49 lines
1.2 KiB
Rust
49 lines
1.2 KiB
Rust
use store::iter::{BlockRootsIterator, StateRootsIterator};
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use types::{Hash256, Slot};
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pub type ReverseBlockRootIterator<'a, E, S> =
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ReverseHashAndSlotIterator<BlockRootsIterator<'a, E, S>>;
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pub type ReverseStateRootIterator<'a, E, S> =
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ReverseHashAndSlotIterator<StateRootsIterator<'a, E, S>>;
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pub type ReverseHashAndSlotIterator<I> = ReverseChainIterator<(Hash256, Slot), I>;
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/// Provides a wrapper for an iterator that returns a given `T` before it starts returning results of
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/// the `Iterator`.
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pub struct ReverseChainIterator<T, I> {
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first_value_used: bool,
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first_value: T,
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iter: I,
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}
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impl<T, I> ReverseChainIterator<T, I>
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where
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T: Sized,
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I: Iterator<Item = T> + Sized,
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{
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pub fn new(first_value: T, iter: I) -> Self {
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Self {
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first_value_used: false,
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first_value,
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iter,
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}
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}
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}
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impl<T, I> Iterator for ReverseChainIterator<T, I>
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where
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T: Clone,
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I: Iterator<Item = T>,
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{
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type Item = T;
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fn next(&mut self) -> Option<Self::Item> {
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if self.first_value_used {
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self.iter.next()
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} else {
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self.first_value_used = true;
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Some(self.first_value.clone())
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}
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}
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}
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