模块:Unicode2Utf8

---

-- unicode_to_utf8
local p = {}
function p.decode(convertStr)

    if type(convertStr)~="string" then
        return convertStr
    end

    local bit = require("bit")
    local resultStr=""
    local i=1
    while true do
        
        local num1=string.byte(convertStr,i)
        local unicode
        
        if num1~=nil and string.sub(convertStr,i,i+1)=="\\u" then
            unicode=tonumber("0x"..string.sub(convertStr,i+2,i+5))
            i=i+6
        elseif num1~=nil then
            unicode=num1
            i=i+1
        else
            break
        end

        if unicode <= 0x007f then
            resultStr=resultStr..string.char(bit.band(unicode,0x7f))
        elseif unicode >= 0x0080 and unicode <= 0x07ff then
            resultStr=resultStr..string.char(bit.bor(0xc0,bit.band(bit.rshift(unicode,6),0x1f)))
            resultStr=resultStr..string.char(bit.bor(0x80,bit.band(unicode,0x3f)))
        elseif unicode >= 0x0800 and unicode <= 0xffff then
            resultStr=resultStr..string.char(bit.bor(0xe0,bit.band(bit.rshift(unicode,12),0x0f)))
            resultStr=resultStr..string.char(bit.bor(0x80,bit.band(bit.rshift(unicode,6),0x3f)))
            resultStr=resultStr..string.char(bit.bor(0x80,bit.band(unicode,0x3f)))
        end
    end
    resultStr=resultStr..'\0'
    return resultStr
end