app::data_store implementation on GNU/Linux

Redefined classes

redef class DataStore

linux :: data_store $ DataStore

Simple data storage facility

All class definitions

redef class DataStore

linux :: data_store $ DataStore

Simple data storage facility
package_diagram linux::data_store data_store app::data_store data_store linux::data_store->app::data_store xdg_basedir xdg_basedir linux::data_store->xdg_basedir sqlite3 sqlite3 linux::data_store->sqlite3 json json linux::data_store->json app::app_base app_base app::data_store->app::app_base serialization serialization app::data_store->serialization core core xdg_basedir->core sqlite3->core json->serialization parser_base parser_base json->parser_base ...>app::app_base ...serialization ... ...serialization->serialization ...core ... ...core->core ...parser_base ... ...parser_base->parser_base linux::ui ui linux::ui->linux::data_store a_star-m a_star-m a_star-m->linux::ui a_star-m... ... a_star-m...->a_star-m


module abstract_collection

core :: abstract_collection

Abstract collection classes and services.
module abstract_text

core :: abstract_text

Abstract class for manipulation of sequences of characters
module app_base

app :: app_base

Base of the app.nit framework, defines App
module array

core :: array

This module introduces the standard array structure.
module bitset

core :: bitset

Services to handle BitSet
module bytes

core :: bytes

Services for byte streams and arrays
module caching

serialization :: caching

Services for caching serialization engines
module circular_array

core :: circular_array

Efficient data structure to access both end of the sequence.
module codec_base

core :: codec_base

Base for codecs to use with streams
module codecs

core :: codecs

Group module for all codec-related manipulations
module collection

core :: collection

This module define several collection classes.
module core

core :: core

Standard classes and methods used by default by Nit programs and libraries.
module engine_tools

serialization :: engine_tools

Advanced services for serialization engines
module environ

core :: environ

Access to the environment variables of the process
module error

core :: error

Standard error-management infrastructure.
module error

json :: error

Intro JsonParseError which is exposed by all JSON reading APIs
module exec

core :: exec

Invocation and management of operating system sub-processes.
module file

core :: file

File manipulations (create, read, write, etc.)
module fixed_ints

core :: fixed_ints

Basic integers of fixed-precision
module fixed_ints_text

core :: fixed_ints_text

Text services to complement fixed_ints
module flat

core :: flat

All the array-based text representations
module gc

core :: gc

Access to the Nit internal garbage collection mechanism
module hash_collection

core :: hash_collection

Introduce HashMap and HashSet.
module inspect

serialization :: inspect

Refine Serializable::inspect to show more useful information
module iso8859_1

core :: iso8859_1

Codec for ISO8859-1 I/O
module kernel

core :: kernel

Most basic classes and methods.
module list

core :: list

This module handle double linked lists
module math

core :: math

Mathematical operations
module meta

meta :: meta

Simple user-defined meta-level to manipulate types of instances as object.
module native

core :: native

Native structures for text and bytes
module native_sqlite3

sqlite3 :: native_sqlite3

Low-level Sqlite3 features
module numeric

core :: numeric

Advanced services for Numeric types
module parser_base

parser_base :: parser_base

Simple base for hand-made parsers of all kinds
module poset

poset :: poset

Pre order sets and partial order set (ie hierarchies)
module protocol

core :: protocol

module queue

core :: queue

Queuing data structures and wrappers
module range

core :: range

Module for range of discrete objects.
module re

core :: re

Regular expression support for all services based on Pattern
module ropes

core :: ropes

Tree-based representation of a String.
module safe

serialization :: safe

Services for safer deserialization engines
module serialization

serialization :: serialization

General serialization services
module serialization_core

serialization :: serialization_core

Abstract services to serialize Nit objects to different formats
module serialization_read

json :: serialization_read

Services to read JSON: deserialize_json and JsonDeserializer
module serialization_write

json :: serialization_write

Services to write Nit objects to JSON strings: serialize_to_json and JsonSerializer
module sorter

core :: sorter

This module contains classes used to compare things and sorts arrays.
module static

json :: static

Static interface to read Nit objects from JSON strings
module stream

core :: stream

Input and output streams of characters
module text

core :: text

All the classes and methods related to the manipulation of text entities
module time

core :: time

Management of time and dates
module union_find

core :: union_find

union–find algorithm using an efficient disjoint-set data structure
module utf8

core :: utf8

Codec for UTF-8 I/O


module data_store

app :: data_store

Key/value storage services
module json

json :: json

Read and write JSON formatted text using the standard serialization services
module sqlite3

sqlite3 :: sqlite3

Services to manipulate a Sqlite3 database
module xdg_basedir

xdg_basedir :: xdg_basedir

Services for using the XDG Base Directory specification


module ui

linux :: ui

Implementation of the app.nit UI module for GNU/Linux


module a_star-m


# `app::data_store` implementation on GNU/Linux
module data_store

import app::data_store
private import xdg_basedir
import sqlite3
private import json

redef class DataStore

	# File path of the Sqlite3 DB file
	fun db_file: String do return "data_store.db"

	# Sqlite3 table used
	fun db_table: String do return "data_store"

	private var db_cache: nullable Sqlite3DB = null

	# Database to use to implement the `DataStore`
	fun db: nullable Sqlite3DB
		var db = db_cache
		if db != null then return db

		# Find DB path
		var config_home = xdg_basedir.config_home.to_s
		var config_dir = config_home.join_path(sys.program_name.basename)
		if not config_dir.file_exists then config_dir.mkdir
		var db_path = config_dir.join_path(db_file)

		# Open DB connection
		db = new
		if not db.is_open then
			print_error "Data store unavaible, cannot load/save data. (at '{db_path}' with '{db.error or else "unknown"}')"
			return null

		# Create DB table
		db.create_table "IF NOT EXISTS {db_table} (key TEXT PRIMARY KEY, value TEXT)"

		db_cache = db
		return db

	redef fun [](key)
		# Get DB
		var db = self.db
		if db == null then return null

		# Prepare SELECT statement
		var stmt ="* FROM {db_table} WHERE key == {key.to_sql_string}")
		if stmt == null then return null

		# Execute statment
		for row in stmt do
			# Get from statement
			var serialized = row[1].to_s

			# Deserialize
			var deserializer = new JsonDeserializer(serialized)
			var deserialized = deserializer.deserialize

			var errors = deserializer.errors
			if errors.not_empty then
				# An update may have broken the versioning compatibility
				print_error "{class_name} error at deserialization: {errors.join(", ")}"
				return null # Let's be safe

			return deserialized

		return null

	redef fun []=(key, value)
		# Get DB
		var db = self.db
		if db == null then return

		# Serialize
		var stream = new StringWriter
		var serializer = new JsonSerializer(stream)
		serializer.serialize value
		var serialized = stream.to_s

		# Save in DB
		db.execute "BEGIN TRANSACTION"
		db.insert "OR REPLACE INTO {db_table} VALUES({key.to_sql_string}, {serialized.to_sql_string})"
		db.execute "COMMIT"