memcmp.cxx

eCos1.31版

//===========================================================================
//
//      memcmp.cxx
//
//      ANSI standard memcmp() routine
//
//===========================================================================
//####COPYRIGHTBEGIN####
//                                                                          
// -------------------------------------------                              
// The contents of this file are subject to the Red Hat eCos Public License 
// Version 1.1 (the "License"); you may not use this file except in         
// compliance with the License.  You may obtain a copy of the License at    
// http://www.redhat.com/                                                   
//                                                                          
// Software distributed under the License is distributed on an "AS IS"      
// basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.  See the 
// License for the specific language governing rights and limitations under 
// the License.                                                             
//                                                                          
// The Original Code is eCos - Embedded Configurable Operating System,      
// released September 30, 1998.                                             
//                                                                          
// The Initial Developer of the Original Code is Red Hat.                   
// Portions created by Red Hat are                                          
// Copyright (C) 1998, 1999, 2000 Red Hat, Inc.                             
// All Rights Reserved.                                                     
// -------------------------------------------                              
//                                                                          
//####COPYRIGHTEND####
//===========================================================================
//#####DESCRIPTIONBEGIN####
//
// Author(s):   jlarmour
// Contributors:  jlarmour
// Date:        1998-02-13
// Purpose:     
// Description: 
// Usage:       
//
//####DESCRIPTIONEND####
//
//===========================================================================

// CONFIGURATION

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

// Include the C library?
#ifdef CYGPKG_LIBC     

// 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 "clibincl/stringsupp.hxx" // Useful string function support and
                                   // prototypes


// EXPORTED SYMBOLS

externC int
memcmp( const void *s1, const void *s2, size_t n ) \
    CYGPRI_LIBC_WEAK_ALIAS("_memcmp");

// FUNCTIONS

int
_memcmp( const void *s1, const void *s2, size_t n )
{
    int retval;

    CYG_REPORT_FUNCNAMETYPE( "_memcmp", "returning %d" );
    CYG_REPORT_FUNCARG3( "s1=%08x, s2=%08x, n=%d", s1, s2, n );

    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__)
    const unsigned char *m1 = (const unsigned char *) s1;
    const unsigned char *m2 = (const unsigned char *) s2;
    
    while (n--)
    {
        if (*m1 != *m2)
        {
            retval = *m1 - *m2;
            CYG_REPORT_RETVAL( retval );
            return retval;
        }
        m1++;
        m2++;
    }
    CYG_REPORT_RETVAL( 0 );
    return 0;
#else  
    const unsigned char *m1 = (const unsigned char *) s1;
    const unsigned char *m2 = (const unsigned char *) s2;
    const CYG_WORD *aligned_m1;
    const CYG_WORD *aligned_m2;
    
    // If the size is too small, or either pointer is unaligned,
    // then we punt to the byte compare loop.  Hopefully this will
    // not turn up in inner loops.
    if (CYG_LIBC_STR_OPT_TOO_SMALL(n) || CYG_LIBC_STR_UNALIGNED2(m1,m2))
    {
        while (n--)
        {
            if (*m1 != *m2)
            {
                retval = *m1 - *m2;
                CYG_REPORT_RETVAL( retval );
                return retval;
            }
            m1++;
            m2++;
        }
        CYG_REPORT_RETVAL( 0 );
        return 0;
    }
    
    // Otherwise, load and compare the blocks of memory one 
    // word at a time.
    aligned_m1 = (const CYG_WORD *) m1;
    aligned_m2 = (const CYG_WORD *) m2;
    while (n > CYG_LIBC_STR_OPT_LITTLEBLOCKSIZE)
    {
        if (*aligned_m1 != *aligned_m2) 
        {
            // This block of characters has a mismatch, somewhere.
            // xoring them together and then testing for null would
            // be fastest, but this is clearer code.
            m1 = (const unsigned char *)aligned_m1;
            m2 = (const unsigned char *)aligned_m2;
            while (n--)
            {
                if (*m1 != *m2)
                {
                    retval = *m1 - *m2;
                    CYG_REPORT_RETVAL( retval );
                    return retval;
                }
                m1++;
                m2++;
            }
            // NOT REACHED
        }
        aligned_m1++;
        aligned_m2++;
        n -= CYG_LIBC_STR_OPT_LITTLEBLOCKSIZE;
    }
    
    // checking the last few characters
    
    m1 = (const unsigned char *)aligned_m1;
    m2 = (const unsigned char *)aligned_m2;
    
    while (n--)
    {
        if (*m1 != *m2)
        {
            retval = *m1 - *m2;
            CYG_REPORT_RETVAL( retval );
            return retval;
        }
        m1++;
        m2++;
    }
    
    CYG_REPORT_RETVAL( 0 );
    return 0;
#endif // not defined(CYGIMP_LIBC_STRING_PREFER_SMALL_TO_FAST) ||
       //     defined(__OPTIMIZE_SIZE__)
} // _memcmp()

#endif // CYGPKG_LIBC     

// EOF memcmp.cxx