47 lines
1.4 KiB
Rust
47 lines
1.4 KiB
Rust
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use super::*;
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use ssz::{Decode, DecodeError};
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fn get_block_bytes<T: Store>(store: &T, root: Hash256) -> Result<Option<Vec<u8>>, Error> {
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store.get_bytes(BeaconBlock::db_column().into(), &root[..])
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}
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fn read_slot_from_block_bytes(bytes: &[u8]) -> Result<Slot, DecodeError> {
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let end = std::cmp::min(Slot::ssz_fixed_len(), bytes.len());
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Slot::from_ssz_bytes(&bytes[0..end])
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}
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fn read_previous_block_root_from_block_bytes(bytes: &[u8]) -> Result<Hash256, DecodeError> {
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let previous_bytes = Slot::ssz_fixed_len();
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let slice = bytes
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.get(previous_bytes..previous_bytes + Hash256::ssz_fixed_len())
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.ok_or_else(|| DecodeError::BytesInvalid("Not enough bytes.".to_string()))?;
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Hash256::from_ssz_bytes(slice)
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}
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pub fn get_block_at_preceeding_slot<T: Store>(
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store: &T,
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slot: Slot,
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start_root: Hash256,
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) -> Result<Option<(Hash256, BeaconBlock)>, Error> {
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let mut root = start_root;
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loop {
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if let Some(bytes) = get_block_bytes(store, root)? {
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let this_slot = read_slot_from_block_bytes(&bytes)?;
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if this_slot == slot {
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let block = BeaconBlock::from_ssz_bytes(&bytes)?;
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break Ok(Some((root, block)));
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} else if this_slot < slot {
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break Ok(None);
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} else {
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root = read_previous_block_root_from_block_bytes(&bytes)?;
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}
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} else {
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break Ok(None);
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}
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}
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}
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