jpc_math.c

在x86平台上运行不可信任代码的sandbox。

/*
 * Copyright (c) 1999-2000 Image Power, Inc. and the University of
 *   British Columbia.
 * Copyright (c) 2001-2002 Michael David Adams.
 * All rights reserved.
 */

/* __START_OF_JASPER_LICENSE__
 * 
 * JasPer License Version 2.0
 * 
 * Copyright (c) 1999-2000 Image Power, Inc.
 * Copyright (c) 1999-2000 The University of British Columbia
 * Copyright (c) 2001-2003 Michael David Adams
 * 
 * All rights reserved.
 * 
 * Permission is hereby granted, free of charge, to any person (the
 * "User") obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without restriction,
 * including without limitation the rights to use, copy, modify, merge,
 * publish, distribute, and/or sell copies of the Software, and to permit
 * persons to whom the Software is furnished to do so, subject to the
 * following conditions:
 * 
 * 1.  The above copyright notices and this permission notice (which
 * includes the disclaimer below) shall be included in all copies or
 * substantial portions of the Software.
 * 
 * 2.  The name of a copyright holder shall not be used to endorse or
 * promote products derived from the Software without specific prior
 * written permission.
 * 
 * THIS DISCLAIMER OF WARRANTY CONSTITUTES AN ESSENTIAL PART OF THIS
 * LICENSE.  NO USE OF THE SOFTWARE IS AUTHORIZED HEREUNDER EXCEPT UNDER
 * THIS DISCLAIMER.  THE SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS
 * "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.  IN NO
 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, OR ANY SPECIAL
 * INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES WHATSOEVER RESULTING
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 * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
 * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.  NO ASSURANCES ARE
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 * THE FAILURE OF THE SOFTWARE OR SYSTEM COULD LEAD DIRECTLY TO DEATH,
 * PERSONAL INJURY, OR SEVERE PHYSICAL OR ENVIRONMENTAL DAMAGE ("HIGH
 * RISK ACTIVITIES").  THE COPYRIGHT HOLDERS SPECIFICALLY DISCLAIM ANY
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 */

/*
 * Math Library
 *
 * $Id: jpc_math.c 1918 2005-07-24 14:12:08Z baford $
 */

/******************************************************************************\
* Includes
\******************************************************************************/

#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
#include <stdarg.h>

#include "jpc_math.h"

/******************************************************************************\
* Miscellaneous Functions
\******************************************************************************/

/* Calculate the integer quantity floor(log2(x)), where x is a positive
  integer. */
int jpc_floorlog2(int x)
{
	int y;

	/* The argument must be positive. */
	assert(x > 0);

	y = 0;
	while (x > 1) {
		x >>= 1;
		++y;
	}
	return y;
}

/* Calculate the bit position of the first leading one in a nonnegative
  integer. */
/* This function is the basically the same as ceillog2(x), except that the
  allowable range for x is slightly different. */
int jpc_firstone(int x)
{
	int n;

	/* The argument must be nonnegative. */
	assert(x >= 0);

	n = -1;
	while (x > 0) {
		x >>= 1;
		++n;
	}
	return n;
}