218 lines
8.3 KiB
Lua
218 lines
8.3 KiB
Lua
--[[
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zip.lua — A zip writer module for LÖVE 2D
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==========================================
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Uses love.math.compress (zlib/DEFLATE) and a pure-Lua CRC-32 table.
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No external dependencies required.
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Requires: LÖVE 11.0+
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Usage:
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local Zip = require("zip")
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local z = Zip.new()
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z:add("level1.lua", love.filesystem.read("level1.lua"))
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z:add("tiles/grass.png", love.filesystem.read("tiles/grass.png"))
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local data = z:build()
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love.filesystem.write("levels.zip", data)
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API:
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Zip.new() → creates a new Zip writer
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zip:add(path, data) → adds a file entry (path uses forward slashes)
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zip:build() → returns the zip file as a string
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]]
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local Zip = {}
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Zip.__index = Zip
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-- ── helpers ──────────────────────────────────────────────────────────────────
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--- Pack bytes into a little-endian binary string.
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local function pack_u16(n)
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return string.char(n % 256, math.floor(n / 256) % 256)
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end
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local function pack_u32(n)
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return string.char(
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n % 256,
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math.floor(n / 256) % 256,
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math.floor(n / 65536) % 256,
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math.floor(n / 16777216) % 256
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)
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end
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-- LuaJIT (used by LOVE) provides the 'bit' library for bitwise operations.
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local bxor = bit.bxor
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local band = bit.band
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local rshift = bit.rshift
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--- CRC-32 lookup table (standard IEEE 802.3 polynomial 0xEDB88320, reflected).
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local _crc_table = (function()
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local t = {}
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for i = 0, 255 do
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local c = i
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for _ = 1, 8 do
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if band(c, 1) == 1 then
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c = bxor(rshift(c, 1), 0xEDB88320)
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else
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c = rshift(c, 1)
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end
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end
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t[i] = c
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end
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return t
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end)()
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--- Compute CRC-32 of a string (LuaJIT / LOVE compatible).
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local function crc32(data)
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local crc = 0xFFFFFFFF
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for i = 1, #data do
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local idx = band(bxor(crc, data:byte(i)), 0xFF)
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crc = bxor(rshift(crc, 8), _crc_table[idx])
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end
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return band(bxor(crc, 0xFFFFFFFF), 0xFFFFFFFF)
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end
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--- Deflate-compress data using love.math.compress.
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--- Returns compressed_string, or nil if compression made it larger.
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local function deflate(data)
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-- "zlib" wraps DEFLATE with a 2-byte header and 4-byte Adler-32 checksum.
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-- For ZIP we need raw DEFLATE, which we get by stripping the zlib envelope.
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-- love.math.compress( rawstring, format, level )
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-- love.data.compress( container, format, rawstring, level )
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local zlib_data = love.data.compress("string", "zlib", data, 6) -- level 6 = default
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-- Strip the 2-byte zlib header and 4-byte Adler-32 trailer
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local raw_deflate = zlib_data:sub(3, -5)
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if #raw_deflate >= #data then
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return nil -- not worth compressing
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end
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return raw_deflate
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end
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--- MS-DOS date/time encoding for the current time.
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local function dos_datetime()
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local t = os.date("*t")
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local date = ((t.year - 1980) * 512) + (t.month * 32) + t.day
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local time = (t.hour * 2048) + (t.min * 32) + math.floor(t.sec / 2)
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return pack_u16(time), pack_u16(date)
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end
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-- ── Zip writer ────────────────────────────────────────────────────────────────
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--- Create a new Zip writer instance.
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function Zip.new()
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return setmetatable({ _entries = {}, _offset = 0 }, Zip)
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end
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--- Add a file to the zip.
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-- @param path string Archive path, e.g. "maps/level1.lua". Use '/' separators.
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-- @param data string Raw file contents.
