[staking] use vector for pending delegations

crates/sui-config/tests/snapshots/snapshot_tests__populated_genesis_snapshot_matches-5.snap

@@ -222,8 +222,7 @@ validators:
           value: 0
         delegation_token_supply:
           value: 0
-        pending_delegations:
-          contents: []
+        pending_delegations: []
   pending_validators: []
   pending_removals: []
   next_epoch_validators:

crates/sui-cost/tests/snapshots/empirical_transaction_cost__good_snapshot.snap

@@ -4,12 +4,12 @@ expression: common_costs
 ---
 {
   "MergeCoin": {
-    "computation_cost": 485,
+    "computation_cost": 482,
     "storage_cost": 32,
     "storage_rebate": 0
   },
   "Publish": {
-    "computation_cost": 543,
+    "computation_cost": 541,
     "storage_cost": 83,
     "storage_rebate": 0
   },
@@ -29,7 +29,7 @@ expression: common_costs
     "storage_rebate": 15
   },
   "SplitCoin": {
-    "computation_cost": 596,
+    "computation_cost": 593,
     "storage_cost": 80,
     "storage_rebate": 0
   },

crates/sui-framework/sources/governance/staking_pool.move

@@ -11,7 +11,7 @@ module sui::staking_pool {
     use sui::object::{Self, UID};
     use sui::locked_coin;
     use sui::coin;
-    use sui::vec_map::{Self, VecMap};
+    use std::vector;
 
     friend sui::validator;
     friend sui::validator_set;
@@ -43,7 +43,7 @@ module sui::staking_pool {
         /// Delegations requested during the current epoch. We will activate these delegation at the end of current epoch
         /// and distribute staking pool tokens at the end-of-epoch exchange rate after the rewards for the current epoch
         /// have been deposited.
-        pending_delegations: VecMap<address, u64>,
+        pending_delegations: vector<PendingDelegationEntry>,
     }
 
     /// An inactive staking pool associated with an inactive validator.
@@ -56,6 +56,12 @@ module sui::staking_pool {
     /// The staking pool token.
     struct DelegationToken has drop {}
 
+    /// Struct representing a pending delegation.
+    struct PendingDelegationEntry has store, drop {
+        delegator: address, 
+        sui_amount: u64,
+    }
+
     /// A self-custodial delegation object, serving as evidence that the delegator
     /// has delegated to a staking pool.
     struct Delegation has key {
@@ -90,7 +96,7 @@ module sui::staking_pool {
             sui_balance: 0,
             rewards_pool: balance::zero(),
             delegation_token_supply: balance::create_supply(DelegationToken {}),
-            pending_delegations: vec_map::empty(),
+            pending_delegations: vector::empty(),
         }
     }
 
@@ -100,16 +106,17 @@ module sui::staking_pool {
         balance::join(&mut pool.rewards_pool, rewards);
 
         // distribute pool tokens at new exchange rate.
-        while (!vec_map::is_empty(&pool.pending_delegations)) {
-            let (delegator, sui_amount) = vec_map::pop(&mut pool.pending_delegations);
-            distribute_delegation_tokens(pool, delegator, sui_amount, ctx);
+        while (!vector::is_empty(&pool.pending_delegations)) {
+            let PendingDelegationEntry { delegator, sui_amount } = vector::pop_back(&mut pool.pending_delegations);
+            mint_delegation_tokens_to_delegator(pool, delegator, sui_amount, ctx);
             pool.sui_balance = pool.sui_balance + sui_amount
         };
 
         // Record the epoch starting balance.
         pool.epoch_starting_sui_balance = pool.sui_balance;
     }
 
+    // TODO: implement rate limiting new delegations per epoch.
     /// Request to delegate to a staking pool. The delegation gets counted at the beginning of the next epoch,
     /// when the delegation object containing the pool tokens is distributed to the delegator.
     public(friend) fun request_add_delegation(
@@ -121,15 +128,8 @@ module sui::staking_pool {
         let sui_amount = balance::value(&stake);
         assert!(sui_amount > 0, 0);
         let delegator = tx_context::sender(ctx);
-        // insert delegation info into the vec map. 
-        let idx_opt = vec_map::get_idx_opt(&pool.pending_delegations, &delegator);
-        if (option::is_some(&idx_opt)) {
-            let (_, entry_mut_ref) = 
-                vec_map::get_entry_by_idx_mut(&mut pool.pending_delegations, option::extract(&mut idx_opt));
-            *entry_mut_ref = *entry_mut_ref + sui_amount;
-        } else {
-            vec_map::insert(&mut pool.pending_delegations, delegator, sui_amount);
-        };
+        // insert delegation info into the pendng_delegations vector.         
+        vector::push_back(&mut pool.pending_delegations, PendingDelegationEntry { delegator, sui_amount });
         let staked_sui = StakedSui {
             id: object::new(ctx),
             principal: stake,
@@ -142,7 +142,7 @@ module sui::staking_pool {
     /// `pool_tokens` field of the delegation object.
     /// After activation, the delegation officially counts toward the staking power of the validator.
     /// Aborts if the pool mismatches, the delegation is already activated, or the delegation cannot be activated yet. 
-    public(friend) fun distribute_delegation_tokens(
+    public(friend) fun mint_delegation_tokens_to_delegator(
         pool: &mut StakingPool, 
         delegator: address, 
         sui_amount: u64, 

crates/sui-types/src/sui_system_state.rs

@@ -31,21 +31,6 @@ pub struct MoveOption<T> {
     pub vec: Vec<T>,
 }
 
-/// Rust version of the Move sui::vec_map::VecMap type.
-/// Putting it in this file because it's only used here.
-#[derive(Debug, Serialize, Deserialize, Clone, Eq, PartialEq)]
-pub struct VecMap<K, V> {
-    pub contents: Vec<VecMapEntry<K, V>>,
-}
-
-/// Rust version of the Move sui::vec_map::Entry type.
-/// Putting it in this file because it's only used here.
-#[derive(Debug, Serialize, Deserialize, Clone, Eq, PartialEq)]
-pub struct VecMapEntry<K, V> {
-    pub key: K,
-    pub value: V,
-}
-
 #[derive(Debug, Serialize, Deserialize, Clone, Eq, PartialEq)]
 pub struct ValidatorMetadata {
     pub sui_address: AccountAddress,
@@ -70,6 +55,13 @@ pub struct Validator {
     pub delegation_staking_pool: StakingPool,
 }
 
+/// Rust version of the Move sui::staking_pool::PendingDelegationEntry type.
+#[derive(Debug, Serialize, Deserialize, Clone, Eq, PartialEq)]
+pub struct PendingDelegationEntry {
+    pub delegator: AccountAddress,
+    pub sui_amount: u64,
+}
+
 /// Rust version of the Move sui::staking_pool::StakingPool type
 #[derive(Debug, Serialize, Deserialize, Clone, Eq, PartialEq)]
 pub struct StakingPool {
@@ -79,7 +71,7 @@ pub struct StakingPool {
     pub sui_balance: u64,
     pub rewards_pool: Balance,
     pub delegation_token_supply: Supply,
-    pub pending_delegations: VecMap<AccountAddress, u64>,
+    pub pending_delegations: Vec<PendingDelegationEntry>,
 }
 
 /// Rust version of the Move sui::validator_set::ValidatorSet type