glib/gqsort.c
Jonathan Blandford 2645aaf59c Patch from David Benson <daveb@idealab.com> to add user_data support to
Mon Nov 20 18:55:17 2000  Jonathan Blandford  <jrb@redhat.com>

	* gtree.[hc]: Patch from David Benson <daveb@idealab.com> to add
	user_data support to gtree functions.

Mon Nov 13 18:35:52 2000  Jonathan Blandford  <jrb@redhat.com>

	* gtypes.h (GCompareFuncData): new func type to let you use user
	data when comparing nodes.

	* gslist.c (g_list_sort_with_data): new function to sort with
	user_data.

	* glist.c (g_list_sort_with_data): new function to sort with
	user_data.

	* garray.[ch]: Added convenience functions to sort arrays.
2000-11-20 23:59:32 +00:00

270 lines
8.4 KiB
C

/* GLIB - Library of useful routines for C programming
* Copyright (C) 1991, 1992, 1996, 1997 Free Software Foundation, Inc.
* Copyright (C) 2000 Eazel, Inc.
* Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
/*
* This file was originally part of the GNU C Library, and was modified to allow
* user data to be passed in to the sorting function.
*
* Written by Douglas C. Schmidt (schmidt@ics.uci.edu).
* Modified by Maciej Stachowiak (mjs@eazel.com)
*
* Modified by the GLib Team and others 1997-2000. See the AUTHORS
* file for a list of people on the GLib Team. See the ChangeLog
* files for a list of changes. These files are distributed with
* GLib at ftp://ftp.gtk.org/pub/gtk/. */
#include <string.h>
#include "glib.h"
/* Byte-wise swap two items of size SIZE. */
#define SWAP(a, b, size) \
do \
{ \
register size_t __size = (size); \
register char *__a = (a), *__b = (b); \
do \
{ \
char __tmp = *__a; \
*__a++ = *__b; \
*__b++ = __tmp; \
} while (--__size > 0); \
} while (0)
/* Discontinue quicksort algorithm when partition gets below this size.
This particular magic number was chosen to work best on a Sun 4/260. */
#define MAX_THRESH 4
/* Stack node declarations used to store unfulfilled partition obligations. */
typedef struct
{
char *lo;
char *hi;
}
stack_node;
/* The next 4 #defines implement a very fast in-line stack abstraction. */
#define STACK_SIZE (8 * sizeof(unsigned long int))
#define PUSH(low, high) ((void) ((top->lo = (low)), (top->hi = (high)), ++top))
#define POP(low, high) ((void) (--top, (low = top->lo), (high = top->hi)))
#define STACK_NOT_EMPTY (stack < top)
/* Order size using quicksort. This implementation incorporates
* four optimizations discussed in Sedgewick:
*
* 1. Non-recursive, using an explicit stack of pointer that store the next
* array partition to sort. To save time, this maximum amount of space
* required to store an array of MAX_INT is allocated on the stack. Assuming
* a 32-bit integer, this needs only 32 * sizeof(stack_node) == 136 bits.
* Pretty cheap, actually.
*
* 2. Chose the pivot element using a median-of-three decision tree. This
* reduces the probability of selecting a bad pivot value and eliminates
* certain * extraneous comparisons.
*
* 3. Only quicksorts TOTAL_ELEMS / MAX_THRESH partitions, leaving insertion
* sort to order the MAX_THRESH items within each partition. This is a big
* win, since insertion sort is faster for small, mostly sorted array
* segments.
*
* 4. The larger of the two sub-partitions is always pushed onto the stack
* first, with the algorithm then concentrating on the smaller partition.
* This *guarantees* no more than log (n) stack size is needed (actually O(1)
* in this case)!
*/
void
g_qsort_with_data (gconstpointer pbase,
gint total_elems,
size_t size,
GCompareFuncData compare_func,
gpointer user_data)
{
register char *base_ptr = (char *) pbase;
/* Allocating SIZE bytes for a pivot buffer facilitates a better
* algorithm below since we can do comparisons directly on the pivot.
*/
char *pivot_buffer = (char *) alloca (size);
const size_t max_thresh = MAX_THRESH * size;
