program: add market index offset trait (#287)

* sdk: update description in package.json

* program: add SIZE trait

* program: add trait for market index offset

* add CHANGELOG

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Features
 
+program: add market index offset trait ([#287](https://github.com/drift-labs/protocol-v2/pull/287))
 program: add size trait to accounts and events ([#286](https://github.com/drift-labs/protocol-v2/pull/286))
 
 ### Fixes

programs/drift/src/state/perp_market.rs

@@ -23,7 +23,7 @@ use crate::math::stats;
 
 use crate::state::oracle::{HistoricalOracleData, OracleSource};
 use crate::state::spot_market::{SpotBalance, SpotBalanceType};
-use crate::state::traits::Size;
+use crate::state::traits::{MarketIndexOffset, Size};
 use crate::{AMM_TO_QUOTE_PRECISION_RATIO, PRICE_PRECISION};
 use borsh::{BorshDeserialize, BorshSerialize};
 
@@ -142,6 +142,10 @@ impl Size for PerpMarket {
     const SIZE: usize = 1216;
 }
 
+impl MarketIndexOffset for PerpMarket {
+    const MARKET_INDEX_OFFSET: usize = 1160;
+}
+
 impl PerpMarket {
     pub fn is_active(&self, now: i64) -> DriftResult<bool> {
         let status_ok = !matches!(

programs/drift/src/state/spot_market.rs

@@ -18,7 +18,7 @@ use crate::math::spot_balance::get_token_amount;
 
 use crate::state::oracle::{HistoricalIndexData, HistoricalOracleData, OracleSource};
 use crate::state::perp_market::{MarketStatus, PoolBalance};
-use crate::state::traits::Size;
+use crate::state::traits::{MarketIndexOffset, Size};
 
 #[account(zero_copy)]
 #[derive(PartialEq, Eq, Debug)]
@@ -133,6 +133,10 @@ impl Size for SpotMarket {
     const SIZE: usize = 776;
 }
 
+impl MarketIndexOffset for SpotMarket {
+    const MARKET_INDEX_OFFSET: usize = 684;
+}
+
 impl SpotMarket {
     pub fn is_active(&self, now: i64) -> DriftResult<bool> {
         let status_ok = !matches!(

programs/drift/src/state/traits.rs

@@ -4,3 +4,7 @@ mod tests;
 pub trait Size {
     const SIZE: usize;
 }
+
+pub trait MarketIndexOffset {
+    const MARKET_INDEX_OFFSET: usize;
+}

programs/drift/src/state/traits/tests.rs

@@ -63,3 +63,41 @@ mod size {
         assert_eq!(actual_size, expected_size);
     }
 }
+
+mod market_index_offset {
+    use crate::create_anchor_account_info;
+    use crate::state::perp_market::PerpMarket;
+    use crate::state::spot_market::SpotMarket;
+    use crate::state::traits::MarketIndexOffset;
+    use crate::test_utils::*;
+    use anchor_lang::prelude::*;
+    use arrayref::array_ref;
+
+    #[test]
+    fn spot_market() {
+        let mut spot_market = SpotMarket {
+            market_index: 11,
+            ..SpotMarket::default()
+        };
+        create_anchor_account_info!(spot_market, SpotMarket, spot_market_account_info);
+
+        let data = spot_market_account_info.try_borrow_data().unwrap();
+        let market_index =
+            u16::from_le_bytes(*array_ref![data, SpotMarket::MARKET_INDEX_OFFSET, 2]);
+        assert_eq!(market_index, spot_market.market_index);
+    }
+
+    #[test]
+    fn perp_market() {
+        let mut perp_market = PerpMarket {
+            market_index: 11,
+            ..PerpMarket::default()
+        };
+        create_anchor_account_info!(perp_market, PerpMarket, perp_market_account_info);
+
+        let data = perp_market_account_info.try_borrow_data().unwrap();
+        let market_index =
+            u16::from_le_bytes(*array_ref![data, PerpMarket::MARKET_INDEX_OFFSET, 2]);
+        assert_eq!(market_index, perp_market.market_index);
+    }
+}