EOS 合约 hex 字符串与checksum256互转

hex to checksum256

eosio::checksum256 hex_to_checksum256(const std::string& in) {
    eosio::check(in.length() == 64, "checksum size is error");
    std::string hex{"0123456789abcdef"};
    eosio::checksum256 out;
    for (int i = 0; i < 32; i++) {
      auto d1 = hex.find(in[2 * i]);
      auto d2 = hex.find(in[2 * i + 1]);
      eosio::check(d1 != std::string::npos || d2 != std::string::npos,
                  "invalid sha256");

      // checksum256 is composed of little endian int128_t
      reinterpret_cast<char*>(out.data())[i / 16 * 16 + 15 - (i % 16)] =
          (d1 << 4) + d2;
    }
    return out;
}

checksum256 to hex string

static string to_hex(const checksum256 &hashed) {
    // Construct variables
    string result;
    const char *hex_chars = "0123456789abcdef";
    const auto bytes = hashed.extract_as_byte_array();
    // Iterate hash and build result
    for (uint32_t i = 0; i < bytes.size(); ++i) {
        (result += hex_chars[(bytes.at(i) >> 4)]) += hex_chars[(bytes.at(i) & 0x0f)];
    }
    // Return string
    return result;
}

参考

https://github.com/EOSIO/eos/issues/4012