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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/kernel.h> |
| 8 | #include <linux/module.h> |
| 9 | #include <linux/sort.h> |
| 10 | #include <linux/slab.h> |
| 11 | |
| 12 | static void u32_swap(void *a, void *b, int size) |
| 13 | { |
| 14 | u32 t = *(u32 *)a; |
| 15 | *(u32 *)a = *(u32 *)b; |
| 16 | *(u32 *)b = t; |
| 17 | } |
| 18 | |
| 19 | static void generic_swap(void *a, void *b, int size) |
| 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 | |
| 30 | /** |
| 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 |
| 37 | * |
| 38 | * This function does a heapsort on the given array. You may provide a |
| 39 | * swap_func 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_func)(const void *, const void *), |
| 49 | void (*swap_func)(void *, void *, int size)) |
| 50 | { |
| 51 | /* pre-scale counters for performance */ |
| 52 | int i = (num/2 - 1) * size, n = num * size, c, r; |
| 53 | |
| 54 | if (!swap_func) |
| 55 | swap_func = (size == 4 ? u32_swap : generic_swap); |
| 56 | |
| 57 | /* heapify */ |
| 58 | for ( ; i >= 0; i -= size) { |
| 59 | for (r = i; r * 2 + size < n; r = c) { |
| 60 | c = r * 2 + size; |
| 61 | if (c < n - size && |
| 62 | cmp_func(base + c, base + c + size) < 0) |
| 63 | c += size; |
| 64 | if (cmp_func(base + r, base + c) >= 0) |
| 65 | break; |
| 66 | swap_func(base + r, base + c, size); |
| 67 | } |
| 68 | } |
| 69 | |
| 70 | /* sort */ |
| 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) { |
| 74 | c = r * 2 + size; |
| 75 | if (c < i - size && |
| 76 | cmp_func(base + c, base + c + size) < 0) |
| 77 | c += size; |
| 78 | if (cmp_func(base + r, base + c) >= 0) |
| 79 | break; |
| 80 | swap_func(base + r, base + c, size); |
| 81 | } |
| 82 | } |
| 83 | } |
| 84 | |
| 85 | EXPORT_SYMBOL(sort); |
| 86 | |
| 87 | #if 0 |
| 88 | /* a simple boot-time regression test */ |
| 89 | |
| 90 | int cmpint(const void *a, const void *b) |
| 91 | { |
| 92 | return *(int *)a - *(int *)b; |
| 93 | } |
| 94 | |
| 95 | static int sort_test(void) |
| 96 | { |
| 97 | int *a, i, r = 1; |
| 98 | |
| 99 | a = kmalloc(1000 * sizeof(int), GFP_KERNEL); |
| 100 | BUG_ON(!a); |
| 101 | |
| 102 | printk("testing sort()\n"); |
| 103 | |
| 104 | for (i = 0; i < 1000; i++) { |
| 105 | r = (r * 725861) % 6599; |
| 106 | a[i] = r; |
| 107 | } |
| 108 | |
| 109 | sort(a, 1000, sizeof(int), cmpint, NULL); |
| 110 | |
| 111 | for (i = 0; i < 999; i++) |
| 112 | if (a[i] > a[i+1]) { |
| 113 | printk("sort() failed!\n"); |
| 114 | break; |
| 115 | } |
| 116 | |
| 117 | kfree(a); |
| 118 | |
| 119 | return 0; |
| 120 | } |
| 121 | |
| 122 | module_init(sort_test); |
| 123 | #endif |
| 124 |
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