1/* Copyright (c) 2000, 2007 MySQL AB
2 Use is subject to license terms
3
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; version 2 of the License.
7
8 This program is distributed in the hope that it will be useful,
9 but WITHOUT ANY WARRANTY; without even the implied warranty of
10 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 GNU General Public License for more details.
12
13 You should have received a copy of the GNU General Public License
14 along with this program; if not, write to the Free Software
15 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA */
16
17/*
18 Radixsort for pointers to fixed length strings.
19 A very quick sort for not to long (< 20 char) strings.
20 Neads a extra buffers of number_of_elements pointers but is
21 2-3 times faster than quicksort
22*/
23
24#include "mysys_priv.h"
25#include <m_string.h>
26
27 /* Radixsort */
28
29my_bool radixsort_is_appliccable(uint n_items, size_t size_of_element)
30{
31 return size_of_element <= 20 && n_items >= 1000 && n_items < 100000;
32}
33
34void radixsort_for_str_ptr(uchar **base, uint number_of_elements, size_t size_of_element, uchar **buffer)
35{
36 uchar **end,**ptr,**buffer_ptr;
37 uint32 *count_ptr,*count_end,count[256];
38 int pass;
39
40 end=base+number_of_elements; count_end=count+256;
41 for (pass=(int) size_of_element-1 ; pass >= 0 ; pass--)
42 {
43 bzero((uchar*) count,sizeof(uint32)*256);
44 for (ptr= base ; ptr < end ; ptr++)
45 count[ptr[0][pass]]++;
46 if (count[0] == number_of_elements)
47 goto next;
48 for (count_ptr=count+1 ; count_ptr < count_end ; count_ptr++)
49 {
50 if (*count_ptr == number_of_elements)
51 goto next;
52 (*count_ptr)+= *(count_ptr-1);
53 }
54 for (ptr= end ; ptr-- != base ;)
55 buffer[--count[ptr[0][pass]]]= *ptr;
56 for (ptr=base, buffer_ptr=buffer ; ptr < end ;)
57 (*ptr++) = *buffer_ptr++;
58 next:;
59 }
60}
61