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local function tochar(code)
return string.char((code >> 8) & 0xFF, code & 0xFF)
end
local function tobyte(s, i)
local h, l = string.byte(s, i, i+1)
return (h << 8) | l
end
local function char(code)
if code <= 0xFFFF then
return tochar(code)
end
code = code - 0x10000
return tochar(0xD800 + (code >> 10))..tochar(0xDC00 + (code & 0x3FF))
end
local m = {}
function m.encode(s)
local r = {}
for _, c in utf8.codes(s, true) do
r[#r+1] = char(c)
end
return table.concat(r)
end
function m.decode(s)
local r = {}
local i = 1
while i < #s do
local code1 = tobyte(s, i)
if code1 >= 0xD800 and code1 < 0xE000 then
i = i + 2
local code2 = tobyte(s, i)
local code = 0x10000 + ((code1 - 0xD800) << 10) + ((code2 - 0xDC00) & 0x3FF)
r[#r+1] = utf8.char(code)
else
r[#r+1] = utf8.char(code1)
end
i = i + 2
end
return table.concat(r)
end
return m
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