mirror of
https://github.com/torvalds/linux
synced 2024-11-05 18:23:50 +00:00
d28c2bc8d1
The regression test in lib/sort.c is currently worthless because the array that is generated for sorting will be all zeros. This patch fixes things so that the array that is generated will contain unsorted integers (that are not all identical) as was probably intended. Signed-off-by Daniel Dickman <didickman@yahoo.com> Signed-off-by: Domen Puncer <domen@coderock.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
119 lines
2.4 KiB
C
119 lines
2.4 KiB
C
/*
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* A fast, small, non-recursive O(nlog n) sort for the Linux kernel
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*
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* Jan 23 2005 Matt Mackall <mpm@selenic.com>
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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void u32_swap(void *a, void *b, int size)
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{
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u32 t = *(u32 *)a;
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*(u32 *)a = *(u32 *)b;
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*(u32 *)b = t;
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}
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void generic_swap(void *a, void *b, int size)
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{
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char t;
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do {
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t = *(char *)a;
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*(char *)a++ = *(char *)b;
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*(char *)b++ = t;
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} while (--size > 0);
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}
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/*
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* sort - sort an array of elements
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* @base: pointer to data to sort
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* @num: number of elements
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* @size: size of each element
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* @cmp: pointer to comparison function
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* @swap: pointer to swap function or NULL
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*
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* This function does a heapsort on the given array. You may provide a
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* swap function optimized to your element type.
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*
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* Sorting time is O(n log n) both on average and worst-case. While
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* qsort is about 20% faster on average, it suffers from exploitable
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* O(n*n) worst-case behavior and extra memory requirements that make
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* it less suitable for kernel use.
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*/
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void sort(void *base, size_t num, size_t size,
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int (*cmp)(const void *, const void *),
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void (*swap)(void *, void *, int size))
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{
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/* pre-scale counters for performance */
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int i = (num/2) * size, n = num * size, c, r;
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if (!swap)
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swap = (size == 4 ? u32_swap : generic_swap);
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/* heapify */
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for ( ; i >= 0; i -= size) {
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for (r = i; r * 2 < n; r = c) {
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c = r * 2;
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if (c < n - size && cmp(base + c, base + c + size) < 0)
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c += size;
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if (cmp(base + r, base + c) >= 0)
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break;
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swap(base + r, base + c, size);
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}
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}
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/* sort */
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for (i = n - size; i >= 0; i -= size) {
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swap(base, base + i, size);
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for (r = 0; r * 2 < i; r = c) {
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c = r * 2;
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if (c < i - size && cmp(base + c, base + c + size) < 0)
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c += size;
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if (cmp(base + r, base + c) >= 0)
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break;
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swap(base + r, base + c, size);
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}
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}
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}
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EXPORT_SYMBOL(sort);
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#if 0
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/* a simple boot-time regression test */
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int cmpint(const void *a, const void *b)
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{
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return *(int *)a - *(int *)b;
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}
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static int sort_test(void)
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{
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int *a, i, r = 1;
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a = kmalloc(1000 * sizeof(int), GFP_KERNEL);
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BUG_ON(!a);
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printk("testing sort()\n");
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for (i = 0; i < 1000; i++) {
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r = (r * 725861) % 6599;
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a[i] = r;
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}
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sort(a, 1000, sizeof(int), cmpint, NULL);
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for (i = 0; i < 999; i++)
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if (a[i] > a[i+1]) {
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printk("sort() failed!\n");
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break;
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}
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kfree(a);
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return 0;
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}
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module_init(sort_test);
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#endif
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