Re: [FUN] Compress number in 2 bytes

[Xmilia Hermit <xmilia.hermit@...>]

How about:

-- compressor.lua
local num_bits = 64

local function Encode(what)
    local tab = {}
    for i = 1, num_bits do
        if what & (1 << (i - 1)) ~= 0 then
            tab[i + 0.5] = true
        end
    end
    for k, v in pairs(tab) do
        tab[k] = nil
    end
    return tab
end

return Encode(...)

-- decompressor.lua
local num_bits = 64

function Decode(tab)
    local num = 0
    for i = 1, num_bits do
        if pcall(next, tab, i + 0.5) then
            num = num | (1 << (i - 1))
        end
    end
    return num
end

return Decode(...)

It is simpler, smaller, uses less memory.

And another one using callbacks via __gc metamethod:

-- compressor.lua
local function Encode(what)
    local tab = {}
    local function gc()
        if not tab.pass then
            setmetatable({}, {__gc = gc})
        else
            tab.res = what
        end
    end
    gc()
    return tab
end

return Encode(...)

-- decompressor.lua
local function ForceGC()
    local gc = false
    setmetatable({}, {__gc = function() gc = true end})
    local mem = {}
    while not gc do
        mem = {mem}
    end
end

local function Decode(tab)
    tab.pass = true
    ForceGC()
    return tab.res
end

return Decode(...)

Regards,
Xmilia