methods `get_mut` and `set_position` can trivially be marked as const due to #57349 being stabilised.
