wallet: Introduce database handle wrapper

Abstract database handle from explicit strFilename into
CWalletDBWrapper.

Also move CWallet::Backup to db.cpp - as it deals with representation
details this is a database specific operation.

Author: laanwj

src/qt/test/wallettests.cpp

@@ -86,7 +86,8 @@ void WalletTests::walletTests()
     TestChain100Setup test;
     test.CreateAndProcessBlock({}, GetScriptForRawPubKey(test.coinbaseKey.GetPubKey()));
     bitdb.MakeMock();
-    CWallet wallet("wallet_test.dat");
+    std::unique_ptr<CWalletDBWrapper> dbw(new CWalletDBWrapper(&bitdb, "wallet_test.dat"));
+    CWallet wallet(std::move(dbw));
     bool firstRun;
     wallet.LoadWallet(firstRun);
     {

src/wallet/db.cpp

@@ -359,13 +359,12 @@ void CDBEnv::CheckpointLSN(const std::string& strFile)
 }
 
 
-CDB::CDB(const std::string& strFilename, const char* pszMode, bool fFlushOnCloseIn) : pdb(NULL), activeTxn(NULL)
+CDB::CDB(CWalletDBWrapper& dbw, const char* pszMode, bool fFlushOnCloseIn) : pdb(NULL), activeTxn(NULL)
 {
     int ret;
     fReadOnly = (!strchr(pszMode, '+') && !strchr(pszMode, 'w'));
     fFlushOnClose = fFlushOnCloseIn;
-    if (strFilename.empty())
-        return;
+    const std::string& strFilename = dbw.strFile;
 
     bool fCreate = strchr(pszMode, 'c') != NULL;
     unsigned int nFlags = DB_THREAD;
@@ -472,8 +471,12 @@ bool CDBEnv::RemoveDb(const std::string& strFile)
     return (rc == 0);
 }
 
-bool CDB::Rewrite(const std::string& strFile, const char* pszSkip)
+bool CDB::Rewrite(CWalletDBWrapper& dbw, const char* pszSkip)
 {
+    if (!dbw.env) {
+        return true;
+    }
+    const std::string& strFile = dbw.strFile;
     while (true) {
         {
             LOCK(bitdb.cs_db);
@@ -487,7 +490,7 @@ bool CDB::Rewrite(const std::string& strFile, const char* pszSkip)
                 LogPrintf("CDB::Rewrite: Rewriting %s...\n", strFile);
                 std::string strFileRes = strFile + ".rewrite";
                 { // surround usage of db with extra {}
-                    CDB db(strFile.c_str(), "r");
+                    CDB db(dbw, "r");
                     Db* pdbCopy = new Db(bitdb.dbenv, 0);
 
                     int ret = pdbCopy->open(NULL,               // Txn pointer
@@ -596,9 +599,10 @@ void CDBEnv::Flush(bool fShutdown)
     }
 }
 
-bool CDB::PeriodicFlush(std::string strFile)
+bool CDB::PeriodicFlush(CWalletDBWrapper& dbw)
 {
     bool ret = false;
+    const std::string& strFile = dbw.strFile;
     TRY_LOCK(bitdb.cs_db,lockDb);
     if (lockDb)
     {
@@ -633,3 +637,45 @@ bool CDB::PeriodicFlush(std::string strFile)
 
     return ret;
 }
+
+bool CWalletDBWrapper::Rewrite(const char* pszSkip)
+{
+    return CDB::Rewrite(*this, pszSkip);
+}
+
+bool CWalletDBWrapper::Backup(const std::string& strDest)
+{
+    if (!env) {
+        return false;
+    }
+    while (true)
+    {
+        {
+            LOCK(bitdb.cs_db);
+            if (!bitdb.mapFileUseCount.count(strFile) || bitdb.mapFileUseCount[strFile] == 0)
+            {
+                // Flush log data to the dat file
+                bitdb.CloseDb(strFile);
+                bitdb.CheckpointLSN(strFile);
+                bitdb.mapFileUseCount.erase(strFile);
+
+                // Copy wallet file
+                fs::path pathSrc = GetDataDir() / strFile;
+                fs::path pathDest(strDest);
+                if (fs::is_directory(pathDest))
+                    pathDest /= strFile;
+
+                try {
+                    fs::copy_file(pathSrc, pathDest, fs::copy_option::overwrite_if_exists);
+                    LogPrintf("copied %s to %s\n", strFile, pathDest.string());
+                    return true;
+                } catch (const fs::filesystem_error& e) {
+                    LogPrintf("error copying %s to %s - %s\n", strFile, pathDest.string(), e.what());
+                    return false;
+                }
+            }
+        }
+        MilliSleep(100);
+    }
+    return false;
+}

