Downloader.h

/**************************************************************************
 * basf2 (Belle II Analysis Software Framework)                           *
 * Author: The Belle II Collaboration                                     *
 *                                                                        *
 * See git log for contributors and copyright holders.                    *
 * This file is licensed under LGPL-3.0, see LICENSE.md.                  *
 **************************************************************************/
 
#pragma once
 
#include <framework/utilities/ScopeGuard.h>
 
#include <iosfwd>
#include <memory>
#include <random>
 
namespace Belle2::Conditions {
  struct CurlSession;

  class Downloader final {
  public:
    Downloader() = default;
    ~Downloader();

    static Downloader& getDefaultInstance();
    bool startSession();
    void finishSession();
    ScopeGuard ensureSession()
    {
      bool started = startSession();
      return ScopeGuard([this, started] {if (started) finishSession();});
    }

    unsigned int getConnectionTimeout() const { return m_connectionTimeout; }
    unsigned int getStalledTimeout() const { return m_stalledTimeout; }
    unsigned int getMaxRetries() const { return m_maxRetries; }
    unsigned int getBackoffFactor() const { return m_backoffFactor; }
    void setConnectionTimeout(unsigned int timeout);
    void setStalledTimeout(unsigned int timeout);
    void setMaxRetries(unsigned int retries) { m_maxRetries = retries; }
    void setBackoffFactor(unsigned int factor) { m_backoffFactor = std::max(1u, factor); }
    bool download(const std::string& url, std::ostream& stream, bool silentOnMissing = false);

    bool verifyChecksum(std::istream& input, const std::string& checksum) { return calculateChecksum(input) == checksum; }
    std::string escapeString(const std::string& text);
    std::string joinWithSlash(const std::string& base, const std::string& second);
 
  private:

    static std::string calculateChecksum(std::istream& input);

    std::unique_ptr<CurlSession> m_session;
    static bool s_globalInit;
    unsigned int m_connectionTimeout{60};
    unsigned int m_stalledTimeout{60};
    unsigned int m_maxRetries{5};
    unsigned int m_backoffFactor{3};

    void initializeRandomGeneratorSeed();
    std::unique_ptr<std::mt19937> m_rnd{std::make_unique<std::mt19937>()};
    std::unique_ptr<std::uniform_real_distribution<double>> m_rndDistribution{std::make_unique<std::uniform_real_distribution<double>>()};
    bool m_rndIsInitialized{false};
  };
} // namespace Belle2::Conditions