Lua CSV解析：带引号转义的状态机

-- 错误：按逗号盲切，引号内逗号被误切
for seg in line:gmatch("[^,]+") do
    fields[#fields + 1] = seg
end

local function parseCSVLine(line)
    local fields, cur = {}, {}
    local inQuote = false
    local i = 1
    while i <= #line do
        local ch = line:sub(i, i)
        if inQuote then
            if ch == '"' then
                if line:sub(i + 1, i + 1) == '"' then
                    cur[#cur + 1] = '"'
                    i = i + 1
                else
                    inQuote = false
                end
            else
                cur[#cur + 1] = ch
            end
        else
            if ch == '"' then
                inQuote = true
            elseif ch == "," then
                fields[#fields + 1] =
                    table.concat(cur)
                cur = {}
            else
                cur[#cur + 1] = ch
            end
        end
        i = i + 1
    end
    fields[#fields + 1] = table.concat(cur)
    return fields
end