memory.H

/*
 * This file is part of the "Archon" framework.
 * (http://files3d.sourceforge.net)
 *
 * Copyright © 2006 by Kristian Spangsege and Brian Kristiansen.
 *
 * Permission to use, copy, modify, and distribute this software and
 * its documentation under the terms of the GNU General Public License is
 * hereby granted. No representations are made about the suitability of
 * this software for any purpose. It is provided "as is" without express
 * or implied warranty. See the GNU General Public License
 * (http://www.gnu.org/copyleft/gpl.html) for more details.
 *
 * The characters in this file are ISO8859-1 encoded.
 *
 * The documentation in this file is in "Doxygen" style
 * (http://www.doxygen.org).
 */

#ifndef ARCHON_UTILITIES_MEMORY_H
#define ARCHON_UTILITIES_MEMORY_H

#include <algorithm>
#include <limits>
#include <vector>

namespace Archon
{
  namespace Utilities
  {
    using namespace std;

    inline int findLeastSignificantBit(unsigned v)
    {
      if(!v) return -1;
      int i = numeric_limits<unsigned char>::digits * sizeof(v) - 1;
      v <<= 1;
      while(v) { v <<= 1; --i; }
      return i;
    }


    inline int findMostSignificantBit(unsigned v)
    {
      if(!v) return -1;
      int i = 0;
      v >>= 1; // Does not introduce new bits since v is unsigned.
      while(v) { v >>= 1; ++i; }
      return i;
    }


    vector<bool> detectNativeEndianness();


    bool compareEndianness(const vector<bool> &a,
                           const vector<bool> &b = vector<bool>(),
                           int levels = 0);


    vector<int> computeBytePermutation(const vector<bool> &endianness, int levels);


    template<typename T>
    inline T readWithBytePermutation(const char *data,
                                     const vector<int> &bytePermutation)
    {
      T v;
      char *p = reinterpret_cast<char *>(&v);
      for(int i=0; i<static_cast<int>(sizeof(T)); ++i)
        p[bytePermutation[i]] = data[i];
      return v;
    }


    template<typename T>
    inline T readWithSpecificEndianness(const char *data,
                                        const vector<bool> &endianness)
    {
      vector<int> bytePermutation =
        computeBytePermutation(endianness, findMostSignificantBit(sizeof(T)));
      return readWithBytePermutation<T>(data, bytePermutation);
    }


    template<typename T>
    struct Array
    {
      Array(T *p = 0): p(p) {}

      Array(size_t n): p(new T[n]) {}

      Array(size_t n, T v): p(new T[n])
      {
        fill(p, p+n, v);
      }

      ~Array() { delete[] p; }

      const T *get() const { return p; }

      T *get() { return p; }

      T *out() { T *q=p; p=0; return q; }

      void reset(T *q = 0)
      {
        if(p == q) return;
        delete[] p;
        p = q;
      }

      void reset(size_t n)
      {
        reset(new T[n]);
      }

      void reset(size_t n, T v)
      {
        reset(new T[n]);
        fill(p, p+n, v);
      }

      const T &operator[](int i) const { return p[i]; }

      T &operator[](int i) { return p[i]; }

      operator bool() const { return p; }

    private:
      T *p;
    };

    typedef Array<char> MemoryBuffer;
  }
}

#endif // ARCHON_UTILITIES_MEMORY_H

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