68 lines
1.3 KiB
Rust
68 lines
1.3 KiB
Rust
use std::ops::Index;
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use alloc::vec::Vec;
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#[derive(Debug, Clone)]
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pub struct LazyBuffer<I: Iterator> {
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pub it: I,
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done: bool,
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buffer: Vec<I::Item>,
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}
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impl<I> LazyBuffer<I>
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where
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I: Iterator,
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{
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pub fn new(it: I) -> LazyBuffer<I> {
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LazyBuffer {
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it,
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done: false,
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buffer: Vec::new(),
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}
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}
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pub fn len(&self) -> usize {
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self.buffer.len()
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}
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pub fn get_next(&mut self) -> bool {
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if self.done {
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return false;
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}
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let next_item = self.it.next();
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match next_item {
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Some(x) => {
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self.buffer.push(x);
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true
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}
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None => {
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self.done = true;
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false
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}
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}
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}
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pub fn prefill(&mut self, len: usize) {
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let buffer_len = self.buffer.len();
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if !self.done && len > buffer_len {
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let delta = len - buffer_len;
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self.buffer.extend(self.it.by_ref().take(delta));
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self.done = self.buffer.len() < len;
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}
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}
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}
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impl<I, J> Index<J> for LazyBuffer<I>
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where
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I: Iterator,
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I::Item: Sized,
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Vec<I::Item>: Index<J>
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{
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type Output = <Vec<I::Item> as Index<J>>::Output;
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fn index(&self, _index: J) -> &Self::Output {
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self.buffer.index(_index)
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}
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}
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