mirror of https://github.com/jorio/Pomme.git
127 lines
3.8 KiB
C++
127 lines
3.8 KiB
C++
/* Copyright (C) 1988-1991 Apple Computer, Inc.
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* All rights reserved.
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*
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* Machine-independent I/O routines for IEEE floating-point numbers.
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*
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* NaN's and infinities are converted to HUGE_VAL or HUGE, which
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* happens to be infinity on IEEE machines. Unfortunately, it is
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* impossible to preserve NaN's in a machine-independent way.
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* Infinities are, however, preserved on IEEE machines.
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*
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* These routines have been tested on the following machines:
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* Apple Macintosh, MPW 3.1 C compiler
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* Apple Macintosh, THINK C compiler
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* Silicon Graphics IRIS, MIPS compiler
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* Cray X/MP and Y/MP
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* Digital Equipment VAX
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*
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*
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* Implemented by Malcolm Slaney and Ken Turkowski.
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*
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* Malcolm Slaney contributions during 1988-1990 include big- and little-
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* endian file I/O, conversion to and from Motorola's extended 80-bit
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* floating-point format, and conversions to and from IEEE single-
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* precision floating-point format.
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*
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* In 1991, Ken Turkowski implemented the conversions to and from
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* IEEE double-precision format, added more precision to the extended
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* conversions, and accommodated conversions involving +/- infinity,
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* NaN's, and denormalized numbers.
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*/
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#include <math.h>
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#include "IEEEExtended.h"
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#ifndef HUGE_VAL
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# define HUGE_VAL HUGE
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#endif
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#define FloatToUnsigned(f) ((unsigned long)(((long)(f - 2147483648.0)) + 2147483647L) + 1)
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#define UnsignedToFloat(u) (((double)((long)(u - 2147483647L - 1))) + 2147483648.0)
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void ConvertToIeeeExtended(double num, char* bytes)
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{
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int sign;
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int expon;
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double fMant, fsMant;
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unsigned long hiMant, loMant;
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if (num < 0) {
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sign = 0x8000;
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num *= -1;
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} else {
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sign = 0;
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}
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if (num == 0) {
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expon = 0; hiMant = 0; loMant = 0;
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}
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else {
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fMant = frexp(num, &expon);
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if ((expon > 16384) || !(fMant < 1)) { /* Infinity or NaN */
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expon = sign|0x7FFF; hiMant = 0; loMant = 0; /* infinity */
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}
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else { /* Finite */
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expon += 16382;
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if (expon < 0) { /* denormalized */
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fMant = ldexp(fMant, expon);
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expon = 0;
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}
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expon |= sign;
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fMant = ldexp(fMant, 32);
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fsMant = floor(fMant);
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hiMant = FloatToUnsigned(fsMant);
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fMant = ldexp(fMant - fsMant, 32);
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fsMant = floor(fMant);
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loMant = FloatToUnsigned(fsMant);
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}
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}
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bytes[0] = char(expon >> 8);
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bytes[1] = char(expon);
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bytes[2] = char(hiMant >> 24);
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bytes[3] = char(hiMant >> 16);
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bytes[4] = char(hiMant >> 8);
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bytes[5] = char(hiMant);
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bytes[6] = char(loMant >> 24);
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bytes[7] = char(loMant >> 16);
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bytes[8] = char(loMant >> 8);
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bytes[9] = char(loMant);
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}
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double ConvertFromIeeeExtended(const unsigned char* bytes /* LCN */)
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{
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double f;
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int expon;
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unsigned long hiMant, loMant;
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expon = ((bytes[0] & 0x7F) << 8) | (bytes[1] & 0xFF);
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hiMant = ((unsigned long)(bytes[2] & 0xFF) << 24)
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| ((unsigned long)(bytes[3] & 0xFF) << 16)
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| ((unsigned long)(bytes[4] & 0xFF) << 8)
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| ((unsigned long)(bytes[5] & 0xFF));
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loMant = ((unsigned long)(bytes[6] & 0xFF) << 24)
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| ((unsigned long)(bytes[7] & 0xFF) << 16)
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| ((unsigned long)(bytes[8] & 0xFF) << 8)
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| ((unsigned long)(bytes[9] & 0xFF));
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if (expon == 0 && hiMant == 0 && loMant == 0) {
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f = 0;
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}
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else {
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if (expon == 0x7FFF) { /* Infinity or NaN */
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f = HUGE_VAL;
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}
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else {
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expon -= 16383;
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f = ldexp(UnsignedToFloat(hiMant), expon-=31);
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f += ldexp(UnsignedToFloat(loMant), expon-=32);
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}
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}
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if (bytes[0] & 0x80)
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return -f;
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else
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return f;
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}
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