text: // Copyright (c) 2017-2019 The Emircoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include <wallet/walletutil.h>
  
  #include <logging.h>
  #include <util/system.h>
  
  fs::path GetWalletDir()
  {
      fs::path path;
  
      if (gArgs.IsArgSet("-walletdir")) {
          path = gArgs.GetArg("-walletdir", "");
          if (!fs::is_directory(path)) {
              // If the path specified doesn't exist, we return the deliberately
              // invalid empty string.
              path = "";
          }
      } else {
          path = GetDataDir();
          // If a wallets directory exists, use that, otherwise default to GetDataDir
          if (fs::is_directory(path / "wallets")) {
              path /= "wallets";
          }
      }
  
      return path;
  }
  
  static bool IsBerkeleyBtree(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;
  }
  
  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;
          }
  
          // 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 && IsBerkeleyBtree(it->path() / "wallet.dat")) {
              // 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 && IsBerkeleyBtree(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 emircoin
                  // 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);
              }
          }
      }
  
      return paths;
  }
  
  WalletLocation::WalletLocation(const std::string& name)
      : m_name(name)
      , m_path(fs::absolute(name, GetWalletDir()))
  {
  }
  
  bool WalletLocation::Exists() const
  {
      return fs::symlink_status(m_path).type() != fs::file_not_found;
  }
  