rust/hg-core/src/config/mod.rs

49949:3c37cb7bce61

    /// Yields (key, value) pairs for everything in the given section
    pub fn iter_section<'a>(
        &'a self,
        section: &'a [u8],
    ) -> impl Iterator<Item = (&[u8], &[u8])> + 'a {
        // TODO: Use `Iterator`’s `.peekable()` when its `peek_mut` is
        // available:
        // https://doc.rust-lang.org/nightly/std/iter/struct.Peekable.html#method.peek_mut
        struct Peekable<I: Iterator> {
            iter: I,
            /// Remember a peeked value, even if it was None.
            peeked: Option<Option<I::Item>>,
        }

        impl<I: Iterator> Peekable<I> {
            fn new(iter: I) -> Self {
                Self { iter, peeked: None }
            }

            fn next(&mut self) {
                self.peeked = None
            }

            fn peek_mut(&mut self) -> Option<&mut I::Item> {
                let iter = &mut self.iter;
                self.peeked.get_or_insert_with(|| iter.next()).as_mut()
            }
        }

        // Deduplicate keys redefined in multiple layers
        let mut keys_already_seen = HashSet::new();
        let mut key_is_new =
            move |&(key, _value): &(&'a [u8], &'a [u8])| -> bool {
                keys_already_seen.insert(key)
            };
        // This is similar to `flat_map` + `filter_map`, except with a single
        // closure that owns `key_is_new` (and therefore the
        // `keys_already_seen` set):
        let mut layer_iters = Peekable::new(
            self.layers
                .iter()
                .rev()
                .map(move |layer| layer.iter_section(section)),
        );
        std::iter::from_fn(move || loop {
            if let Some(pair) = layer_iters.peek_mut()?.find(&mut key_is_new) {
                return Some(pair);
            } else {
                layer_iters.next();

49954:a11237723332

    /// Yields (key, value) pairs for everything in the given section
    pub fn iter_section<'a>(
        &'a self,
        section: &'a [u8],
    ) -> impl Iterator<Item = (&[u8], &[u8])> + 'a {
        // Deduplicate keys redefined in multiple layers
        let mut keys_already_seen = HashSet::new();
        let mut key_is_new =
            move |&(key, _value): &(&'a [u8], &'a [u8])| -> bool {
                keys_already_seen.insert(key)
            };
        // This is similar to `flat_map` + `filter_map`, except with a single
        // closure that owns `key_is_new` (and therefore the
        // `keys_already_seen` set):
        let mut layer_iters = self
            .layers
            .iter()
            .rev()
            .map(move |layer| layer.iter_section(section))
            .peekable();
        std::iter::from_fn(move || loop {
            if let Some(pair) = layer_iters.peek_mut()?.find(&mut key_is_new) {
                return Some(pair);
            } else {
                layer_iters.next();