walletdb: Add KeyFilterFn to ReadKeyValue

Add a KeyFilterFn callback to ReadKeyValue which allows the caller to
specify which types to actually deserialize. A KeyFilterFn takes the
type as the parameter and returns a bool indicating whether
deserialization should continue.

Author: achow101

src/wallet/walletdb.cpp

@@ -263,13 +263,17 @@ class CWalletScanState {
 
 static bool
 ReadKeyValue(CWallet* pwallet, CDataStream& ssKey, CDataStream& ssValue,
-             CWalletScanState &wss, std::string& strType, std::string& strErr) EXCLUSIVE_LOCKS_REQUIRED(pwallet->cs_wallet)
+             CWalletScanState &wss, std::string& strType, std::string& strErr, const KeyFilterFn& filter_fn = nullptr) EXCLUSIVE_LOCKS_REQUIRED(pwallet->cs_wallet)
 {
     try {
         // Unserialize
         // Taking advantage of the fact that pair serialization
         // is just the two items serialized one after the other
         ssKey >> strType;
+        // If we have a filter, check if this matches the filter
+        if (filter_fn && !filter_fn(strType)) {
+            return true;
+        }
         if (strType == DBKeys::NAME) {
             std::string strAddress;
             ssKey >> strAddress;
@@ -668,11 +672,11 @@ ReadKeyValue(CWallet* pwallet, CDataStream& ssKey, CDataStream& ssValue,
     return true;
 }
 
-bool ReadKeyValue(CWallet* pwallet, CDataStream& ssKey, CDataStream& ssValue, std::string& strType, std::string& strErr)
+bool ReadKeyValue(CWallet* pwallet, CDataStream& ssKey, CDataStream& ssValue, std::string& strType, std::string& strErr, const KeyFilterFn& filter_fn)
 {
     CWalletScanState dummy_wss;
     LOCK(pwallet->cs_wallet);
-    return ReadKeyValue(pwallet, ssKey, ssValue, dummy_wss, strType, strErr);
+    return ReadKeyValue(pwallet, ssKey, ssValue, dummy_wss, strType, strErr, filter_fn);
 }
 
 bool WalletBatch::IsKeyType(const std::string& strType)

src/wallet/walletdb.h

@@ -280,8 +280,11 @@ class WalletBatch
 //! Compacts BDB state so that wallet.dat is self-contained (if there are changes)
 void MaybeCompactWalletDB();
 
+//! Callback for filtering key types to deserialize in ReadKeyValue
+using KeyFilterFn = std::function<bool(const std::string&)>;
+
 //! Unserialize a given Key-Value pair and load it into the wallet
-bool ReadKeyValue(CWallet* pwallet, CDataStream& ssKey, CDataStream& ssValue, std::string& strType, std::string& strErr);
+bool ReadKeyValue(CWallet* pwallet, CDataStream& ssKey, CDataStream& ssValue, std::string& strType, std::string& strErr, const KeyFilterFn& filter_fn = nullptr);
 
 /** Return whether a wallet database is currently loaded. */
 bool IsWalletLoaded(const fs::path& wallet_path);