mirror of
https://github.com/MariaDB/server.git
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154 lines
3.4 KiB
C
154 lines
3.4 KiB
C
/* Copyright (C) 2000 MySQL AB
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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/*
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get_ptr_compare(len) returns a pointer to a optimal byte-compare function
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for a array of stringpointer where all strings have size len.
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The bytes are compare as unsigned chars.
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*/
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#include "mysys_priv.h"
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static int ptr_compare(uint *compare_length, uchar **a, uchar **b);
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static int ptr_compare_0(uint *compare_length, uchar **a, uchar **b);
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static int ptr_compare_1(uint *compare_length, uchar **a, uchar **b);
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static int ptr_compare_2(uint *compare_length, uchar **a, uchar **b);
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static int ptr_compare_3(uint *compare_length, uchar **a, uchar **b);
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/* Get a pointer to a optimal byte-compare function for a given size */
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qsort2_cmp get_ptr_compare (uint size)
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{
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if (size < 4)
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return (qsort2_cmp) ptr_compare;
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switch (size & 3) {
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case 0: return (qsort2_cmp) ptr_compare_0;
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case 1: return (qsort2_cmp) ptr_compare_1;
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case 2: return (qsort2_cmp) ptr_compare_2;
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case 3: return (qsort2_cmp) ptr_compare_3;
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}
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return 0; /* Impossible */
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}
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/*
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Compare to keys to see witch is smaller.
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Loop unrolled to make it quick !!
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*/
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#define cmp(N) if (first[N] != last[N]) return (int) first[N] - (int) last[N]
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static int ptr_compare(uint *compare_length, uchar **a, uchar **b)
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{
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reg3 int length= *compare_length;
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reg1 uchar *first,*last;
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first= *a; last= *b;
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while (--length)
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{
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if (*first++ != *last++)
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return (int) first[-1] - (int) last[-1];
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}
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return (int) first[0] - (int) last[0];
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}
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static int ptr_compare_0(uint *compare_length,uchar **a, uchar **b)
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{
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reg3 int length= *compare_length;
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reg1 uchar *first,*last;
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first= *a; last= *b;
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loop:
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cmp(0);
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cmp(1);
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cmp(2);
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cmp(3);
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if ((length-=4))
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{
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first+=4;
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last+=4;
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goto loop;
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}
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return (0);
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}
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static int ptr_compare_1(uint *compare_length,uchar **a, uchar **b)
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{
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reg3 int length= *compare_length-1;
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reg1 uchar *first,*last;
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first= *a+1; last= *b+1;
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cmp(-1);
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loop:
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cmp(0);
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cmp(1);
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cmp(2);
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cmp(3);
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if ((length-=4))
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{
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first+=4;
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last+=4;
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goto loop;
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}
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return (0);
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}
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static int ptr_compare_2(uint *compare_length,uchar **a, uchar **b)
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{
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reg3 int length= *compare_length-2;
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reg1 uchar *first,*last;
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first= *a +2 ; last= *b +2;
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cmp(-2);
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cmp(-1);
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loop:
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cmp(0);
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cmp(1);
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cmp(2);
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cmp(3);
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if ((length-=4))
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{
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first+=4;
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last+=4;
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goto loop;
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}
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return (0);
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}
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static int ptr_compare_3(uint *compare_length,uchar **a, uchar **b)
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{
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reg3 int length= *compare_length-3;
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reg1 uchar *first,*last;
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first= *a +3 ; last= *b +3;
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cmp(-3);
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cmp(-2);
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cmp(-1);
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loop:
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cmp(0);
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cmp(1);
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cmp(2);
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cmp(3);
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if ((length-=4))
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{
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first+=4;
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last+=4;
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goto loop;
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}
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return (0);
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}
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