53 lines
1.5 KiB
C
53 lines
1.5 KiB
C
/*
|
|
* Copyright (c) 2006-2018, RT-Thread Development Team
|
|
*
|
|
* SPDX-License-Identifier: Apache-2.0
|
|
*
|
|
* Change Logs:
|
|
* Date Author Notes
|
|
*/
|
|
#include <sys/types.h>
|
|
#include <stdlib.h>
|
|
|
|
static void exch(char* base,size_t size,size_t a,size_t b) {
|
|
char* x=base+a*size;
|
|
char* y=base+b*size;
|
|
while (size) {
|
|
char z=*x;
|
|
*x=*y;
|
|
*y=z;
|
|
--size; ++x; ++y;
|
|
}
|
|
}
|
|
|
|
/* Quicksort with 3-way partitioning, ala Sedgewick */
|
|
/* Blame him for the scary variable names */
|
|
/* http://www.cs.princeton.edu/~rs/talks/QuicksortIsOptimal.pdf */
|
|
static void quicksort(char* base,size_t size,ssize_t l,ssize_t r,
|
|
int (*compar)(const void*,const void*)) {
|
|
ssize_t i=l-1, j=r, p=l-1, q=r, k;
|
|
char* v=base+r*size;
|
|
if (r<=l) return;
|
|
for (;;) {
|
|
while (++i != r && compar(base+i*size,v)<0) ;
|
|
while (compar(v,base+(--j)*size)<0) if (j == l) break;
|
|
if (i >= j) break;
|
|
exch(base,size,i,j);
|
|
if (compar(base+i*size,v)==0) exch(base,size,++p,i);
|
|
if (compar(v,base+j*size)==0) exch(base,size,j,--q);
|
|
}
|
|
exch(base,size,i,r); j = i-1; ++i;
|
|
for (k=l; k<p; k++, j--) exch(base,size,k,j);
|
|
for (k=r-1; k>q; k--, i++) exch(base,size,i,k);
|
|
quicksort(base,size,l,j,compar);
|
|
quicksort(base,size,i,r,compar);
|
|
}
|
|
|
|
void qsort(void* base,size_t nmemb,size_t size,int (*compar)(const void*,const void*)) {
|
|
/* check for integer overflows */
|
|
if (nmemb >= (((size_t)-1)>>1) ||
|
|
size >= (((size_t)-1)>>1)) return;
|
|
if (nmemb>1)
|
|
quicksort(base,size,0,nmemb-1,compar);
|
|
}
|