strncmp.cxx

eCos操作系统源码

//===========================================================================
//
//      strncmp.cxx
//
//      ANSI standard strncmp() routine
//
//===========================================================================
//####ECOSGPLCOPYRIGHTBEGIN####
// -------------------------------------------
// This file is part of eCos, the Embedded Configurable Operating System.
// Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.
//
// eCos is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
// Software Foundation; either version 2 or (at your option) any later version.
//
// eCos is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// for more details.
//
// You should have received a copy of the GNU General Public License along
// with eCos; if not, write to the Free Software Foundation, Inc.,
// 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
//
// As a special exception, if other files instantiate templates or use macros
// or inline functions from this file, or you compile this file and link it
// with other works to produce a work based on this file, this file does not
// by itself cause the resulting work to be covered by the GNU General Public
// License. However the source code for this file must still be made available
// in accordance with section (3) of the GNU General Public License.
//
// This exception does not invalidate any other reasons why a work based on
// this file might be covered by the GNU General Public License.
//
// Alternative licenses for eCos may be arranged by contacting Red Hat, Inc.
// at http://sources.redhat.com/ecos/ecos-license/
// -------------------------------------------
//####ECOSGPLCOPYRIGHTEND####
//===========================================================================
//#####DESCRIPTIONBEGIN####
//
// Author(s):    jlarmour
// Contributors: 
// Date:         2000-04-14
// Purpose:     
// Description: 
// Usage:       
//
//####DESCRIPTIONEND####
//
//===========================================================================

// CONFIGURATION

#include <pkgconf/libc_string.h>   // Configuration header

// INCLUDES

#include <cyg/infra/cyg_type.h>    // Common type definitions
#include <cyg/infra/cyg_trac.h>    // Tracing support
#include <cyg/infra/cyg_ass.h>     // Assertion support
#include <string.h>                // Header for this file
#include <stddef.h>         // Compiler definitions such as size_t, NULL etc.
#include <cyg/libc/string/stringsupp.hxx> // Useful string function support and
                                          // prototypes

// EXPORTED SYMBOLS

externC int 
strncmp( const char *s1, const char *s2, size_t n ) \
    CYGBLD_ATTRIB_WEAK_ALIAS(__strncmp);

// FUNCTIONS

int 
__strncmp( const char *s1, const char *s2, size_t n )
{
    int retval;

    CYG_REPORT_FUNCNAMETYPE( "__strncmp", "returning %d" );
    CYG_REPORT_FUNCARG3( "s1=%08x, s2=%08x, n=%d", s1, s2, n );
    
    if (n == 0)
    {
        CYG_REPORT_RETVAL( 0 );
        return 0;
    }

    CYG_CHECK_DATA_PTR( s1, "s1 is not a valid pointer!" );
    CYG_CHECK_DATA_PTR( s2, "s2 is not a valid pointer!" );

#if defined(CYGIMP_LIBC_STRING_PREFER_SMALL_TO_FAST) || defined(__OPTIMIZE_SIZE__)
    while (n-- != 0 && *s1 == *s2)
    {
        if (n == 0 || *s1 == '\0' || *s2 == '\0')
            break;
        s1++;
        s2++;
    }
    
    retval = (*(unsigned char *) s1) - (*(unsigned char *) s2);

    CYG_REPORT_RETVAL( retval );

    return retval;
#else
    const CYG_WORD *aligned_s1;
    const CYG_WORD *aligned_s2;
    
    // If s1 or s2 are unaligned, then compare bytes.
    if (CYG_LIBC_STR_UNALIGNED2 (s1, s2))
    {  
        while (n-- != 0 && *s1 == *s2)
        {
            // If we've run out of bytes or hit a null, return zero
            // since we already know *s1 == *s2.
            if (n == 0 || *s1 == '\0')
                return 0;
            s1++;
            s2++;
        }
        retval = (*(unsigned char *) s1) - (*(unsigned char *) s2);

        CYG_REPORT_RETVAL( retval );

        return retval;
    } //if
    
    // If s1 and s2 are word-aligned, compare them a word at a time.
    aligned_s1 = (const CYG_WORD *)s1;
    aligned_s2 = (const CYG_WORD *)s2;
    while (n >= sizeof(CYG_WORD) && *aligned_s1 == *aligned_s2)
    {
        n -= sizeof (CYG_WORD);
        
        // If we've run out of bytes or hit a null, return zero
        // since we already know *aligned_s1 == *aligned_s2.
        if (n == 0 || CYG_LIBC_STR_DETECTNULL (*aligned_s1))
        {
            CYG_REPORT_RETVAL( 0 );
            return 0;
        } // if
        
        aligned_s1++;
        aligned_s2++;
    } // while
    
    // A difference was detected in last few bytes of s1, so search bytewise
    s1 = (const char *)aligned_s1;
    s2 = (const char *)aligned_s2;
    
    while (n-- > 0 && *s1 == *s2)
    {
        // If we've run out of bytes or hit a null, return zero
        // since we already know *s1 == *s2.
        if (n == 0 || *s1 == '\0')
        {
            CYG_REPORT_RETVAL( 0 );
            return 0;
        } // if
        s1++;
        s2++;
    } // while

    retval = (*(unsigned char *) s1) - (*(unsigned char *) s2);

    CYG_REPORT_RETVAL( retval );
    
    return retval;

#endif // not defined(CYGIMP_LIBC_STRING_PREFER_SMALL_TO_FAST) ||
       //     defined(__OPTIMIZE_SIZE__)
} // __strncmp()

// EOF strncmp.cxx