Merge pull request #6 from sigp/v2.1-helpers

[WIP] v2.1 helpers

lighthouse/main.rs

@@ -8,7 +8,6 @@ extern crate futures;
 
 pub mod db;
 pub mod client;
-pub mod shuffling;
 pub mod state;
 pub mod sync;
 pub mod utils;

lighthouse/state/chain_config.rs

@@ -0,0 +1,15 @@
+pub struct ChainConfig {
+    pub cycle_length: u8,
+    pub shard_count: u16,
+    pub min_committee_size: u64,
+}
+
+impl ChainConfig {
+    pub fn standard() -> Self {
+        Self {
+            cycle_length: 8,
+            shard_count: 1024,
+            min_committee_size: 128,
+        }
+    }
+}

lighthouse/state/config.rs

@@ -1,11 +0,0 @@
-pub struct Config {
-    pub cycle_length: u8,
-}
-
-impl Config {
-    pub fn standard() -> Self {
-        Self {
-            cycle_length: 8,
-        }
-    }
-}

lighthouse/state/mod.rs

@@ -9,8 +9,9 @@ use super::utils;
 pub mod active_state;
 pub mod attestation_record;
 pub mod crystallized_state;
-pub mod config;
+pub mod chain_config;
 pub mod block;
 pub mod crosslink_record;
 pub mod shard_and_committee;
+pub mod transition;
 pub mod validator_record;

lighthouse/state/shard_and_committee.rs

@@ -1,6 +1,8 @@
+
+#[derive(Clone,Debug)]
 pub struct ShardAndCommittee {
     pub shard_id: u16,
-    pub committee: Vec<u32>
+    pub committee: Vec<usize>
 }
 
