File FileStorage.php | ICanBoogie/Storage 1.2.x

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<?php

/*
 * This file is part of the ICanBoogie package.
 *
 * (c) Olivier Laviale <olivier.laviale@gmail.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace ICanBoogie\Storage;

/**
 * A storage using the file system.
 */
class FileStorage implements Storage, \ArrayAccess, \IteratorAggregate
{
    use ArrayAccessTrait;

    /**
     * Magic pattern used to recognize automatically serialized values.
     *
     * @var string
     */
    const MAGIC = "VAR\0SLZ\0";

    /**
     * Length of the magic pattern {@link MAGIC}.
     *
     * @var int
     */
    const MAGIC_LENGTH = 8;

    static private $release_after;

    /**
     * Absolute path to the storage directory.
     *
     * @var string
     */
    protected $path;

    /**
     * Constructor.
     *
     * @param string $path Absolute path to the storage directory.
     */
    public function __construct($path)
    {
        $this->path = rtrim($path, DIRECTORY_SEPARATOR) . DIRECTORY_SEPARATOR;

        if (self::$release_after === null)
        {
            self::$release_after = strpos(PHP_OS, 'WIN') === 0 ? false : true;
        }
    }

    /**
     * Normalizes a key into a valid filename.
     *
     * @param string $key
     *
     * @return string
     */
    protected function normalize_key($key)
    {
        return str_replace('/', '--', $key);
    }

    /**
     * Formats a key into an absolute pathname.
     *
     * @param string $key
     *
     * @return string
     */
    protected function format_pathname($key)
    {
        return $this->path . $this->normalize_key($key);
    }

    /**
     * Formats a pathname with a TTL extension.
     *
     * @param string $pathname
     *
     * @return string
     */
    protected function format_pathname_with_ttl($pathname)
    {
        return $pathname . '.ttl';
    }

    /**
     * Serializes a value so that it can be stored.
     *
     * @param mixed $value
     *
     * @return string
     */
    protected function serialize($value)
    {
        #
        # If the value is an array or a string it is serialized and prepended with a magic
        # identifier.
        #

        if (is_array($value) || is_object($value))
        {
            return self::MAGIC . serialize($value);
        }

        return $value;
    }

    /**
     * Unserializes a value retrieved from storage.
     *
     * @param string $value
     *
     * @return mixed
     */
    protected function unserialize($value)
    {
        if (substr($value, 0, self::MAGIC_LENGTH) == self::MAGIC)
        {
            return unserialize(substr($value, self::MAGIC_LENGTH));
        }

        return $value;
    }

    /**
     * @inheritdoc
     *
     * @throws \Exception when a file operation fails.
     */
    public function store($key, $value, $ttl = 0)
    {
        $this->check_writable();

        $pathname = $this->format_pathname($key);
        $ttl_mark = $this->format_pathname_with_ttl($pathname);

        if ($ttl)
        {
            $future = time() + $ttl;

            touch($ttl_mark, $future, $future);
        }
        elseif (file_exists($ttl_mark))
        {
            unlink($ttl_mark);
        }

        if ($value === true)
        {
            touch($pathname);

            return;
        }

        if ($value === false || $value === null)
        {
            $this->eliminate($key);

            return;
        }

        set_error_handler(function() {});

        try
        {
            $this->safe_store($pathname, $this->serialize($value));
        }
        catch (\Exception $e)
        {
            throw $e;
        }
        finally
        {
            restore_error_handler();
        }
    }

    /**
     * Safely store the value.
     *
     * @param $pathname
     * @param $value
     *
     * @throws \Exception if an error occurs.
     */
    private function safe_store($pathname, $value)
    {
        $dir = dirname($pathname);
        $uniqid = uniqid(mt_rand(), true);
        $tmp_pathname = $dir . '/var-' . $uniqid;
        $garbage_pathname = $dir . '/garbage-var-' . $uniqid;

        #
        # We lock the file create/update, but we write the data in a temporary file, which is then
        # renamed once the data is written.
        #

        $fh = fopen($pathname, 'a+');

        if (!$fh)
        {
            throw new \Exception("Unable to open $pathname.");
        }

        if (self::$release_after && !flock($fh, LOCK_EX))
        {
            throw new \Exception("Unable to get to exclusive lock on $pathname.");
        }

        file_put_contents($tmp_pathname, $value);

        #
        # Windows, this is for you
        #
        if (!self::$release_after)
        {
            fclose($fh);
        }

        if (!rename($pathname, $garbage_pathname))
        {
            throw new \Exception("Unable to rename $pathname as $garbage_pathname.");
        }

        if (!rename($tmp_pathname, $pathname))
        {
            throw new \Exception("Unable to rename $tmp_pathname as $pathname.");
        }

        if (!unlink($garbage_pathname))
        {
            throw new \Exception("Unable to delete $garbage_pathname.");
        }

        #
        # Unix, this is for you
        #
        if (self::$release_after)
        {
            flock($fh, LOCK_UN);
            fclose($fh);
        }
    }

    /**
     * @inheritdoc
     *
     * @param mixed $default The value returned if the key does not exists. Defaults to `null`.
     */
    public function retrieve($key, $default = null)
    {
        $this->check_writable();

        $pathname = $this->format_pathname($key);
        $ttl_mark = $this->format_pathname_with_ttl($pathname);

        if (file_exists($ttl_mark) && fileatime($ttl_mark) < time() || !file_exists($pathname))
        {
            return $default;
        }

        return $this->unserialize(file_get_contents($pathname));
    }

    /**
     * @inheritdoc
     */
    public function eliminate($key)
    {
        $pathname = $this->format_pathname($key);

        if (!file_exists($pathname))
        {
            return;
        }

        unlink($pathname);
    }

    /**
     * @inheritdoc
     */
    public function exists($key)
    {
        return file_exists($this->format_pathname($key));
    }

    public function clear()
    {
        throw new \Exception("The method clear() is not implemented");
    }

    /**
     * Returns an iterator for the storage.
     *
     * @return FileStorageIterator
     */
    public function getIterator()
    {
        return new FileStorageIterator(new \DirectoryIterator($this->path));
    }

    /**
     * Returns an iterator for the keys matching a specified regex.
     *
     * @param string $regex
     *
     * @return FileStorageIterator
     */
    public function matching($regex)
    {
        return new FileStorageIterator(new \RegexIterator(new \DirectoryIterator($this->path), $regex));
    }

    private $is_writable;

    /**
     * Checks whether the storage directory is writable.
     *
     * @return bool
     *
     * @throws \Exception when the storage directory is not writable.
     */
    public function check_writable()
    {
        if ($this->is_writable)
        {
            return true;
        }

        $path = $this->path;

        if (!file_exists($path))
        {
            set_error_handler(function() {});
            mkdir($path, 0705, true);
            restore_error_handler();
        }

        if (!is_writable($path))
        {
            throw new \Exception("The directory $path is not writable.");
        }

        return $this->is_writable = true;
    }
}

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