src/common/extended.c

   1 /*****************************************************************************
   2 ** Name:        extended.c
   3 ** Purpose:     IEEE Extended<->Double routines to save floats to file
   4 ** Maintainer:  Ryan Norton
   5 ** Modified by:
   6 ** Created:     11/24/04
   7 ** RCS-ID:      $Id$
   8 *****************************************************************************/
   9
  10
  11 #include "wx/defs.h"
  12
  13 #if wxUSE_APPLE_IEEE
  14
  15 #include <math.h>
  16
  17 /* Copyright (C) 1989-1991 Ken Turkowski. <turk@computer.org>
  18  *
  19  * All rights reserved.
  20  *
  21  * Warranty Information
  22  *  Even though I have reviewed this software, I make no warranty
  23  *  or representation, either express or implied, with respect to this
  24  *  software, its quality, accuracy, merchantability, or fitness for a
  25  *  particular purpose.  As a result, this software is provided "as is,"
  26  *  and you, its user, are assuming the entire risk as to its quality
  27  *  and accuracy.
  28  *
  29  * This code may be used and freely distributed as long as it includes
  30  * this copyright notice and the above warranty information.
  31  *
  32  * Machine-independent I/O routines for IEEE floating-point numbers.
  33  *
  34  * NaN's and infinities are converted to HUGE_VAL or HUGE, which
  35  * happens to be infinity on IEEE machines.  Unfortunately, it is
  36  * impossible to preserve NaN's in a machine-independent way.
  37  * Infinities are, however, preserved on IEEE machines.
  38  *
  39  * These routines have been tested on the following machines:
  40  *      Apple Macintosh, MPW 3.1 C compiler
  41  *      Apple Macintosh, THINK C compiler
  42  *      Silicon Graphics IRIS, MIPS compiler
  43  *      Cray X/MP and Y/MP
  44  *      Digital Equipment VAX
  45  *      Sequent Balance (Multiprocesor 386)
  46  *      NeXT
  47  *
  48  *
  49  * Implemented by Malcolm Slaney and Ken Turkowski.
  50  *
  51  * Malcolm Slaney contributions during 1988-1990 include big- and little-
  52  * endian file I/O, conversion to and from Motorola's extended 80-bit
  53  * floating-point format, and conversions to and from IEEE single-
  54  * precision floating-point format.
  55  *
  56  * In 1991, Ken Turkowski implemented the conversions to and from
  57  * IEEE double-precision format, added more precision to the extended
  58  * conversions, and accommodated conversions involving +/- infinity,
  59  * NaN's, and denormalized numbers.
  60  */
  61
  62 #ifndef HUGE_VAL
  63 # define HUGE_VAL HUGE
  64 #endif /*HUGE_VAL*/
  65
  66
  67 /****************************************************************
  68  * The following two routines make up for deficiencies in many
  69  * compilers to convert properly between unsigned integers and
  70  * floating-point.  Some compilers which have this bug are the
  71  * THINK_C compiler for the Macintosh and the C compiler for the
  72  * Silicon Graphics MIPS-based Iris.
  73  ****************************************************************/
  74
  75 #ifdef applec   /* The Apple C compiler works */
  76 # define FloatToUnsigned(f)     ((wxUint32)(f))
  77 # define UnsignedToFloat(u)     ((wxFloat64)(u))
  78 #else /*applec*/
  79 # define FloatToUnsigned(f)     ((wxUint32)((((wxInt32)((f) - 2147483648.0)) + 2147483647L) + 1))
  80 # define UnsignedToFloat(u)     (((wxFloat64)((wxInt32)((u) - 2147483647L - 1))) + 2147483648.0)
  81 #endif /*applec*/
  82
  83
  84
  85 /****************************************************************
  86  * Extended precision IEEE floating-point conversion routines.
  87  * Extended is an 80-bit number as defined by Motorola,
  88  * with a sign bit, 15 bits of exponent (offset 16383?),
  89  * and a 64-bit mantissa, with no hidden bit.
  90  ****************************************************************/
  91
  92 wxFloat64 ConvertFromIeeeExtended(wxInt8* bytes)
  93 {
  94         wxFloat64       f;
  95         wxInt32 expon;
  96         wxUint32 hiMant, loMant;
  97
  98         expon = ((bytes[0] & 0x7F) << 8) | (bytes[1] & 0xFF);
  99         hiMant  =       ((wxUint32)(bytes[2] & 0xFF) << 24)
 100                         |       ((wxUint32)(bytes[3] & 0xFF) << 16)
 101                         |       ((wxUint32)(bytes[4] & 0xFF) << 8)
 102                         |       ((wxUint32)(bytes[5] & 0xFF));
 103         loMant  =       ((wxUint32)(bytes[6] & 0xFF) << 24)
 104                         |       ((wxUint32)(bytes[7] & 0xFF) << 16)
 105                         |       ((wxUint32)(bytes[8] & 0xFF) << 8)
 106                         |       ((wxUint32)(bytes[9] & 0xFF));
 107
 108         if (expon == 0 && hiMant == 0 && loMant == 0) {
 109                 f = 0;
 110         }
 111         else {
 112                 if (expon == 0x7FFF) {  /* Infinity or NaN */
 113                         f = HUGE_VAL;
 114                 }
 115                 else {
 116                         expon -= 16383;
 117                         f  = ldexp(UnsignedToFloat(hiMant), expon-=31);
 118                         f += ldexp(UnsignedToFloat(loMant), expon-=32);
 119                 }
 120         }
 121
 122         if (bytes[0] & 0x80)
 123                 return -f;
 124         else
 125                 return f;
 126 }
 127
 128
 129 /****************************************************************/
 130
 131
 132 void ConvertToIeeeExtended(wxFloat64 num, wxInt8 *bytes)
 133 {
 134         wxInt32 sign;
 135         wxInt32 expon;
 136         wxFloat64 fMant, fsMant;
 137         wxUint32 hiMant, loMant;
 138
 139         if (num < 0) {
 140                 sign = 0x8000;
 141                 num *= -1;
 142         } else {
 143                 sign = 0;
 144         }
 145
 146         if (num == 0) {
 147                 expon = 0; hiMant = 0; loMant = 0;
 148         }
 149         else {
 150                 fMant = frexp(num, &expon);
 151                 if ((expon > 16384) || !(fMant < 1)) {  /* Infinity or NaN */
 152                         expon = sign|0x7FFF; hiMant = 0; loMant = 0; /* infinity */
 153                 }
 154                 else {  /* Finite */
 155                         expon += 16382;
 156                         if (expon < 0) {        /* denormalized */
 157                                 fMant = ldexp(fMant, expon);
 158                                 expon = 0;
 159                         }
 160                         expon |= sign;
 161                         fMant = ldexp(fMant, 32);          fsMant = floor(fMant); hiMant = FloatToUnsigned(fsMant);
 162                         fMant = ldexp(fMant - fsMant, 32); fsMant = floor(fMant); loMant = FloatToUnsigned(fsMant);
 163                 }
 164         }
 165
 166         bytes[0] = expon >> 8;
 167         bytes[1] = expon;
 168         bytes[2] = hiMant >> 24;
 169         bytes[3] = hiMant >> 16;
 170         bytes[4] = hiMant >> 8;
 171         bytes[5] = hiMant;
 172         bytes[6] = loMant >> 24;
 173         bytes[7] = loMant >> 16;
 174         bytes[8] = loMant >> 8;
 175         bytes[9] = loMant;
 176 }
 177
 178
 179
 180 #endif /* wxUSE_APPLE_IEEE */