From e86a77c55781b5390851775943e0469b0c4eea6d Mon Sep 17 00:00:00 2001
From: Sean Gilligan <sean@msgilligan.com>
Date: Fri, 25 Mar 2022 15:37:12 -0700
Subject: [PATCH] Peer: construct getdata a little bit more functionally and
 atomically in downloadDependencies()

Build GetDataMessage in a private method.
---
 core/src/main/java/org/bitcoinj/core/Peer.java | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/core/src/main/java/org/bitcoinj/core/Peer.java b/core/src/main/java/org/bitcoinj/core/Peer.java
index b16fbbe76..49a7b695f 100644
--- a/core/src/main/java/org/bitcoinj/core/Peer.java
+++ b/core/src/main/java/org/bitcoinj/core/Peer.java
@@ -812,11 +812,10 @@ public class Peer extends PeerSocketHandler {
         try {
             // Build the request for the missing dependencies.
             List<CompletableFuture<Transaction>> futures = new ArrayList<>();
-            GetDataMessage getdata = new GetDataMessage(params);
+            GetDataMessage getdata = buildMultiTransactionDataMessage(txIdsToRequest);
             if (txIdsToRequest.size() > 1)
                 log.info("{}: Requesting {} transactions for depth {} dep resolution", getAddress(), txIdsToRequest.size(), depth + 1);
             for (Sha256Hash hash : txIdsToRequest) {
-                getdata.addTransaction(hash, vPeerVersionMessage.isWitnessSupported());
                 GetDataRequest req = new GetDataRequest(hash);
                 futures.add(req.future);
                 getDataFutures.add(req);
@@ -870,6 +869,18 @@ public class Peer extends PeerSocketHandler {
         return resultFuture;
     }
 
+    /**
+     * Build a GetDataMessage to query multiple transactions by ID
+     * @param txIds A set of transaction IDs to query
+     * @return A GetDataMessage that will query those IDs
+     */
+    private GetDataMessage buildMultiTransactionDataMessage(Set<Sha256Hash> txIds) {
+        GetDataMessage getdata = new GetDataMessage(params);
+        txIds.forEach(txId ->
+            getdata.addTransaction(txId, vPeerVersionMessage.isWitnessSupported()));
+        return getdata;
+    }
+
     /**
      * Combine the direct results and the child dependencies. Make sure to filter out nulls from
      * {@code Futures.successfulAsList}.