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function Zip:add(path, data)
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assert(type(path) == "string", "path must be a string")
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assert(type(data) == "string", "data must be a string")
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assert(not path:match("^/"), "path must not start with '/'")
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local crc = crc32(data)
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local original = #data
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local compressed, method
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local deflated = deflate(data)
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if deflated then
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compressed = deflated
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method = 8 -- DEFLATE
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else
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compressed = data
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method = 0 -- Stored
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end
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table.insert(self._entries, {
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path = path,
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data = data, -- uncompressed (kept for the central dir)
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compressed = compressed,
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method = method,
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crc = crc,
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size_orig = original,
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size_comp = #compressed,
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offset = self._offset,
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})
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-- Local file header = 30 bytes + filename length + compressed data length
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self._offset = self._offset + 30 + #path + #compressed
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end
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--- Build and return the full zip file as a binary string.
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function Zip:build()
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local parts = {}
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-- ── Local file headers + data ────────────────────────────────────────────
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for _, e in ipairs(self._entries) do
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local dos_time, dos_date = dos_datetime()
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-- Local file header signature
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parts[#parts+1] = "\x50\x4B\x03\x04" -- PK\3\4
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parts[#parts+1] = "\x14\x00" -- version needed: 2.0
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parts[#parts+1] = "\x00\x00" -- general purpose bit flag
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parts[#parts+1] = pack_u16(e.method)
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parts[#parts+1] = dos_time
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parts[#parts+1] = dos_date
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parts[#parts+1] = pack_u32(e.crc)
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parts[#parts+1] = pack_u32(e.size_comp)
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parts[#parts+1] = pack_u32(e.size_orig)
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parts[#parts+1] = pack_u16(#e.path) -- filename length
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parts[#parts+1] = "\x00\x00" -- extra field length
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parts[#parts+1] = e.path
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parts[#parts+1] = e.compressed
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end
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local central_dir_offset = 0
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for _, p in ipairs(parts) do central_dir_offset = central_dir_offset + #p end
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-- ── Central directory ────────────────────────────────────────────────────
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local central_parts = {}
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for _, e in ipairs(self._entries) do
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local dos_time, dos_date = dos_datetime()
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central_parts[#central_parts+1] = "\x50\x4B\x01\x02" -- PK\1\2
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central_parts[#central_parts+1] = "\x14\x00" -- version made by: 2.0
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central_parts[#central_parts+1] = "\x14\x00" -- version needed: 2.0
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central_parts[#central_parts+1] = "\x00\x00" -- general purpose bit flag
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central_parts[#central_parts+1] = pack_u16(e.method)
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central_parts[#central_parts+1] = dos_time
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central_parts[#central_parts+1] = dos_date
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central_parts[#central_parts+1] = pack_u32(e.crc)
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central_parts[#central_parts+1] = pack_u32(e.size_comp)
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central_parts[#central_parts+1] = pack_u32(e.size_orig)
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central_parts[#central_parts+1] = pack_u16(#e.path) -- filename length
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central_parts[#central_parts+1] = "\x00\x00" -- extra field length
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central_parts[#central_parts+1] = "\x00\x00" -- file comment length
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central_parts[#central_parts+1] = "\x00\x00" -- disk number start
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central_parts[#central_parts+1] = "\x00\x00" -- internal attributes
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central_parts[#central_parts+1] = "\x00\x00\x00\x00" -- external attributes
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central_parts[#central_parts+1] = pack_u32(e.offset) -- offset of local header
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central_parts[#central_parts+1] = e.path
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end
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local central_dir_size = 0
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for _, p in ipairs(central_parts) do central_dir_size = central_dir_size + #p end
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-- ── End of central directory record ─────────────────────────────────────
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local num_entries = #self._entries
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local eocd = table.concat({
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"\x50\x4B\x05\x06", -- PK\5\6 (EOCD signature)
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"\x00\x00", -- disk number
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"\x00\x00", -- disk with central dir start
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pack_u16(num_entries), -- entries on this disk
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pack_u16(num_entries), -- total entries
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pack_u32(central_dir_size), -- central dir size
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pack_u32(central_dir_offset), -- central dir offset
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"\x00\x00", -- comment length
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})
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return table.concat(parts)
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.. table.concat(central_parts)
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.. eocd
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end
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return Zip
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