File: ieee_float.C

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// ieee_float.C

/******************************************************************************
 *
 *  MiXViews - an X window system based sound & data editor/processor
 *
 *  Copyright (c) 1993, 1994 Regents of the University of California
 *
 *  Author:     Douglas Scott
 *  Date:       December 13, 1994
 *
 *  Permission to use, copy and modify this software and its documentation
 *  for research and/or educational purposes and without fee is hereby granted,
 *  provided that the above copyright notice appear in all copies and that
 *  both that copyright notice and this permission notice appear in
 *  supporting documentation. The author reserves the right to distribute this
 *  software and its documentation.  The University of California and the author
 *  make no representations about the suitability of this software for any 
 *  purpose, and in no event shall University of California be liable for any
 *  damage, loss of data, or profits resulting from its use.
 *  It is provided "as is" without express or implied warranty.
 *
 ******************************************************************************/

#ifdef __GNUG__
#pragma implementation
#endif

#include <math.h>
#include <string.h>
#include "ieee_float.h"

IEEE_Float::IEEE_Float(double value) {
	setTo(value);
}

IEEE_Float::IEEE_Float(const IEEE_Float& f) {
	*this = f;
}

const IEEE_Float &
IEEE_Float::operator = (const IEEE_Float& rhs) {
	strncpy(chars, rhs.chars, 10);
	return *this;
}

double
IEEE_Float::operator = (double rhs) {
	setTo(rhs);
	return *this;
}

IEEE_Float::operator float() const {
	return ConvertFromIeeeExtended((const unsigned char*) chars);
}

IEEE_Float::operator double() const {
	return float(*this);
}

void
IEEE_Float::setTo(double value) {
	ConvertToIeeeExtended(value, chars);
}

/*
 * C O N V E R T   T O   I E E E   E X T E N D E D
 */

/* Copyright (C) 1988-1991 Apple Computer, Inc.
 * All rights reserved.
 *
 * Machine-independent I/O routines for IEEE floating-point numbers.
 *
 * NaN's and infinities are converted to HUGE_VAL or HUGE, which
 * happens to be infinity on IEEE machines.  Unfortunately, it is
 * impossible to preserve NaN's in a machine-independent way.
 * Infinities are, however, preserved on IEEE machines.
 *
 * These routines have been tested on the following machines:
 *    Apple Macintosh, MPW 3.1 C compiler
 *    Apple Macintosh, THINK C compiler
 *    Silicon Graphics IRIS, MIPS compiler
 *    Cray X/MP and Y/MP
 *    Digital Equipment VAX
 *
 *
 * Implemented by Malcolm Slaney and Ken Turkowski.
 *
 * Malcolm Slaney contributions during 1988-1990 include big- and little-
 * endian file I/O, conversion to and from Motorola's extended 80-bit
 * floating-point format, and conversions to and from IEEE single-
 * precision floating-point format.
 *
 * In 1991, Ken Turkowski implemented the conversions to and from
 * IEEE double-precision format, added more precision to the extended
 * conversions, and accommodated conversions involving +/- infinity,
 * NaN's, and denormalized numbers.
 */

#ifndef HUGE_VAL
# define HUGE_VAL HUGE
#endif /*HUGE_VAL*/

inline unsigned long FloatToUnsigned(float f) {
	return ((unsigned long)(((long)(f - 2147483648.0)) + 2147483647L) + 1);
}

void
IEEE_Float::ConvertToIeeeExtended(double num, char* bytes) {
    int    sign;
    int expon;
    double fMant, fsMant;
    unsigned long hiMant, loMant;

    if (num < 0) {
        sign = 0x8000;
        num *= -1;
    } else {
        sign = 0;
    }

