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<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
/**
* The library file for the file cache store.
*
* This file is part of the file cache store, it contains the API for interacting with an instance of the store.
* This is used as a default cache store within the Cache API. It should never be deleted.
*
* @package cachestore_file
* @category cache
* @copyright 2012 Sam Hemelryk
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
/**
* The file store class.
*
* Configuration options
* path: string: path to the cache directory, if left empty one will be created in the cache directory
* autocreate: true, false
* prescan: true, false
*
* @copyright 2012 Sam Hemelryk
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class cachestore_file extends cache_store implements cache_is_key_aware, cache_is_configurable, cache_is_searchable {
/**
* The name of the store.
* @var string
*/
protected $name;
/**
* The path used to store files for this store and the definition it was initialised with.
* @var string
*/
protected $path = false;
/**
* The path in which definition specific sub directories will be created for caching.
* @var string
*/
protected $filestorepath = false;
/**
* Set to true when a prescan has been performed.
* @var bool
*/
protected $prescan = false;
/**
* Set to true if we should store files within a single directory.
* By default we use a nested structure in order to reduce the chance of conflicts and avoid any file system
* limitations such as maximum files per directory.
* @var bool
*/
protected $singledirectory = false;
/**
* Set to true when the path should be automatically created if it does not yet exist.
* @var bool
*/
protected $autocreate = false;
/**
* Set to true if a custom path is being used.
* @var bool
*/
protected $custompath = false;
/**
* An array of keys we are sure about presently.
* @var array
*/
protected $keys = array();
/**
* True when the store is ready to be initialised.
* @var bool
*/
protected $isready = false;
/**
* The cache definition this instance has been initialised with.
* @var cache_definition
*/
protected $definition;
/**
* A reference to the global $CFG object.
*
* You may be asking yourself why on earth this is here, but there is a good reason.
* By holding onto a reference of the $CFG object we can be absolutely sure that it won't be destroyed before
* we are done with it.
* This makes it possible to use a cache within a destructor method for the purposes of
* delayed writes. Like how the session mechanisms work.
*
* @var stdClass
*/
private $cfg = null;
/**
* Constructs the store instance.
*
* Noting that this function is not an initialisation. It is used to prepare the store for use.
* The store will be initialised when required and will be provided with a cache_definition at that time.
*
* @param string $name
* @param array $configuration
*/
public function __construct($name, array $configuration = array()) {
global $CFG;
if (isset($CFG)) {
// Hold onto a reference of the global $CFG object.
$this->cfg = $CFG;
}
$this->name = $name;
if (array_key_exists('path', $configuration) && $configuration['path'] !== '') {
$this->custompath = true;
$this->autocreate = !empty($configuration['autocreate']);
$path = (string)$configuration['path'];
if (!is_dir($path)) {
if ($this->autocreate) {
if (!make_writable_directory($path, false)) {
$path = false;
debugging('Error trying to autocreate file store path. '.$path, DEBUG_DEVELOPER);
}
} else {
$path = false;
debugging('The given file cache store path does not exist. '.$path, DEBUG_DEVELOPER);
}
}
if ($path !== false && !is_writable($path)) {
$path = false;
debugging('The file cache store path is not writable for `'.$name.'`', DEBUG_DEVELOPER);
}
} else {
$path = make_cache_directory('cachestore_file/'.preg_replace('#[^a-zA-Z0-9\.\-_]+#', '', $name));
}
$this->isready = $path !== false;
$this->filestorepath = $path;
// This will be updated once the store has been initialised for a definition.
$this->path = $path;
// Check if we should prescan the directory.
if (array_key_exists('prescan', $configuration)) {
$this->prescan = (bool)$configuration['prescan'];
} else {
// Default is no, we should not prescan.
$this->prescan = false;
}
// Check if we should be storing in a single directory.
if (array_key_exists('singledirectory', $configuration)) {
$this->singledirectory = (bool)$configuration['singledirectory'];
} else {
// Default: No, we will use multiple directories.
$this->singledirectory = false;
}
}
/**
* Performs any necessary operation when the file store instance has been created.
*/
public function instance_created() {
if ($this->isready && !$this->prescan) {
// It is supposed the store instance to expect an empty folder.
