a.c

uint32_t MokaFramer::crc32Step(uint32_t crc, uint8_t byte) {
    crc ^= byte;

    for (uint32_t j = 0; j < 8; j++) {
        uint32_t mask = (uint32_t) -(crc & 1U);
        crc = (crc >> 1) ^ (0xedb88320U & mask);
    }
  
    return crc;
}

a.cr

def crc_step(crc : UInt32, byte : UInt8)
    crc ^= byte

    [0..7].each do |j|
        mask = (crc & 1_u32)
        mask = -1 * mask
        crc = (crc >> 1_u32) ^ (0xedb88320_u32 & mask)
    end

    crc
end