From f4df8ff5b3b6d4fe41f4cab26f333065c1c90cfa Mon Sep 17 00:00:00 2001
From: Greg Fitzgerald <greg@solana.com>
Date: Thu, 21 Feb 2019 09:45:36 -0700
Subject: [PATCH] Add slot_height() and epoch_height() methods to Bank

---
 runtime/src/bank.rs | 58 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 57 insertions(+), 1 deletion(-)

diff --git a/runtime/src/bank.rs b/runtime/src/bank.rs
index ce22f6c3c..17a19eba1 100644
--- a/runtime/src/bank.rs
+++ b/runtime/src/bank.rs
@@ -23,7 +23,10 @@ use solana_sdk::signature::{Keypair, Signature};
 use solana_sdk::storage_program;
 use solana_sdk::system_program;
 use solana_sdk::system_transaction::SystemTransaction;
-use solana_sdk::timing::{duration_as_us, MAX_ENTRY_IDS, NUM_TICKS_PER_SECOND};
+use solana_sdk::timing::{
+    duration_as_us, DEFAULT_SLOTS_PER_EPOCH, DEFAULT_TICKS_PER_SLOT, MAX_ENTRY_IDS,
+    NUM_TICKS_PER_SECOND,
+};
 use solana_sdk::token_program;
 use solana_sdk::transaction::Transaction;
 use solana_sdk::vote_program::{self, VoteState};
@@ -606,10 +609,31 @@ impl Bank {
             .collect()
     }
 
+    /// Return the number of ticks since genesis.
     pub fn tick_height(&self) -> u64 {
         self.last_id_queue.read().unwrap().tick_height
     }
 
+    /// Return the number of ticks since the last slot boundary.
+    pub fn tick_index(&self) -> u64 {
+        self.tick_height() % DEFAULT_TICKS_PER_SLOT
+    }
+
+    /// Return the slot_height of the last registered tick.
+    pub fn slot_height(&self) -> u64 {
+        self.tick_height() / DEFAULT_TICKS_PER_SLOT
+    }
+
+    /// Return the number of slots since the last epoch boundary.
+    pub fn slot_index(&self) -> u64 {
+        self.slot_height() % DEFAULT_SLOTS_PER_EPOCH
+    }
+
+    /// Return the epoch height of the last registered tick.
+    pub fn epoch_height(&self) -> u64 {
+        self.slot_height() / DEFAULT_SLOTS_PER_EPOCH
+    }
+
     #[cfg(test)]
     pub fn last_ids(&self) -> &RwLock<LastIdQueue> {
         &self.last_id_queue
@@ -885,6 +909,38 @@ mod tests {
         assert_eq!(bank.get_balance(&dummy_leader_id), 1);
     }
 
+    // Register n ticks and return the tick, slot and epoch indexes.
+    fn register_ticks(bank: &Bank, n: u64) -> (u64, u64, u64) {
+        for _ in 0..n {
+            bank.register_tick(&Hash::default());
+        }
+        (bank.tick_index(), bank.slot_index(), bank.epoch_height())
+    }
+
+    #[test]
+    fn test_tick_slot_epoch_indexes() {
+        let (genesis_block, _) = GenesisBlock::new(5);
+        let bank = Bank::new(&genesis_block);
+        let ticks_per_slot = DEFAULT_TICKS_PER_SLOT;
+        let slots_per_epoch = DEFAULT_SLOTS_PER_EPOCH;
+        let ticks_per_epoch = ticks_per_slot * slots_per_epoch;
+
+        // All indexes are zero-based.
+        assert_eq!(register_ticks(&bank, 0), (0, 0, 0));
+
+        // Slot index remains zero through the last tick.
+        assert_eq!(
+            register_ticks(&bank, ticks_per_slot - 1),
+            (ticks_per_slot - 1, 0, 0)
+        );
+
+        // Cross a slot boundary.
+        assert_eq!(register_ticks(&bank, 1), (0, 1, 0));
+
+        // Cross an epoch boundary.
+        assert_eq!(register_ticks(&bank, ticks_per_epoch), (0, 1, 1));
+    }
+
     #[test]
     fn test_interleaving_locks() {
         let (genesis_block, mint_keypair) = GenesisBlock::new(3);