bundle_loader.lua

-- bundle loader module: runs when a bundled executable starts.
-- also runs when a new luastate is created (see bundle_luastate).
-- returns a "main" function which is called with the args from cmdline.
-- Written by Cosmin Apreutesei. Public domain.

local ffi = require'ffi'

return function(...)

	local function S(s)
		return ffi.abi'win' and s:gsub('/', '\\') or s
	end

	--remove current directory and luapower's dir (../..) from search paths.
	--keep only $exedir/lua and $exedir/clib.
	local function strip(s)
		return s
			:gsub(S'^%./[^;]+;', '') --remove current dir
			:gsub(S';[^;]-/%.%./%.%.[^;]+', '') --remove luapower dir
	end
	package.path = strip(package.path)
	package.cpath = strip(package.cpath)

	local rel_path
	if ffi.os == 'Windows' then
		function rel_path(s)
			return not s:find'^[A-Z]%:' and not s:find'^[\\/]'
		end
	else
		function rel_path(s)
			return not s:find'^/'
		end
	end

	local exedir = require'package.exedir'
	local so_ext = package.cpath:match'%.([%w]+);'

	local function in_exe_dir(name)
		if rel_path(name) then
			local filename = name:find('%.'..so_ext..'$') and name or name..'.'..so_ext
			local filepath = exedir..'/'..filename
			local f = io.open(filepath, 'rb')
			if f then
				f:close()
				return true
			end
		end
		return false
	end

	local libs_str = require'bundle_libs'
	local libs = {}
	for lib in libs_str:gmatch'[^%s]+' do
		libs[lib] = true
	end

	--overload ffi.load to fallback to ffi.C for bundled libs.
	local ffi_load = ffi.load
	function ffi.load(name, ...)
		local ok, C = xpcall(ffi_load, debug.traceback, name, ...)
		if not ok then
			if libs[name] then
				return ffi.C
			else
				error(C, 2)
			end
		elseif libs[name] and not in_exe_dir(name) then
			--prevent loading bundled libs from system paths
			return ffi.C
		else
			return C
		end
	end

	--check if we have a main module, as set by bundle.c:bundle_main().
	local m = arg[-1]
	if not m then
		return true --no module specified: fallback to luajit frontend
	end

	--find a module in package.loaders, like require() does.
	local function find_module(name)
		for _, loader in ipairs(package.loaders) do
			local chunk = loader(name)
			if type(chunk) == 'function' then
				return chunk
			end
		end
	end

	--find the main module
	m = find_module(m)
	if not m then
		return true --module not found: fallback to luajit frontend
	end

	--run the main module, passing it all the command-line args.
	m(...)
end