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/* Copyright (c) 2000, 2007 MySQL AB
Use is subject to license terms
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA */
/*
Radixsort for pointers to fixed length strings.
A very quick sort for not to long (< 20 char) strings.
Neads a extra buffers of number_of_elements pointers but is
2-3 times faster than quicksort
*/
#include "mysys_priv.h"
#include <m_string.h>
/* Radixsort */
my_bool radixsort_is_appliccable(uint n_items, size_t size_of_element)
{
return size_of_element <= 20 && n_items >= 1000 && n_items < 100000;
}
void radixsort_for_str_ptr(uchar **base, uint number_of_elements, size_t size_of_element, uchar **buffer)
{
uchar **end,**ptr,**buffer_ptr;
uint32 *count_ptr,*count_end,count[256];
int pass;
end=base+number_of_elements; count_end=count+256;
for (pass=(int) size_of_element-1 ; pass >= 0 ; pass--)
{
bzero((uchar*) count,sizeof(uint32)*256);
for (ptr= base ; ptr < end ; ptr++)
count[ptr[0][pass]]++;
if (count[0] == number_of_elements)
goto next;
for (count_ptr=count+1 ; count_ptr < count_end ; count_ptr++)
{
if (*count_ptr == number_of_elements)
goto next;
(*count_ptr)+= *(count_ptr-1);
}
for (ptr= end ; ptr-- != base ;)
buffer[--count[ptr[0][pass]]]= *ptr;
for (ptr=base, buffer_ptr=buffer ; ptr < end ;)
(*ptr++) = *buffer_ptr++;
next:;
}
}
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