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 <stdio.h>
  12 #include <stdlib.h>
  13 #include <ctype.h>
  14 #include <limits.h>
  15 #include <string.h>
  16 #include "wx/defs.h"
  17
  18 #if wxUSE_APPLE_IEEE
  19
  20 #include "wx/math.h"
  21
  22 /* Copyright (C) 1989-1991 Ken Turkowski. <turk@computer.org>
  23  *
  24  * All rights reserved.
  25  *
  26  * Warranty Information
  27  *  Even though I have reviewed this software, I make no warranty
  28  *  or representation, either express or implied, with respect to this
  29  *  software, its quality, accuracy, merchantability, or fitness for a
  30  *  particular purpose.  As a result, this software is provided "as is,"
  31  *  and you, its user, are assuming the entire risk as to its quality
  32  *  and accuracy.
  33  *
  34  * This code may be used and freely distributed as long as it includes
  35  * this copyright notice and the above warranty information.
  36  *
  37  * Machine-independent I/O routines for IEEE floating-point numbers.
  38  *
  39  * NaN's and infinities are converted to HUGE_VAL or HUGE, which
  40  * happens to be infinity on IEEE machines.  Unfortunately, it is
  41  * impossible to preserve NaN's in a machine-independent way.
  42  * Infinities are, however, preserved on IEEE machines.
  43  *
  44  * These routines have been tested on the following machines:
  45  *    Apple Macintosh, MPW 3.1 C compiler
  46  *    Apple Macintosh, THINK C compiler
  47  *    Silicon Graphics IRIS, MIPS compiler
  48  *    Cray X/MP and Y/MP
  49  *    Digital Equipment VAX
  50  *    Sequent Balance (Multiprocesor 386)
  51  *    NeXT
  52  *
  53  *
  54  * Implemented by Malcolm Slaney and Ken Turkowski.
  55  *
  56  * Malcolm Slaney contributions during 1988-1990 include big- and little-
  57  * endian file I/O, conversion to and from Motorola's extended 80-bit
  58  * floating-point format, and conversions to and from IEEE single-
  59  * precision floating-point format.
  60  *
  61  * In 1991, Ken Turkowski implemented the conversions to and from
  62  * IEEE double-precision format, added more precision to the extended
  63  * conversions, and accommodated conversions involving +/- infinity,
  64  * NaN's, and denormalized numbers.
  65  */
  66
  67 #ifndef HUGE_VAL
  68 # define HUGE_VAL HUGE
  69 #endif /*HUGE_VAL*/
  70
  71
  72 /****************************************************************
  73  * The following two routines make up for deficiencies in many
  74  * compilers to convert properly between unsigned integers and
  75  * floating-point.  Some compilers which have this bug are the
  76  * THINK_C compiler for the Macintosh and the C compiler for the
  77  * Silicon Graphics MIPS-based Iris.
  78  ****************************************************************/
  79
  80 #ifdef applec    /* The Apple C compiler works */
  81 # define FloatToUnsigned(f)   ((wxUint32)(f))
  82 # define UnsignedToFloat(u)   ((wxFloat64)(u))
  83 #else /*applec*/
  84 # define FloatToUnsigned(f)   ((wxUint32)(((wxInt32)((f) - 2147483648.0)) + 2147483647L) + 1)
  85 # define UnsignedToFloat(u)   (((wxFloat64)((wxInt32)((u) - 2147483647L - 1))) + 2147483648.0)
  86 #endif /*applec*/
  87
  88
  89
  90 /****************************************************************
  91  * Extended precision IEEE floating-point conversion routines.
  92  * Extended is an 80-bit number as defined by Motorola,
  93  * with a sign bit, 15 bits of exponent (offset 16383?),
  94  * and a 64-bit mantissa, with no hidden bit.
  95  ****************************************************************/
  96
  97 wxFloat64 ConvertFromIeeeExtended(wxInt8* bytes)
  98 {
  99     wxFloat64 f;
 100     wxInt32 expon;
 101     wxUint32 hiMant, loMant;
 102
 103     expon = ((bytes[0] & 0x7F) << 8) | (bytes[1] & 0xFF);
 104     hiMant = ((wxUint32)(bytes[2] & 0xFF) << 24)
 105             | ((wxUint32)(bytes[3] & 0xFF) << 16)
 106             | ((wxUint32)(bytes[4] & 0xFF) << 8)
 107             | ((wxUint32)(bytes[5] & 0xFF));
 108     loMant = ((wxUint32)(bytes[6] & 0xFF) << 24)
 109             | ((wxUint32)(bytes[7] & 0xFF) << 16)
 110             | ((wxUint32)(bytes[8] & 0xFF) << 8)
 111             | ((wxUint32)(bytes[9] & 0xFF));
 112
 113     if (expon == 0 && hiMant == 0 && loMant == 0) {
 114         f = 0;
 115     }
 116     else {
 117         if (expon == 0x7FFF) { /* Infinity or NaN */
 118             f = HUGE_VAL;
 119         }
 120         else {
 121             expon -= 16383;
 122             f  = ldexp(UnsignedToFloat(hiMant), expon-=31);
 123             f += ldexp(UnsignedToFloat(loMant), expon-=32);
 124         }
 125     }
 126
 127     if (bytes[0] & 0x80)
 128         return -f;
 129     else
 130         return f;
 131 }
 132
 133
 134 /****************************************************************/
 135
 136
 137 void ConvertToIeeeExtended(wxFloat64 num, wxInt8 *bytes)
 138 {
 139     wxInt32 sign;
 140     wxInt32 expon;
 141     wxFloat64 fMant, fsMant;
 142     wxUint32 hiMant, loMant;
 143
 144     if (num < 0) {
 145         sign = 0x8000;
 146         num *= -1;
 147     } else {
 148         sign = 0;
 149     }
 150
 151     if (num == 0) {
 152         expon = 0; hiMant = 0; loMant = 0;
 153     }
 154     else {
 155         fMant = frexp(num, &expon);
 156         if ((expon > 16384) || !(fMant < 1)) { /* Infinity or NaN */
 157             expon = sign|0x7FFF; hiMant = 0; loMant = 0; /* infinity */
 158         }
 159         else { /* Finite */
 160             expon += 16382;
 161             if (expon < 0) { /* denormalized */
 162                 fMant = ldexp(fMant, expon);
 163                 expon = 0;
 164             }
 165             expon |= sign;
 166             fMant = ldexp(fMant, 32);          fsMant = floor(fMant); hiMant = FloatToUnsigned(fsMant);
 167             fMant = ldexp(fMant - fsMant, 32); fsMant = floor(fMant); loMant = FloatToUnsigned(fsMant);
 168         }
 169     }
 170
 171     bytes[0] = expon >> 8;
 172     bytes[1] = expon;
 173     bytes[2] = hiMant >> 24;
 174     bytes[3] = hiMant >> 16;
 175     bytes[4] = hiMant >> 8;
 176     bytes[5] = hiMant;
 177     bytes[6] = loMant >> 24;
 178     bytes[7] = loMant >> 16;
 179     bytes[8] = loMant >> 8;
 180     bytes[9] = loMant;
 181 }
 182
 183
 184
 185 #endif /* wxUSE_APPLE_IEEE */