Lua环形缓冲：固定容量的头尾回绕

-- 错误：无限追加，内存只涨不降
logs[#logs + 1] = text

local CAP = 100
local buf, w = {}, 0
local function pushLog(text)
    w = w % CAP + 1
    buf[w] = text
end
local function dumpAll()
    local out = {}
    for i = 1, CAP do
        local v = buf[(w + i - 1) % CAP + 1]
        if v then out[#out + 1] = v end
    end
    return out
end