[txpackages] add canonical way to get hash of package

2 files changed, 23 insertions, 0 deletions

diff --git a/src/policy/packages.cpp b/src/policy/packages.cpp
index 3a63a9fe46..99d2a6d514 100644
--- a/src/policy/packages.cpp
+++ b/src/policy/packages.cpp
@@ -147,3 +147,21 @@ bool IsChildWithParentsTree(const Package& package)
         return true;
     });
 }
+
+uint256 GetPackageHash(const std::vector<CTransactionRef>& transactions)
+{
+    // Create a vector of the wtxids.
+    std::vector<Wtxid> wtxids_copy;
+    std::transform(transactions.cbegin(), transactions.cend(), std::back_inserter(wtxids_copy),
+        [](const auto& tx){ return tx->GetWitnessHash(); });
+
+    // Sort in ascending order
+    std::sort(wtxids_copy.begin(), wtxids_copy.end(), [](const auto& lhs, const auto& rhs) { return lhs.GetHex() < rhs.GetHex(); });
+
+    // Get sha256 hash of the wtxids concatenated in this order
+    HashWriter hashwriter;
+    for (const auto& wtxid : wtxids_copy) {
+        hashwriter << wtxid;
+    }
+    return hashwriter.GetSHA256();
+}
diff --git a/src/policy/packages.h b/src/policy/packages.h
index 537d8476e2..3050320122 100644
--- a/src/policy/packages.h
+++ b/src/policy/packages.h
@@ -88,4 +88,9 @@ bool IsChildWithParents(const Package& package);
  * other (the package is a "tree").
  */
 bool IsChildWithParentsTree(const Package& package);
+
+/** Get the hash of these transactions' wtxids, concatenated in lexicographical order (treating the
+ * wtxids as little endian encoded uint256, smallest to largest). */
+uint256 GetPackageHash(const std::vector<CTransactionRef>& transactions);
+
 #endif // BITCOIN_POLICY_PACKAGES_H