std/sys_common/
wstr.rs

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1//! This module contains constructs to work with 16-bit characters (UCS-2 or UTF-16)
2#![allow(dead_code)]
3
4use crate::marker::PhantomData;
5use crate::num::NonZero;
6use crate::ptr::NonNull;
7
8/// A safe iterator over a LPWSTR
9/// (aka a pointer to a series of UTF-16 code units terminated by a NULL).
10pub struct WStrUnits<'a> {
11    // The pointer must never be null...
12    lpwstr: NonNull<u16>,
13    // ...and the memory it points to must be valid for this lifetime.
14    lifetime: PhantomData<&'a [u16]>,
15}
16
17impl WStrUnits<'_> {
18    /// Creates the iterator. Returns `None` if `lpwstr` is null.
19    ///
20    /// SAFETY: `lpwstr` must point to a null-terminated wide string that lives
21    /// at least as long as the lifetime of this struct.
22    pub unsafe fn new(lpwstr: *const u16) -> Option<Self> {
23        Some(Self { lpwstr: NonNull::new(lpwstr as _)?, lifetime: PhantomData })
24    }
25
26    pub fn peek(&self) -> Option<NonZero<u16>> {
27        // SAFETY: It's always safe to read the current item because we don't
28        // ever move out of the array's bounds.
29        unsafe { NonZero::new(*self.lpwstr.as_ptr()) }
30    }
31
32    /// Advance the iterator while `predicate` returns true.
33    /// Returns the number of items it advanced by.
34    pub fn advance_while<P: FnMut(NonZero<u16>) -> bool>(&mut self, mut predicate: P) -> usize {
35        let mut counter = 0;
36        while let Some(w) = self.peek() {
37            if !predicate(w) {
38                break;
39            }
40            counter += 1;
41            self.next();
42        }
43        counter
44    }
45}
46
47impl Iterator for WStrUnits<'_> {
48    // This can never return zero as that marks the end of the string.
49    type Item = NonZero<u16>;
50
51    fn next(&mut self) -> Option<Self::Item> {
52        // SAFETY: If NULL is reached we immediately return.
53        // Therefore it's safe to advance the pointer after that.
54        unsafe {
55            let next = self.peek()?;
56            self.lpwstr = NonNull::new_unchecked(self.lpwstr.as_ptr().add(1));
57            Some(next)
58        }
59    }
60}
std/sys_common/wstr.rs

std/sys_common/
wstr.rs
