ircproxy  The Ultimate Cyborg

---

Index.h

#ifndef INDEX_H
#define INDEX_H

#ifndef _GNU_SOURCE
#define _GNU_SOURCE     // Needed before <cstring> for ffsl().
#endif

#ifndef USE_PCH
#include <iostream>
#include <cstring>
#include "debug.h"
#endif

//! @brief Index generator for instances of type INDEX_POOL_TYPE.
//
// INDEX_POOL_TYPE must be derived from Index.
// For each instance of class INDEX_POOL_TYPE index() will
// return an integer unique for that instance that will
// be constant throughout the life-time of that instance.
template<typename INDEX_POOL_TYPE>
  class Index {
    public:
      static int const max_index = 8 * sizeof(long);            //!< The maximum number of allowed INDEX_POOL_TYPE instances.

    private:
      static long S_index_pool;                                 //!< A mask to keep track of used indices (a set bit marks a FREE index).
      int const M_index;                                        //!< The index of this instance.

    protected:
      //! Construct an Index base class, automatically setting M_index to a free index.
      Index(void) : M_index(ffsl(S_index_pool) - 1) { ASSERT(M_index != -1); S_index_pool &= ~(1UL << M_index); }
      //! Destructor. Frees up the index for reuse.
      ~Index(void) { S_index_pool |= (1 << M_index); }

    public:
      //! Return a small integer, unique for the instance and constant throughout it's life time.
      int index(void) const { return M_index; }

      //! Return the size of a vector that would be needed for the largest index currently in use.
      static int size(void) { int r = 0; unsigned long i = (~static_cast<unsigned long>(S_index_pool)) << 1; while(i >>= 1) ++r; return r; }

    private:
      static void sanity_check(void)
          {
            // INDEX_POOL_TYPE must be derived from Index.
            (void)static_cast<Index*>((INDEX_POOL_TYPE*)0);
          }
  };

template<class INDEX_POOL_TYPE>
  long Index<INDEX_POOL_TYPE>::S_index_pool = ~0;       // Initialize to all 1's: no index is in use yet.

#endif // INDEX_H

---