| #include "crc.hpp" |
| |
| namespace host_tool |
| { |
| |
| /* |
| * This implementation tracks the specification given at |
| * http://srecord.sourceforge.net/crc16-ccitt.html |
| * Code copied from internal portable sources. |
| */ |
| std::uint16_t generateCrc(const std::vector<std::uint8_t>& data) |
| { |
| const std::uint16_t kPoly = 0x1021; |
| const std::uint16_t kLeftBit = 0x8000; |
| const int kExtraRounds = 2; |
| const std::uint8_t* bytes = data.data(); |
| std::uint16_t crc = 0xFFFF; |
| std::size_t i; |
| std::size_t j; |
| std::size_t size = data.size(); |
| |
| for (i = 0; i < size + kExtraRounds; ++i) |
| { |
| for (j = 0; j < 8; ++j) |
| { |
| bool xor_flag = (crc & kLeftBit) ? 1 : 0; |
| crc <<= 1; |
| // If this isn't an extra round and the current byte's j'th bit from |
| // the left is set, increment the CRC. |
| if (i < size && (bytes[i] & (1 << (7 - j)))) |
| { |
| crc++; |
| } |
| if (xor_flag) |
| { |
| crc ^= kPoly; |
| } |
| } |
| } |
| |
| return crc; |
| } |
| |
| } // namespace host_tool |