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uleelx 2015-04-06 21:44:20 +08:00
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/db/*

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# FlatDB FlatDB
A simple NoSQL database written in Lua ===========
FlatDB is a lua library that implements a serverless, zero-configuration, NoSQL database engine.<br>
It provides a key-value storage system using plain Lua tables.
When To Use FlatDB
===========
When you want to use SQLite to store data, just take a glance at FlatDB.<br>
When Lua acts in your program as the major language or the embedded scripting language, just try using FlatDB.
Usage
==========
Copy *flatdb.lua* file to your project or where your lua libraries stored.<br>
Then write this in any Lua file where you want to use it:
```lua
local flatdb = require 'flatdb'
```
1. Bind a directory as a database
```lua
local db = flatdb('./db')
```
2. Open or create a book
```lua
if not db.book then
db.book = {}
end
```
3. Store key-value items
```lua
db.book.key = 'value'
-- equivalent to db.book['key'] = 'value'
```
4. Retrieve items
```lua
print(db.book.key) -- prints 'value'
```
5. Save to file
```lua
db:save()
-- 'book' will be saved to './db/book'
```
More usage can be found in the *cli.lua*(a Redis-like command line interface example using FlatDB).
Quick Look
==========
```lua
local flatdb = require("flatdb")
-- open a directory as a database, 'db' is just a plain empty Lua table that can contain books
local db = flatdb("./db")
-- open or create a book named "default", it also a plain empty Lua table where key-value data stored in
if not db.default then
db.default = {}
end
-- extend db methods for getting values from 'default' book
flatdb.hack.get = function(db, key)
return db.default[key]
end
-- extend db methods for setting values to 'default' book
flatdb.hack.set = function(db, key, value)
db.default[key] = value
end
-- extend db methods for watching new key
flatdb.hack.guard = function(db, f)
setmetatable(db.default, {__newindex = f})
end
-- get key-value data from 'default' book
print(db:get("hello"))
-- set key-value data to 'default' book
db:set("hello", "world")
-- get key-value data from 'default' book
print(db:get("hello"))
-- set guard function
db:guard(function(book, key, value)
print("CREATE KEY permission denied!")
end)
-- try creating new key-value data to 'default' book
db:set("key1", 1)
db:set("key2", 2)
-- update an existing key-value item
db:set("hello", "bye")
print(db:get("key1")) -- prints nil
print(db:get("key2")) -- prints nil
print(db:get("hello")) -- prints 'bye'
-- store 'default' book to './db/default' file
db:save()
```
API
==========
- **Functions**
- **flatdb(dir) --> db**
Bind a directory as a database, returns nil if 'dir' doesn't exists. Otherwise, it returns a 'db' obeject.
- **db:save([book])**
Save all books or the given book(if specified) contained in db to file. The 'book' argument is a string, the book's name.
- **Tables**
- **flatdb.hack**
The 'hack' table contains db's methods. There is only one method 'save(db, book)' in it by default.
It is usually used to extend db methods.
Dependencies
=======
- [pp](https://github.com/luapower/pp)
- [lfs](http://keplerproject.github.io/luafilesystem/)
All above libraries can be found in [LuaPower](https://luapower.com/).
License
=======
FlatDB is distributed under the MIT license.

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local flatdb = require("flatdb")
local pp = require("pp")
local function split(s, sep, maxsplit, plain)
assert(sep and sep ~= "")
maxsplit = maxsplit or 1/0
local items = {}
if #s > 0 then
local init = 1
for i = 1, maxsplit do
local m, n = s:find(sep, init, plain)
if m and m <= n then
table.insert(items, s:sub(init, m - 1))
init = n + 1
else
break
end
end
table.insert(items, s:sub(init))
end
return items
end
local db = assert(flatdb("./db"))
local book = "default"
local function handle(input)
local c = split(input, " ", 2)
local cmd, key, value = string.upper(c[1]), c[2], c[3]
if cmd == "GET" then
print(pp.format(db[book][key]))
elseif cmd == "SET" then
local ok, tmp = pcall(load("return "..tostring(value), "=(load)", "t", db))
db[book][key] = ok and tmp or value
print("OK")
elseif cmd == "SAVE" then
print(db:save(key) and "OK" or "ERROR")
elseif cmd == "TOUCH" then
if not db[key] then
db[key] = {}
end
print("OK")
elseif cmd == "OPEN" then
if db[key] then
book = key
print("OK")
else
print("ERROR")
end
elseif cmd == "INCR" then
if not db[book][key] then
db[book][key] = 0
end
db[book][key] = db[book][key] + 1
print("OK")
elseif cmd == "DECR" then
if not db[book][key] then
db[book][key] = 0
end
db[book][key] = db[book][key] - 1
print("OK")
end
end
local function main()
if not db.default then
db.default = {}
end
io.stdout:setvbuf("no")
while true do
io.write("> ")
local input = io.read("*l")
if string.upper(input) == "EXIT" then
break
end
handle(input)
end
end
main()

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local lfs = require("lfs")
local pp = require("pp")
local function isFile(path)
return lfs.attributes(path, "mode") == "file"
end
local function isDir(path)
return lfs.attributes(path, "mode") == "directory"
end
local function load_book(path)
return dofile(path)
end
local function store_book(path, book)
if type(book) == "table" then
local f = io.open(path, "wb")
if f then
f:write("return ")
f:write(pp.format(book))
f:close()
return true
end
end
return false
end
local pool = {}
local db_funcs = {
save = function(db, bk)
if bk then
if type(bk) == "string" and type(db[bk]) == "table" then
return store_book(pool[db].."/"..bk, db[bk])
else
return false
end
end
for bk, book in pairs(db) do
store_book(pool[db].."/"..bk, book)
end
return true
end
}
local mt = {
__index = function(db, k)
if db_funcs[k] then return db_funcs[k] end
if isFile(pool[db].."/"..k) then
db[k] = load_book(pool[db].."/"..k)
end
return rawget(db, k)
end
}
pool.hack = db_funcs
return setmetatable(pool, {
__mode = "kv",
__call = function(pool, path)
if pool[path] then return pool[path] end
if not isDir(path) then return end
local db = {}
setmetatable(db, mt)
pool[path] = db
pool[db] = path
return db
end
})