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Rollup merge of rust-lang#56216 - SimonSapin:array-tryfrom-slice, r=w…
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…ithoutboats

Add TryFrom<&[T]> for [T; $N] where T: Copy

`TryFrom<&[T]> for &[T; $N]` (note *reference* to an array) already exists, but not needing to dereference makes type inference easier for example when using `u32::from_be_bytes`.

Also add doc examples doing just that.
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kennytm committed Nov 30, 2018
2 parents c3950c8 + 057e6d3 commit f7c407e
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9 changes: 9 additions & 0 deletions src/libcore/array.rs
Original file line number Diff line number Diff line change
Expand Up @@ -148,6 +148,15 @@ macro_rules! array_impls {
}
}

#[unstable(feature = "try_from", issue = "33417")]
impl<'a, T> TryFrom<&'a [T]> for [T; $N] where T: Copy {
type Error = TryFromSliceError;

fn try_from(slice: &[T]) -> Result<[T; $N], TryFromSliceError> {
<&Self>::try_from(slice).map(|r| *r)
}
}

#[unstable(feature = "try_from", issue = "33417")]
impl<'a, T> TryFrom<&'a [T]> for &'a [T; $N] {
type Error = TryFromSliceError;
Expand Down
78 changes: 78 additions & 0 deletions src/libcore/num/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1989,6 +1989,19 @@ big endian.
```
let value = ", stringify!($SelfT), "::from_be_bytes(", $be_bytes, ");
assert_eq!(value, ", $swap_op, ");
```
When starting from a slice rather than an array, fallible conversion APIs can be used:
```
#![feature(try_from)]
use std::convert::TryInto;
fn read_be_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " {
let (int_bytes, rest) = input.split_at(std::mem::size_of::<", stringify!($SelfT), ">());
*input = rest;
", stringify!($SelfT), "::from_be_bytes(int_bytes.try_into().unwrap())
}
```"),
#[stable(feature = "int_to_from_bytes", since = "1.32.0")]
#[rustc_const_unstable(feature = "const_int_conversion")]
Expand All @@ -2008,6 +2021,19 @@ little endian.
```
let value = ", stringify!($SelfT), "::from_le_bytes(", $le_bytes, ");
assert_eq!(value, ", $swap_op, ");
```
When starting from a slice rather than an array, fallible conversion APIs can be used:
```
#![feature(try_from)]
use std::convert::TryInto;
fn read_be_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " {
let (int_bytes, rest) = input.split_at(std::mem::size_of::<", stringify!($SelfT), ">());
*input = rest;
", stringify!($SelfT), "::from_be_bytes(int_bytes.try_into().unwrap())
}
```"),
#[stable(feature = "int_to_from_bytes", since = "1.32.0")]
#[rustc_const_unstable(feature = "const_int_conversion")]
Expand Down Expand Up @@ -2037,6 +2063,19 @@ let value = ", stringify!($SelfT), "::from_ne_bytes(if cfg!(target_endian = \"bi
", $le_bytes, "
});
assert_eq!(value, ", $swap_op, ");
```
When starting from a slice rather than an array, fallible conversion APIs can be used:
```
#![feature(try_from)]
use std::convert::TryInto;
fn read_be_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " {
let (int_bytes, rest) = input.split_at(std::mem::size_of::<", stringify!($SelfT), ">());
*input = rest;
", stringify!($SelfT), "::from_be_bytes(int_bytes.try_into().unwrap())
}
```"),
#[stable(feature = "int_to_from_bytes", since = "1.32.0")]
#[rustc_const_unstable(feature = "const_int_conversion")]
Expand Down Expand Up @@ -3719,6 +3758,19 @@ big endian.
```
let value = ", stringify!($SelfT), "::from_be_bytes(", $be_bytes, ");
assert_eq!(value, ", $swap_op, ");
```
When starting from a slice rather than an array, fallible conversion APIs can be used:
```
#![feature(try_from)]
use std::convert::TryInto;
fn read_be_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " {
let (int_bytes, rest) = input.split_at(std::mem::size_of::<", stringify!($SelfT), ">());
*input = rest;
", stringify!($SelfT), "::from_be_bytes(int_bytes.try_into().unwrap())
}
```"),
#[stable(feature = "int_to_from_bytes", since = "1.32.0")]
#[rustc_const_unstable(feature = "const_int_conversion")]
Expand All @@ -3738,6 +3790,19 @@ little endian.
```
let value = ", stringify!($SelfT), "::from_le_bytes(", $le_bytes, ");
assert_eq!(value, ", $swap_op, ");
```
When starting from a slice rather than an array, fallible conversion APIs can be used:
```
#![feature(try_from)]
use std::convert::TryInto;
fn read_be_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " {
let (int_bytes, rest) = input.split_at(std::mem::size_of::<", stringify!($SelfT), ">());
*input = rest;
", stringify!($SelfT), "::from_be_bytes(int_bytes.try_into().unwrap())
}
```"),
#[stable(feature = "int_to_from_bytes", since = "1.32.0")]
#[rustc_const_unstable(feature = "const_int_conversion")]
Expand Down Expand Up @@ -3767,6 +3832,19 @@ let value = ", stringify!($SelfT), "::from_ne_bytes(if cfg!(target_endian = \"bi
", $le_bytes, "
});
assert_eq!(value, ", $swap_op, ");
```
When starting from a slice rather than an array, fallible conversion APIs can be used:
```
#![feature(try_from)]
use std::convert::TryInto;
fn read_be_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " {
let (int_bytes, rest) = input.split_at(std::mem::size_of::<", stringify!($SelfT), ">());
*input = rest;
", stringify!($SelfT), "::from_be_bytes(int_bytes.try_into().unwrap())
}
```"),
#[stable(feature = "int_to_from_bytes", since = "1.32.0")]
#[rustc_const_unstable(feature = "const_int_conversion")]
Expand Down

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