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