text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2020 The Bitcoin Core developers
  // 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>
  
  std::vector<fs::path> ListDatabases(const fs::path& wallet_dir)
  {
      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 &&
                  (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 && IsBDBFile(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 spiffcoin
                      // 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;
  }
  
  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.
          return wallet_path;
      } else {
          // Normal case: Interpret wallet path as a directory path containing
          // data and log files.
          return wallet_path / "wallet.dat";
      }
  }
  
  fs::path SQLiteDataFile(const fs::path& path)
  {
      return path / "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;
  }
  