This commit was manufactured by cvs2svn to create branch 'vserver'.

[linux-2.6.git] / lib / sort.c

diff --git a/lib/sort.c b/lib/sort.c
new file mode 100644 (file)
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+++ b/lib/sort.c
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+/*
+ * A fast, small, non-recursive O(nlog n) sort for the Linux kernel
+ *
+ * Jan 23 2005  Matt Mackall <mpm@selenic.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+void u32_swap(void *a, void *b, int size)
+{
+       u32 t = *(u32 *)a;
+       *(u32 *)a = *(u32 *)b;
+       *(u32 *)b = t;
+}
+
+void generic_swap(void *a, void *b, int size)
+{
+       char t;
+
+       do {
+               t = *(char *)a;
+               *(char *)a++ = *(char *)b;
+               *(char *)b++ = t;
+       } while (--size > 0);
+}
+
+/*
+ * sort - sort an array of elements
+ * @base: pointer to data to sort
+ * @num: number of elements
+ * @size: size of each element
+ * @cmp: pointer to comparison function
+ * @swap: pointer to swap function or NULL
+ *
+ * This function does a heapsort on the given array. You may provide a
+ * swap function optimized to your element type.
+ *
+ * Sorting time is O(n log n) both on average and worst-case. While
+ * qsort is about 20% faster on average, it suffers from exploitable
+ * O(n*n) worst-case behavior and extra memory requirements that make
+ * it less suitable for kernel use.
+ */
+
+void sort(void *base, size_t num, size_t size,
+         int (*cmp)(const void *, const void *),
+         void (*swap)(void *, void *, int size))
+{
+       /* pre-scale counters for performance */
+       int i = (num/2) * size, n = num * size, c, r;
+
+       if (!swap)
+               swap = (size == 4 ? u32_swap : generic_swap);
+
+       /* heapify */
+       for ( ; i >= 0; i -= size) {
+               for (r = i; r * 2 < n; r  = c) {
+                       c = r * 2;
+                       if (c < n - size && cmp(base + c, base + c + size) < 0)
+                               c += size;
+                       if (cmp(base + r, base + c) >= 0)
+                               break;
+                       swap(base + r, base + c, size);
+               }
+       }
+
+       /* sort */
+       for (i = n - size; i >= 0; i -= size) {
+               swap(base, base + i, size);
+               for (r = 0; r * 2 < i; r = c) {
+                       c = r * 2;
+                       if (c < i - size && cmp(base + c, base + c + size) < 0)
+                               c += size;
+                       if (cmp(base + r, base + c) >= 0)
+                               break;
+                       swap(base + r, base + c, size);
+               }
+       }
+}
+
+EXPORT_SYMBOL(sort);
+
+#if 0
+/* a simple boot-time regression test */
+
+int cmpint(const void *a, const void *b)
+{
+       return *(int *)a - *(int *)b;
+}
+
+static int sort_test(void)
+{
+       int *a, i, r = 1;
+
+       a = kmalloc(1000 * sizeof(int), GFP_KERNEL);
+       BUG_ON(!a);
+
+       printk("testing sort()\n");
+
+       for (i = 0; i < 1000; i++) {
+               r = (r * 725861) % 6599;
+               a[i] = r;
+       }
+
+       sort(a, 1000, sizeof(int), cmpint, NULL);
+
+       for (i = 0; i < 999; i++)
+               if (a[i] > a[i+1]) {
+                       printk("sort() failed!\n");
+                       break;
+               }
+
+       kfree(a);
+
+       return 0;
+}
+
+module_init(sort_test);
+#endif