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|
// { dg-options "-w" }
#![feature(intrinsics)]
#[lang = "sized"]
pub trait Sized {}
mod intrinsics {
extern "rust-intrinsic" {
#[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
pub fn offset<T>(ptr: *const T, count: isize) -> *const T;
}
}
mod mem {
extern "rust-intrinsic" {
fn size_of<T>() -> usize;
}
}
extern "C" {
fn printf(s: *const i8, ...);
}
struct FatPtr<T> {
data: *const T,
len: usize,
}
pub union Repr<T> {
rust: *const [T],
rust_mut: *mut [T],
raw: FatPtr<T>,
}
pub enum Option<T> {
None,
Some(T),
}
#[lang = "Range"]
pub struct Range<Idx> {
pub start: Idx,
pub end: Idx,
}
#[lang = "const_slice_ptr"]
impl<T> *const [T] {
pub const fn len(self) -> usize {
unsafe { Repr { rust: self }.raw.len }
}
pub const fn as_ptr(self) -> *const T {
self as *const T
}
}
#[lang = "const_ptr"]
impl<T> *const T {
pub const unsafe fn offset(self, count: isize) -> *const T {
unsafe { intrinsics::offset(self, count) }
}
pub const unsafe fn add(self, count: usize) -> Self {
unsafe { self.offset(count as isize) }
}
pub const fn as_ptr(self) -> *const T {
self as *const T
}
}
const fn slice_from_raw_parts<T>(data: *const T, len: usize) -> *const [T] {
unsafe {
Repr {
raw: FatPtr { data, len },
}
.rust
}
}
#[lang = "index"]
trait Index<Idx> {
type Output;
fn index(&self, index: Idx) -> &Self::Output;
}
impl<T> [T] {
pub const fn is_empty(&self) -> bool {
self.len() == 0
}
pub const fn len(&self) -> usize {
unsafe { Repr { rust: self }.raw.len }
}
}
pub unsafe trait SliceIndex<T> {
type Output;
fn get(self, slice: &T) -> Option<&Self::Output>;
unsafe fn get_unchecked(self, slice: *const T) -> *const Self::Output;
fn index(self, slice: &T) -> &Self::Output;
}
unsafe impl<T> SliceIndex<[T]> for usize {
type Output = T;
fn get(self, slice: &[T]) -> Option<&T> {
unsafe { Option::Some(&*self.get_unchecked(slice)) }
}
unsafe fn get_unchecked(self, slice: *const [T]) -> *const T {
// SAFETY: the caller guarantees that `slice` is not dangling, so it
// cannot be longer than `isize::MAX`. They also guarantee that
// `self` is in bounds of `slice` so `self` cannot overflow an `isize`,
// so the call to `add` is safe.
unsafe { slice.as_ptr().add(self) }
}
fn index(self, slice: &[T]) -> &T {
unsafe { &*self.get_unchecked(slice) }
}
}
unsafe impl<T> SliceIndex<[T]> for Range<usize> {
type Output = [T];
fn get(self, slice: &[T]) -> Option<&[T]> {
if self.start > self.end || self.end > slice.len() {
Option::None
} else {
unsafe { Option::Some(&*self.get_unchecked(slice)) }
}
}
unsafe fn get_unchecked(self, slice: *const [T]) -> *const [T] {
unsafe {
let a: *const T = slice.as_ptr();
let b: *const T = a.add(self.start);
slice_from_raw_parts(b, self.end - self.start)
}
}
fn index(self, slice: &[T]) -> &[T] {
unsafe { &*self.get_unchecked(slice) }
}
}
impl<T, I> Index<I> for [T]
where
I: SliceIndex<[T]>,
{
type Output = I::Output;
fn index(&self, index: I) -> &I::Output {
unsafe {
let a = "slice-index\n\0";
let b = a as *const str;
let c = b as *const i8;
printf(c);
}
index.index(self)
}
}
fn main() -> i32 {
let a = [1, 2, 3, 4, 5];
let b = a[1];
b - 2
}
|
