release/src/router/mysql/mysys/mf_radix.c

   1 /* Copyright (c) 2000, 2007 MySQL AB
   2
   3    This program is free software; you can redistribute it and/or modify
   4    it under the terms of the GNU General Public License as published by
   5    the Free Software Foundation; version 2 of the License.
   6
   7    This program is distributed in the hope that it will be useful,
   8    but WITHOUT ANY WARRANTY; without even the implied warranty of
   9    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10    GNU General Public License for more details.
  11
  12    You should have received a copy of the GNU General Public License
  13    along with this program; if not, write to the Free Software
  14    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA */
  15
  16 /*
  17   Radixsort for pointers to fixed length strings.
  18   A very quick sort for not to long (< 20 char) strings.
  19   Neads a extra buffers of number_of_elements pointers but is
  20   2-3 times faster than quicksort
  21 */
  22
  23 #include "mysys_priv.h"
  24 #include <m_string.h>
  25
  26         /* Radixsort */
  27
  28 void radixsort_for_str_ptr(uchar **base, uint number_of_elements, size_t size_of_element, uchar **buffer)
  29 {
  30   uchar **end,**ptr,**buffer_ptr;
  31   uint32 *count_ptr,*count_end,count[256];
  32   int pass;
  33
  34   end=base+number_of_elements; count_end=count+256;
  35   for (pass=(int) size_of_element-1 ; pass >= 0 ; pass--)
  36   {
  37     bzero((uchar*) count,sizeof(uint32)*256);
  38     for (ptr= base ; ptr < end ; ptr++)
  39       count[ptr[0][pass]]++;
  40     if (count[0] == number_of_elements)
  41       goto next;
  42     for (count_ptr=count+1 ; count_ptr < count_end ; count_ptr++)
  43     {
  44       if (*count_ptr == number_of_elements)
  45         goto next;
  46       (*count_ptr)+= *(count_ptr-1);
  47     }
  48     for (ptr= end ; ptr-- != base ;)
  49       buffer[--count[ptr[0][pass]]]= *ptr;
  50     for (ptr=base, buffer_ptr=buffer ; ptr < end ;)
  51       (*ptr++) = *buffer_ptr++;
  52   next:;
  53   }
  54 }