const ( ieee = u32(0xedb88320) castagnoli = u32(0x82f63b78) koopman = u32(0xeb31d82e) )
polynomials
fn new(poly int) &Crc32
pass the polynomial to use
fn sum(b []u8) u32
calculate crc32 using ieee
fn (c &Crc32) checksum(b []u8) u32