rstrncmp.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 172 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
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*    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR
*    NON-INFRINGEMENT. Please see the License for the specific language
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*  ========================================================================
*
* Description:  WHEN YOU FIGURE OUT WHAT THIS FILE DOES, PLEASE
*               DESCRIBE IT HERE!
*
****************************************************************************/


#include "widechar.h"
#include <string.h>
#include "riscstr.h"


int __F_NAME(strncmp,wcsncmp)( const CHAR_TYPE *s1, const CHAR_TYPE *s2,
                               size_t n )
/**********************************************************************/
{
    RISC_DATA_LOCALREF;
    UINT *           dw1 = ROUND(s1); // round down to dword
    UINT *           dw2 = ROUND(s2);
    UINT             dword1, dword2;
    INT              shr1, shr2, shl1, shl2;
    INT              tmpchar, tmpdword1, tmpdword2;

    #ifdef __WIDECHAR__
        if( OFFSET(s1) % 2  ||  OFFSET(s2) % 2 ) {
            return( __simple_wcsncmp( s1, s2, n ) );
        }
    #endif

    /*** Initialize locals ***/
    shr1 = OFFSET(s1) << 3; // sift right  = offset * 8
    shr2 = OFFSET(s2) << 3;
    shl1 = INT_SIZE - shr1; // shift left = 32 - shift right
    shl2 = INT_SIZE - shr2;

    if (shr1 != 0) {
        dword1 = *dw1++;
    }
    if (shr2 != 0) {
        dword2 = *dw2++;
    }

    /*** Scan in aligned 4-byte groups ***/
    for( ;; ) {
        if( n == 0 )  return( 0 ); // nothing left to compare

        if( shr1 == 0 ) {
            tmpdword1 = *dw1++;
        } else {
            tmpdword1 = dword1 >> shr1;
            dword1 = *dw1++;
            tmpdword1 |= (dword1 << shl1);
        }

        if( shr2 == 0 ) {
            tmpdword2 = *dw2++;
        } else {
            tmpdword2 = dword2 >> shr2;
            dword2 = *dw2++;
            tmpdword2 |= (dword2 << shl2);
        }

        if( n < CHARS_PER_WORD ) {      // some bytes can be set to 00
            tmpdword1 = FRONT_CHRS(tmpdword1,n);
            tmpdword2 = FRONT_CHRS(tmpdword2,n);
            break;
        }

        /*** Did s1 end already? ***/
        if( GOT_NIL(tmpdword1) )  break;
        /*** Are s1 and s2 still the same? ***/
        #ifdef __WIDECHAR__
            if( tmpdword1 != tmpdword2 ) {
                tmpchar = CHR1(tmpdword1) - CHR1(tmpdword2);
                if( tmpchar )  return( tmpchar );

                return( CHR2(tmpdword1) - CHR2(tmpdword2) );
            }
        #else
            if( tmpdword1 != tmpdword2 ) {
                tmpchar = CHR1(tmpdword1) - CHR1(tmpdword2);
                if( tmpchar )  return( tmpchar );

                tmpchar = CHR2(tmpdword1) - CHR2(tmpdword2);
                if( tmpchar )  return( tmpchar );

                tmpchar = CHR3(tmpdword1) - CHR3(tmpdword2);
                if( tmpchar )  return( tmpchar );

                return( CHR4(tmpdword1) - CHR4(tmpdword2) );
            }
        #endif

        n -= CHARS_PER_WORD;
    }


    /*** Scan the last byte(s) in the string ***/
    if( tmpdword1 == tmpdword2 )  return( 0 );

    /* we have a null char somewhere in the last dword */
    #ifdef __WIDECHAR__
        tmpchar = CHR1(tmpdword1);
        if( tmpchar == 0 ) {                            /* 1st char is null */
            return( tmpchar - CHR1(tmpdword2) );
        }

        tmpchar = CHR1(tmpdword1) - CHR1(tmpdword2);    /* 2nd char is null */
        if( tmpchar )  return( tmpchar );
        return( CHR2(tmpdword1) - CHR2(tmpdword2) );
    #else
        tmpchar = CHR1(tmpdword1);
        if( tmpchar == 0 ) {            // first char in the dword is null
            return( tmpchar - CHR1(tmpdword2));
        }

        if( CHR2(tmpdword1) == 0 ) {     // second char in the dword is null
            tmpchar = tmpchar - CHR1(tmpdword2);
            if (tmpchar) return ( tmpchar) ;

            return ( CHR2(tmpdword1) - CHR2(tmpdword2) ) ;
        }

        if( CHR3(tmpdword1) == 0 ) {     // third char in the dword is null
            tmpchar = tmpchar - CHR1(tmpdword2);
            if (tmpchar) return ( tmpchar) ;

            tmpchar = CHR2(tmpdword1) - CHR2(tmpdword2);
            if (tmpchar) return ( tmpchar) ;

            return ( CHR3(tmpdword1) - CHR3(tmpdword2) ) ;
        }

        // 4th char in the dword is null
        tmpchar = tmpchar - CHR1(tmpdword2);
        if (tmpchar) return ( tmpchar );

        tmpchar = CHR2(tmpdword1) - CHR2(tmpdword2);
        if (tmpchar) return ( tmpchar );

        tmpchar = CHR3(tmpdword1) - CHR3(tmpdword2);
        if (tmpchar) return ( tmpchar );

        return ( CHR4(tmpdword1) - CHR4(tmpdword2) );
    #endif
}