crc.h ソースファイル

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 // 
 // Copyright (c) 2003-2011, MIST Project, Nagoya University
 // All rights reserved.
 // 
 // Redistribution and use in source and binary forms, with or without modification,
 // are permitted provided that the following conditions are met:
 // 
 // 1. Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 // 
 // 2. Redistributions in binary form must reproduce the above copyright notice,
 // this list of conditions and the following disclaimer in the documentation
 // and/or other materials provided with the distribution.
 // 
 // 3. Neither the name of the Nagoya University nor the names of its contributors
 // may be used to endorse or promote products derived from this software
 // without specific prior written permission.
 // 
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
 // IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 // FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 // CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
 // IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 // THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 // 
 
 #ifndef __INCLUDE_CRC__
 #define __INCLUDE_CRC__
 
 #ifndef __INCLUDE_MIST_CONF_H__
 #include "config/mist_conf.h"
 #endif
 
 // mist名前空間の始まり
 _MIST_BEGIN
 
 
 namespace crc_generator_polynominal
 {
 
     template < int BIT > struct crc_default
     {
         _MIST_CONST( size_t, gen_poly, 0 );
     };
 
     template < > struct crc_default< 8 >
     {
         _MIST_CONST( size_t, gen_poly, 0x07 );
     };
 
     template < > struct crc_default< 16 >
     {
         _MIST_CONST( size_t, gen_poly, 0x8005 );
     };
 
     template < > struct crc_default< 32 >
     {
         _MIST_CONST( size_t, gen_poly, 0x04c11db7 );
     };
 }
 
 
 template < int BIT >
 struct crc
 {
 
     static size_t generate( const unsigned char * pdata, size_t len, size_t gen_poly = crc_generator_polynominal::crc_default< BIT >::gen_poly )
     {
         size_t  crc = 0;
         size_t  mask;
         size_t  n, m;
         unsigned char   data;
 
         mask = 1 << ( BIT - 1 );
 
         for( n = 0 ; n < len ; n++ )
         {
             data = pdata[ n ];
 
             for( m = 0 ; m < 8 ; m++ )
             {
                 if( ( crc & mask ) != 0 )
                 {
                     crc <<= 1;
                     crc ^= gen_poly;
                 }
                 else
                 {
                     crc <<= 1;
                 }
 
                 if( ( data & 0x80 ) != 0 )
                 {
                     crc ^= 0x01;
                 }
 
                 data <<= 1;
             }
         }
 
         for( n = 0 ; n < ( BIT >> 3 ) ; n++ )
         {
             for( m = 0 ; m < 8 ; m++ )
             {
                 if( ( crc & mask ) != 0 )
                 {
                     crc <<= 1;
                     crc ^= gen_poly;
                 }
                 else
                 {
                     crc <<= 1;
                 }
             }
         }
 
         return ( crc & ( ( mask << 1 ) - 1 ) );
     }
 
 
     static bool check( const unsigned char * pdata, size_t len, size_t crc_, size_t gen_poly = crc_generator_polynominal::crc_default< BIT >::gen_poly )
     {
         return ( generate( pdata, len, gen_poly ) == crc_ );
     }
 
 
     static size_t generate_implant( unsigned char * pdata, size_t len, size_t gen_poly = crc_generator_polynominal::crc_default< BIT >::gen_poly )
     {
         size_t  crc = 0;
         size_t  mask;
         size_t  n, m;
         unsigned char   data;
 
         mask = 1 << ( BIT - 1 );
 
         for( n = 0 ; n < len - BIT / 8 ; n++ )
         {
             data = pdata[ n ];
 
             for( m = 0 ; m < 8 ; m++ )
             {
                 if( ( crc & mask ) != 0 )
                 {
                     crc <<= 1;
                     crc ^= gen_poly;
                 }
                 else
                 {
                     crc <<= 1;
                 }
 
                 if( ( data & 0x80 ) != 0 )
                 {
                     crc ^= 0x01;
                 }
 
                 data <<= 1;
             }
         }
 
         for( n = 0 ; n < ( BIT >> 3 ) ; n++ )
         {
             for( m = 0 ; m < 8 ; m++ )
             {
                 if( ( crc & mask ) != 0 )
                 {
                     crc <<= 1;
                     crc ^= gen_poly;
                 }
                 else
                 {
                     crc <<= 1;
                 }
             }
         }
 
         // endian 変換．要修正．
         for( n = 0 ; n < ( BIT >> 3 ) ; n++ )
         {
             pdata[ len - ( BIT >> 3 ) + n ] = static_cast< unsigned char >( crc >> ( ( ( BIT >> 3 ) - 1 - n ) << 3 ) ) & 0xff;
         }
 
         return ( crc & ( ( mask << 1 ) - 1 ) );
     }
 
 
     static bool check_implant( const unsigned char * pdata, size_t len, size_t gen_poly = crc_generator_polynominal::crc_default< BIT >::gen_poly )
     {
         return ( generate( pdata, len, gen_poly ) == 0 );
     }
 };
 
 
 // mist名前空間の終わり
 _MIST_END
 
 
 #endif // __INCLUDE_CRC__
 