2 * A fast, small, non-recursive O(nlog n) sort for the Linux kernel
4 * Jan 23 2005 Matt Mackall <mpm@selenic.com>
7 #include <linux/kernel.h>
8 #include <linux/module.h>
9 #include <linux/sort.h>
10 #include <linux/slab.h>
12 static void u32_swap(void *a
, void *b
, int size
)
15 *(u32
*)a
= *(u32
*)b
;
19 static void generic_swap(void *a
, void *b
, int size
)
25 *(char *)a
++ = *(char *)b
;
31 * sort - sort an array of elements
32 * @base: pointer to data to sort
33 * @num: number of elements
34 * @size: size of each element
35 * @cmp_func: pointer to comparison function
36 * @swap_func: pointer to swap function or NULL
38 * This function does a heapsort on the given array. You may provide a
39 * swap_func function optimized to your element type.
41 * Sorting time is O(n log n) both on average and worst-case. While
42 * qsort is about 20% faster on average, it suffers from exploitable
43 * O(n*n) worst-case behavior and extra memory requirements that make
44 * it less suitable for kernel use.
47 void sort(void *base
, size_t num
, size_t size
,
48 int (*cmp_func
)(const void *, const void *),
49 void (*swap_func
)(void *, void *, int size
))
51 /* pre-scale counters for performance */
52 int i
= (num
/2 - 1) * size
, n
= num
* size
, c
, r
;
55 swap_func
= (size
== 4 ? u32_swap
: generic_swap
);
58 for ( ; i
>= 0; i
-= size
) {
59 for (r
= i
; r
* 2 + size
< n
; r
= c
) {
62 cmp_func(base
+ c
, base
+ c
+ size
) < 0)
64 if (cmp_func(base
+ r
, base
+ c
) >= 0)
66 swap_func(base
+ r
, base
+ c
, size
);
71 for (i
= n
- size
; i
> 0; i
-= size
) {
72 swap_func(base
, base
+ i
, size
);
73 for (r
= 0; r
* 2 + size
< i
; r
= c
) {
76 cmp_func(base
+ c
, base
+ c
+ size
) < 0)
78 if (cmp_func(base
+ r
, base
+ c
) >= 0)
80 swap_func(base
+ r
, base
+ c
, size
);
88 /* a simple boot-time regression test */
90 int cmpint(const void *a
, const void *b
)
92 return *(int *)a
- *(int *)b
;
95 static int sort_test(void)
99 a
= kmalloc(1000 * sizeof(int), GFP_KERNEL
);
102 printk("testing sort()\n");
104 for (i
= 0; i
< 1000; i
++) {
105 r
= (r
* 725861) % 6599;
109 sort(a
, 1000, sizeof(int), cmpint
, NULL
);
111 for (i
= 0; i
< 999; i
++)
113 printk("sort() failed!\n");
122 module_init(sort_test
);
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