refactor: Consolidate redundant wallet database path and exists functions

No change in behavior. Just remove a little bit of code, reduce macro usage,
remove duplicative functions, and make BDB and SQLite implementations more
consistent with each other.

8 files changed, 38 insertions, 54 deletions

diff --git a/src/wallet/bdb.cpp b/src/wallet/bdb.cpp
index c289f94c78..6ed48593fb 100644
--- a/src/wallet/bdb.cpp
+++ b/src/wallet/bdb.cpp
@@ -53,16 +53,13 @@ bool WalletDatabaseFileId::operator==(const WalletDatabaseFileId& rhs) const
 }
 
 /**
- * @param[in] wallet_path Path to wallet directory. Or (for backwards compatibility only) a path to a berkeley btree data file inside a wallet directory.
- * @param[out] database_filename Filename of berkeley btree data file inside the wallet directory.
+ * @param[in] env_directory Path to environment directory
  * @return A shared pointer to the BerkeleyEnvironment object for the wallet directory, never empty because ~BerkeleyEnvironment
  * erases the weak pointer from the g_dbenvs map.
  * @post A new BerkeleyEnvironment weak pointer is inserted into g_dbenvs if the directory path key was not already in the map.
  */
-std::shared_ptr<BerkeleyEnvironment> GetWalletEnv(const fs::path& wallet_path, std::string& database_filename)
+std::shared_ptr<BerkeleyEnvironment> GetBerkeleyEnv(const fs::path& env_directory)
 {
-    fs::path env_directory;
-    SplitWalletPath(wallet_path, env_directory, database_filename);
     LOCK(cs_db);
     auto inserted = g_dbenvs.emplace(env_directory.string(), std::weak_ptr<BerkeleyEnvironment>());
     if (inserted.second) {
@@ -808,21 +805,14 @@ std::unique_ptr<DatabaseBatch> BerkeleyDatabase::MakeBatch(bool flush_on_close)
     return MakeUnique<BerkeleyBatch>(*this, false, flush_on_close);
 }
 
-bool ExistsBerkeleyDatabase(const fs::path& path)
-{
-    fs::path env_directory;
-    std::string data_filename;
-    SplitWalletPath(path, env_directory, data_filename);
-    return IsBDBFile(env_directory / data_filename);
-}
-
 std::unique_ptr<BerkeleyDatabase> MakeBerkeleyDatabase(const fs::path& path, const DatabaseOptions& options, DatabaseStatus& status, bilingual_str& error)
 {
+    fs::path data_file = BDBDataFile(path);
     std::unique_ptr<BerkeleyDatabase> db;
     {
         LOCK(cs_db); // Lock env.m_databases until insert in BerkeleyDatabase constructor
-        std::string data_filename;
-        std::shared_ptr<BerkeleyEnvironment> env = GetWalletEnv(path, data_filename);
+        std::string data_filename = data_file.filename().string();
+        std::shared_ptr<BerkeleyEnvironment> env = GetBerkeleyEnv(data_file.parent_path());
         if (env->m_databases.count(data_filename)) {
             error = Untranslated(strprintf("Refusing to load database. Data file '%s' is already loaded.", (env->Directory() / data_filename).string()));
             status = DatabaseStatus::FAILED_ALREADY_LOADED;
diff --git a/src/wallet/bdb.h b/src/wallet/bdb.h
index 935d0f947d..bf1617d67f 100644
--- a/src/wallet/bdb.h
+++ b/src/wallet/bdb.h
@@ -83,8 +83,8 @@ public:
     }
 };
 
-/** Get BerkeleyEnvironment and database filename given a wallet path. */
-std::shared_ptr<BerkeleyEnvironment> GetWalletEnv(const fs::path& wallet_path, std::string& database_filename);
+/** Get BerkeleyEnvironment given a directory path. */
+std::shared_ptr<BerkeleyEnvironment> GetBerkeleyEnv(const fs::path& env_directory);
 
 class BerkeleyBatch;
 
@@ -223,9 +223,6 @@ public:
 
 std::string BerkeleyDatabaseVersion();
 
