CRC32.lua

--!strict
local POLYNOMIAL = 0xEDB88320

local HASH_TABLE = {}

for index = 0, 255 do
	local value = index

	for _ = 1, 8 do
		if value % 2 == 1 then
			value = bit32.bxor(POLYNOMIAL, bit32.rshift(value, 1))
		else
			value = bit32.rshift(value, 1)
		end
	end

	HASH_TABLE[index] = value
end

local function CreateCRC32Hash(value: string): string
	local hash = 0xFFFFFFFF

	for index = 1, #value do
		local character = string.byte(value, index)

		hash = bit32.bxor(HASH_TABLE[bit32.band(bit32.bxor(hash, character), 0xFF)], bit32.rshift(hash, 8))
	end

	return string.format("%08x", bit32.bxor(hash, 0xFFFFFFFF))
end

local function VerifyCRC32Hash(value: string, hash: string): boolean
	return CreateCRC32Hash(value) == hash
end

return {
	hash = CreateCRC32Hash,
	verify = VerifyCRC32Hash,
}