alphanum.cpp

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/*
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 $ 

   slightly modified version, the main function is unaltered, but the
   interface definitions are changed to better suit hugins needs 
   */

#include <hugin_utils/alphanum.h>
#include <stdlib.h>

namespace doj
{

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=isdigit(l_char)!=0, r_digit=isdigit(r_char)!=0;
                // 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
        {
            // get the left number
            char* end;
            unsigned long l_int=strtoul(l, &end, 10);
            l=end;

            // get the right number
            unsigned long r_int=strtoul(r, &end, 10);
            r=end;

            // 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;
}

int alphanum_comp(const std::string& l, const std::string& r)
{
    return alphanum_impl(l.c_str(), r.c_str());
}

int alphanum_comp(const char* l, const char* r)
{
    return alphanum_impl(l, r);
}


bool alphanum_less::operator()(const std::string& left, const std::string& right) const
{
    return alphanum_comp(left, right) < 0;
}

} //namespace doj

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