mf_radix.c
上传用户:romrleung
上传日期:2022-05-23
资源大小:18897k
文件大小:2k
- /* Copyright (C) 2000 MySQL AB
- 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; either version 2 of the License, or
- (at your option) any later version.
- 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 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 */
- void radixsort_for_str_ptr(uchar **base, uint number_of_elements, size_s 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((gptr) 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:;
- }
- }