sm64pc/tools/audiofile-0.3.6/libaudiofile/extended.c

/* Copyright (C) 1989-1991 Apple Computer, Inc.
 *
 * All rights reserved.
 *
 * Warranty Information
 *  Even though Apple has reviewed this software, Apple makes no warranty
 *  or representation, either express or implied, with respect to this
 *  software, its quality, accuracy, merchantability, or fitness for a
 *  particular purpose.  As a result, this software is provided "as is,"
 *  and you, its user, are assuming the entire risk as to its quality
 *  and accuracy.
 *
 * This code may be used and freely distributed as long as it includes
 * this copyright notice and the above warranty information.
 *
 * 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
 *	Sequent Balance (Multiprocesor 386)
 *	NeXT
 *
 *
 * 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.
 */

/****************************************************************
 * Extended precision IEEE floating-point conversion routines.
 * Extended is an 80-bit number as defined by Motorola,
 * with a sign bit, 15 bits of exponent (offset 16383?),
 * and a 64-bit mantissa, with no hidden bit.
 ****************************************************************/

#include "extended.h"

#include <math.h>

#ifndef HUGE_VAL
#define HUGE_VAL HUGE
#endif

#define FloatToUnsigned(f) ((unsigned long) (((long) (f - 2147483648.0)) + 2147483647L) + 1)

void _af_convert_to_ieee_extended (double num, unsigned 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] = expon >> 8;
	bytes[1] = expon;
	bytes[2] = hiMant >> 24;
	bytes[3] = hiMant >> 16;
	bytes[4] = hiMant >> 8;
	bytes[5] = hiMant;
	bytes[6] = loMant >> 24;
	bytes[7] = loMant >> 16;
	bytes[8] = loMant >> 8;
	bytes[9] = loMant;
}

#define UnsignedToFloat(u) (((double) ((long) (u - 2147483647L - 1))) + 2147483648.0)

double _af_convert_from_ieee_extended (const unsigned char *bytes)
{
	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;
}