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1/*
2 * A fast, small, non-recursive O(nlog n) sort for the Linux kernel
3 *
4 * Jan 23 2005 Matt Mackall <mpm@selenic.com>
5 */
6
7#include <linux/types.h>
8#include <linux/export.h>
9#include <linux/sort.h>
10
11static int alignment_ok(const void *base, int align)
12{
13 return IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) ||
14 ((unsigned long)base & (align - 1)) == 0;
15}
16
17static void u32_swap(void *a, void *b, int size)
18{
19 u32 t = *(u32 *)a;
20 *(u32 *)a = *(u32 *)b;
21 *(u32 *)b = t;
22}
23
24static void u64_swap(void *a, void *b, int size)
25{
26 u64 t = *(u64 *)a;
27 *(u64 *)a = *(u64 *)b;
28 *(u64 *)b = t;
29}
30
31static void generic_swap(void *a, void *b, int size)
32{
33 char t;
34
35 do {
36 t = *(char *)a;
37 *(char *)a++ = *(char *)b;
38 *(char *)b++ = t;
39 } while (--size > 0);
40}
41
42/**
43 * sort - sort an array of elements
44 * @base: pointer to data to sort
45 * @num: number of elements
46 * @size: size of each element
47 * @cmp_func: pointer to comparison function
48 * @swap_func: pointer to swap function or NULL
49 *
50 * This function does a heapsort on the given array. You may provide a
51 * swap_func function optimized to your element type.
52 *
53 * Sorting time is O(n log n) both on average and worst-case. While
54 * qsort is about 20% faster on average, it suffers from exploitable
55 * O(n*n) worst-case behavior and extra memory requirements that make
56 * it less suitable for kernel use.
57 */
58
59void sort(void *base, size_t num, size_t size,
60 int (*cmp_func)(const void *, const void *),
61 void (*swap_func)(void *, void *, int size))
62{
63 /* pre-scale counters for performance */
64 int i = (num/2 - 1) * size, n = num * size, c, r;
65
66 if (!swap_func) {
67 if (size == 4 && alignment_ok(base, 4))
68 swap_func = u32_swap;
69 else if (size == 8 && alignment_ok(base, 8))
70 swap_func = u64_swap;
71 else
72 swap_func = generic_swap;
73 }
74
75 /* heapify */
76 for ( ; i >= 0; i -= size) {
77 for (r = i; r * 2 + size < n; r = c) {
78 c = r * 2 + size;
79 if (c < n - size &&
80 cmp_func(base + c, base + c + size) < 0)
81 c += size;
82 if (cmp_func(base + r, base + c) >= 0)
83 break;
84 swap_func(base + r, base + c, size);
85 }
86 }
87
88 /* sort */
89 for (i = n - size; i > 0; i -= size) {
90 swap_func(base, base + i, size);
91 for (r = 0; r * 2 + size < i; r = c) {
92 c = r * 2 + size;
93 if (c < i - size &&
94 cmp_func(base + c, base + c + size) < 0)
95 c += size;
96 if (cmp_func(base + r, base + c) >= 0)
97 break;
98 swap_func(base + r, base + c, size);
99 }
100 }
101}
102
103EXPORT_SYMBOL(sort);
104
105#if 0
106#include <linux/slab.h>
107/* a simple boot-time regression test */
108
109int cmpint(const void *a, const void *b)
110{
111 return *(int *)a - *(int *)b;
112}
113
114static int sort_test(void)
115{
116 int *a, i, r = 1;
117
118 a = kmalloc(1000 * sizeof(int), GFP_KERNEL);
119 BUG_ON(!a);
120
121 printk("testing sort()\n");
122
123 for (i = 0; i < 1000; i++) {
124 r = (r * 725861) % 6599;
125 a[i] = r;
126 }
127
128 sort(a, 1000, sizeof(int), cmpint, NULL);
129
130 for (i = 0; i < 999; i++)
131 if (a[i] > a[i+1]) {
132 printk("sort() failed!\n");
133 break;
134 }
135
136 kfree(a);
137
138 return 0;
139}
140
141module_init(sort_test);
142#endif
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * A fast, small, non-recursive O(nlog n) sort for the Linux kernel
4 *
5 * Jan 23 2005 Matt Mackall <mpm@selenic.com>
6 */
7
8#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9
10#include <linux/types.h>
11#include <linux/export.h>
12#include <linux/sort.h>
13
14static int alignment_ok(const void *base, int align)
15{
16 return IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) ||
17 ((unsigned long)base & (align - 1)) == 0;
18}
19
20static void u32_swap(void *a, void *b, int size)
21{
22 u32 t = *(u32 *)a;
23 *(u32 *)a = *(u32 *)b;
24 *(u32 *)b = t;
25}
26
27static void u64_swap(void *a, void *b, int size)
28{
29 u64 t = *(u64 *)a;
30 *(u64 *)a = *(u64 *)b;
31 *(u64 *)b = t;
32}
33
34static void generic_swap(void *a, void *b, int size)
35{
36 char t;
37
38 do {
39 t = *(char *)a;
40 *(char *)a++ = *(char *)b;
41 *(char *)b++ = t;
42 } while (--size > 0);
43}
44
45/**
46 * sort - sort an array of elements
47 * @base: pointer to data to sort
48 * @num: number of elements
49 * @size: size of each element
50 * @cmp_func: pointer to comparison function
51 * @swap_func: pointer to swap function or NULL
52 *
53 * This function does a heapsort on the given array. You may provide a
54 * swap_func function optimized to your element type.
55 *
56 * Sorting time is O(n log n) both on average and worst-case. While
57 * qsort is about 20% faster on average, it suffers from exploitable
58 * O(n*n) worst-case behavior and extra memory requirements that make
59 * it less suitable for kernel use.
60 */
61
62void sort(void *base, size_t num, size_t size,
63 int (*cmp_func)(const void *, const void *),
64 void (*swap_func)(void *, void *, int size))
65{
66 /* pre-scale counters for performance */
67 int i = (num/2 - 1) * size, n = num * size, c, r;
68
69 if (!swap_func) {
70 if (size == 4 && alignment_ok(base, 4))
71 swap_func = u32_swap;
72 else if (size == 8 && alignment_ok(base, 8))
73 swap_func = u64_swap;
74 else
75 swap_func = generic_swap;
76 }
77
78 /* heapify */
79 for ( ; i >= 0; i -= size) {
80 for (r = i; r * 2 + size < n; r = c) {
81 c = r * 2 + size;
82 if (c < n - size &&
83 cmp_func(base + c, base + c + size) < 0)
84 c += size;
85 if (cmp_func(base + r, base + c) >= 0)
86 break;
87 swap_func(base + r, base + c, size);
88 }
89 }
90
91 /* sort */
92 for (i = n - size; i > 0; i -= size) {
93 swap_func(base, base + i, size);
94 for (r = 0; r * 2 + size < i; r = c) {
95 c = r * 2 + size;
96 if (c < i - size &&
97 cmp_func(base + c, base + c + size) < 0)
98 c += size;
99 if (cmp_func(base + r, base + c) >= 0)
100 break;
101 swap_func(base + r, base + c, size);
102 }
103 }
104}
105
106EXPORT_SYMBOL(sort);