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 11 static void u32_swap(void *a, void *b, int size) 12 { 13 u32 t = *(u32 *)a; 14 *(u32 *)a = *(u32 *)b; 15 *(u32 *)b = t; 16 } 17 18 static void generic_swap(void *a, void *b, int size) 19 { 20 char t; 21 22 do { 23 t = *(char *)a; 24 *(char *)a++ = *(char *)b; 25 *(char *)b++ = t; 26 } while (--size > 0); 27 } 28 29 /** 30 * sort - sort an array of elements 31 * @base: pointer to data to sort 32 * @num: number of elements 33 * @size: size of each element 34 * @cmp_func: pointer to comparison function 35 * @swap_func: pointer to swap function or NULL 36 * 37 * This function does a heapsort on the given array. You may provide a 38 * swap_func function optimized to your element type. 39 * 40 * Sorting time is O(n log n) both on average and worst-case. While 41 * qsort is about 20% faster on average, it suffers from exploitable 42 * O(n*n) worst-case behavior and extra memory requirements that make 43 * it less suitable for kernel use. 44 */ 45 46 void sort(void *base, size_t num, size_t size, 47 int (*cmp_func)(const void *, const void *), 48 void (*swap_func)(void *, void *, int size)) 49 { 50 /* pre-scale counters for performance */ 51 int i = (num/2 - 1) * size, n = num * size, c, r; 52 53 if (!swap_func) 54 swap_func = (size == 4 ? u32_swap : generic_swap); 55 56 /* heapify */ 57 for ( ; i >= 0; i -= size) { 58 for (r = i; r * 2 + size < n; r = c) { 59 c = r * 2 + size; 60 if (c < n - size && 61 cmp_func(base + c, base + c + size) < 0) 62 c += size; 63 if (cmp_func(base + r, base + c) >= 0) 64 break; 65 swap_func(base + r, base + c, size); 66 } 67 } 68 69 /* sort */ 70 for (i = n - size; i > 0; i -= size) { 71 swap_func(base, base + i, size); 72 for (r = 0; r * 2 + size < i; r = c) { 73 c = r * 2 + size; 74 if (c < i - size && 75 cmp_func(base + c, base + c + size) < 0) 76 c += size; 77 if (cmp_func(base + r, base + c) >= 0) 78 break; 79 swap_func(base + r, base + c, size); 80 } 81 } 82 } 83 84 EXPORT_SYMBOL(sort); 85 86 #if 0 87 #include <linux/slab.h> 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