glib/glib/gprimes.c
2014-01-31 14:31:55 +01:00

97 lines
2.1 KiB
C

/* GLIB - Library of useful routines for C programming
* 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, see <http://www.gnu.org/licenses/>.
*/
/*
* 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/.
*/
/*
* MT safe
*/
#include "config.h"
#include "gprimes.h"
static const guint g_primes[] =
{
11,
19,
37,
73,
109,
163,
251,
367,
557,
823,
1237,
1861,
2777,
4177,
6247,
9371,
14057,
21089,
31627,
47431,
71143,
106721,
160073,
240101,
360163,
540217,
810343,
1215497,
1823231,
2734867,
4102283,
6153409,
9230113,
13845163,
};
/**
* g_spaced_primes_closest:
* @num: a #guint
*
* Gets the smallest prime number from a built-in array of primes which
* is larger than @num. This is used within GLib to calculate the optimum
* size of a #GHashTable.
*
* The built-in array of primes ranges from 11 to 13845163 such that
* each prime is approximately 1.5-2 times the previous prime.
*
* Returns: the smallest prime number from a built-in array of primes
* which is larger than @num
*/
guint
g_spaced_primes_closest (guint num)
{
gint i;
for (i = 0; i < G_N_ELEMENTS (g_primes); i++)
if (g_primes[i] > num)
return g_primes[i];
return g_primes[G_N_ELEMENTS (g_primes) - 1];
}