uncpio.lua

local args = {...}
local file = io.open(args[1], "rb")

local dent = {
    magic = 0,
    dev = 0,
    ino = 0,
    mode = 0,
    uid = 0,
    gid = 0,
    nlink = 0,
    rdev = 0,
    mtime = 0,
    namesize = 0,
    filesize = 0,
}

local function readint(amt, rev)
    local tmp = 0
    for i=(rev and amt) or 1, (rev and 1) or amt, (rev and -1) or 1 do
        tmp = tmp | (file:read(1):byte() << ((i-1)*8))
    end
    return tmp
end

local filesystem = filesystem or require("filesystem")

local function fwrite()
    local dir = dent.name:match("(.+)/.*%.?.+")
    if (dir) then
        filesystem.makeDirectory(os.getenv("PWD").."/"..dir)
    end
    local hand = io.open(dent.name, "w")
    hand:write(file:read(dent.filesize))
    hand:close()
end

while true do
    dent.magic = readint(2)
    local rev = false
    if (dent.magic ~= tonumber("070707", 8)) then rev = true end
    dent.dev = readint(2)
    dent.ino = readint(2)
    dent.mode = readint(2)
    dent.uid = readint(2)
    dent.gid = readint(2)
    dent.nlink = readint(2)
    dent.rdev = readint(2)
    dent.mtime = (readint(2) << 16) | readint(2)
    dent.namesize = readint(2)
    dent.filesize = (readint(2) << 16) | readint(2)
    local name = file:read(dent.namesize):sub(1, dent.namesize-1)
    if (name == "TRAILER!!!") then break end
    --for k, v in pairs(dent) do
    --  print(k, v)
    --end
    dent.name = name
    print(name)
    if (dent.namesize % 2 ~= 0) then
        file:seek("cur", 1)
    end
    if (dent.mode & 32768 ~= 0) then
        fwrite()
    end
    if (dent.filesize % 2 ~= 0) then
        file:seek("cur", 1)
    end
end