MOVEONLY: Move IsBDBFile, IsSQLiteFile, and ListWalletDir

This commit does not change to any code and behavior. It it is easily reviewed
with the --color-moved=dimmed_zebra git diff option.

Motivation for this change is to:

- Consolidate redundant functions
  IsBDBFile /ExistsBerkeleyDatabase / SplitWalletPath, and
  IsSQLiteFile / ExistsSQLiteDatabase in the next commits

- Detect SQLite wallets consistently regardless whether bitcoin is built with
  SQLite support in the next commits

- Avoid attempting to open SQLite databases with the BDB library when bitcoin
  is built without SQLite support in the next commits

1 files changed, 118 insertions, 0 deletions

diff --git a/src/wallet/db.cpp b/src/wallet/db.cpp
index bd1d114730..85aeaeb3ab 100644
--- a/src/wallet/db.cpp
+++ b/src/wallet/db.cpp
@@ -3,11 +3,70 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <chainparams.h>
 #include <fs.h>
+#include <logging.h>
 #include <wallet/db.h>
 
 #include <string>
 
+fs::path GetWalletDir();
+
+#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> ListWalletDir()
+{
+    const fs::path wallet_dir = GetWalletDir();
+    const size_t offset = wallet_dir.string().size() + 1;
+    std::vector<fs::path> paths;
+    boost::system::error_code ec;
+
+    for (auto it = fs::recursive_directory_iterator(wallet_dir, ec); it != fs::recursive_directory_iterator(); it.increment(ec)) {
+        if (ec) {
+            LogPrintf("%s: %s %s\n", __func__, ec.message(), it->path().string());
+            continue;
+        }
+
+        try {
+            // Get wallet path relative to walletdir by removing walletdir from the wallet path.
+            // This can be replaced by boost::filesystem::lexically_relative once boost is bumped to 1.60.
+            const fs::path path = it->path().string().substr(offset);
+
+            if (it->status().type() == fs::directory_file &&
+                (ExistsBerkeleyDatabase(it->path()) || ExistsSQLiteDatabase(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())) {
+                if (it->path().filename() == "wallet.dat") {
+                    // Found top-level wallet.dat btree file, add top level directory ""
+                    // as a wallet.
+                    paths.emplace_back();
+                } else {
+                    // Found top-level btree file not called wallet.dat. Current bitcoin
+                    // software will never create these files but will allow them to be
+                    // opened in a shared database environment for backwards compatibility.
+                    // Add it to the list of available wallets.
+                    paths.emplace_back(path);
+                }
+            }
+        } catch (const std::exception& e) {
+            LogPrintf("%s: Error scanning %s: %s\n", __func__, it->path().string(), e.what());
+            it.no_push();
+        }
+    }
+
+    return paths;
+}
+
 void SplitWalletPath(const fs::path& wallet_path, fs::path& env_directory, std::string& database_filename)
 {
     if (fs::is_regular_file(wallet_path)) {
@@ -23,3 +82,62 @@ void SplitWalletPath(const fs::path& wallet_path, fs::path& env_directory, std::
         database_filename = "wallet.dat";
     }
 }
+
+bool IsBDBFile(const fs::path& path)
+{
+    if (!fs::exists(path)) return false;
+
+    // A Berkeley DB Btree file has at least 4K.
+    // This check also prevents opening lock files.
+    boost::system::error_code ec;
+    auto size = fs::file_size(path, ec);
+    if (ec) LogPrintf("%s: %s %s\n", __func__, ec.message(), path.string());
+    if (size < 4096) return false;
+
+    fsbridge::ifstream file(path, std::ios::binary);
+    if (!file.is_open()) return false;
+
+    file.seekg(12, std::ios::beg); // Magic bytes start at offset 12
+    uint32_t data = 0;
+    file.read((char*) &data, sizeof(data)); // Read 4 bytes of file to compare against magic
+
+    // Berkeley DB Btree magic bytes, from:
+    //  https://github.com/file/file/blob/5824af38469ec1ca9ac3ffd251e7afe9dc11e227/magic/Magdir/database#L74-L75
+    //  - big endian systems - 00 05 31 62
+    //  - little endian systems - 62 31 05 00
+    return data == 0x00053162 || data == 0x62310500;
+}
+
+bool IsSQLiteFile(const fs::path& path)
+{
+    if (!fs::exists(path)) return false;
+
+    // A SQLite Database file is at least 512 bytes.
+    boost::system::error_code ec;
+    auto size = fs::file_size(path, ec);
+    if (ec) LogPrintf("%s: %s %s\n", __func__, ec.message(), path.string());
+    if (size < 512) return false;
+
+    fsbridge::ifstream file(path, std::ios::binary);
+    if (!file.is_open()) return false;
+
+    // Magic is at beginning and is 16 bytes long
+    char magic[16];
+    file.read(magic, 16);
+
+    // Application id is at offset 68 and 4 bytes long
+    file.seekg(68, std::ios::beg);
+    char app_id[4];
+    file.read(app_id, 4);
+
+    file.close();
+
+    // Check the magic, see https://sqlite.org/fileformat2.html
+    std::string magic_str(magic, 16);
+    if (magic_str != std::string("SQLite format 3", 16)) {
+        return false;
+    }
+
+    // Check the application id matches our network magic
+    return memcmp(Params().MessageStart(), app_id, 4) == 0;
+}