#!/usr/local/bin/lua51

progname = "sectorize"

if not arg[1] then
	print("usage: " .. progname .. " file")
	os.exit(1)
end

local file = io.open(arg[1], "rb")

if file == nil then
	print(progname .. ": failed to open " .. arg[1])
	os.exit(1)
end

local size = file:seek("end")
file:close(0)

local rem = size % 512

if rem == 0 then
	print(progname .. ": file is already a multiple of 512 bytes")
	os.exit(1)
end

if rem < 512 then
	rem = 512 - rem
end

file = io.open(arg[1], "r+")

if file == nil then
	print(progname .. ": failed to open " .. arg[1])
	os.exit(1)
end

file:seek("set", size)

for i = 1, rem do
	file:write(string.char(0))
end

file:close()