ECC Functions

function adler32(input)
    local a = 1
    local b = 0
    for i=1, #input do
        a = (a + input[i]) % 65521
        b = (b + a) % 65521
    end
    return (b * 65536) + a
end

function fletcher32(input)
    local a,b = 0, 0
    for i=1, #input, 2 do
        a = (a + (input[i]*256) + input[i+1]) % 65535
        b = (b + a) % 65535
    end
    return (b * 65536) + a
end

function crc16(input) -- poly = 0x1021 (CRC-16-CCITT)
    local rem = 0
    for i=1, #input do
        rem = bit.bxor(rem, bit.blshift(input[i], 8))
        for j=1, 8 do
            rem = bit.blshift(rem, 1)
            if bit.band(rem, 0x8000) > 0 then
                rem = bit.bxor(rem, 0x1021)
            end
            rem = bit.band(rem, 0xFFFF)
        end
    end
    return rem
end

function crc32(input) -- poly = 0x04C11DB7 (CRC-32)
    local rem = 0
    for i=1, #input do
        rem = bit.bxor(rem, bit.blshift(input[i], 24))
        for j=1, 8 do
            rem = bit.blshift(rem, 1)
            if bit.band(rem, 0x80000000) > 0 then
                rem = bit.bxor(rem, 0x04C11DB7)
            end
            rem = bit.band(rem, 0xFFFFFFFF)
        end
    end
    return rem
end