src/wallet/db.h

@@ -86,6 +86,36 @@ class CDBEnv
 
 extern CDBEnv bitdb;
 
+/** An instance of this class represents one database.
+ * For BerkeleyDB this is just a (env, strFile) tuple.
+ **/
+class CWalletDBWrapper
+{
+    friend class CDB;
+public:
+    CWalletDBWrapper(CDBEnv *env_in, const std::string &strFile_in):
+        env(env_in), strFile(strFile_in)
+    {
+    }
+
+    /** Rewrite the entire database on disk, with the exception of key pszSkip if non-zero
+     */
+    bool Rewrite(const char* pszSkip=nullptr);
+
+    /** Back up the entire database to a file.
+     */
+    bool Backup(const std::string& strDest);
+
+    /** Get a name for this database, for debugging etc.
+     */
+    std::string GetName() const { return strFile; }
+
+private:
+    /** BerkeleyDB specific */
+    CDBEnv *env;
+    std::string strFile;
+};
+
 
 /** RAII class that provides access to a Berkeley database */
 class CDB
@@ -97,7 +127,7 @@ class CDB
     bool fReadOnly;
     bool fFlushOnClose;
 
-    explicit CDB(const std::string& strFilename, const char* pszMode = "r+", bool fFlushOnCloseIn=true);
+    explicit CDB(CWalletDBWrapper& dbw, const char* pszMode = "r+", bool fFlushOnCloseIn=true);
     ~CDB() { Close(); }
 
 public:
@@ -107,7 +137,7 @@ class CDB
 
     /* flush the wallet passively (TRY_LOCK)
        ideal to be called periodically */
-    static bool PeriodicFlush(std::string strFile);
+    static bool PeriodicFlush(CWalletDBWrapper& dbw);
     /* verifies the database environment */
     static bool VerifyEnvironment(const std::string& walletFile, const fs::path& dataDir, std::string& errorStr);
     /* verifies the database file */
@@ -310,7 +340,7 @@ class CDB
         return Write(std::string("version"), nVersion);
     }
 
-    bool static Rewrite(const std::string& strFile, const char* pszSkip = NULL);
+    bool static Rewrite(CWalletDBWrapper& dbw, const char* pszSkip = NULL);
 };
 
 #endif // BITCOIN_WALLET_DB_H

src/wallet/rpcwallet.cpp

@@ -2076,7 +2076,7 @@ UniValue walletpassphrase(const JSONRPCRequest& request)
 
     int64_t nSleepTime = request.params[1].get_int64();
     pwallet->nRelockTime = GetTime() + nSleepTime;
-    RPCRunLater(strprintf("lockwallet(%s)", pwallet->strWalletFile), boost::bind(LockWallet, pwallet), nSleepTime);
+    RPCRunLater(strprintf("lockwallet(%s)", pwallet->GetName()), boost::bind(LockWallet, pwallet), nSleepTime);
 
     return NullUniValue;
 }

src/wallet/test/wallet_test_fixture.cpp

@@ -14,7 +14,8 @@ WalletTestingSetup::WalletTestingSetup(const std::string& chainName):
     bitdb.MakeMock();
 
     bool fFirstRun;
-    pwalletMain = new CWallet("wallet_test.dat");
+    std::unique_ptr<CWalletDBWrapper> dbw(new CWalletDBWrapper(&bitdb, "wallet_test.dat"));
+    pwalletMain = new CWallet(std::move(dbw));
     pwalletMain->LoadWallet(fFirstRun);
     RegisterValidationInterface(pwalletMain);