std/sys/helpers/
wstr.rs

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

std/sys/helpers/
wstr.rs
