Lua实现的Base64编码

ZZBase64 = {}local string = stringZZBase64.__code = {            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',            'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',            'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',            'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/',        };ZZBase64.__decode = {}for k,v in pairs(ZZBase64.__code) do    ZZBase64.__decode[string.byte(v,1)] = k - 1endfunction ZZBase64.encode(text)    local len = string.len(text)    local left = len % 3    len = len - left    local res = {}    local index  = 1    for i = 1, len, 3 do        local a = string.byte(text, i )        local b = string.byte(text, i + 1)        local c = string.byte(text, i + 2)        -- num = a<<16 + b<<8 + c        local num = a * 65536 + b * 256 + c         for j = 1, 4 do            --tmp = num >> ((4 -j) * 6)            local tmp = math.floor(num / (2 ^ ((4-j) * 6)))            --curPos = tmp&0x3f            local curPos = tmp % 64 + 1            res[index] = ZZBase64.__code[curPos]            index = index + 1        end    end    if left == 1 then        ZZBase64.__left1(res, index, text, len)    elseif left == 2 then        ZZBase64.__left2(res, index, text, len)            end    return table.concat(res)endfunction ZZBase64.__left2(res, index, text, len)    local num1 = string.byte(text, len + 1)    num1 = num1 * 1024 --lshift 10     local num2 = string.byte(text, len + 2)    num2 = num2 * 4 --lshift 2     local num = num1 + num2       local tmp1 = math.floor(num / 4096) --rShift 12    local curPos = tmp1 % 64 + 1    res[index] = ZZBase64.__code[curPos]        local tmp2 = math.floor(num / 64)    curPos = tmp2 % 64 + 1    res[index + 1] = ZZBase64.__code[curPos]    curPos = num % 64 + 1    res[index + 2] = ZZBase64.__code[curPos]        res[index + 3] = "=" endfunction ZZBase64.__left1(res, index,text, len)    local num = string.byte(text, len + 1)    num = num * 16         tmp = math.floor(num / 64)    local curPos = tmp % 64 + 1    res[index ] = ZZBase64.__code[curPos]        curPos = num % 64 + 1    res[index + 1] = ZZBase64.__code[curPos]        res[index + 2] = "="     res[index + 3] = "=" endfunction ZZBase64.decode(text)    local len = string.len(text)    local left = 0     if string.sub(text, len - 1) == "==" then        left = 2         len = len - 4    elseif string.sub(text, len) == "=" then        left = 1        len = len - 4    end    local res = {}    local index = 1    local decode = ZZBase64.__decode    for i =1, len, 4 do        local a = decode[string.byte(text,i    )]         local b = decode[string.byte(text,i + 1)]         local c = decode[string.byte(text,i + 2)]         local d = decode[string.byte(text,i + 3)]        --num = a<<18 + b<<12 + c<<6 + d        local num = a * 262144 + b * 4096 + c * 64 + d                local e = string.char(num % 256)        num = math.floor(num / 256)        local f = string.char(num % 256)        num = math.floor(num / 256)        res[index ] = string.char(num % 256)        res[index + 1] = f        res[index + 2] = e        index = index + 3    end    if left == 1 then        ZZBase64.__decodeLeft1(res, index, text, len)    elseif left == 2 then        ZZBase64.__decodeLeft2(res, index, text, len)    end    return table.concat(res)endfunction ZZBase64.__decodeLeft1(res, index, text, len)    local decode = ZZBase64.__decode    local a = decode[string.byte(text, len + 1)]     local b = decode[string.byte(text, len + 2)]     local c = decode[string.byte(text, len + 3)]     local num = a * 4096 + b * 64 + c        local num1 = math.floor(num / 1024) % 256    local num2 = math.floor(num / 4) % 256    res[index] = string.char(num1)    res[index + 1] = string.char(num2)endfunction ZZBase64.__decodeLeft2(res, index, text, len)    local decode = ZZBase64.__decode    local a = decode[string.byte(text, len + 1)]     local b = decode[string.byte(text, len + 2)]    local num = a * 64 + b    num = math.floor(num / 16)    res[index] = string.char(num)endfunction ZZBase64.test()    local data = "a\193\207="    local abc = ZZBase64.encode(data)    print(abc)    def = ZZBase64.decode(abc)    if def == data then        print("yes")    endendZZBase64.test()