Improve documentation for slice swap/copy/clone operations.
Fixes#45636.
- Demonstrate how to use these operations with slices of differing
lengths
- Demonstrate how to swap/copy/clone sub-slices of a slice using
`split_at_mut`
Stabilize some `ascii_ctype` methods
As discussed in #39658, this PR stabilizes those methods for `u8` and `char`. All inherent `ascii_ctype` for `[u8]` and `str` are removed as we prefer the more explicit version `s.chars().all(|c| c.is_ascii_())`.
This PR doesn't modify the `AsciiExt` trait. There, the `ascii_ctype` methods are still unstable. It is planned to remove those in the future (I think). I had to modify some code in `ascii.rs` to properly implement `AsciiExt` for all types.
Fixes#39658.
Introduce LinkedList::drain_filter
This introduces `LinkedList::remove_if`.
This operation embodies one of the use-cases where `LinkedList` would typically be preferred over `Vec`: random removal and retrieval.
There are a number of considerations with this:
Should there be two `remove_if` methods? One where elements are only removed, one which returns a collection of removed elements.
Should this be implemented using a draining iterator pattern that covers both cases? I suspect that would incur a bit of overhead (moving the element into the iterator, then into a new collection). But I'm not sure. Maybe that's an acceptable compromise to maximize flexibility.
I don't feel I've had enough exposure to unsafe programming in rust to be certain the implementation is correct. This relies quite heavily on moving around copies of Shared pointers to make the code reasonable. Please help me out :).
Relates to rust-lang/rfcs#2140 - drain_filter for all collections
`drain_filter` is implemented instead of `LinkedList::remove_if` based
on review feedback.
Fixes#45636.
- Demonstrate how to use these operations with slices of differing
lengths
- Demonstrate how to swap/copy/clone sub-slices of a slice using
`split_at_mut`
Rename param in `[T]::swap_with_slice` from `src` to `other`.
The idea of ‘source’ and ‘destination’ aren’t very applicable for this
operation since both slices can both be considered sources and
destinations.
Add Box::leak<'a>(Box<T>) -> &'a mut T where T: 'a
Adds:
```rust
impl<T: ?Sized> Box<T> {
pub fn leak<'a>(b: Box<T>) -> &'a mut T where T: 'a {
unsafe { &mut *Box::into_raw(b) }
}
}
```
which is useful for when you just want to put some stuff on the heap and then have a reference to it for the remainder of the program.
r? @sfackler
cc @durka
The GNU C library (glibc) is documented to always allocate with an alignment
of at least 8 or 16 bytes, on 32-bit or 64-bit platforms:
https://www.gnu.org/software/libc/manual/html_node/Aligned-Memory-Blocks.html
This matches our use of `MIN_ALIGN` before this commit.
However, even when libc is glibc, the program might be linked
with another allocator that redefines the `malloc` symbol and friends.
(The `alloc_jemalloc` crate does, in some cases.)
So `alloc_system` doesn’t know which allocator it calls,
and needs to be conservative in assumptions it makes.
The C standard says:
https://port70.net/%7Ensz/c/c11/n1570.html#7.22.3
> The pointer returned if the allocation succeeds is suitably aligned
> so that it may be assigned to a pointer to any type of object
> with a fundamental alignment requirement
https://port70.net/~nsz/c/c11/n1570.html#6.2.8p2
> A fundamental alignment is represented by an alignment less than
> or equal to the greatest alignment supported by the implementation
> in all contexts, which is equal to `_Alignof (max_align_t)`.
`_Alignof (max_align_t)` depends on the ABI and doesn’t seem to have
a clear definition, but it seems to match our `MIN_ALIGN` in practice.
However, the size of objects is rounded up to the next multiple
of their alignment (since that size is also the stride used in arrays).
Conversely, the alignment of a non-zero-size object is at most its size.
So for example it seems ot be legal for `malloc(8)` to return a pointer
that’s only 8-bytes-aligned, even if `_Alignof (max_align_t)` is 16.
This has been discussed in #39658. It's a bit ambiguous how those
methods work for a sequence of ascii values. We prefer users writing
`s.iter().all(|b| b.is_ascii_...())` explicitly.
The AsciiExt methods still exist and are implemented for `str`
and `[u8]`. We will deprecated or remove those later.
get() example should use get() not get_mut()
I'm really new to Rust, this is the first thing I've ever actually pushed to github in a rust project, so please double check that it's correct. I noticed that the in-doc example for the string's get() function was referring to get_mut(). Looks like a copy/paste issue.
```rust
fn main() {
let v = String::from("🗻∈🌏");
assert_eq!(Some("🗻"), v.get(0..4));
// indices not on UTF-8 sequence boundaries
assert!(v.get(1..).is_none());
assert!(v.get(..8).is_none());
// out of bounds
assert!(v.get(..42).is_none());
}
```
results in:
```
jhford-work:~/rust/redish $ cat get-example.rs
fn main() {
let v = String::from("🗻∈🌏");
assert_eq!(Some("🗻"), v.get(0..4));
// indices not on UTF-8 sequence boundaries
assert!(v.get(1..).is_none());
assert!(v.get(..8).is_none());
// out of bounds
assert!(v.get(..42).is_none());
}
jhford-work:~/rust/redish $ rustc get-example.rs
jhford-work:~/rust/redish $ ./get-example ; echo $?
0
```
I did not build an entire rust toolchain as I'm not totally sure how to do that.
This commit removes the `rand` crate from the standard library facade as
well as the `__rand` module in the standard library. Neither of these
were used in any meaningful way in the standard library itself. The only
need for randomness in libstd is to initialize the thread-local keys of
a `HashMap`, and that unconditionally used `OsRng` defined in the
standard library anyway.