$this->purge_all_definitions();
}
}
/**
* Returns true if this store instance is ready to be used.
* @return bool
*/
public function is_ready() {
return $this->isready;
}
/**
* Returns true once this instance has been initialised.
*
* @return bool
*/
public function is_initialised() {
return true;
}
/**
* Returns the supported features as a combined int.
*
* @param array $configuration
* @return int
*/
public static function get_supported_features(array $configuration = array()) {
$supported = self::SUPPORTS_DATA_GUARANTEE +
self::SUPPORTS_NATIVE_TTL +
self::IS_SEARCHABLE +
self::DEREFERENCES_OBJECTS;
return $supported;
}
/**
* Returns false as this store does not support multiple identifiers.
* (This optional function is a performance optimisation; it must be
* consistent with the value from get_supported_features.)
*
* @return bool False
*/
public function supports_multiple_identifiers() {
return false;
}
/**
* Returns the supported modes as a combined int.
*
* @param array $configuration
* @return int
*/
public static function get_supported_modes(array $configuration = array()) {
return self::MODE_APPLICATION + self::MODE_SESSION;
}
/**
* Returns true if the store requirements are met.
*
* @return bool
*/
public static function are_requirements_met() {
return true;
}
/**
* Returns true if the given mode is supported by this store.
*
* @param int $mode One of cache_store::MODE_*
* @return bool
*/
public static function is_supported_mode($mode) {
return ($mode === self::MODE_APPLICATION || $mode === self::MODE_SESSION);
}
/**
* Initialises the cache.
*
* Once this has been done the cache is all set to be used.
*
* @param cache_definition $definition
*/
public function initialise(cache_definition $definition) {
$this->definition = $definition;
$hash = preg_replace('#[^a-zA-Z0-9]+#', '_', $this->definition->get_id());
$this->path = $this->filestorepath.'/'.$hash;
make_writable_directory($this->path, false);
if ($this->prescan && $definition->get_mode() !== self::MODE_REQUEST) {
$this->prescan = false;
}
if ($this->prescan) {
$this->prescan_keys();
}
}
/**
* Pre-scan the cache to see which keys are present.
*/
protected function prescan_keys() {
$files = glob($this->glob_keys_pattern(), GLOB_MARK | GLOB_NOSORT);
if (is_array($files)) {
foreach ($files as $filename) {
$this->keys[basename($filename)] = filemtime($filename);
}
}
}
/**
* Gets a pattern suitable for use with glob to find all keys in the cache.
*
* @param string $prefix A prefix to use.
* @return string The pattern.
*/
protected function glob_keys_pattern($prefix = '') {
if ($this->singledirectory) {
return $this->path . '/'.$prefix.'*.cache';
} else {
return $this->path . '/*/'.$prefix.'*.cache';
}
}
/**
* Returns the file path to use for the given key.
*
* @param string $key The key to generate a file path for.
* @param bool $create If set to the true the directory structure the key requires will be created.
* @return string The full path to the file that stores a particular cache key.
*/
protected function file_path_for_key($key, $create = false) {
if ($this->singledirectory) {
// Its a single directory, easy, just the store instances path + the file name.
return $this->path . '/' . $key . '.cache';
} else {
// We are using a single subdirectory to achieve 1 level.
// We suffix the subdir so it does not clash with any windows
// reserved filenames like 'con'.
$subdir = substr($key, 0, 3) . '-cache';
$dir = $this->path . '/' . $subdir;
if ($create) {
// Create the directory. This function does it recursivily!
make_writable_directory($dir, false);
}
return $dir . '/' . $key . '.cache';
}
}
/**
* Retrieves an item from the cache store given its key.
*
* @param string $key The key to retrieve
* @return mixed The data that was associated with the key, or false if the key did not exist.
*/
public function get($key) {
$filename = $key.'.cache';
$file = $this->file_path_for_key($key);
$ttl = $this->definition->get_ttl();
$maxtime = 0;
if ($ttl) {
$maxtime = cache::now() - $ttl;
}
$readfile = false;
if ($this->prescan && array_key_exists($filename, $this->keys)) {
if ((!$ttl || $this->keys[$filename] >= $maxtime) && file_exists($file)) {
$readfile = true;
} else {
$this->delete($key);
}
} else if (file_exists($file) && (!$ttl || filemtime($file) >= $maxtime)) {
$readfile = true;
}
if (!$readfile) {
return false;
}
// Open ensuring the file for reading in binary format.
if (!$handle = fopen($file, 'rb')) {
return false;
}
// Lock it up!
