In a followup to PR #26849, improve one more location for I/O where
we can use `Vec::resize` to ensure better performance when zeroing
buffers.
Use the `vec![elt; n]` macro everywhere we can in the tree. It replaces
`repeat(elt).take(n).collect()` which is more verbose, requires type
hints, and right now produces worse code. `vec![]` is preferable for vector
initialization.
The `vec![]` replacement touches upon one I/O path too, Stdin::read
for windows, and that should be a small improvement.
r? @alexcrichton
Improve zerofill in Vec::resize and Read::read_to_end
We needed a more efficient way to zerofill the vector in read_to_end.
This to reduce the memory intialization overhead to a minimum.
Use the implementation of `std::vec::from_elem` (used for the vec![]
macro) for Vec::resize as well. For simple element types like u8, this
compiles to memset, so it makes Vec::resize much more efficient.
Use the vec![] macro directly to create a sized, zeroed vector.
This should result in a big speedup when creating BufReader, because
vec![0; cap] compiles to a memset call, while the previous extend code
currently did not.
We needed a more efficient way to zerofill the vector in read_to_end.
This to reduce the memory intialization overhead to a minimum.
Use the implementation of `std::vec::from_elem` (used for the vec![]
macro) for Vec::resize as well. For simple element types like u8, this
compiles to memset, so it makes Vec::resize much more efficient.
Closes#25977
The various `stdfoo_raw` methods in std::io now return `io::Result`s,
since they may not exist on Windows. They will always return `Ok` on
Unix-like platforms.
[breaking-change]
Closes#25977
The various `stdfoo_raw` methods in std::io now return `io::Result`s,
since they may not exist on Windows. They will always return `Ok` on
Unix-like platforms.
[breaking-change]
This takes the cases from InvalidInput where a data format error
was encountered. This is different from the documented semantics
of InvalidInput, which more likely indicate a programming error.
An automated script was run against the `.rs` and `.md` files,
subsituting every occurrence of `task` with `thread`. In the `.rs`
files, only the texts in the comment blocks were affected.
As pointed out in #17136 the semantics of a `BufStream` aren't always what one
expects, and it looks like other [languages like C#][c-sharp] implement a
buffered stream with only one underlying buffer. For now this commit
destabilizes the primitive in the `std::io` module to give us some more time in
figuring out what to do with it.
[c-sharp]: https://msdn.microsoft.com/en-us/library/system.io.bufferedstream%28v=vs.110%29.aspx
[breaking-change]
These implementations were intended to be unstable, but currently the stability
attributes cannot handle a stable trait with an unstable `impl` block. This
commit also audits the rest of the standard library for explicitly-`#[unstable]`
impl blocks. No others were removed but some annotations were changed to
`#[stable]` as they're defacto stable anyway.
One particularly interesting `impl` marked `#[stable]` as part of this commit
is the `Add<&[T]>` impl for `Vec<T>`, which uses `push_all` and implicitly
clones all elements of the vector provided.
Closes#24791
[breaking-change]
These implementations were intended to be unstable, but currently the stability
attributes cannot handle a stable trait with an unstable `impl` block. This
commit also audits the rest of the standard library for explicitly-`#[unstable]`
impl blocks. No others were removed but some annotations were changed to
`#[stable]` as they're defacto stable anyway.
One particularly interesting `impl` marked `#[stable]` as part of this commit
is the `Add<&[T]>` impl for `Vec<T>`, which uses `push_all` and implicitly
clones all elements of the vector provided.
Closes#24791
This commit brings the `Error` trait in line with the [Error interoperation
RFC](https://github.com/rust-lang/rfcs/pull/201) by adding downcasting,
which has long been intended. This change means that for any `Error`
trait objects that are `'static`, you can downcast to concrete error
types.
To make this work, it is necessary for `Error` to inherit from
`Reflect` (which is currently used to mark concrete types as "permitted
for reflection, aka downcasting"). This is a breaking change: it means
that impls like
```rust
impl<T> Error for MyErrorType<T> { ... }
```
must change to something like
```rust
impl<T: Reflect> Error for MyErrorType<T> { ... }
```
except that `Reflect` is currently unstable (and should remain so for
the time being). For now, code can instead bound by `Any`:
```rust
impl<T: Any> Error for MyErrorType<T> { ... }
```
which *is* stable and has `Reflect` as a super trait. The downside is
that this imposes a `'static` constraint, but that only
constrains *when* `Error` is implemented -- it does not actually
constrain the types that can implement `Error`.
[breaking-change]
As pointed out in #17136 the semantics of a `BufStream` aren't always what one
expects, and it looks like other [languages like C#][c-sharp] implement a
buffered stream with only one underlying buffer. For now this commit
destabilizes the primitive in the `std::io` module to give us some more time in
figuring out what to do with it.
[c-sharp]: https://msdn.microsoft.com/en-us/library/system.io.bufferedstream%28v=vs.110%29.aspx
[breaking-change]
Steve Klabnik