alphanum.hpp

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#ifndef ALPHANUM__HPP
#define ALPHANUM__HPP

/*
The Alphanum Algorithm is an improved sorting algorithm for strings
containing numbers.  Instead of sorting numbers in ASCII order like a
standard sort, this algorithm sorts numbers in numeric order.

The Alphanum Algorithm is discussed at http://www.DaveKoelle.com

This implementation is Copyright (c) 2008 Dirk Jagdmann <doj@cubic.org>.
It is a cleanroom implementation of the algorithm and not derived by
other's works. In contrast to the versions written by Dave Koelle this
source code is distributed with the libpng/zlib license.

This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:

    1. The origin of this software must not be misrepresented; you
       must not claim that you wrote the original software. If you use
       this software in a product, an acknowledgment in the product
       documentation would be appreciated but is not required.

    2. Altered source versions must be plainly marked as such, and
       must not be misrepresented as being the original software.

    3. This notice may not be removed or altered from any source
       distribution. */

/* $Header: /code/doj/alphanum.hpp,v 1.3 2008/01/28 23:06:47 doj Exp $ */

#include <cassert>
#include <functional>
#include <string>
#include <sstream>

#ifdef ALPHANUM_LOCALE
#include <cctype>
#endif

#ifdef DOJDEBUG
#include <iostream>
#include <typeinfo>
#endif

// TODO: make comparison with hexadecimal numbers. Extend the alphanum_comp() function by traits to choose between decimal and hexadecimal.

namespace doj
{

  // anonymous namespace for functions we use internally. But if you
  // are coding in C, you can use alphanum_impl() directly, since it
  // uses not C++ features.
  namespace {

    // if you want to honour the locale settings for detecting digit
    // characters, you should define ALPHANUM_LOCALE
#ifdef ALPHANUM_LOCALE

    bool alphanum_isdigit(int c)
    {
      return isdigit(c);
    }
#else

    bool alphanum_isdigit(const char c)
    {
      return c>='0' && c<='9';
    }
#endif

    int alphanum_impl(const char *l, const char *r)
    {
      enum mode_t { STRING, NUMBER } mode=STRING;

      while(*l && *r)
        {
          if(mode == STRING)
            {
              char l_char, r_char;
              while((l_char=*l) && (r_char=*r))
                {
                  // check if this are digit characters
                  const bool l_digit=alphanum_isdigit(l_char), r_digit=alphanum_isdigit(r_char);
                  // if both characters are digits, we continue in NUMBER mode
                  if(l_digit && r_digit)
                    {
                      mode=NUMBER;
                      break;
                    }
                  // if only the left character is a digit, we have a result
                  if(l_digit) return -1;
                  // if only the right character is a digit, we have a result
                  if(r_digit) return +1;
                  // compute the difference of both characters
                  const int diff=l_char - r_char;
                  // if they differ we have a result
                  if(diff != 0) return diff;
                  // otherwise process the next characters
                  ++l;
                  ++r;
                }
            }
          else // mode==NUMBER
            {
#ifdef ALPHANUM_LOCALE
              // get the left number
              char *end;
              unsigned long l_int=strtoul(l, &end, 0);
              l=end;

              // get the right number
              unsigned long r_int=strtoul(r, &end, 0);
              r=end;
#else
              // get the left number
              unsigned long l_int=0;
              while(*l && alphanum_isdigit(*l))
                {
                  // TODO: this can overflow
                  l_int=l_int*10 + *l-'0';
                  ++l;
                }

              // get the right number
              unsigned long r_int=0;
              while(*r && alphanum_isdigit(*r))
                {
                  // TODO: this can overflow
                  r_int=r_int*10 + *r-'0';
                  ++r;
                }
#endif

              // if the difference is not equal to zero, we have a comparison result
              const long diff=l_int-r_int;
              if(diff != 0)
                return diff;

              // otherwise we process the next substring in STRING mode
              mode=STRING;
            }
        }

      if(*r) return -1;
      if(*l) return +1;
      return 0;
    }

  }

  template <typename lT, typename rT>
  int alphanum_comp(const lT& left, const rT& right)
  {
#ifdef DOJDEBUG
    std::clog << "alphanum_comp<" << typeid(left).name() << "," << typeid(right).name() << "> " << left << "," << right << std::endl;
#endif
    std::ostringstream l; l << left;
    std::ostringstream r; r << right;
    return alphanum_impl(l.str().c_str(), r.str().c_str());
  }

  template <>
  int alphanum_comp<std::string>(const std::string& l, const std::string& r)
  {
#ifdef DOJDEBUG
    std::clog << "alphanum_comp<std::string,std::string> " << l << "," << r << std::endl;
#endif
    return alphanum_impl(l.c_str(), r.c_str());
  }


  // now follow a lot of overloaded alphanum_comp() functions to get a
  // direct call to alphanum_impl() upon the various combinations of c
  // and c++ strings.

  int alphanum_comp(char* l, char* r)
  {
    assert(l);
    assert(r);
#ifdef DOJDEBUG
    std::clog << "alphanum_comp<char*,char*> " << l << "," << r << std::endl;
#endif
    return alphanum_impl(l, r);
  }

  int alphanum_comp(const char* l, const char* r)
  {
    assert(l);
    assert(r);
#ifdef DOJDEBUG
    std::clog << "alphanum_comp<const char*,const char*> " << l << "," << r << std::endl;
#endif
    return alphanum_impl(l, r);
  }

  int alphanum_comp(char* l, const char* r)
  {
    assert(l);
    assert(r);
#ifdef DOJDEBUG
    std::clog << "alphanum_comp<char*,const char*> " << l << "," << r << std::endl;
#endif
    return alphanum_impl(l, r);
  }

  int alphanum_comp(const char* l, char* r)
  {
    assert(l);
    assert(r);
#ifdef DOJDEBUG
    std::clog << "alphanum_comp<const char*,char*> " << l << "," << r << std::endl;
#endif
    return alphanum_impl(l, r);
  }

  int alphanum_comp(const std::string& l, char* r)
  {
    assert(r);
#ifdef DOJDEBUG
    std::clog << "alphanum_comp<std::string,char*> " << l << "," << r << std::endl;
#endif
    return alphanum_impl(l.c_str(), r);
  }

  int alphanum_comp(char* l, const std::string& r)
  {
    assert(l);
#ifdef DOJDEBUG
    std::clog << "alphanum_comp<char*,std::string> " << l << "," << r << std::endl;
#endif
    return alphanum_impl(l, r.c_str());
  }

  int alphanum_comp(const std::string& l, const char* r)
  {
    assert(r);
#ifdef DOJDEBUG
    std::clog << "alphanum_comp<std::string,const char*> " << l << "," << r << std::endl;
#endif
    return alphanum_impl(l.c_str(), r);
  }

  int alphanum_comp(const char* l, const std::string& r)
  {
    assert(l);
#ifdef DOJDEBUG
    std::clog << "alphanum_comp<const char*,std::string> " << l << "," << r << std::endl;
#endif
    return alphanum_impl(l, r.c_str());
  }


  template<class Ty>
  struct alphanum_less : public std::binary_function<Ty, Ty, bool>
  {
    bool operator()(const Ty& left, const Ty& right) const
    {
      return alphanum_comp(left, right) < 0;
    }
  };

}


#endif