 impl ShardAndCommittee {

lighthouse/state/transition/attestation_parent_hashes.rs

@@ -0,0 +1,223 @@
+use super::Hash256;
+use super::TransitionError;
+
+/// This function is used to select the hashes used in
+/// the signing of an AttestationRecord.
+///
+/// It either returns Result with a vector of length `cycle_length,` or
+/// returns an Error.
+///
+/// This function corresponds to the `get_signed_parent_hashes` function
+/// in the Python reference implentation.
+///
+/// See this slide for more information:
+/// https://tinyurl.com/ybzn2spw
+pub fn attestation_parent_hashes(
+    cycle_length: &u8,
+    block_slot: &u64,
+    attestation_slot: &u64,
+    current_hashes: &Vec<Hash256>,
+    oblique_hashes: &Vec<Hash256>)
+    -> Result<Vec<Hash256>, TransitionError>
+{
+    // This cast places a limit on cycle_length. If you change it, check math
+    // for overflow.
+    let cycle_length: u64 = *cycle_length as u64;
+
+    if current_hashes.len() as u64 != (cycle_length * 2) {
+        return Err(TransitionError::InvalidInput(String::from(
+                    "current_hashes.len() must equal cycle_length * 2")));
+    }
+    if attestation_slot >= block_slot {
+        return Err(TransitionError::InvalidInput(String::from(
+                    "attestation_slot must be less than block_slot")));
+    }
+    if oblique_hashes.len() as u64 > cycle_length {
+        return Err(TransitionError::InvalidInput(String::from(
+                    "oblique_hashes.len() must be <= cycle_length * 2")));
+    }
+
+    /*
+     * Cannot underflow as block_slot cannot be less
+     * than attestation_slot.
+     */
+    let attestation_distance = block_slot - attestation_slot;
+
+    if attestation_distance > cycle_length {
+        return Err(TransitionError::InvalidInput(String::from(
+                    "attestation_slot must be withing one cycle of block_slot")));
+    }
+
+    /*
+     * Cannot underflow because attestation_distance cannot
+     * be larger than cycle_length.
+     */
+    let start = cycle_length - attestation_distance;
+
+    /*
+     * Overflow is potentially impossible, but proof is complicated
+     * enough to just use checked math.
+     *
+     * Arithmetic is:
+     * start + cycle_length - oblique_hashes.len()
+     */
+    let end = start.checked_add(cycle_length)
+        .and_then(|x| x.checked_sub(oblique_hashes.len() as u64))
+        .ok_or(TransitionError::IntWrapping)?;
+
+
+    let mut hashes = Vec::new();
+    hashes.extend_from_slice(
+        &current_hashes[(start as usize)..(end as usize)]);
+    hashes.append(&mut oblique_hashes.clone());
+
+    Ok(hashes)
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn get_range_of_hashes(from: usize, to: usize) -> Vec<Hash256> {
+        (from..to).map(|i| get_hash(&vec![i as u8])).collect()
+    }
+
+    fn get_hash(value: &[u8]) -> Hash256 {
+        Hash256::from_slice(value)
+    }
+
+    #[test]
+    fn test_get_signed_hashes_oblique_scenario_1() {
+        /*
+         * Two oblique hashes.
+         */
+        let cycle_length: u8 = 8;
+        let block_slot: u64 = 19;
+        let attestation_slot: u64 = 15;
+        let current_hashes = get_range_of_hashes(3, 19);
+        let oblique_hashes = get_range_of_hashes(100, 102);
+        let result = attestation_parent_hashes(
+            &cycle_length,
+            &block_slot,
+            &attestation_slot,
+            &current_hashes,
+            &oblique_hashes);
+        assert!(result.is_ok());
+        let result = result.unwrap();
+        assert_eq!(result.len(), cycle_length as usize);
+
+        let mut expected_result = get_range_of_hashes(7, 13);
+        expected_result.append(&mut get_range_of_hashes(100, 102));
+        assert_eq!(result, expected_result);
+    }
+
+    #[test]
+    fn test_get_signed_hashes_oblique_scenario_2() {
+        /*
+         * All oblique hashes.
+         */
+        let cycle_length: u8 = 8;
+        let block_slot: u64 = 19;
+        let attestation_slot: u64 = 15;
+        let current_hashes = get_range_of_hashes(3, 19);
+        let oblique_hashes = get_range_of_hashes(100, 108);
+        let result = attestation_parent_hashes(
+            &cycle_length,
+            &block_slot,
+            &attestation_slot,
+            &current_hashes,
+            &oblique_hashes);
+        assert!(result.is_ok());
+        let result = result.unwrap();
+        assert_eq!(result.len(), cycle_length as usize);
+
+        let expected_result = get_range_of_hashes(100, 108);
+        assert_eq!(result, expected_result);
+    }
+
+    #[test]
+    fn test_get_signed_hashes_scenario_1() {
+        /*
+         * Google Slides example.
+         * https://tinyurl.com/ybzn2spw
+         */
+        let cycle_length: u8 = 8;
+        let block_slot: u64 = 19;
+        let attestation_slot: u64 = 15;
+        let current_hashes = get_range_of_hashes(3, 19);
+        let oblique_hashes = vec![];
+        let result = attestation_parent_hashes(
+            &cycle_length,
+            &block_slot,
+            &attestation_slot,
+            &current_hashes,
+            &oblique_hashes);
+        assert!(result.is_ok());
+        let result = result.unwrap();
+        assert_eq!(result.len(), cycle_length as usize);
+        let expected_result = get_range_of_hashes(7, 15);
+        assert_eq!(result, expected_result);
+    }
+
+    #[test]
+    fn test_get_signed_hashes_scenario_2() {
+        /*
+         * Block 1, attestation 0.
+         */
+        let cycle_length: u8 = 8;
+        let block_slot: u64 = 1;
+        let attestation_slot: u64 = 0;
+        let current_hashes = get_range_of_hashes(0, 16);
+        let oblique_hashes = vec![];
+        let result = attestation_parent_hashes(
+            &cycle_length,
+            &block_slot,
+            &attestation_slot,
+            &current_hashes,
+            &oblique_hashes);
+        assert!(result.is_ok());
+        let result = result.unwrap();
+        assert_eq!(result.len(), cycle_length as usize);
+        let expected_result = get_range_of_hashes(7, 15);
+        assert_eq!(result, expected_result);
+    }
+
+    #[test]
+    fn test_get_signed_hashes_scenario_3() {
+        /*
+         * attestation_slot too large
+         */
+        let cycle_length: u8 = 8;
+        let block_slot: u64 = 100;
+        let attestation_slot: u64 = 100;
+        let current_hashes = get_range_of_hashes(0, 16);
+        let oblique_hashes = vec![];
+        let result = attestation_parent_hashes(
+            &cycle_length,
+            &block_slot,
+            &attestation_slot,
+            &current_hashes,
+            &oblique_hashes);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn test_get_signed_hashes_scenario_4() {
+        /*
+         * Current hashes too small
+         */
+        let cycle_length: u8 = 8;
+        let block_slot: u64 = 100;
+        let attestation_slot: u64 = 99;
+        let current_hashes = get_range_of_hashes(0, 15);
+        let oblique_hashes = vec![];
+        let result = attestation_parent_hashes(
+            &cycle_length,
+            &block_slot,
+            &attestation_slot,
+            &current_hashes,
+            &oblique_hashes);
+        assert!(result.is_err());
+    }
+}

lighthouse/state/transition/mod.rs

@@ -0,0 +1,17 @@
+use super::super::utils::types::Hash256;
+
+mod attestation_parent_hashes;
+mod shuffling;
+
+pub use self::attestation_parent_hashes::attestation_parent_hashes;
+pub use self::shuffling::shuffle;
+
+#[derive(Debug)]
+pub enum TransitionError {
+    IntWrapping,
+    OutOfBounds,
+    InvalidInput(String),
+}
+
+
+

lighthouse/state/transition/shuffling/README.md

@@ -0,0 +1,2 @@
+This module includes the fundamental shuffling function. It does not do the
+full validator delegation amongst slots.