i386/gen/isinf.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * Copyright (c) 1987 NeXT, INC.
  24  */
  25
  26 struct words {
  27 #if defined(__BIG_ENDIAN__)
  28         unsigned int hi;
  29         unsigned int lo;
  30 #else
  31         unsigned int lo;
  32         unsigned int hi;
  33 #endif
  34 };
  35
  36 union double_words {
  37         double d;
  38         struct words w;
  39 };
  40
  41 /*
  42  * isinf -- returns 1 if positive IEEE infinity, -1 if negative
  43  *          IEEE infinity, 0 otherwise.
  44  */
  45 int
  46 isinf(d)
  47 double d;
  48 {
  49         union double_words dw;
  50         dw.d = d;
  51         if (dw.w.hi == 0x7ff00000)
  52              return(1);
  53         if (dw.w.hi == 0xfff00000)
  54                 return(-1);
  55         return(0);
  56 }