Add vectored read and write support
This functionality has lived for a while in the tokio ecosystem, where
it can improve performance by minimizing copies.
r? @alexcrichton
Refactor Windows stdio and remove stdin double buffering
I was looking for something nice and small to work on, tried to tackle a few FIXME's in Windows stdio, and things grew from there.
This part of the standard library contains some tricky code, and has changed over the years to handle more corner cases. It could use some refactoring and extra comments.
Changes/fixes:
- Made `StderrRaw` `pub(crate)`, to remove the `Write` implementations on `sys::Stderr` (used unsynchronised for panic output).
- Remove the unused `Read` implementation on `sys::windows::stdin`
- The `windows::stdio::Output` enum made sense when we cached the handles, but we can use simple functions like `is_console` now that we get the handle on every read/write
- `write` can now calculate the number of written bytes as UTF-8 when we can't write all `u16`s.
- If `write` could only write one half of a surrogate pair, attempt another write for the other because user code can't reslice in any way that would allow us to write it otherwise.
- Removed the double buffering on stdin. Documentation on the unexposed `StdinRaw` says: 'This handle is not synchronized or buffered in any fashion'; which is now true.
- `sys::windows::Stdin` now always only partially fills its buffer, so we can guarantee any arbitrary UTF-16 can be re-encoded without losing any data.
- `sys::windows::STDIN_BUF_SIZE` is slightly larger to compensate. There should be no real change in the number of syscalls the buffered `Stdin` does. This buffer is a little larger, while the extra buffer on Stdin is gone.
- `sys::windows::Stdin` now attempts to handle unpaired surrogates at its buffer boundary.
- `sys::windows::Stdin` no langer allocates for its buffer, but the UTF-16 decoding still does.
### Testing
I did some manual testing of reading and writing to console. The console does support UTF-16 in some sense, but doesn't supporting displaying characters outside the BMP.
- compile stage 1 stdlib with a tiny value for `MAX_BUFFER_SIZE` to make it easier to catch corner cases
- run a simple test program that reads on stdin, and echo's to stdout
- write some lines with plenty of ASCII and emoji in a text editor
- copy and paste in console to stdin
- return with `\r\n\` or CTRL-Z
- copy and paste in text editor
- check it round-trips
-----
Fixes https://github.com/rust-lang/rust/issues/23344. All but one of the suggestions in that issue are now implemented. the missing one is:
> * When reading data, we require the entire set of input to be valid UTF-16. We should instead attempt to read as much of the input as possible as valid UTF-16, only returning an error for the actual invalid elements. For example if we read 10 elements, 5 of which are valid UTF-16, the 6th is bad, and then the remaining are all valid UTF-16, we should probably return the first 5 on a call to `read`, then return an error, then return the remaining on the next call to `read`.
Stdin in Console mode is dealing with text directly input by a user. In my opinion getting an unpaired surrogate is quite unlikely in that case, and a valid reason to error on the entire line of input (which is probably short). Dealing with it is incompatible with an unbuffered stdin, which seems the more interesting guarantee to me.
Simplify the unix `Weak` functionality
- We can avoid allocation by adding a NUL to the function name.
- We can get `Option<F>` directly, rather than aliasing the inner `AtomicUsize`.
Turn duration consts into associated consts
As suggested in https://github.com/rust-lang/rust/issues/57391#issuecomment-459658236, I'm moving `Duration` constants (`SECOND`, `MILLISECOND` and so on; currently behind unstable `duration_constants` feature) into the `impl Duration` block.
cc @frewsxcv @SimonSapin
Explain a panic in test case net::tcp::tests::double_bind
Those who try to build libstd on the Windows Subsystem for Linux experience a single failing test, where the point of failure is an explicit but anonymous panic, as reported in https://github.com/rust-lang/rust/issues/49367
This commit somewhat explains why and allows diagnosing a little.
Add alias methods to PathBuf for underlying OsString (#58234)
Implemented the following methods on PathBuf which forward to the underlying OsString.
- capacity
- with_capacity
- clear
- reserve
- reserve_exact
- shrink_to_fit
- shrink_to
These methods have been documented with reference to the original docs for `OsString`. @Mark-Simulacrum please let me know if you feel this does not suffice.
Further, I've not yet included tests for these definitions - please advise on how comprehensive tests need to be for methods such as these that simply alias other (already tested) methods.
(This PR addresses issue #58234)
Monomorphize less code in fs::{read|write}
Since the generic-ness is only for the as_refs, might as well have std just compile the important part once instead of on every use.
There are two big categories of changes in here
- Removing lifetimes from common traits that can essentially never user a lifetime from an input (particularly `Drop` & `Debug`)
- Forwarding impls that are only possible because the lifetime doesn't matter (like `impl<R: Read + ?Sized> Read for &mut R`)
I omitted things that seemed like they could be more controversial, like the handful of iterators that have a `Item: 'static` despite the iterator having a lifetime or the `PartialEq` implementations where the flipped one cannot elide the lifetime.
- Fixed incorrect `mut` usage
- Fixed style in accordance with tidy
- Marked all methods as unstable
- Changed feature identifier to path_buf_alias_os_string_methods
Implemented the following methods on PathBuf which
forward to the underlying OsString.
- capacity
- with_capacity
- clear
- reserve
- reserve_exact
- shrink_to_fit
- shrink_to
Use posix_spawn_file_actions_addchdir_np when possible
This is a non-POSIX extension implemented in Solaris and in glibc 2.29.
With this we can still use `posix_spawn()` when `Command::current_dir()`
has been set, otherwise we fallback to `fork(); chdir(); exec()`.
Update the future/task API
This change updates the future and task API as discussed in the stabilization RFC at https://github.com/rust-lang/rfcs/pull/2592.
Changes:
- Replacing UnsafeWake with RawWaker and RawWakerVtable
- Removal of LocalWaker
- Removal of Arc-based Wake trait