g_return_if_fail (total_elems > 0);
g_return_if_fail (pbase != NULL);
g_return_if_fail (compare_func != NULL);
if (total_elems > MAX_THRESH)
{
char *lo = base_ptr;
char *hi = &lo[size * (total_elems - 1)];
/* Largest size needed for 32-bit int!!! */
stack_node stack[STACK_SIZE];
stack_node *top = stack + 1;
while (STACK_NOT_EMPTY)
{
char *left_ptr;
char *right_ptr;
char *pivot = pivot_buffer;
/* Select median value from among LO, MID, and HI. Rearrange
* LO and HI so the three values are sorted. This lowers the
* probability of picking a pathological pivot value and
* skips a comparison for both the LEFT_PTR and RIGHT_PTR. */
char *mid = lo + size * ((hi - lo) / size >> 1);
if ((*compare_func) ((void *) mid, (void *) lo, user_data) < 0)
SWAP (mid, lo, size);
if ((*compare_func) ((void *) hi, (void *) mid, user_data) < 0)
SWAP (mid, hi, size);
else
goto jump_over;
if ((*compare_func) ((void *) mid, (void *) lo, user_data) < 0)
SWAP (mid, lo, size);
jump_over:;
memcpy (pivot, mid, size);
pivot = pivot_buffer;
left_ptr = lo + size;
right_ptr = hi - size;
/* Here's the famous ``collapse the walls'' section of quicksort.
* Gotta like those tight inner loops! They are the main reason
* that this algorithm runs much faster than others. */
do
{
while ((*compare_func)
((void *) left_ptr, (void *) pivot,
user_data) < 0)
left_ptr += size;
while ((*compare_func)
((void *) pivot, (void *) right_ptr,
user_data) < 0)
right_ptr -= size;
if (left_ptr < right_ptr)
{
SWAP (left_ptr, right_ptr, size);
left_ptr += size;
right_ptr -= size;
}
else if (left_ptr == right_ptr)
{
left_ptr += size;
right_ptr -= size;
break;
}
}
while (left_ptr <= right_ptr);
/* Set up pointers for next iteration. First determine whether
* left and right partitions are below the threshold size. If so,
* ignore one or both. Otherwise, push the larger partition's
* bounds on the stack and continue sorting the smaller one. */
if ((size_t) (right_ptr - lo) <= max_thresh)
{
if ((size_t) (hi - left_ptr) <= max_thresh)
/* Ignore both small partitions. */
POP (lo, hi);
else
/* Ignore small left partition. */
lo = left_ptr;
}
else if ((size_t) (hi - left_ptr) <= max_thresh)
/* Ignore small right partition. */
hi = right_ptr;
else if ((right_ptr - lo) > (hi - left_ptr))
{
/* Push larger left partition indices. */
PUSH (lo, right_ptr);
lo = left_ptr;
}
else
{
/* Push larger right partition indices. */
PUSH (left_ptr, hi);
hi = right_ptr;
}
}
}
/* Once the BASE_PTR array is partially sorted by quicksort the rest
* is completely sorted using insertion sort, since this is efficient
* for partitions below MAX_THRESH size. BASE_PTR points to the beginning
* of the array to sort, and END_PTR points at the very last element in
* the array (*not* one beyond it!). */
{
char *const end_ptr = &base_ptr[size * (total_elems - 1)];
char *tmp_ptr = base_ptr;
char *thresh = MIN (end_ptr, base_ptr + max_thresh);
register char *run_ptr;
/* Find smallest element in first threshold and place it at the
* array's beginning. This is the smallest array element,
* and the operation speeds up insertion sort's inner loop. */
for (run_ptr = tmp_ptr + size; run_ptr <= thresh;
run_ptr +=
size) if ((*compare_func) ((void *) run_ptr, (void *) tmp_ptr,
user_data) < 0)
tmp_ptr = run_ptr;
if (tmp_ptr != base_ptr)
SWAP (tmp_ptr, base_ptr, size);
/* Insertion sort, running from left-hand-side up to right-hand-side. */
run_ptr = base_ptr + size;
while ((run_ptr += size) <= end_ptr)
{
tmp_ptr = run_ptr - size;
while ((*compare_func)
((void *) run_ptr, (void *) tmp_ptr,
user_data) < 0)
tmp_ptr -= size;
tmp_ptr += size;
if (tmp_ptr != run_ptr)
{
char *trav;
trav = run_ptr + size;
while (--trav >= run_ptr)
{
char c = *trav;
char *hi, *lo;
for (hi = lo = trav;
(lo -= size) >= tmp_ptr; hi = lo)
*hi = *lo;
*hi = c;
}
}
}
}
}