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/*
* sort.c - Sample ELF module providing a quick sort function
*
* Created on: Aug 11, 2008
* Author: Stefan Bucur <stefanb@zytor.com>
*/
#include <stdlib.h>
#include <sys/module.h>
/**
* sort_init - Module entry point.
*/
static int sort_init() {
return 0; // Nothing to do; return success
}
static inline void swap(int *x, int *y) {
int tmp;
tmp = *x;
*x = *y;
*y = tmp;
}
static inline int randint(int l, int u) {
return l + (rand() % (u-l+1));
}
/**
* quick_sort_range - A small and efficient version of quicksort.
* @nums: The numbers to sort
* @l: The lower index in the vector (inclusive)
* @u: The upper index in the vector (inclusive)
*
* The implementation is taken from "Beautiful Code", by O'Reilly, the
* book students received from Google as a gift for their acceptance
* in the GSoC 2008 program. The code belongs to Jon Bentley, who
* wrote the third chapter of the book. Since ELF modules were written
* as part of this program, the author of the module considered
* the book had to be put at some use. :)
*/
static void quick_sort_range(int *nums, int l, int u) {
int i, m;
if (l >= u) return;
swap(&nums[l], &nums[randint(l, u)]);
m = l;
for (i = l+1; i <= u; i++) {
if (nums[i] < nums[l])
swap(&nums[++m], &nums[i]);
}
swap(&nums[l], &nums[m]);
quick_sort_range(nums, l, m-1);
quick_sort_range(nums, m+1, u);
}
void quick_sort(int *nums, int count) {
quick_sort_range(nums, 0, count-1);
}
/**
* sort_exit - Module exit point.
*/
static void sort_exit() {
// Nothing to do
}
// Define entry and exit points.
MODULE_INIT(sort_init);
MODULE_EXIT(sort_exit);
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