kolibrios/programs/develop/open watcom/trunk/clib/string/fstrncmp.c

/****************************************************************************
*
*                            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
*    NON-INFRINGEMENT. Please see the License for the specific language
*    governing rights and limitations under the License.
*
*  ========================================================================
*
* Description:  WHEN YOU FIGURE OUT WHAT THIS FILE DOES, PLEASE
*               DESCRIBE IT HERE!
*
****************************************************************************/


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

#ifdef  M_I86

extern int _fast_strncmp( const char _WCFAR *, const char _WCFAR *, size_t );

#pragma aux    _fast_strncmp = \
        0x1e            /* push ds   */ \
        0x96            /* xchg si,ax */\
        0x8e 0xd8       /* mov ds,ax  */\
        0x89 0xfa       /* mov dx,di */ \
        0x30 0xc0       /* xor al,al */ \
        0xf2 0xae       /* repne scasb */ \
        0x89 0xf9       /* mov cx,di */ \
        0x89 0xd7       /* mov di,dx */ \
        0x29 0xf9       /* sub cx,di */ \
        0xf3 0xa6       /* repe cmpsb */ \
        0x74 0x05       /* je L1 */ \
        0x19 0xc9       /* sbb cx,cx */ \
        0x83 0xd9 0xff  /* sbb cx,ffffh */ \
                        /* L1: */ \
        0x1f            /* pop ds */\
        parm caller [si ax] [es di] [cx] \
        value [cx] \
        modify exact [dx ax di cx si];
#endif

/* return <0 if s<t, 0 if s==t, >0 if s>t */

_WCRTLINK int _fstrncmp( const char _WCFAR *s, const char _WCFAR *t, size_t n )
    {
#if defined(M_I86)
        if( n ) {
            return( _fast_strncmp( s, t, n ) );
        }
        return( 0 );
#else
        for(;;) {
            if( n == 0 )     return( 0 );       /* equal */
            if( *s != *t )   return( *s - *t ); /* less than or greater than */
            if( *s == '\0' ) return( 0 );       /* equal */
            ++s;
            ++t;
            --n;
        }
#endif
    }