StringKey.h

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* (c) Copyright 1998-2025 CERN for the benefit of the LHCb and ATLAS collaborations *
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* This software is distributed under the terms of the Apache version 2 licence,     *
* copied verbatim in the file "LICENSE".                                            *
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#pragma once
 
#include <GaudiKernel/Kernel.h>
#include <GaudiKernel/StatusCode.h>
#include <algorithm>
#include <functional>
#include <iosfwd>
#include <string>
#include <vector>
 
namespace Gaudi {
  class GAUDI_API StringKey {
  public:
    StringKey( const char* key = "" ) : StringKey{ std::string{ key } } {}
    //
    StringKey( std::string key ); // constructor, perform hashing
  public:
    const std::string& str() const { return m_str; }
    operator const std::string&() const { return str(); }
    bool empty() const { return m_str.empty(); }
    bool operator!() const { return empty(); }
 
  public:
    friend bool operator==( const StringKey& lhs, const StringKey& rhs ) {
      return lhs.m_hash == rhs.m_hash && lhs.m_str == rhs.m_str;
    }
    friend bool operator==( const StringKey& lhs, const std::string& rhs ) { return lhs.m_str == rhs; }
    friend bool operator==( const std::string& lhs, const StringKey& rhs ) { return rhs == lhs; }
    friend bool operator==( const StringKey& lhs, std::string_view rhs ) { return lhs.m_str == rhs; }
    friend bool operator==( std::string_view lhs, const StringKey& rhs ) { return rhs == lhs; }
 
  public: // non-equality
    friend bool operator!=( const StringKey& lhs, const StringKey& rhs ) { return !( lhs == rhs ); }
    friend bool operator!=( const StringKey& lhs, std::string_view rhs ) { return !( lhs == rhs ); }
    friend bool operator!=( const StringKey& lhs, const std::string& rhs ) { return !( lhs == rhs ); }
    friend bool operator!=( std::string_view lhs, const StringKey& rhs ) { return !( lhs == rhs ); }
    friend bool operator!=( const std::string& lhs, const StringKey& rhs ) { return !( lhs == rhs ); }
    // ordering
  public:
    friend bool operator<( const StringKey& lhs, const StringKey& rhs ) {
      return lhs.m_hash == rhs.m_hash ? lhs.m_str < rhs.m_str : lhs.m_hash < rhs.m_hash;
    }
    friend bool operator>( const StringKey& lhs, const StringKey& rhs ) { return rhs < lhs; }
    friend bool operator<=( const StringKey& lhs, const StringKey& rhs ) { return !( lhs > rhs ); }
    friend bool operator>=( const StringKey& lhs, const StringKey& rhs ) { return !( lhs < rhs ); }
    // few helper methods for indirect usage, mainly for Python
  public:
    std::size_t __hash__() const { return m_hash; }
    const std::string& __str__() const; // the representation of the object
    std::string __repr__() const; // the representation of the object
    bool __eq__( const StringKey& right ) const;
    bool __eq__( std::string_view right ) const;
    bool __neq__( const StringKey& right ) const;
    bool __neq__( const std::string_view right ) const;
 
  public:
    std::string toString() const; // string representation (for properties)
  private:
    std::string m_str; // the actual string
    std::size_t m_hash; //          the hash
  };
  inline std::size_t hash_value( const Gaudi::StringKey& key ) { return key.__hash__(); }
} // namespace Gaudi
// interoperability with std::string and const char*
inline std::string operator+( const std::string& lhs, const Gaudi::StringKey& rhs ) { return lhs + rhs.str(); }
inline std::string operator+( const char* lhs, const Gaudi::StringKey& rhs ) { return lhs + rhs.str(); }
inline std::string operator+( const Gaudi::StringKey& lhs, const std::string& rhs ) { return lhs.str() + rhs; }
inline std::string operator+( const Gaudi::StringKey& lhs, const char* rhs ) { return lhs.str() + rhs; }
// Streaming  value -> string
namespace Gaudi {
  namespace Utils {
    GAUDI_API std::ostream& toStream( const Gaudi::StringKey& key, std::ostream& s );
  } // namespace Utils
  inline std::ostream& operator<<( std::ostream& o, const Gaudi::StringKey& key ) { return o << key.str(); }
} // namespace Gaudi
// Parsing : string -> value
namespace Gaudi {
  namespace Parsers {
    GAUDI_API StatusCode parse( Gaudi::StringKey& result, std::string_view input );
    GAUDI_API StatusCode parse( std::vector<Gaudi::StringKey>& result, std::string_view input );
  } // namespace Parsers
} // namespace Gaudi
namespace std {
  template <>
  struct hash<Gaudi::StringKey> {
    inline std::size_t operator()( Gaudi::StringKey const& s ) const { return hash_value( s ); }
  };
} // namespace std