The cruft of the `rand` crate and the extra `rand` support in the
standard library makes libstd slightly more difficult to port to new
platforms, namely WebAssembly which doesn't have any randomness at all
(without interfacing with JS). The purpose of this commit is to clarify
and streamline randomness in libstd, focusing on how it's only required
in one location, hashmap seeds.
Note that the `rand` crate out of tree has almost always been a drop-in
replacement for the `rand` crate in-tree, so any usage (accidental or
purposeful) of the crate in-tree should switch to the `rand` crate on
crates.io. This then also has the further benefit of avoiding
duplication (mostly) between the two crates!
I'm really new to Rust, this is the first thing I've ever actually pushed to github in a rust project, so please double check that it's correct. I noticed that the in-doc example for the string's get() function was referring to get_mut(). Looks like a copy/paste issue.
```rust
fn main() {
let v = String::from("🗻∈🌏");
assert_eq!(Some("🗻"), v.get(0..4));
// indices not on UTF-8 sequence boundaries
assert!(v.get(1..).is_none());
assert!(v.get(..8).is_none());
// out of bounds
assert!(v.get(..42).is_none());
}
```
results in:
```
jhford-work:~/rust/redish $ cat get-example.rs
fn main() {
let v = String::from("🗻∈🌏");
assert_eq!(Some("🗻"), v.get(0..4));
// indices not on UTF-8 sequence boundaries
assert!(v.get(1..).is_none());
assert!(v.get(..8).is_none());
// out of bounds
assert!(v.get(..42).is_none());
}
jhford-work:~/rust/redish $ rustc get-example.rs
jhford-work:~/rust/redish $ ./get-example ; echo $?
0
```
I did not build an entire rust toolchain as I'm not totally sure how to do that.
Copy all `AsciiExt` methods to the primitive types directly in order to deprecate it later
**EDIT:** [this PR is ready now](https://github.com/rust-lang/rust/pull/44042#issuecomment-333883548). I edited this post to reflect the current status of discussion, which is (apart from code review) pretty much settled.
---
This is my current progress in order to prepare stabilization of #39658. As discussed there (and in #39659), the idea is to deprecated `AsciiExt` and copy all methods to the type directly. Apparently there isn't really a reason to have those methods in an extension trait¹.
~~This is **work in progress**: copy&pasting code while slightly modifying the documentation isn't the most exciting thing to do. Therefore I wanted to already open this WIP PR after doing basically 1/4 of the job (copying methods to `&[u8]`, `char` and `&str` is still missing) to get some feedback before I continue. Some questions possibly worth discussing:~~
1. ~~Does everyone agree that deprecating `AsciiExt` is a good idea? Does everyone agree with the goal of this PR?~~ => apparently yes
2. ~~Are my changes OK so far? Did I do something wrong?~~
3. ~~The issue of the unstable-attribute is currently set to 0. I would wait until you say "Ok" to the whole thing, then create a tracking issue and then insert the correct issue id. Is that ok?~~
4. ~~I tweaked `eq_ignore_ascii_case()`: it now takes the argument `other: u8` instead of `other: &u8`. The latter was enforced by the trait. Since we're not bound to a trait anymore, we can drop the reference, ok?~~ => I reverted this, because the interface has to match the `AsciiExt` interface exactly.
¹ ~~Could it be that we can't write `impl [u8] {}`? This might be the reason for `AsciiExt`. If that is the case: is there a good reason we can't write such an impl block? What can we do instead?~~ => we couldn't at the time this PR was opened, but Simon made it possible.
/cc @SimonSapin @zackw
We don't want to stabilize them now already. The goal of this set of
commits is just to add inherent methods to the four types. Stabilizing
all of those methods can be done later.
Many AsciiExt imports have become useless thanks to the inherent ascii
methods added in the last commits. These were removed. In some places, I
fully specified the ascii method being called to enforce usage of the
AsciiExt trait. Note that some imports are not removed but tagged with
a `#[cfg(stage0)]` attribute. This is necessary, because certain ascii
methods are not yet available in stage0. All those imports will be
removed later.
Additionally, failing tests were fixed. The test suite should exit
successfully now.
This is done in order to deprecate AsciiExt eventually. Note that
this commit contains a bunch of `cfg(stage0)` statements. This is
due to a new compiler feature this commit depends on: the
`slice_u8` lang item. Once this lang item is available in the
stage0 compiler, all those cfg flags (and more) can be removed.
This is done in order to deprecate AsciiExt eventually. Note that
this commit contains a bunch of `cfg(stage0)` statements. This is
due to a new compiler feature I am using: the `slice_u8` lang item.
Once this lang item is available in the stage0 compiler, all those
cfg flags (and more) can be removed.
Bring back slice::ref_slice as slice::from_ref.
These functions were deprecated and removed in 1.5, but such simple
functionality shouldn't require using unsafe code, and it isn't
cluttering libstd too much.
The original removal was quite contentious (see #27774), since then
we've had precedent for including such nuggets of functionality (see rust-lang/rfcs#1789),
and @nikomatsakis has provided a lot of use cases in https://github.com/rust-lang/rfcs/pull/1789#issuecomment-314640034.
Hence this PR.
I'm not too sure what to do with stability, feel free to correct me.
It seems pointless to go through stabilization for these functions though.
cc @aturon
These functions were deprecated and removed in 1.5, but such simple
functionality shouldn't require using unsafe code, and it isn't
cluttering libstd too much.
