ComputerCraft archive format

archive.lua

-- a computercraft archive format
-- by randomdude999

local function get_rel_path(file, prefix)
    local file = fs.combine(file,'') -- make path more correct
    local prefix = fs.combine(prefix, '')
    return fs.combine(file:gsub(prefix, ''), '')
end

local function recurseList(start)
    local function yieldRecurseList(startPath, start)
        local list = fs.list(startPath)
        for _, file in ipairs(list) do
            local path = fs.combine(startPath, file)
            coroutine.yield(path, get_rel_path(path, start), fs.isDir(path))
            if fs.isDir(path) then
                yieldRecurseList(path, start)
            end
        end
    end
    return coroutine.wrap(function() yieldRecurseList(start or "/", start) end)
end

-- Binary file operations
-- Just in case the files contain some weird stuff

local function bin_read(path)
    local f = fs.open(path, 'r')
    local out = f.readAll()
    f.close()
    return out
end

local function bin_write(path, data)
    local f = fs.open(path, 'w')
    f.write(data)
    f.close()
end

-- Escape functions
-- 0x00 is like an escape character
-- 0x00 0x01 is an escaped null (easier to parse than 0x00 0x00)
-- 0x00 0x02 is end of filename, beginning of file
-- 0x00 0x03 is end of file
-- 0x00 0x04 is beginning of file
-- 0x00 0x05 as contents means file is actually directory

local function escape(str)
    return str:gsub("\0", "\0\1")
end

local function unescape(str)
    return str:gsub("\0\1", "\0")
end

local function escape_file(file, str)
    return "\0\4" .. escape(file) .. "\0\2" .. escape(str) .. "\0\3"
end

local function escape_dir(loc)
    return "\0\4" .. escape(loc) .. "\0\2".."\0\5".."\0\3"
end

local function get_files(str)
    local files = {}
    local dirs = {}
    for name, contents in str:gmatch("\0\4(.-)\0\2(.-)\0\3") do
        if contents == "\0\5" then
            dirs[#dirs+1] = name
        else
            files[name] = contents
        end
    end
    for k, v in pairs(files) do
        files[k] = unescape(v)
    end
    table.sort(dirs)
    return files, dirs
end

function pack(dir)
    if not fs.isDir(dir) then
        error("Not a folder", 2)
    end
    local out = escape(fs.getName(dir))
    for path, rel_path, isdir in recurseList(dir) do
        if isdir then
            out = out .. escape_dir(rel_path)
        else
            out = out .. escape_file(rel_path, bin_read(path))
        end
    end
    return out
end

function unpack(str, to_where)
    if not fs.isDir(to_where) then
        error("Target must be directory", 2)
    end
    local name = str:match("^(.-)\0\4")
    local location = fs.combine(to_where, name)
    local files, dirs = get_files(str)
    for _,dir in pairs(dirs) do
        fs.makeDir(fs.combine(location, dir))
    end
    for fname,data in pairs(files) do
        bin_write(fs.combine(location, fname), data)
    end
end