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/*
get_ptr_compare(len) returns a pointer to a optimal byte-compare function
for a array of stringpointer where all strings have size len.
The bytes are compare as unsigned chars.
Because the size is saved in a static variable.
When using threads the program must have called my_init and the thread
my_init_thread()
*/
#include <global.h>
#include "m_string.h"
static int ptr_compare(uchar **a, uchar **b);
static int ptr_compare_0(uchar **a, uchar **b);
static int ptr_compare_1(uchar **a, uchar **b);
static int ptr_compare_2(uchar **a, uchar **b);
static int ptr_compare_3(uchar **a, uchar **b);
#ifdef THREAD
#include <my_pthread.h>
#define compare_length my_thread_var->cmp_length
#else
static uint compare_length;
#endif
/* Get a pointer to a optimal byte-compare function for a given size */
qsort_cmp get_ptr_compare (uint size)
{
compare_length=size; /* Remember for loop */
if (size < 4)
return (qsort_cmp) ptr_compare;
switch (size & 3) {
case 0: return (qsort_cmp) ptr_compare_0;
case 1: return (qsort_cmp) ptr_compare_1;
case 2: return (qsort_cmp) ptr_compare_2;
case 3: return (qsort_cmp) ptr_compare_3;
}
return 0; /* Impossible */
}
/*
Compare to keys to see witch is smaller.
Loop unrolled to make it quick !!
*/
#define cmp(N) if (first[N] != last[N]) return (int) first[N] - (int) last[N]
static int ptr_compare(uchar **a, uchar **b)
{
reg3 int length= compare_length;
reg1 uchar *first,*last;
first= *a; last= *b;
while (--length)
{
if (*first++ != *last++)
return (int) first[-1] - (int) last[-1];
}
return (int) first[0] - (int) last[0];
}
static int ptr_compare_0(uchar **a, uchar **b)
{
reg3 int length= compare_length;
reg1 uchar *first,*last;
first= *a; last= *b;
loop:
cmp(0);
cmp(1);
cmp(2);
cmp(3);
if ((length-=4))
{
first+=4;
last+=4;
goto loop;
}
return (0);
}
static int ptr_compare_1(uchar **a, uchar **b)
{
reg3 int length= compare_length-1;
reg1 uchar *first,*last;
first= *a+1; last= *b+1;
cmp(-1);
loop:
cmp(0);
cmp(1);
cmp(2);
cmp(3);
if ((length-=4))
{
first+=4;
last+=4;
goto loop;
}
return (0);
}
static int ptr_compare_2(uchar **a, uchar **b)
{
reg3 int length= compare_length-2;
reg1 uchar *first,*last;
first= *a +2 ; last= *b +2;
cmp(-2);
cmp(-1);
loop:
cmp(0);
cmp(1);
cmp(2);
cmp(3);
if ((length-=4))
{
first+=4;
last+=4;
goto loop;
}
return (0);
}
static int ptr_compare_3(uchar **a, uchar **b)
{
reg3 int length= compare_length-3;
reg1 uchar *first,*last;
first= *a +3 ; last= *b +3;
cmp(-3);
cmp(-2);
cmp(-1);
loop:
cmp(0);
cmp(1);
cmp(2);
cmp(3);
if ((length-=4))
{
first+=4;
last+=4;
goto loop;
}
return (0);
}
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