Add CWallet::BlockUntilSyncedToCurrentChain()

This blocks until the wallet has synced up to the current height.

Author: TheBlueMatt

src/wallet/wallet.cpp

@@ -33,6 +33,7 @@
 #include "wallet/fees.h"
 
 #include <assert.h>
+#include <future>
 
 #include <boost/algorithm/string/replace.hpp>
 #include <boost/thread.hpp>
@@ -1232,6 +1233,8 @@ void CWallet::BlockConnected(const std::shared_ptr<const CBlock>& pblock, const
     for (size_t i = 0; i < pblock->vtx.size(); i++) {
         SyncTransaction(pblock->vtx[i], pindex, i);
     }
+
+    m_last_block_processed = pindex;
 }
 
 void CWallet::BlockDisconnected(const std::shared_ptr<const CBlock>& pblock) {
@@ -1244,6 +1247,36 @@ void CWallet::BlockDisconnected(const std::shared_ptr<const CBlock>& pblock) {
 
 
 
+void CWallet::BlockUntilSyncedToCurrentChain() {
+    AssertLockNotHeld(cs_main);
+    AssertLockNotHeld(cs_wallet);
+
+    {
+        // Skip the queue-draining stuff if we know we're caught up with
+        // chainActive.Tip()...
+        // We could also take cs_wallet here, and call m_last_block_processed
+        // protected by cs_wallet instead of cs_main, but as long as we need
+        // cs_main here anyway, its easier to just call it cs_main-protected.
+        LOCK(cs_main);
+        const CBlockIndex* initialChainTip = chainActive.Tip();
+
+        if (m_last_block_processed->GetAncestor(initialChainTip->nHeight) == initialChainTip) {
+            return;
+        }
+    }
+
+    // ...otherwise put a callback in the validation interface queue and wait
+    // for the queue to drain enough to execute it (indicating we are caught up
+    // at least with the time we entered this function).
+
+    std::promise<void> promise;
+    CallFunctionInValidationInterfaceQueue([&promise] {
+        promise.set_value();
+    });
+    promise.get_future().wait();
+}
+
+
 isminetype CWallet::IsMine(const CTxIn &txin) const
 {
     {
@@ -3900,8 +3933,6 @@ CWallet* CWallet::CreateWalletFromFile(const std::string walletFile)
 
     LogPrintf(" wallet      %15dms\n", GetTimeMillis() - nStart);
 
-    RegisterValidationInterface(walletInstance);
-
     // Try to top up keypool. No-op if the wallet is locked.
     walletInstance->TopUpKeyPool();
 
@@ -3913,6 +3944,10 @@ CWallet* CWallet::CreateWalletFromFile(const std::string walletFile)
         if (walletdb.ReadBestBlock(locator))
             pindexRescan = FindForkInGlobalIndex(chainActive, locator);
     }
+
+    walletInstance->m_last_block_processed = chainActive.Tip();
+    RegisterValidationInterface(walletInstance);
+
     if (chainActive.Tip() && chainActive.Tip() != pindexRescan)
     {
         //We can't rescan beyond non-pruned blocks, stop and throw an error

src/wallet/wallet.h

@@ -722,6 +722,18 @@ class CWallet final : public CCryptoKeyStore, public CValidationInterface
 
     std::unique_ptr<CWalletDBWrapper> dbw;
 
+    /**
+     * The following is used to keep track of how far behind the wallet is
+     * from the chain sync, and to allow clients to block on us being caught up.
+     *
+     * Note that this is *not* how far we've processed, we may need some rescan
+     * to have seen all transactions in the chain, but is only used to track
+     * live BlockConnected callbacks.
+     *
+     * Protected by cs_main (see BlockUntilSyncedToCurrentChain)
+     */
+    const CBlockIndex* m_last_block_processed;
+
 public:
     /*
      * Main wallet lock.
@@ -1106,6 +1118,14 @@ class CWallet final : public CCryptoKeyStore, public CValidationInterface
        caller must ensure the current wallet version is correct before calling
        this function). */
     bool SetHDMasterKey(const CPubKey& key);
+
+    /**
+     * Blocks until the wallet state is up-to-date to /at least/ the current
+     * chain at the time this function is entered
+     * Obviously holding cs_main/cs_wallet when going into this call may cause
+     * deadlock
+     */
+    void BlockUntilSyncedToCurrentChain();
 };
 
 /** A key allocated from the key pool. */