mirror of
https://github.com/libretro/scummvm.git
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124 lines
2.7 KiB
C++
124 lines
2.7 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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*/
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#include "glk/glulxe/glulxe.h"
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namespace Glk {
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namespace Glulxe {
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uint Glulxe::encode_float(gfloat32 val) {
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gfloat32 absval;
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uint sign;
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int expo;
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gfloat32 mant;
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uint fbits;
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if (signbit(val)) {
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sign = 0x80000000;
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absval = -val;
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} else {
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sign = 0x0;
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absval = val;
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}
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if (isinf(val)) {
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return sign | 0x7f800000; /* infinity */
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}
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if (isnan(val)) {
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return sign | 0x7fc00000;
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}
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mant = frexpf(absval, &expo);
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/* Normalize mantissa to be in the range [1.0, 2.0) */
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if (0.5 <= mant && mant < 1.0) {
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mant *= 2.0;
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expo--;
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} else if (mant == 0.0) {
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expo = 0;
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} else {
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return sign | 0x7f800000; /* infinity */
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}
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if (expo >= 128) {
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return sign | 0x7f800000; /* infinity */
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} else if (expo < -126) {
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/* Denormalized (very small) number */
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mant = ldexpf(mant, 126 + expo);
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expo = 0;
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} else if (!(expo == 0 && mant == 0.0)) {
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expo += 127;
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mant -= 1.0; /* Get rid of leading 1 */
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}
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mant *= 8388608.0; /* 2^23 */
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fbits = (uint)(mant + 0.5); /* round mant to nearest int */
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if (fbits >> 23) {
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/* The carry propagated out of a string of 23 1 bits. */
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fbits = 0;
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expo++;
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if (expo >= 255) {
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return sign | 0x7f800000; /* infinity */
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}
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}
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return (sign) | ((uint)(expo << 23)) | (fbits);
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}
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gfloat32 Glulxe::decode_float(uint val) {
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int sign;
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int expo;
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uint mant;
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gfloat32 res;
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/* First byte */
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sign = ((val & 0x80000000) != 0);
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expo = (val >> 23) & 0xFF;
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mant = val & 0x7FFFFF;
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if (expo == 255) {
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if (mant == 0) {
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/* Infinity */
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return (sign ? (-INFINITY) : (INFINITY));
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} else {
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/* Not a number */
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return (sign ? (-NAN) : (NAN));
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}
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}
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res = (gfloat32)mant / 8388608.0;
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if (expo == 0) {
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expo = -126;
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} else {
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res += 1.0;
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expo -= 127;
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}
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res = ldexpf(res, expo);
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return (sign ? (-res) : (res));
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}
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} // End of namespace Glulxe
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} // End of namespace Glk
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