Checksum Algorithm

EPD POD1 POD2 POD3 POD4 POD5 POD6 Terminal Reality Home

• Checksum Algorithm
• Compression Algorithm
• Audit Trail
• String Helpers
• Version History
• Related Software

Checksum algorithm in use for EPD/POD2 and up is CRC-32/MPEG-2 available in crcle

poly    : 0x04C11DB7
ref_in  : false
ref_out : false
xor_in  : 0xFFFFFFFF
xor_out : 0

Checksum ranges

/*    checksum */
POD2 : offset=sizeof(ident)+sizeof(checksum) count=sizeof(file  )-offset
POD3 : offset=sizeof(ident)+sizeof(checksum) count=sizeof(header)-offset=280
POD4 : offset=sizeof(ident)+sizeof(checksum) count=sizeof(header)-offset
POD5 : offset=sizeof(ident)+sizeof(checksum) count=sizeof(header)-offset
EPD  : offset=sizeof(header)                 count=sizeof(file  )-offset
/* no checksum */
POD6 : offset=sizeof(header)                 count=sizeof(file  )-offset
POD1 : offset=sizeof(header)=4+80            count=sizeof(file  )-offset

enum section
{
     none   = 0,
     file   = 1,
     header = 2,
     extra  = 3,
     entry  = 4,
     audit  = 5,
};

const std::pair<u32<1>, enum section> range[last] =
{
     { 0u                                                                      , section::none   },
     { sizeof(tr::pod<1>::header)                                              , section::file   },
     { sizeof(tr::pod<2>::header::ident) + sizeof(tr::pod<2>::header::checksum), section::file   },
     { sizeof(tr::pod<3>::header::ident) + sizeof(tr::pod<3>::header::checksum), section::header },
     { sizeof(tr::pod<4>::header::ident) + sizeof(tr::pod<4>::header::checksum), section::header },
     { sizeof(tr::pod<5>::header::ident) + sizeof(tr::pod<5>::header::checksum), section::header },
     { sizeof(tr::pod<6>::header)                                              , section::file   },
     { sizeof(tr::epd::header)                                                 , section::file   },
};

template<enum version version>
constexpr inline size_t section_size(size_t size)
{
     switch(range[version].second)
     {
           case section::entry:
           case section::file:
               return size;
           case section::header:
               return sizeof(tr::pod<version>::header);
           case section::none:
           default:
               return 0;
     }
}

template<enum version version>
constexpr inline size_t section_offset()
{
     switch(range[version].second)
     {
           case section::header:
           case section::file:
               return range[version].first;
           case section::entry:
           case section::none:
           default:
               return 0;
     }
}

template<enum version version>
constexpr inline u32<1> checksum(uint8_t* buf, size_t size)
{
     return crc32::mpeg2::compute(buf + section_offset<version>(), section_size<version>(size) - section_offset<version>());
}