Complete attestation_validation, bar tests

beacon_chain/attestation_validation/src/shard_block.rs

@@ -0,0 +1,46 @@
+use super::db::ClientDB;
+use super::types::{AttestationData, BeaconState};
+use super::{Error, Invalid, Outcome};
+
+/// Check that an attestation is valid with reference to some state.
+pub fn validate_attestation_data_shard_block_hash<T>(
+    data: &AttestationData,
+    state: &BeaconState,
+) -> Result<Outcome, Error>
+where
+    T: ClientDB + Sized,
+{
+    /*
+     * The `shard_block_hash` in the state's `latest_crosslinks` must match either the
+     * `latest_crosslink_hash` or the `shard_block_hash` on the attestation.
+     *
+     * TODO: figure out the reasoning behind this.
+     */
+    match state.latest_crosslinks.get(data.shard as usize) {
+        None => reject!(Invalid::UnknownShard),
+        Some(crosslink) => {
+            let local_shard_block_hash = crosslink.shard_block_hash;
+            let shard_block_hash_is_permissable = {
+                (local_shard_block_hash == data.latest_crosslink_hash)
+                    || (local_shard_block_hash == data.shard_block_hash)
+            };
+            verify_or!(
+                shard_block_hash_is_permissable,
+                reject!(Invalid::ShardBlockHashMismatch)
+            );
+        }
+    };
+    accept!()
+}
+
+#[cfg(test)]
+mod tests {
+    /*
+     * TODO: Implement tests.
+     *
+     * These tests will require the `BeaconBlock` and `BeaconBlockBody` updates, which are not
+     * yet included in the code base. Adding tests now will result in duplicated work.
+     *
+     * https://github.com/sigp/lighthouse/issues/97
+     */
+}