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/types.h>
8 #include <linux/export.h>
9 #include <linux/sort.h>
11 static int alignment_ok(const void *base, int align)
13 return IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) ||
14 ((unsigned long)base & (align - 1)) == 0;
17 static void u32_swap(void *a, void *b, int size)
20 *(u32 *)a = *(u32 *)b;
24 static void u64_swap(void *a, void *b, int size)
27 *(u64 *)a = *(u64 *)b;
31 static void generic_swap(void *a, void *b, int size)
37 *(char *)a++ = *(char *)b;
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
50 * This function does a heapsort on the given array. You may provide a
51 * swap_func function optimized to your element type.
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.
59 void 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))
63 /* pre-scale counters for performance */
64 int i = (num/2 - 1) * size, n = num * size, c, r;
67 if (size == 4 && alignment_ok(base, 4))
69 else if (size == 8 && alignment_ok(base, 8))
72 swap_func = generic_swap;
76 for ( ; i >= 0; i -= size) {
77 for (r = i; r * 2 + size < n; r = c) {
80 cmp_func(base + c, base + c + size) < 0)
82 if (cmp_func(base + r, base + c) >= 0)
84 swap_func(base + r, base + c, size);
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) {
94 cmp_func(base + c, base + c + size) < 0)
96 if (cmp_func(base + r, base + c) >= 0)
98 swap_func(base + r, base + c, size);
106 #include <linux/slab.h>
107 /* a simple boot-time regression test */
109 int cmpint(const void *a, const void *b)
111 return *(int *)a - *(int *)b;
114 static int sort_test(void)
118 a = kmalloc(1000 * sizeof(int), GFP_KERNEL);
121 printk("testing sort()\n");
123 for (i = 0; i < 1000; i++) {
124 r = (r * 725861) % 6599;
128 sort(a, 1000, sizeof(int), cmpint, NULL);
130 for (i = 0; i < 999; i++)
132 printk("sort() failed!\n");
141 module_init(sort_test);