107 lines
2.5 KiB
C
107 lines
2.5 KiB
C
|
// SPDX-License-Identifier: GPL-2.0
|
||
|
|
/*
|
||
|
|
* A fast, small, non-recursive O(nlog n) sort for the Linux kernel
|
||
|
|
*
|
||
|
|
* Jan 23 2005 Matt Mackall <mpm@selenic.com>
|
||
|
|
*/
|
||
|
|
|
||
|
|
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
|
||
|
|
|
||
|
|
#include <linux/types.h>
|
||
|
|
#include <linux/export.h>
|
||
|
|
#include <linux/sort.h>
|
||
|
|
|
||
|
|
static int alignment_ok(const void *base, int align)
|
||
|
|
{
|
||
|
|
return IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) ||
|
||
|
|
((unsigned long)base & (align - 1)) == 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
static void u32_swap(void *a, void *b, int size)
|
||
|
|
{
|
||
|
|
u32 t = *(u32 *)a;
|
||
|
|
*(u32 *)a = *(u32 *)b;
|
||
|
|
*(u32 *)b = t;
|
||
|
|
}
|
||
|
|
|
||
|
|
static void u64_swap(void *a, void *b, int size)
|
||
|
|
{
|
||
|
|
u64 t = *(u64 *)a;
|
||
|
|
*(u64 *)a = *(u64 *)b;
|
||
|
|
*(u64 *)b = t;
|
||
|
|
}
|
||
|
|
|
||
|
|
static 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_func: pointer to comparison function
|
||
|
|
* @swap_func: pointer to swap function or NULL
|
||
|
|
*
|
||
|
|
* This function does a heapsort on the given array. You may provide a
|
||
|
|
* swap_func 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_func)(const void *, const void *),
|
||
|
|
void (*swap_func)(void *, void *, int size))
|
||
|
|
{
|
||
|
|
/* pre-scale counters for performance */
|
||
|
|
int i = (num/2 - 1) * size, n = num * size, c, r;
|
||
|
|
|
||
|
|
if (!swap_func) {
|
||
|
|
if (size == 4 && alignment_ok(base, 4))
|
||
|
|
swap_func = u32_swap;
|
||
|
|
else if (size == 8 && alignment_ok(base, 8))
|
||
|
|
swap_func = u64_swap;
|
||
|
|
else
|
||
|
|
swap_func = generic_swap;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* heapify */
|
||
|
|
for ( ; i >= 0; i -= size) {
|
||
|
|
for (r = i; r * 2 + size < n; r = c) {
|
||
|
|
c = r * 2 + size;
|
||
|
|
if (c < n - size &&
|
||
|
|
cmp_func(base + c, base + c + size) < 0)
|
||
|
|
c += size;
|
||
|
|
if (cmp_func(base + r, base + c) >= 0)
|
||
|
|
break;
|
||
|
|
swap_func(base + r, base + c, size);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/* sort */
|
||
|
|
for (i = n - size; i > 0; i -= size) {
|
||
|
|
swap_func(base, base + i, size);
|
||
|
|
for (r = 0; r * 2 + size < i; r = c) {
|
||
|
|
c = r * 2 + size;
|
||
|
|
if (c < i - size &&
|
||
|
|
cmp_func(base + c, base + c + size) < 0)
|
||
|
|
c += size;
|
||
|
|
if (cmp_func(base + r, base + c) >= 0)
|
||
|
|
break;
|
||
|
|
swap_func(base + r, base + c, size);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
EXPORT_SYMBOL(sort);
|