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README.md
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README.md
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# FlatDB
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A simple NoSQL database written in Lua
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FlatDB
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===========
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FlatDB is a lua library that implements a serverless, zero-configuration, NoSQL database engine.<br>
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It provides a key-value storage system using plain Lua tables.
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When To Use FlatDB
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===========
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When you want to use SQLite to store data, just take a glance at FlatDB.<br>
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When Lua acts in your program as the major language or the embedded scripting language, just try using FlatDB.
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Usage
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==========
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Copy *flatdb.lua* file to your project or where your lua libraries stored.<br>
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Then write this in any Lua file where you want to use it:
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```lua
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local flatdb = require 'flatdb'
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```
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1. Bind a directory as a database
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```lua
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local db = flatdb('./db')
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```
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2. Open or create a book
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```lua
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if not db.book then
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db.book = {}
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end
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```
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3. Store key-value items
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```lua
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db.book.key = 'value'
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-- equivalent to db.book['key'] = 'value'
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```
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4. Retrieve items
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```lua
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print(db.book.key) -- prints 'value'
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```
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5. Save to file
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```lua
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db:save()
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-- 'book' will be saved to './db/book'
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```
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More usage can be found in the *cli.lua*(a Redis-like command line interface example using FlatDB).
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Quick Look
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==========
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```lua
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local flatdb = require("flatdb")
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-- open a directory as a database, 'db' is just a plain empty Lua table that can contain books
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local db = flatdb("./db")
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-- open or create a book named "default", it also a plain empty Lua table where key-value data stored in
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if not db.default then
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db.default = {}
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end
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-- extend db methods for getting values from 'default' book
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flatdb.hack.get = function(db, key)
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return db.default[key]
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end
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-- extend db methods for setting values to 'default' book
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flatdb.hack.set = function(db, key, value)
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db.default[key] = value
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end
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-- extend db methods for watching new key
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flatdb.hack.guard = function(db, f)
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setmetatable(db.default, {__newindex = f})
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end
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-- get key-value data from 'default' book
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print(db:get("hello"))
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-- set key-value data to 'default' book
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db:set("hello", "world")
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-- get key-value data from 'default' book
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print(db:get("hello"))
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-- set guard function
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db:guard(function(book, key, value)
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print("CREATE KEY permission denied!")
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end)
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-- try creating new key-value data to 'default' book
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db:set("key1", 1)
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db:set("key2", 2)
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-- update an existing key-value item
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db:set("hello", "bye")
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print(db:get("key1")) -- prints nil
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print(db:get("key2")) -- prints nil
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print(db:get("hello")) -- prints 'bye'
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-- store 'default' book to './db/default' file
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db:save()
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```
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API
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==========
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- **Functions**
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- **flatdb(dir) --> db**
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Bind a directory as a database, returns nil if 'dir' doesn't exists. Otherwise, it returns a 'db' obeject.
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- **db:save([book])**
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Save all books or the given book(if specified) contained in db to file. The 'book' argument is a string, the book's name.
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- **Tables**
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- **flatdb.hack**
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The 'hack' table contains db's methods. There is only one method 'save(db, book)' in it by default.
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It is usually used to extend db methods.
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Dependencies
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=======
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- [pp](https://github.com/luapower/pp)
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- [lfs](http://keplerproject.github.io/luafilesystem/)
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All above libraries can be found in [LuaPower](https://luapower.com/).
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License
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=======
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FlatDB is distributed under the MIT license.
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80
cli.lua
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80
cli.lua
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local flatdb = require("flatdb")
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local pp = require("pp")
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local function split(s, sep, maxsplit, plain)
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assert(sep and sep ~= "")
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maxsplit = maxsplit or 1/0
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local items = {}
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if #s > 0 then
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local init = 1
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for i = 1, maxsplit do
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local m, n = s:find(sep, init, plain)
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if m and m <= n then
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table.insert(items, s:sub(init, m - 1))
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init = n + 1
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else
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break
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end
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end
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table.insert(items, s:sub(init))
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end
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return items
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end
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local db = assert(flatdb("./db"))
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local book = "default"
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local function handle(input)
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local c = split(input, " ", 2)
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local cmd, key, value = string.upper(c[1]), c[2], c[3]
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if cmd == "GET" then
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print(pp.format(db[book][key]))
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elseif cmd == "SET" then
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local ok, tmp = pcall(load("return "..tostring(value), "=(load)", "t", db))
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db[book][key] = ok and tmp or value
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print("OK")
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elseif cmd == "SAVE" then
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print(db:save(key) and "OK" or "ERROR")
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elseif cmd == "TOUCH" then
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if not db[key] then
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db[key] = {}
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end
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print("OK")
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elseif cmd == "OPEN" then
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if db[key] then
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book = key
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print("OK")
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else
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print("ERROR")
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end
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elseif cmd == "INCR" then
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if not db[book][key] then
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db[book][key] = 0
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end
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db[book][key] = db[book][key] + 1
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print("OK")
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elseif cmd == "DECR" then
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if not db[book][key] then
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db[book][key] = 0
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end
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db[book][key] = db[book][key] - 1
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print("OK")
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end
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end
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local function main()
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if not db.default then
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db.default = {}
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end
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io.stdout:setvbuf("no")
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while true do
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io.write("> ")
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local input = io.read("*l")
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if string.upper(input) == "EXIT" then
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break
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end
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handle(input)
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end
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end
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main()
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70
flatdb.lua
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70
flatdb.lua
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local lfs = require("lfs")
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local pp = require("pp")
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local function isFile(path)
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return lfs.attributes(path, "mode") == "file"
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end
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local function isDir(path)
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return lfs.attributes(path, "mode") == "directory"
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end
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local function load_book(path)
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return dofile(path)
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end
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local function store_book(path, book)
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if type(book) == "table" then
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local f = io.open(path, "wb")
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if f then
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f:write("return ")
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f:write(pp.format(book))
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f:close()
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return true
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end
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end
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return false
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end
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local pool = {}
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local db_funcs = {
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save = function(db, bk)
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if bk then
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if type(bk) == "string" and type(db[bk]) == "table" then
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return store_book(pool[db].."/"..bk, db[bk])
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else
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return false
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end
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end
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for bk, book in pairs(db) do
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store_book(pool[db].."/"..bk, book)
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end
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return true
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end
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}
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local mt = {
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__index = function(db, k)
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if db_funcs[k] then return db_funcs[k] end
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if isFile(pool[db].."/"..k) then
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db[k] = load_book(pool[db].."/"..k)
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end
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return rawget(db, k)
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end
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}
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pool.hack = db_funcs
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return setmetatable(pool, {
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__mode = "kv",
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__call = function(pool, path)
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if pool[path] then return pool[path] end
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if not isDir(path) then return end
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local db = {}
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setmetatable(db, mt)
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pool[path] = db
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pool[db] = path
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return db
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end
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})
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