using database as filesystem

DBStorageStream.php

<?php

class DBStorageStream
{	
	const DDL = <<<EOF
CREATE TABLE IF NOT EXISTS `table_dbfs` (
	`path` VARCHAR(255) NOT NULL PRIMARY KEY,
	`data` LONGTEXT,
	`is_dir` CHAR(1) NOT NULL DEFAULT 'N',
	`created_at` DATETIME,
	`updated_at` DATETIME
);
EOF;

	private $pdo;
	private $mode;
	private $path;
	private $row;
	private $posotion = 0;

	public function stream_open($path, $mode, $options, &$opened_path)
	{
		$parsed = parse_url($path);
		$dbinfo = $GLOBALS['__dbfs_' . $parsed['host']];
		if (!isset($dbinfo))
			throw new Exception($parsed['host'] . ' is not mounted');

		$this->pdo = new PDO($dbinfo['dsn'], $dbinfo['username'], $dbinfo['password']);
		$this->mode = $mode;
		$this->path = $parsed['path'];
		if ($mode == 'r') {
			try {
				$sql = "SELECT * FROM `table_dbfs` WHERE `path`=?";
				$stmt = $this->pdo->prepare($sql);
				$stmt->execute(array($this->path));
				$this->row = $stmt->fetch();
				$this->position = 0;
			} catch (PDOException $e) {
				return false;
			}
		}
		return true;
	}
	
	private function create_table()
	{
		$this->pdo->execute(self::DDL);
	}
	
	public function stream_read($count)
	{
		if (!$this->row)
			return false;
		$bytes = substr($this->row['data'], $this->position, $count);
		$this->position += $count;
		return $bytes;
	}
	
	public function stream_write($data)
	{
		if ($this->mode != 'w')
			return 0;
		$sql = "INSERT INTO `table_dbfs` (`path`, `data`, `created_at`, `updated_at`)" .
			"VALUES(?, ?, NOW(), NOW())";
		$stmt = $this->pdo->prepare($sql);
		$stmt->execute(array($this->path, $data));
		return strlen($data);
	}

	public function stream_eof()
	{
		if (null === $this->row)
			return true;
		return ($this->position == sizeof($this->row['data']));
	}

	public function stream_stat()
	{
		$stat = array();

		$stat[0] = $stat['dev'] = 0;
		$stat[1] = $stat['ino'] = 0;
		$stat[2] = $stat['mode'] = 0;
		$stat[3] = $stat['nlink'] = 0;
		$stat[4] = $stat['uid'] = 0;
		$stat[5] = $stat['gid'] = 0;
		$stat[6] = $stat['rdev'] = 0;
		if ($this->row) {
			$stat[7] = $stat['size'] = strlen($this->row['data']);
			$stat[8] = $stat['atime'] = date('U');
			$stat[9] = $stat['mtime'] = $this->row['updated_at'];
			$stat[10] = $stat['ctime'] = $this->row['created_at'];
		}
		$stat[11] = $stat['blksize'] = -1;
		$stat[12] = $stat['blocks'] = -1;
		return $stat;
	}

	public function stream_close()
	{
		// TODO: close pdo handle
		$this->pdo = null;
	}
	
	public function unlink($path)
	{
		$sql = "DELETE FROM `table_dbfs` WHERE `path`=?";
		$stmt = $this->pdo->prepare($sql);
		$rows = $stmt->execute(array($path));
		return ($rows == 1);
	}
	
	public function rename($path_from, $path_to)
	{
		$sql = "UPDATE `table_dbfs` SET `path`=? WHERE `path`=?";
		$stmt = $this->pdo->prepare($sql);
		$rows = $stmt->execute(array($path_to, $path_from));
		return ($rows == 1);
	}
	
	public function mkdir($path, $mode, $options)
	{
		$sql = "INSERT INTO `table_dbfs` (`path`, `is_dir`, `created_at`, `updated_at`) " .
			"VALUES (?, 'Y', NOW(), NOW())";
		$stmt = $this->pdo->prepare($sql);
		$rows = $stmt->execute(array($path));
		return ($row == 1);
	}
	
	public function rmdir($path)
	{
		return $this->unlink($path);
	}
}

function dbfs_mount($local, $path)
{
	$parsed = parse_url($path);
	$GLOBALS['__dbfs_' . $local] = $dbinfo = array(
		'dsn' => $parsed['scheme'] . ':host=' . $parsed['host'] .
			';dbname=' . substr($parsed['path'], 1),
		'username' => $parsed['user'],
		'password' => $parsed['pass']
	);
	
	// check if table exists
	try {
		$fp = fopen('dbfs://' . $local . '/foo', 'r');
		$waste = fread($fp, 1);
		fclose($fp);
	} catch (PDOException $e) {
		if (1146 == $e->getCode()) {	// XXX: mysql only for now
			$pdo = new PDO($dbinfo['dsn'], $dbinfo['username'], $dbinfo['password']);
			$pdo->exec(DBStorageStream::DDL);
			// catch exception again?
		}
	}
}
stream_register_wrapper('dbfs', 'DBStorageStream');
?>

test_dbfs.php

<?php
require_once 'DBStorageStream.php';

dbfs_mount('test', 'mysql://user:pass@localhost/dbfs');

$fp = fopen('dbfs://test/image.jpg', 'w'); 
fwrite($fp, file_get_contents('image.jpg'));
fclose($fp);

$fp = fopen('dbfs://test/image.jpg', 'r'); 
echo fread($fp, 1024);
fclose($fp);
?>