kolibrios-gitea/programs/develop/open watcom/trunk/clib/string/fstrncpy.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
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* Description:  WHEN YOU FIGURE OUT WHAT THIS FILE DOES, PLEASE
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****************************************************************************/


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

#ifdef M_I86

extern char _WCFAR *fast_strncpy( char _WCFAR *, const char _WCFAR *, size_t );

#pragma aux fast_strncpy = \
        0x1e            /* push ds    */\
        0x96            /* xchg si,ax */\
        0x8e 0xd8       /* mov ds,ax  */\
        0x57            /* push di */\
        0xac            /* L1: lodsb */\
        0xaa            /* stosb */\
        0x84 0xc0       /* test al,al */\
        0xe0 0xfa       /* loopne L1 */\
        0x31 0xc0       /* xor ax,ax */\
        0xd1 0xe9       /* shr cx,1 */\
        0xf3 0xab       /* rep stosw */\
        0x11 0xc9       /* adc cx,cx */\
        0xf3 0xaa       /* rep stosb */\
        0x58            /* pop ax */\
        0x1f            /* pop ds */\
        parm caller     [es di] [si ax] [cx]\
        value           [es ax] \
        modify exact    [ax cx si di];
#endif

_WCRTLINK char _WCFAR *_fstrncpy( char _WCFAR *dst, const char _WCFAR *src, size_t len )
    {
#ifdef M_I86
        if( len ) {
            return( fast_strncpy( dst, src, len ) );
        }
        return( dst );
#else
        char _WCFAR *ret;

        ret = dst;
        for(;len; --len ) {
            if( *src == '\0' ) break;
            *dst++ = *src++;
        }
        while( len != 0 ) {
            *dst++ = '\0';      /* pad destination string with null chars */
            --len;
        }
        return( ret );
#endif
    }