prefer const string& over char* in CDB and CWalletDB constructor

- also make parameter of CDBEnv::CheckpointLSN a constant reference

src/db.cpp

@@ -215,7 +215,7 @@ bool CDBEnv::Salvage(std::string strFile, bool fAggressive,
 }
 
 
-void CDBEnv::CheckpointLSN(std::string strFile)
+void CDBEnv::CheckpointLSN(const std::string& strFile)
 {
     dbenv.txn_checkpoint(0, 0, 0);
     if (fMockDb)
@@ -224,12 +224,12 @@ void CDBEnv::CheckpointLSN(std::string strFile)
 }
 
 
-CDB::CDB(const char *pszFile, const char* pszMode) :
+CDB::CDB(const std::string& strFilename, const char* pszMode) :
     pdb(NULL), activeTxn(NULL)
 {
     int ret;
     fReadOnly = (!strchr(pszMode, '+') && !strchr(pszMode, 'w'));
-    if (pszFile == NULL)
+    if (strFilename.empty())
         return;
 
     bool fCreate = strchr(pszMode, 'c') != NULL;
@@ -242,7 +242,7 @@ CDB::CDB(const char *pszFile, const char* pszMode) :
         if (!bitdb.Open(GetDataDir()))
             throw runtime_error("CDB : Failed to open database environment.");
 
-        strFile = pszFile;
+        strFile = strFilename;
         ++bitdb.mapFileUseCount[strFile];
         pdb = bitdb.mapDb[strFile];
         if (pdb == NULL)
@@ -255,12 +255,12 @@ CDB::CDB(const char *pszFile, const char* pszMode) :
                 DbMpoolFile*mpf = pdb->get_mpf();
                 ret = mpf->set_flags(DB_MPOOL_NOFILE, 1);
                 if (ret != 0)
-                    throw runtime_error(strprintf("CDB : Failed to configure for no temp file backing for database %s", pszFile));
+                    throw runtime_error(strprintf("CDB : Failed to configure for no temp file backing for database %s", strFile));
             }
 
             ret = pdb->open(NULL, // Txn pointer
-                            fMockDb ? NULL : pszFile,   // Filename
+                            fMockDb ? NULL : strFile.c_str(), // Filename
-                            fMockDb ? pszFile : "main", // Logical db name
+                            fMockDb ? strFile.c_str() : "main", // Logical db name
                             DB_BTREE, // Database type
                             nFlags, // Flags
                             0);
@@ -271,7 +271,7 @@ CDB::CDB(const char *pszFile, const char* pszMode) :
                 pdb = NULL;
                 --bitdb.mapFileUseCount[strFile];
                 strFile = "";
-                throw runtime_error(strprintf("CDB : Error %d, can't open database %s", ret, pszFile));
+                throw runtime_error(strprintf("CDB : Error %d, can't open database %s", ret, strFile));
             }
 
             if (fCreate && !Exists(string("version")))

src/db.h

@@ -69,7 +69,7 @@ public:
     bool Open(const boost::filesystem::path &path);
     void Close();
     void Flush(bool fShutdown);
-    void CheckpointLSN(std::string strFile);
+    void CheckpointLSN(const std::string& strFile);
 
     void CloseDb(const std::string& strFile);
     bool RemoveDb(const std::string& strFile);
@@ -96,11 +96,13 @@ protected:
     DbTxn *activeTxn;
     bool fReadOnly;
 
-    explicit CDB(const char* pszFile, const char* pszMode="r+");
+    explicit CDB(const std::string& strFilename, const char* pszMode="r+");
     ~CDB() { Close(); }
+
 public:
     void Flush();
     void Close();
+
 private:
     CDB(const CDB&);
     void operator=(const CDB&);

src/walletdb.h

@@ -75,7 +75,7 @@ public:
 class CWalletDB : public CDB
 {
 public:
-    CWalletDB(std::string strFilename, const char* pszMode="r+") : CDB(strFilename.c_str(), pszMode)
+    CWalletDB(const std::string& strFilename, const char* pszMode = "r+") : CDB(strFilename, pszMode)
     {
     }
 private: