chore: refactor out the shrink_hashmap (#5492)

Description
---
Refactor shrink map to a separate file. And also shrink it to the size
that it will not be shrink again on next call.

Breaking Changes
---

- [x] None
- [ ] Requires data directory on base node to be deleted
- [ ] Requires hard fork
- [ ] Other - Please specify

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footer -->
<!-- BREAKING CHANGE: Description what the user should do, e.g. delete a
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base_layer/core/src/mempool/mod.rs

@@ -44,6 +44,7 @@ pub use rpc::create_mempool_rpc_service;
 pub use rpc::{MempoolRpcClient, MempoolRpcServer, MempoolRpcService, MempoolService};
 #[cfg(feature = "base_node")]
 mod metrics;
+mod shrink_hashmap;
 #[cfg(feature = "base_node")]
 mod unconfirmed_pool;
 

base_layer/core/src/mempool/reorg_pool/reorg_pool.rs

@@ -22,7 +22,6 @@
 
 use std::{
     collections::{HashMap, HashSet},
-    hash::Hash,
     sync::Arc,
 };
 
@@ -31,7 +30,11 @@ use serde::{Deserialize, Serialize};
 use tari_common_types::types::{PrivateKey, Signature};
 use tari_utilities::hex::Hex;
 
-use crate::{blocks::Block, transactions::transaction_components::Transaction};
+use crate::{
+    blocks::Block,
+    mempool::shrink_hashmap::shrink_hashmap,
+    transactions::transaction_components::Transaction,
+};
 
 pub const LOG_TARGET: &str = "c::mp::reorg_pool::reorg_pool_storage";
 
@@ -317,16 +320,6 @@ impl ReorgPool {
     #[allow(clippy::cast_possible_truncation)]
     #[allow(clippy::cast_sign_loss)]
     pub fn compact(&mut self) {
-        fn shrink_hashmap<K: Eq + Hash, V>(map: &mut HashMap<K, V>) -> (usize, usize) {
-            let cap = map.capacity();
-            let extra_cap = cap - map.len();
-            if extra_cap > 100 {
-                map.shrink_to(map.len() + (extra_cap / 2));
-            }
-
-            (cap, map.capacity())
-        }
-
         let (old, new) = shrink_hashmap(&mut self.tx_by_key);
         shrink_hashmap(&mut self.txs_by_signature);
         shrink_hashmap(&mut self.txs_by_height);

base_layer/core/src/mempool/shrink_hashmap.rs

@@ -0,0 +1,33 @@
+//  Copyright 2019 The Tari Project
+//
+//  Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
+//  following conditions are met:
+//
+//  1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following
+//  disclaimer.
+//
+//  2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
+//  following disclaimer in the documentation and/or other materials provided with the distribution.
+//
+//  3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote
+//  products derived from this software without specific prior written permission.
+//
+//  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+//  INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+//  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+//  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+//  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+//  WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+//  USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+use std::{collections::HashMap, hash::Hash};
+
+pub fn shrink_hashmap<K: Eq + Hash, V>(map: &mut HashMap<K, V>) -> (usize, usize) {
+    let cap = map.capacity();
+    let extra_cap = cap - map.len();
+    if extra_cap > 100 {
+        map.shrink_to(map.len() + 100);
+    }
+
+    (cap, map.capacity())
+}

base_layer/core/src/mempool/unconfirmed_pool/unconfirmed_pool.rs

@@ -22,7 +22,6 @@
 
 use std::{
     collections::{BTreeMap, HashMap, HashSet},
-    hash::Hash,
     sync::Arc,
 };
 
@@ -35,11 +34,13 @@ use crate::{
     blocks::Block,
     mempool::{
         priority::{FeePriority, PrioritizedTransaction},
+        shrink_hashmap::shrink_hashmap,
         unconfirmed_pool::UnconfirmedPoolError,
         FeePerGramStat,
     },
     transactions::{tari_amount::MicroTari, transaction_components::Transaction, weight::TransactionWeight},
 };
+
 pub const LOG_TARGET: &str = "c::mp::unconfirmed_pool::unconfirmed_pool_storage";
 
 type TransactionKey = usize;
@@ -604,16 +605,6 @@ impl UnconfirmedPool {
     #[allow(clippy::cast_possible_truncation)]
     #[allow(clippy::cast_sign_loss)]
     pub fn compact(&mut self) {
-        fn shrink_hashmap<K: Eq + Hash, V>(map: &mut HashMap<K, V>) -> (usize, usize) {
-            let cap = map.capacity();
-            let extra_cap = cap - map.len();
-            if extra_cap > 100 {
-                map.shrink_to(map.len() + (extra_cap / 2));
-            }
-
-            (cap, map.capacity())
-        }
-
         let (old, new) = shrink_hashmap(&mut self.tx_by_key);
         shrink_hashmap(&mut self.txs_by_signature);
         shrink_hashmap(&mut self.txs_by_output);