    if (num == 0) {
        expon = 0; hiMant = 0; loMant = 0;
    }
    else {
        fMant = frexp(num, &expon);
        if ((expon > 16384) || !(fMant < 1)) {    /* Infinity or NaN */
            expon = sign|0x7FFF; hiMant = 0; loMant = 0; /* infinity */
        }
        else {    /* Finite */
            expon += 16382;
            if (expon < 0) {    /* denormalized */
                fMant = ldexp(fMant, expon);
                expon = 0;
            }
            expon |= sign;
            fMant = ldexp(fMant, 32);          
            fsMant = floor(fMant); 
            hiMant = FloatToUnsigned(fsMant);
            fMant = ldexp(fMant - fsMant, 32); 
            fsMant = floor(fMant); 
            loMant = FloatToUnsigned(fsMant);
        }
    }
    
    bytes[0] = char(expon >> 8);
    bytes[1] = char(expon);
    bytes[2] = char(hiMant >> 24);
    bytes[3] = char(hiMant >> 16);
    bytes[4] = char(hiMant >> 8);
    bytes[5] = char(hiMant);
    bytes[6] = char(loMant >> 24);
    bytes[7] = char(loMant >> 16);
    bytes[8] = char(loMant >> 8);
    bytes[9] = char(loMant);
}


/*
 * C O N V E R T   F R O M   I E E E   E X T E N D E D  
 */

/* 
 * Copyright (C) 1988-1991 Apple Computer, Inc.
 * All rights reserved.
 *
 * Machine-independent I/O routines for IEEE floating-point numbers.
 *
 * NaN's and infinities are converted to HUGE_VAL or HUGE, which
 * happens to be infinity on IEEE machines.  Unfortunately, it is
 * impossible to preserve NaN's in a machine-independent way.
 * Infinities are, however, preserved on IEEE machines.
 *
 * These routines have been tested on the following machines:
 *    Apple Macintosh, MPW 3.1 C compiler
 *    Apple Macintosh, THINK C compiler
 *    Silicon Graphics IRIS, MIPS compiler
 *    Cray X/MP and Y/MP
 *    Digital Equipment VAX
 *
 *
 * Implemented by Malcolm Slaney and Ken Turkowski.
 *
 * Malcolm Slaney contributions during 1988-1990 include big- and little-
 * endian file I/O, conversion to and from Motorola's extended 80-bit
 * floating-point format, and conversions to and from IEEE single-
 * precision floating-point format.
 *
 * In 1991, Ken Turkowski implemented the conversions to and from
 * IEEE double-precision format, added more precision to the extended
 * conversions, and accommodated conversions involving +/- infinity,
 * NaN's, and denormalized numbers.
 */

#ifndef HUGE_VAL
# define HUGE_VAL HUGE
#endif /*HUGE_VAL*/

inline float UnsignedToFloat(unsigned long ul) {
	return (((double)((long)(ul - 2147483647L - 1))) + 2147483648.0);
}

/****************************************************************
 * Extended precision IEEE floating-point conversion routine.
 ****************************************************************/

double
IEEE_Float::ConvertFromIeeeExtended(const unsigned char* bytes) {	/* LCN */
    double    f;
    int    expon;
    unsigned long hiMant, loMant;
    
    expon = ((bytes[0] & 0x7F) << 8) | (bytes[1] & 0xFF);
    hiMant    =    ((unsigned long)(bytes[2] & 0xFF) << 24)
            |    ((unsigned long)(bytes[3] & 0xFF) << 16)
            |    ((unsigned long)(bytes[4] & 0xFF) << 8)
            |    ((unsigned long)(bytes[5] & 0xFF));
    loMant    =    ((unsigned long)(bytes[6] & 0xFF) << 24)
            |    ((unsigned long)(bytes[7] & 0xFF) << 16)
            |    ((unsigned long)(bytes[8] & 0xFF) << 8)
            |    ((unsigned long)(bytes[9] & 0xFF));

    if (expon == 0 && hiMant == 0 && loMant == 0) {
        f = 0;
    }
    else {
        if (expon == 0x7FFF) {    /* Infinity or NaN */
            f = HUGE_VAL;
        }
        else {
            expon -= 16383;
            f  = ldexp(UnsignedToFloat(hiMant), expon-=31);
            f += ldexp(UnsignedToFloat(loMant), expon-=32);
        }
    }

    if (bytes[0] & 0x80)
        return -f;
    else
        return f;
}