ZIP module loader for Lua.

zpackage.lua

---
-- ZIP module loader.
--
-- This is a module that contains a custom module loader that
-- loads modules from ZIP files.
--
-- Currently, only pure Lua modules are supported.
--
-- Intended usage:
--
--     local zpackage = require "zpackage"
--
--     -- This also installs the loader.
--     zpackage.addzip("/path/to/file.zip")
--
--     -- `othermod` is assumed to reside either in `othermod.lua` at
--     -- the root of `file.zip`, or in `init.lua` in an `othermod`
--     -- subdirectory inside the ZIP.
--     local othermod = require "othermod"
--
-- @module zpackage
-- @author kaeza <https://github.com/kaeza>

local M = { _NAME=(...) }

-- Lua 5.1/5.3 compat.
local loadstring = loadstring or load

local zip = require "zip"

---
-- Module search path.
--
-- This must be a semicolon-separated list of patterns in
-- the same format as for Lua's `package.path`.
--
-- Each resulting path is looked for in each ZIP file in turn.
-- If the resulting file can be opened, it tries to load it
-- as a Lua
--
-- Default value is `?.lua;?/init.lua`.
M.path = "?.lua;?/init.lua"

local zipfiles = { }
local zipfilesknown = { }

local strfind, strsub = string.find, string.sub
local function split(str, sep)
	local pos, endp = 1, #str+1
	local t, n = { }, 0
	repeat
		local sp, ep = strfind(str, sep, pos, true)
		n = n + 1
		t[n] = strsub(str, pos, sp and sp-1)
		pos = ep and ep+1
	until (not pos) or pos >= endp
	return t
end

local function tryone(zf, paths)
	for _, path in ipairs(paths) do
		local f = zf:open(path)
		if f then
			local data = f:read("*a")
			f:close()
			if data then
				return assert(loadstring(data))
			end
		end
	end
end

local function loader(name)
	if not M.path then return end
	local paths = split(M.path, ";")
	local ename = name:gsub("%%", "%%%%")
	for i, path in ipairs(paths) do
		paths[i] = path:gsub("%?", ename)
	end
	for _, file in ipairs(zipfiles) do
		local zf, err = zip.open(file)
		if zf then
			local m = tryone(zf, paths)
			zf:close()
			if m ~= nil then
				return m
			end
		end
	end
end

local installed

---
-- Add a ZIP file to the search path.
--
-- @tparam string filename  Path to the ZIP file.
-- @tparam ?boolean first  Add to the head of the list (to be
--  searched before others). Default is false.
function M.addzip(filename, first)
	if not installed then
		installed = true
		package.loaders[#package.loaders+1] = loader
	end
	if not zipfilesknown[filename] then
		if first then
			table.insert(zipfiles, 1, filename)
		else
			zipfiles[#zipfiles+1] = filename
		end
		zipfilesknown[filename] = #zipfiles
	end
end

---
-- Remove a ZIP file from the search path.
--
-- @tparam string filename  Path to the ZIP file.
function M.removezip(filename)
	if zipfilesknown[filename] then
		table.remove(zipfiles, zipfilesknown[filename])
		zipfilesknown[filename] = nil
	end
end

return M