diff options
Diffstat (limited to 'third_party/rust/itertools/src/lazy_buffer.rs')
-rw-r--r-- | third_party/rust/itertools/src/lazy_buffer.rs | 63 |
1 files changed, 63 insertions, 0 deletions
diff --git a/third_party/rust/itertools/src/lazy_buffer.rs b/third_party/rust/itertools/src/lazy_buffer.rs new file mode 100644 index 0000000000..ca24062aab --- /dev/null +++ b/third_party/rust/itertools/src/lazy_buffer.rs @@ -0,0 +1,63 @@ +use std::ops::Index; +use alloc::vec::Vec; + +#[derive(Debug, Clone)] +pub struct LazyBuffer<I: Iterator> { + pub it: I, + done: bool, + buffer: Vec<I::Item>, +} + +impl<I> LazyBuffer<I> +where + I: Iterator, +{ + pub fn new(it: I) -> LazyBuffer<I> { + LazyBuffer { + it, + done: false, + buffer: Vec::new(), + } + } + + pub fn len(&self) -> usize { + self.buffer.len() + } + + pub fn get_next(&mut self) -> bool { + if self.done { + return false; + } + if let Some(x) = self.it.next() { + self.buffer.push(x); + true + } else { + self.done = true; + false + } + } + + pub fn prefill(&mut self, len: usize) { + let buffer_len = self.buffer.len(); + + if !self.done && len > buffer_len { + let delta = len - buffer_len; + + self.buffer.extend(self.it.by_ref().take(delta)); + self.done = self.buffer.len() < len; + } + } +} + +impl<I, J> Index<J> for LazyBuffer<I> +where + I: Iterator, + I::Item: Sized, + Vec<I::Item>: Index<J> +{ + type Output = <Vec<I::Item> as Index<J>>::Output; + + fn index(&self, index: J) -> &Self::Output { + self.buffer.index(index) + } +} |