Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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/kernel.h> |
| 8 | #include <linux/module.h> |
Adrian Bunk | ecec4cb | 2005-09-10 00:26:59 -0700 | [diff] [blame] | 9 | #include <linux/sort.h> |
Tim Schmielau | 4e57b68 | 2005-10-30 15:03:48 -0800 | [diff] [blame] | 10 | #include <linux/slab.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 11 | |
Adrian Bunk | ecec4cb | 2005-09-10 00:26:59 -0700 | [diff] [blame] | 12 | static void u32_swap(void *a, void *b, int size) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 13 | { |
| 14 | u32 t = *(u32 *)a; |
| 15 | *(u32 *)a = *(u32 *)b; |
| 16 | *(u32 *)b = t; |
| 17 | } |
| 18 | |
Adrian Bunk | ecec4cb | 2005-09-10 00:26:59 -0700 | [diff] [blame] | 19 | static void generic_swap(void *a, void *b, int size) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 20 | { |
| 21 | char t; |
| 22 | |
| 23 | do { |
| 24 | t = *(char *)a; |
| 25 | *(char *)a++ = *(char *)b; |
| 26 | *(char *)b++ = t; |
| 27 | } while (--size > 0); |
| 28 | } |
| 29 | |
Robert P. J. Day | 72fd4a3 | 2007-02-10 01:45:59 -0800 | [diff] [blame] | 30 | /** |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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: pointer to comparison function |
| 36 | * @swap: pointer to swap function or NULL |
| 37 | * |
| 38 | * This function does a heapsort on the given array. You may provide a |
| 39 | * swap function optimized to your element type. |
| 40 | * |
| 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. |
| 45 | */ |
| 46 | |
| 47 | void sort(void *base, size_t num, size_t size, |
| 48 | int (*cmp)(const void *, const void *), |
| 49 | void (*swap)(void *, void *, int size)) |
| 50 | { |
| 51 | /* pre-scale counters for performance */ |
keios | d3717bd | 2006-10-03 01:13:49 -0700 | [diff] [blame] | 52 | int i = (num/2 - 1) * size, n = num * size, c, r; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 53 | |
| 54 | if (!swap) |
| 55 | swap = (size == 4 ? u32_swap : generic_swap); |
| 56 | |
| 57 | /* heapify */ |
| 58 | for ( ; i >= 0; i -= size) { |
keios | d3717bd | 2006-10-03 01:13:49 -0700 | [diff] [blame] | 59 | for (r = i; r * 2 + size < n; r = c) { |
| 60 | c = r * 2 + size; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 61 | if (c < n - size && cmp(base + c, base + c + size) < 0) |
| 62 | c += size; |
| 63 | if (cmp(base + r, base + c) >= 0) |
| 64 | break; |
| 65 | swap(base + r, base + c, size); |
| 66 | } |
| 67 | } |
| 68 | |
| 69 | /* sort */ |
Subbaiah Venkata | 995e428 | 2007-10-16 23:27:06 -0700 | [diff] [blame^] | 70 | for (i = n - size; i > 0; i -= size) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 71 | swap(base, base + i, size); |
keios | d3717bd | 2006-10-03 01:13:49 -0700 | [diff] [blame] | 72 | for (r = 0; r * 2 + size < i; r = c) { |
| 73 | c = r * 2 + size; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 74 | if (c < i - size && cmp(base + c, base + c + size) < 0) |
| 75 | c += size; |
| 76 | if (cmp(base + r, base + c) >= 0) |
| 77 | break; |
| 78 | swap(base + r, base + c, size); |
| 79 | } |
| 80 | } |
| 81 | } |
| 82 | |
| 83 | EXPORT_SYMBOL(sort); |
| 84 | |
| 85 | #if 0 |
| 86 | /* a simple boot-time regression test */ |
| 87 | |
| 88 | int cmpint(const void *a, const void *b) |
| 89 | { |
| 90 | return *(int *)a - *(int *)b; |
| 91 | } |
| 92 | |
| 93 | static int sort_test(void) |
| 94 | { |
Domen Puncer | d28c2bc | 2005-05-05 16:16:19 -0700 | [diff] [blame] | 95 | int *a, i, r = 1; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 96 | |
| 97 | a = kmalloc(1000 * sizeof(int), GFP_KERNEL); |
| 98 | BUG_ON(!a); |
| 99 | |
| 100 | printk("testing sort()\n"); |
| 101 | |
| 102 | for (i = 0; i < 1000; i++) { |
| 103 | r = (r * 725861) % 6599; |
| 104 | a[i] = r; |
| 105 | } |
| 106 | |
| 107 | sort(a, 1000, sizeof(int), cmpint, NULL); |
| 108 | |
| 109 | for (i = 0; i < 999; i++) |
| 110 | if (a[i] > a[i+1]) { |
| 111 | printk("sort() failed!\n"); |
| 112 | break; |
| 113 | } |
| 114 | |
| 115 | kfree(a); |
| 116 | |
| 117 | return 0; |
| 118 | } |
| 119 | |
| 120 | module_init(sort_test); |
| 121 | #endif |