toolame-02l/ieeefloat.c

   1 /* Copyright (C) 1988-1991 Apple Computer, Inc.
   2  * All Rights Reserved.
   3  *
   4  * Warranty Information
   5  * Even though Apple has reviewed this software, Apple makes no warranty
   6  * or representation, either express or implied, with respect to this
   7  * software, its quality, accuracy, merchantability, or fitness for a
   8  * particular purpose.  As a result, this software is provided "as is,"
   9  * and you, its user, are assuming the entire risk as to its quality
  10  * and accuracy.
  11  *
  12  * This code may be used and freely distributed as long as it includes
  13  * this copyright notice and the warranty information.
  14  *
  15  * Machine-independent I/O routines for IEEE FLOATing-point numbers.
  16  *
  17  * NaN's and infinities are converted to HUGE_VAL or HUGE, which
  18  * happens to be infinity on IEEE machines.  Unfortunately, it is
  19  * impossible to preserve NaN's in a machine-independent way.
  20  * Infinities are, however, preserved on IEEE machines.
  21  *
  22  * These routines have been tested on the following machines:
  23  *      Apple Macintosh, MPW 3.1 C compiler
  24  *      Apple Macintosh, THINK C compiler
  25  *      Silicon Graphics IRIS, MIPS compiler
  26  *      Cray X/MP and Y/MP
  27  *      Digital Equipment VAX
  28  *      Sequent Balance (Multiprocesor 386)
  29  *      NeXT
  30  *
  31  *
  32  * Implemented by Malcolm Slaney and Ken Turkowski.
  33  *
  34  * Malcolm Slaney contributions during 1988-1990 include big- and little-
  35  * endian file I/O, conversion to and from Motorola's extended 80-bit
  36  * FLOATing-point format, and conversions to and from IEEE single-
  37  * precision FLOATing-point format.
  38  *
  39  * In 1991, Ken Turkowski implemented the conversions to and from
  40  * IEEE double-precision format, added more precision to the extended
  41  * conversions, and accommodated conversions involving +/- infinity,
  42  * NaN's, and denormalized numbers.
  43  *
  44  * $Id: ieeefloat.c,v 1.1 2003/10/04 00:11:19 herman Exp $
  45  *
  46  * $Log: ieeefloat.c,v $
  47  * Revision 1.1  2003/10/04 00:11:19  herman
  48  * New file from 1.1.7 (not in 1.1.6) added from Rich's automakified src tree.
  49  *
  50  * Revision 1.1  2003/07/29 04:17:52  heroine
  51  * *** empty log message ***
  52  *
  53  * Revision 1.1  1993/06/11  17:45:46  malcolm
  54  * Initial revision
  55  *
  56  */
  57
  58 #include <stdio.h>
  59 #include <math.h>
  60 #include "ieeefloat.h"
  61 #include "common.h"
  62
  63 # define FloatToUnsigned(f)     ((unsigned long)(((long)((f) - 2147483648.0)) + 2147483647L + 1))
  64 # define UnsignedToFloat(u)     (((double)((long)((u) - 2147483647L - 1))) + 2147483648.0)
  65
  66 double ConvertFromIeeeExtended (bytes)
  67      char *bytes;
  68 {
  69   double f;
  70   long expon;
  71   unsigned long hiMant, loMant;
  72
  73   expon = ((bytes[0] & 0x7F) << 8) | (bytes[1] & 0xFF);
  74   hiMant = ((unsigned long) (bytes[2] & 0xFF) << 24)
  75     | ((unsigned long) (bytes[3] & 0xFF) << 16) |
  76     ((unsigned long) (bytes[4] & 0xFF) << 8) |
  77     ((unsigned long) (bytes[5] & 0xFF));
  78   loMant = ((unsigned long) (bytes[6] & 0xFF) << 24)
  79     | ((unsigned long) (bytes[7] & 0xFF) << 16) |
  80     ((unsigned long) (bytes[8] & 0xFF) << 8) |
  81     ((unsigned long) (bytes[9] & 0xFF));
  82
  83   if (expon == 0 && hiMant == 0 && loMant == 0) {
  84     f = 0;
  85   } else {
  86     if (expon == 0x7FFF) {      /* Infinity or NaN */
  87       f = HUGE_VAL;
  88     } else {
  89       expon -= 16383;
  90       f = ldexp (UnsignedToFloat (hiMant), expon -= 31);
  91       f += ldexp (UnsignedToFloat (loMant), expon -= 32);
  92     }
  93   }
  94
  95   if (bytes[0] & 0x80)
  96     return -f;
  97   else
  98     return f;
  99 }