-//! Check if Berkeley database exists at specified path.
-bool ExistsBerkeleyDatabase(const fs::path& path);
-
 //! Return object giving access to Berkeley database at specified path.
 std::unique_ptr<BerkeleyDatabase> MakeBerkeleyDatabase(const fs::path& path, const DatabaseOptions& options, DatabaseStatus& status, bilingual_str& error);
 
diff --git a/src/wallet/db.cpp b/src/wallet/db.cpp
index e8b8b8abc1..425b14b8f9 100644
--- a/src/wallet/db.cpp
+++ b/src/wallet/db.cpp
@@ -10,17 +10,6 @@
 
 #include <string>
 
-#ifdef USE_BDB
-bool ExistsBerkeleyDatabase(const fs::path& path);
-#else
-#   define ExistsBerkeleyDatabase(path)  (false)
-#endif
-#ifdef USE_SQLITE
-bool ExistsSQLiteDatabase(const fs::path& path);
-#else
-#   define ExistsSQLiteDatabase(path)  (false)
-#endif
-
 std::vector<fs::path> ListDatabases(const fs::path& wallet_dir)
 {
     const size_t offset = wallet_dir.string().size() + 1;
@@ -39,10 +28,10 @@ std::vector<fs::path> ListDatabases(const fs::path& wallet_dir)
             const fs::path path = it->path().string().substr(offset);
 
             if (it->status().type() == fs::directory_file &&
-                (ExistsBerkeleyDatabase(it->path()) || ExistsSQLiteDatabase(it->path()))) {
+                (IsBDBFile(BDBDataFile(it->path())) || IsSQLiteFile(SQLiteDataFile(it->path())))) {
                 // Found a directory which contains wallet.dat btree file, add it as a wallet.
                 paths.emplace_back(path);
-            } else if (it.level() == 0 && it->symlink_status().type() == fs::regular_file && ExistsBerkeleyDatabase(it->path())) {
+            } else if (it.level() == 0 && it->symlink_status().type() == fs::regular_file && IsBDBFile(it->path())) {
                 if (it->path().filename() == "wallet.dat") {
                     // Found top-level wallet.dat btree file, add top level directory ""
                     // as a wallet.
@@ -64,24 +53,31 @@ std::vector<fs::path> ListDatabases(const fs::path& wallet_dir)
     return paths;
 }
 
-void SplitWalletPath(const fs::path& wallet_path, fs::path& env_directory, std::string& database_filename)
+fs::path BDBDataFile(const fs::path& wallet_path)
 {
     if (fs::is_regular_file(wallet_path)) {
         // Special case for backwards compatibility: if wallet path points to an
         // existing file, treat it as the path to a BDB data file in a parent
         // directory that also contains BDB log files.
-        env_directory = wallet_path.parent_path();
-        database_filename = wallet_path.filename().string();
+        return wallet_path;
     } else {
         // Normal case: Interpret wallet path as a directory path containing
         // data and log files.
-        env_directory = wallet_path;
-        database_filename = "wallet.dat";
+        return wallet_path / "wallet.dat";
     }
 }
 
+fs::path SQLiteDataFile(const fs::path& path)
+{
+    return path / "wallet.dat";
+}
+
 bool IsBDBFile(const fs::path& path)
 {
+#ifndef USE_BDB
+    return false;
+#endif
+
     if (!fs::exists(path)) return false;
 
     // A Berkeley DB Btree file has at least 4K.
@@ -107,6 +103,10 @@ bool IsBDBFile(const fs::path& path)
 
 bool IsSQLiteFile(const fs::path& path)
 {
+#ifndef USE_SQLITE
+    return false;
+#endif
+
     if (!fs::exists(path)) return false;
 
     // A SQLite Database file is at least 512 bytes.
diff --git a/src/wallet/db.h b/src/wallet/db.h
index 3d18e5cec0..2c75486a44 100644
--- a/src/wallet/db.h
+++ b/src/wallet/db.h
@@ -228,6 +228,8 @@ std::vector<fs::path> ListDatabases(const fs::path& path);
 
 std::unique_ptr<WalletDatabase> MakeDatabase(const fs::path& path, const DatabaseOptions& options, DatabaseStatus& status, bilingual_str& error);
 
+fs::path BDBDataFile(const fs::path& path);
+fs::path SQLiteDataFile(const fs::path& path);
 bool IsBDBFile(const fs::path& path);
 bool IsSQLiteFile(const fs::path& path);
 
diff --git a/src/wallet/sqlite.cpp b/src/wallet/sqlite.cpp
index 69d96dd27c..0fb3b1d3c4 100644
--- a/src/wallet/sqlite.cpp
+++ b/src/wallet/sqlite.cpp
@@ -17,7 +17,6 @@
 #include <sqlite3.h>
 #include <stdint.h>
 
