Hash.h

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#ifndef DataFormats_Provenance_Hash_h
#define DataFormats_Provenance_Hash_h

#include <string>
#include <functional>

/*----------------------------------------------------------------------
  
Hash:

  Note: The call to 'fixup' in every member function is a temporary
  measure for backwards compatibility. It is necessary in every function
  because Root creates instances of the class *without* using the
  interface of the class, thus making it insufficient to assure that
  all constructors make corrected instances.

----------------------------------------------------------------------*/
namespace cms {
  class Digest;
}

namespace edm {

  namespace detail {
    // This string is the 16-byte, non-printable version.
    std::string const& InvalidHash();
  }  // namespace detail

  namespace hash_detail {
    typedef std::string value_type;
    value_type compactForm_(value_type const& hash);
    void fixup_(value_type& hash);
    bool isCompactForm_(value_type const& hash);
    bool isValid_(value_type const& hash);
    void throwIfIllFormed(value_type const& hash);
    void toString_(std::string& result, value_type const& hash);
    void toDigest_(cms::Digest& digest, value_type const& hash);
    std::ostream& print_(std::ostream& os, value_type const& hash);
    size_t smallHash_(value_type const& hash);
  }  // namespace hash_detail

  template <int I>
  class Hash {
  public:
    typedef hash_detail::value_type value_type;

    Hash();
    explicit Hash(value_type const& v);

    Hash(Hash<I> const&);
    Hash<I>& operator=(Hash<I> const& iRHS);

    Hash(Hash<I>&&) = default;
    Hash<I>& operator=(Hash<I>&&) = default;

    void reset();

    // For now, just check the most basic: a default constructed
    // ParameterSetID is not valid. This is very crude: we are
    // assuming that nobody created a ParameterSetID from an empty
    // string, nor from any string that is not a valid string
    // representation of an MD5 checksum.
    bool isValid() const;

    bool operator<(Hash<I> const& other) const;
    bool operator>(Hash<I> const& other) const;
    bool operator==(Hash<I> const& other) const;
    bool operator!=(Hash<I> const& other) const;
    std::ostream& print(std::ostream& os) const;
    void toString(std::string& result) const;
    void toDigest(cms::Digest& digest) const;
    void swap(Hash<I>& other);

    // Return the 16-byte (non-printable) string form.
    value_type compactForm() const;

    bool isCompactForm() const;

    size_t smallHash() const;

    //Used by ROOT storage
    // CMS_CLASS_VERSION(11) // This macro is not defined here, so expand it.
    static short Class_Version() { return 11; }

  private:
    void throwIfIllFormed() const;

    template <typename Op>
    bool compareUsing(Hash<I> const& iOther, Op op) const {
      bool meCF = hash_detail::isCompactForm_(hash_);
      bool otherCF = hash_detail::isCompactForm_(iOther.hash_);
      if (meCF == otherCF) {
        return op(this->hash_, iOther.hash_);
      }
      //copy constructor will do compact form conversion
      if (meCF) {
        Hash<I> temp(iOther);  // NOLINT(performance-unnecessary-copy-initialization)
        return op(this->hash_, temp.hash_);
      }
      Hash<I> temp(*this);
      return op(temp.hash_, iOther.hash_);
    }

    value_type hash_;
  };

  //--------------------------------------------------------------------
  //
  // Implementation details follow...
  //--------------------------------------------------------------------

  template <int I>
  inline Hash<I>::Hash() : hash_(detail::InvalidHash()) {}

  template <int I>
  inline Hash<I>::Hash(typename Hash<I>::value_type const& v) : hash_(v) {
    hash_detail::fixup_(hash_);
  }

  template <int I>
  inline Hash<I>::Hash(Hash<I> const& iOther) : hash_(iOther.hash_) {
    hash_detail::fixup_(hash_);
  }

  template <int I>
  inline Hash<I>& Hash<I>::operator=(Hash<I> const& iRHS) {
    hash_ = iRHS.hash_;
    hash_detail::fixup_(hash_);
    return *this;
  }

  template <int I>
  inline void Hash<I>::reset() {
    hash_ = detail::InvalidHash();
  }

  template <int I>
  inline bool Hash<I>::isValid() const {
    return hash_detail::isValid_(hash_);
  }

  template <int I>
  inline bool Hash<I>::operator<(Hash<I> const& other) const {
    return this->compareUsing(other, std::less<std::string>());
  }

  template <int I>
  inline bool Hash<I>::operator>(Hash<I> const& other) const {
    return this->compareUsing(other, std::greater<std::string>());
  }

  template <int I>
  inline bool Hash<I>::operator==(Hash<I> const& other) const {
    return this->compareUsing(other, std::equal_to<std::string>());
  }

  template <int I>
  inline bool Hash<I>::operator!=(Hash<I> const& other) const {
    return this->compareUsing(other, std::not_equal_to<std::string>());
  }

  template <int I>
  inline std::ostream& Hash<I>::print(std::ostream& os) const {
    return hash_detail::print_(os, hash_);
  }

  template <int I>
  inline void Hash<I>::toString(std::string& result) const {
    hash_detail::toString_(result, hash_);
  }

  template <int I>
  inline void Hash<I>::toDigest(cms::Digest& digest) const {
    hash_detail::toDigest_(digest, hash_);
  }

  template <int I>
  inline void Hash<I>::swap(Hash<I>& other) {
    hash_.swap(other.hash_);
  }

  template <int I>
  inline typename Hash<I>::value_type Hash<I>::compactForm() const {
    return hash_detail::compactForm_(hash_);
  }

  template <int I>
  inline size_t Hash<I>::smallHash() const {
    return hash_detail::smallHash_(hash_);
  }

  // Note: this template is not declared 'inline' because of the
  // switch statement.

  template <int I>
  inline bool Hash<I>::isCompactForm() const {
    return hash_detail::isCompactForm_(hash_);
  }

  // Free swap function
  template <int I>
  inline void swap(Hash<I>& a, Hash<I>& b) {
    a.swap(b);
  }

  template <int I>
  inline std::ostream& operator<<(std::ostream& os, Hash<I> const& h) {
    return h.print(os);
  }

}  // namespace edm
#endif