simplefp.h

传感器网络中的嵌入式操作系统源代码

// $Id: SimpleFP.h,v 1.1.2.2 2003/08/18 22:09:49 cssharp Exp $

/*									tab:4
 * "Copyright (c) 2000-2003 The Regents of the University  of California.  
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 * two paragraphs and the author appear in all copies of this software.
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 * IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR
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 * OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF
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 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
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 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS."
 *
 * Copyright (c) 2002-2003 Intel Corporation
 * All rights reserved.
 *
 * This file is distributed under the terms in the attached INTEL-LICENSE     
 * file. If you do not find these files, copies can be found by writing to
 * Intel Research Berkeley, 2150 Shattuck Avenue, Suite 1300, Berkeley, CA, 
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 */

#ifndef TOS_SIMPLEFP_H
#define TOS_SIMPLEFP_H

/* A simple fixed-point package, provides unsigned 8.8 precision (easily
   changed) */

enum { FP_BITS = 8 };		/* bits in fraction */
typedef uint16_t FPType;	/* type of fp values */
typedef uint8_t FPIntType;	/* type which can hold integral part of
                                   FPType */
typedef uint32_t FPBigger;

enum { FP_SCALE = 1UL << FP_BITS };

/* + and - can be used directly */
FPType fpMul(FPType fp1, FPType fp2)
{
  return (FPType)(((FPBigger)fp1 * fp2) >> FP_BITS);
}

FPType fpDiv(FPType fp1, FPType fp2)
{
  return (FPType)(((FPBigger)fp1 << FP_BITS) / fp2);
}

FPIntType fpRoundToZero(FPType fp)
{
  return fp >> FP_BITS;
}

FPIntType fpRoundAwayFromZero(FPType fp)
{
  return (fp + (1 << FP_BITS) - 1) >> FP_BITS;
}

FPType intToFp(FPIntType i)
{
  return i << FP_BITS;
}

#endif