-static const char* const DATABASE_FILENAME = "wallet.dat";
 static constexpr int32_t WALLET_SCHEMA_VERSION = 0;
 
 static Mutex g_sqlite_mutex;
@@ -568,17 +567,11 @@ bool SQLiteBatch::TxnAbort()
     return res == SQLITE_OK;
 }
 
-bool ExistsSQLiteDatabase(const fs::path& path)
-{
-    const fs::path file = path / DATABASE_FILENAME;
-    return fs::symlink_status(file).type() == fs::regular_file && IsSQLiteFile(file);
-}
-
 std::unique_ptr<SQLiteDatabase> MakeSQLiteDatabase(const fs::path& path, const DatabaseOptions& options, DatabaseStatus& status, bilingual_str& error)
 {
-    const fs::path file = path / DATABASE_FILENAME;
     try {
-        auto db = MakeUnique<SQLiteDatabase>(path, file);
+        fs::path data_file = SQLiteDataFile(path);
+        auto db = MakeUnique<SQLiteDatabase>(data_file.parent_path(), data_file);
         if (options.verify && !db->Verify(error)) {
             status = DatabaseStatus::FAILED_VERIFY;
             return nullptr;
diff --git a/src/wallet/sqlite.h b/src/wallet/sqlite.h
index 3cb11614db..442563184e 100644
--- a/src/wallet/sqlite.h
+++ b/src/wallet/sqlite.h
@@ -113,7 +113,6 @@ public:
     sqlite3* m_db{nullptr};
 };
 
-bool ExistsSQLiteDatabase(const fs::path& path);
 std::unique_ptr<SQLiteDatabase> MakeSQLiteDatabase(const fs::path& path, const DatabaseOptions& options, DatabaseStatus& status, bilingual_str& error);
 
 std::string SQLiteDatabaseVersion();
diff --git a/src/wallet/test/db_tests.cpp b/src/wallet/test/db_tests.cpp
index 8f0083cd2e..1a28852a6b 100644
--- a/src/wallet/test/db_tests.cpp
+++ b/src/wallet/test/db_tests.cpp
@@ -13,6 +13,13 @@
 
 BOOST_FIXTURE_TEST_SUITE(db_tests, BasicTestingSetup)
 
+static std::shared_ptr<BerkeleyEnvironment> GetWalletEnv(const fs::path& path, std::string& database_filename)
+{
+    fs::path data_file = BDBDataFile(path);
+    database_filename = data_file.filename().string();
+    return GetBerkeleyEnv(data_file.parent_path());
+}
+
 BOOST_AUTO_TEST_CASE(getwalletenv_file)
 {
     std::string test_name = "test_name.dat";
diff --git a/src/wallet/walletdb.cpp b/src/wallet/walletdb.cpp
index c0521d3386..5b72a01939 100644
--- a/src/wallet/walletdb.cpp
+++ b/src/wallet/walletdb.cpp
@@ -1013,13 +1013,10 @@ std::unique_ptr<WalletDatabase> MakeDatabase(const fs::path& path, const Databas
 
     Optional<DatabaseFormat> format;
     if (exists) {
-#ifdef USE_BDB
-        if (ExistsBerkeleyDatabase(path)) {
+        if (IsBDBFile(BDBDataFile(path))) {
             format = DatabaseFormat::BERKELEY;
         }
-#endif
-#ifdef USE_SQLITE
-        if (ExistsSQLiteDatabase(path)) {
+        if (IsSQLiteFile(SQLiteDataFile(path))) {
             if (format) {
                 error = Untranslated(strprintf("Failed to load database path '%s'. Data is in ambiguous format.", path.string()));
                 status = DatabaseStatus::FAILED_BAD_FORMAT;
@@ -1027,7 +1024,6 @@ std::unique_ptr<WalletDatabase> MakeDatabase(const fs::path& path, const Databas
             }
             format = DatabaseFormat::SQLITE;
         }
-#endif
     } else if (options.require_existing) {
         error = Untranslated(strprintf("Failed to load database path '%s'. Path does not exist.", path.string()));
         status = DatabaseStatus::FAILED_NOT_FOUND;