pub fn crc32c_masked(&self, buf: &[u8]) -> u32 {
        let sum = self.crc32c(buf);
        (sum.wrapping_shr(15) | sum.wrapping_shl(17)).wrapping_add(0xA282EAD8)
    }
Returns the "masked" CRC32 checksum of `buf` using the Castagnoli
polynomial. This "masked" checksum is defined by the Snappy frame
format. Masking is supposed to make the checksum robust with respect to
the data that contains the checksum itself.
src/crc32.rs