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Danny Ryan 2019-06-24 17:18:22 -06:00
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specs/core/0_fork-choice.md
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@ -179,23 +179,31 @@ def on_block(store: Store, block: BeaconBlock) -> None:
```python ```python
def on_attestation(store: Store, attestation: Attestation) -> None: def on_attestation(store: Store, attestation: Attestation) -> None:
target_checkpoint = Checkpoint(attestation.data.target_epoch, attestation.data, target_root) target = Checkpoint(attestation.data.target_epoch, attestation.data.target_root)
# Cannot calculate the current shuffling if have not seen the target # Cannot calculate the current shuffling if have not seen the target
assert target_checkpoint.root in store.blocks assert target.root in store.blocks
# Attestations cannot be from future epochs. If they are, their consideration must be delayed until the are in the past.
assert store.time >= pre_state.genesis_time + get_epoch_start_slot(target.epoch) * SECONDS_PER_SLOT
# Store target checkpoint state if not yet seen # Store target checkpoint state if not yet seen
if target_checkpoint not in store.checkpoint_states: if target not in store.checkpoint_states:
base_state = store.block_states[target_checkpoint.root].copy() base_state = store.block_states[target.root].copy()
store.checkpoint_states[target_checkpoint] = process_slots(base_state, get_epoch_start_slot(target_checkpoint.epoch)) store.checkpoint_states[target] = process_slots(base_state, get_epoch_start_slot(target.epoch))
target_state = store.checkpoint_states[target]
# Get state at the `target_checkpoint` to validate attestation and calculate the committees # Attestations can only affect the fork choice of subsequent slots.
state = store.checkpoint_states[target_checkpoint] # Delay consideration in the fork choice until their slot is in the past.
indexed_attestation = convert_to_indexed(state, attestation) attestation_slot = get_attestation_data_slot(target_state, attestation.data)
validate_indexed_attestation(state, indexed_attestation) assert store.time >= (attestation_slot + 1) * SECONDS_PER_SLOT
# Get state at the `target` to validate attestation and calculate the committees
indexed_attestation = convert_to_indexed(target_state, attestation)
validate_indexed_attestation(target_state, indexed_attestation)
# Update latest targets # Update latest targets
for i in indexed_attestation.custody_bit_0_indices + indexed_attestation.custody_bit_1_indices: for i in indexed_attestation.custody_bit_0_indices + indexed_attestation.custody_bit_1_indices:
if i not in store.latest_targets or target_checkpoint.epoch > store.latest_targets[i].epoch: if i not in store.latest_targets or target.epoch > store.latest_targets[i].epoch:
store.latest_targets[i] = target_checkpoint store.latest_targets[i] = target
``` ```