nan_inf.c

来自「开放源码的编译器open watcom 1.6.0版的源代码」· C语言 代码 · 共 57 行

/****************************************************************************
*
*                            Open Watcom Project
*
*    Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved.
*
*  ========================================================================
*
*    This file contains Original Code and/or Modifications of Original
*    Code as defined in and that are subject to the Sybase Open Watcom
*    Public License version 1.0 (the 'License'). You may not use this file
*    except in compliance with the License. BY USING THIS FILE YOU AGREE TO
*    ALL TERMS AND CONDITIONS OF THE LICENSE. A copy of the License is
*    provided with the Original Code and Modifications, and is also
*    available at www.sybase.com/developer/opensource.
*
*    The Original Code and all software distributed under the License are
*    distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
*    EXPRESS OR IMPLIED, AND SYBASE AND ALL CONTRIBUTORS HEREBY DISCLAIM
*    ALL SUCH WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF
*    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR
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*  ========================================================================
*
* Description:  Determine whether value is NaN or infinity.
*
****************************************************************************/


#include "variety.h"
#include <string.h>


int __Nan_Inf( double value, char *buf )
{
    union {
        double          x;
        unsigned short  ui[4];
    } u;
    char    *p;

    u.x = value;
    if( (u.ui[3] & 0x7FF0) == 0x7FF0 ) {    /* NaN or Inf */
        p = buf;
        if( u.ui[3] & 0x8000 )  *p++ = '-';
        if( (u.ui[0] | u.ui[1] | u.ui[2] | (u.ui[3] & 0x000F)) == 0 ) {
            strcpy( p, "inf" );
        } else {
            strcpy( p, "nan" );
        }
        return( 1 );        /* indicate NaN or Inf */
    }
    return( 0 );            /* indicate not a Nan or Inf */
}