[index] Allow TxIndex sync thread to be interrupted.

src/index/txindex.cpp

@@ -30,6 +30,12 @@ TxIndex::TxIndex(std::unique_ptr<TxIndexDB> db) :
     m_db(std::move(db)), m_synced(false), m_best_block_index(nullptr)
 {}
 
+TxIndex::~TxIndex()
+{
+    Interrupt();
+    Stop();
+}
+
 bool TxIndex::Init()
 {
     LOCK(cs_main);
@@ -76,6 +82,11 @@ void TxIndex::ThreadSync()
         int64_t last_log_time = 0;
         int64_t last_locator_write_time = 0;
         while (true) {
+            if (m_interrupt) {
+                WriteBestBlock(pindex);
+                return;
+            }
+
             {
                 LOCK(cs_main);
                 const CBlockIndex* pindex_next = NextSyncBlock(pindex);
@@ -222,6 +233,11 @@ bool TxIndex::FindTx(const uint256& txid, CDiskTxPos& pos) const
     return m_db->ReadTxPos(txid, pos);
 }
 
+void TxIndex::Interrupt()
+{
+    m_interrupt();
+}
+
 void TxIndex::Start()
 {
     // Need to register this ValidationInterface before running Init(), so that