Added hosted transactions cache

This skips the need to check the filesystem if no new files have arrived since the last lookup.

src/main/java/org/qortal/controller/arbitrary/ArbitraryDataManager.java

@@ -703,6 +703,9 @@ public class ArbitraryDataManager extends Thread {
 			repository.discardChanges();
 			repository.getArbitraryRepository().save(arbitraryPeerData);
 			repository.saveChanges();
+
+			// Invalidate the hosted transactions cache as we are now hosting something new
+			ArbitraryDataStorageManager.getInstance().invalidateHostedTransactionsCache();
 		}
 
 		// Check if we have all the files we need for this transaction

src/main/java/org/qortal/controller/arbitrary/ArbitraryDataStorageManager.java

@@ -41,6 +41,8 @@ public class ArbitraryDataStorageManager extends Thread {
     private long totalDirectorySize = 0L;
     private long lastDirectorySizeCheck = 0;
 
+    private List<ArbitraryTransactionData> hostedTransactions;
+
     private static long DIRECTORY_SIZE_CHECK_INTERVAL = 10 * 60 * 1000L; // 10 minutes
 
     /** Treat storage as full at 90% usage, to reduce risk of going over the limit.
@@ -219,6 +221,11 @@ public class ArbitraryDataStorageManager extends Thread {
     // Hosted data
 
     public List<ArbitraryTransactionData> listAllHostedTransactions(Repository repository) throws IOException {
+        // Load from cache if we can, to avoid disk reads
+        if (this.hostedTransactions != null) {
+            return this.hostedTransactions;
+        }
+
         List<ArbitraryTransactionData> arbitraryTransactionDataList = new ArrayList<>();
 
         Path dataPath = Paths.get(Settings.getInstance().getDataPath());
@@ -254,9 +261,16 @@ public class ArbitraryDataStorageManager extends Thread {
             }
         }
 
+        // Update cache
+        this.hostedTransactions = arbitraryTransactionDataList;
+
         return arbitraryTransactionDataList;
     }
 
+    public void invalidateHostedTransactionsCache() {
+        this.hostedTransactions = null;
+    }
+
 
     // Size limits