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@sbrl sbrl/JsonStorageBox.php
Last active Aug 23, 2019

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[JsonStorageBox.php]
<?php
/*
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*/
/**
* Represents a key-value data store.
* @license Apache 2.0
*/
class JsonStorageBox {
/**
* The SQLite database connection.
* @var \PDO
*/
private $db;
/**
* A cache of values.
* @var object[]
*/
private $cache = [];
/**
* A cache of prepared SQL statements.
* @var \PDOStatement[]
*/
private $query_cache = [];
/**
* Initialises a new store connection.
* @param string $filename The filename that the store is located in.
*/
function __construct(string $filename) {
$firstrun = !file_exists($filename);
$this->db = new \PDO("sqlite:" . path_resolve($filename, __DIR__)); // HACK: This might not work on some systems, because it depends on the current working directory
$this->db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
if($firstrun) {
$this->query("CREATE TABLE store (key TEXT UNIQUE NOT NULL, value TEXT)");
}
}
/**
* Makes a query against the database.
* @param string $sql The (potentially parametised) query to make.
* @param array $variables Optional. The variables to substitute into the SQL query.
* @return \PDOStatement The result of the query, as a PDOStatement.
*/
private function query(string $sql, array $variables = []) {
// Add to the query cache if it doesn't exist
if(!isset($this->query_cache[$sql]))
$this->query_cache[$sql] = $this->db->prepare($sql);
$this->query_cache[$sql]->execute($variables);
return $this->query_cache[$sql]; // fetchColumn(), fetchAll(), etc. are defined on the statement, not the return value of execute()
}
/**
* Determines if the given key exists in the store or not.
* @param string $key The key to test.
* @return bool Whether the key exists in the store or not.
*/
public function has(string $key) : bool {
if(isset($this->cache[$key]))
return true;
return $this->query(
"SELECT COUNT(key) FROM store WHERE key = :key;",
[ "key" => $key ]
)->fetchColumn() > 0;
}
/**
* Gets a value from the store.
* @param string $key The key value is stored under.
* @return mixed The stored value.
*/
public function get(string $key) {
// If it's not in the cache, insert it
if(!isset($this->cache[$key])) {
$this->cache[$key] = [ "modified" => false, "value" => json_decode($this->query(
"SELECT value FROM store WHERE key = :key;",
[ "key" => $key ]
)->fetchColumn()) ];
}
return $this->cache[$key]["value"];
}
/**
* Sets a value in the data store.
* Note that this does NOT save changes to disk until you close the connection!
* @param string $key The key to set the value of.
* @param mixed $value The value to store.
*/
public function set(string $key, $value) : void {
if(!isset($this->cache[$key])) $this->cache[$key] = [];
$this->cache[$key]["value"] = $value;
$this->cache[$key]["modified"] = true;
}
/**
* Deletes an item from the data store.
* @param string $key The key of the item to delete.
* @return bool Whether it was really deleted or not. Note that if it doesn't exist, then it can't be deleted.
*/
public function delete(string $key) : bool {
// Remove it from the cache
if(isset($this->cache[$key]))
unset($this->cache[$key]);
// Remove it from disk
$this->query(
"DELETE FROM store WHERE key = :key;",
[ "key" => $key ]
)->rowCount() > 0;
}
/**
* Empties the store.
*/
public function clear() : void {
// Empty the cache;
$this->cache = [];
// Empty the disk
$this->query("DELETE FROM store;");
}
/**
* Syncs changes to disk and closes the PDO connection.
*/
public function close() : void {
$this->db->beginTransaction();
foreach($this->cache as $key => $value_data) {
// If it wasn't modified, there's no point in saving it, is there?
if(!$value_data["modified"])
continue;
$this->query(
"INSERT OR REPLACE INTO store(key, value) VALUES(:key, :value)",
[
"key" => $key,
"value" => json_encode($value_data["value"])
]
);
}
$this->db->commit();
$this->db = null;
}
}
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