[linux-2.6-block.git] / drivers / media / dvb-core / dvb_math.h

/*
 * dvb-math provides some complex fixed-point math
 * operations shared between the dvb related stuff
 *
 * Copyright (C) 2006 Christoph Pfister (christophpfister@gmail.com)
 *
 * 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 2.1 of
 * the License, or (at your option) any later version.
 *
 * This program 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
 */

#ifndef __DVB_MATH_H
#define __DVB_MATH_H

#include <linux/types.h>

/**
 * intlog2 - computes log2 of a value; the result is shifted left by 24 bits
 *
 * @value: The value (must be != 0)
 *
 * to use rational values you can use the following method:
 *
 *   intlog2(value) = intlog2(value * 2^x) - x * 2^24
 *
 * Some usecase examples:
 *
 *	intlog2(8) will give 3 << 24 = 3 * 2^24
 *
 *	intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24
 *
 *	intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24
 *
 *
 * return: log2(value) * 2^24
 */
extern unsigned int intlog2(u32 value);

/**
 * intlog10 - computes log10 of a value; the result is shifted left by 24 bits
 *
 * @value: The value (must be != 0)
 *
 * to use rational values you can use the following method:
 *
 *   intlog10(value) = intlog10(value * 10^x) - x * 2^24
 *
 * An usecase example:
 *
 *	intlog10(1000) will give 3 << 24 = 3 * 2^24
 *
 *   due to the implementation intlog10(1000) might be not exactly 3 * 2^24
 *
 * look at intlog2 for similar examples
 *
 * return: log10(value) * 2^24
 */
extern unsigned int intlog10(u32 value);

#endif
Commit	Line	Data
da22d0e7 CP	1	/*
	2	* dvb-math provides some complex fixed-point math
	3	* operations shared between the dvb related stuff
	4	*
	5	* Copyright (C) 2006 Christoph Pfister (christophpfister@gmail.com)
	6	*
	7	* This library is free software; you can redistribute it and/or modify
	8	* it under the terms of the GNU Lesser General Public License as
	9	* published by the Free Software Foundation; either version 2.1 of
	10	* the License, or (at your option) any later version.
	11	*
	12	* This program is distributed in the hope that it will be useful,
	13	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	14	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	15	* GNU Lesser General Public License for more details.
	16	*
	17	* You should have received a copy of the GNU Lesser General Public
	18	* License along with this library; if not, write to the Free Software
	19	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	20	*/
	21
	22	#ifndef __DVB_MATH_H
	23	#define __DVB_MATH_H
	24
	25	#include <linux/types.h>
	26
	27	/**
e383ce07	28	* intlog2 - computes log2 of a value; the result is shifted left by 24 bits
e08bb6f7 MCC	29	*
e08bb6f7 MCC	30	* @value: The value (must be != 0)
da22d0e7 CP	31	*
da22d0e7 CP	32	* to use rational values you can use the following method:
5b8700e9	33	*
da22d0e7 CP	34	* intlog2(value) = intlog2(value * 2^x) - x * 2^24
da22d0e7 CP	35	*
dc2c8bd3	36	* Some usecase examples:
5b8700e9	37	*
dc2c8bd3	38	* intlog2(8) will give 3 << 24 = 3 * 2^24
5b8700e9	39	*
dc2c8bd3	40	* intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24
5b8700e9	41	*
dc2c8bd3	42	* intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24
da22d0e7	43	*
e08bb6f7 MCC	44	*
e08bb6f7 MCC	45	* return: log2(value) * 2^24
da22d0e7 CP	46	*/
	47	extern unsigned int intlog2(u32 value);
	48
	49	/**
e08bb6f7 MCC	50	* intlog10 - computes log10 of a value; the result is shifted left by 24 bits
	51	*
	52	* @value: The value (must be != 0)
da22d0e7 CP	53	*
da22d0e7 CP	54	* to use rational values you can use the following method:
5b8700e9	55	*
da22d0e7 CP	56	* intlog10(value) = intlog10(value * 10^x) - x * 2^24
da22d0e7 CP	57	*
dc2c8bd3	58	* An usecase example:
5b8700e9	59	*
dc2c8bd3	60	* intlog10(1000) will give 3 << 24 = 3 * 2^24
5b8700e9	61	*
da22d0e7 CP	62	* due to the implementation intlog10(1000) might be not exactly 3 * 2^24
	63	*
	64	* look at intlog2 for similar examples
	65	*
e08bb6f7	66	* return: log10(value) * 2^24
da22d0e7 CP	67	*/
	68	extern unsigned int intlog10(u32 value);
	69
	70	#endif