// We don't care if this succeeds or not, on some systems it will, on some it won't, meah either way.
flock($handle, LOCK_SH);
$data = '';
// Read the data in 1Mb chunks. Small caches will not loop more than once. We don't use filesize as it may
// be cached with a different value than what we need to read from the file.
do {
$data .= fread($handle, 1048576);
} while (!feof($handle));
// Unlock it.
flock($handle, LOCK_UN);
// Return it unserialised.
return $this->prep_data_after_read($data);
}
/**
* Retrieves several items from the cache store in a single transaction.
*
* If not all of the items are available in the cache then the data value for those that are missing will be set to false.
*
* @param array $keys The array of keys to retrieve
* @return array An array of items from the cache. There will be an item for each key, those that were not in the store will
* be set to false.
*/
public function get_many($keys) {
$result = array();
foreach ($keys as $key) {
$result[$key] = $this->get($key);
}
return $result;
}
/**
* Deletes an item from the cache store.
*
* @param string $key The key to delete.
* @return bool Returns true if the operation was a success, false otherwise.
*/
public function delete($key) {
$filename = $key.'.cache';
$file = $this->file_path_for_key($key);
if (@unlink($file)) {
unset($this->keys[$filename]);
return true;
}
return false;
}
/**
* Deletes several keys from the cache in a single action.
*
* @param array $keys The keys to delete
* @return int The number of items successfully deleted.
*/
public function delete_many(array $keys) {
$count = 0;
foreach ($keys as $key) {
if ($this->delete($key)) {
$count++;
}
}
return $count;
}
/**
* Sets an item in the cache given its key and data value.
*
* @param string $key The key to use.
* @param mixed $data The data to set.
* @return bool True if the operation was a success false otherwise.
*/
public function set($key, $data) {
$this->ensure_path_exists();
$filename = $key.'.cache';
$file = $this->file_path_for_key($key, true);
$result = $this->write_file($file, $this->prep_data_before_save($data));
if (!$result) {
// Couldn't write the file.
return false;
}
// Record the key if required.
if ($this->prescan) {
$this->keys[$filename] = cache::now() + 1;
}
// Return true.. it all worked **miracles**.
return true;
}
/**
* Prepares data to be stored in a file.
*
* @param mixed $data
* @return string
*/
protected function prep_data_before_save($data) {
return serialize($data);
}
/**
* Prepares the data it has been read from the cache. Undoing what was done in prep_data_before_save.
*
* @param string $data
* @return mixed
* @throws coding_exception
*/
protected function prep_data_after_read($data) {
$result = @unserialize($data);
if ($result === false) {
throw new coding_exception('Failed to unserialise data from file. Either failed to read, or failed to write.');
}
return $result;
}
/**
* Sets many items in the cache in a single transaction.
*
* @param array $keyvaluearray An array of key value pairs. Each item in the array will be an associative array with two
* keys, 'key' and 'value'.
* @return int The number of items successfully set. It is up to the developer to check this matches the number of items
* sent ... if they care that is.
*/
public function set_many(array $keyvaluearray) {
$count = 0;
foreach ($keyvaluearray as $pair) {
if ($this->set($pair['key'], $pair['value'])) {
$count++;
}
}
return $count;
}
/**
* Checks if the store has a record for the given key and returns true if so.
*
* @param string $key
* @return bool
*/
public function has($key) {
$filename = $key.'.cache';
$maxtime = cache::now() - $this->definition->get_ttl();
if ($this->prescan) {
return array_key_exists($filename, $this->keys) && $this->keys[$filename] >= $maxtime;
}
$file = $this->file_path_for_key($key);
return (file_exists($file) && ($this->definition->get_ttl() == 0 || filemtime($file) >= $maxtime));
}
/**
* Returns true if the store contains records for all of the given keys.
*
* @param array $keys
* @return bool
*/
public function has_all(array $keys) {
foreach ($keys as $key) {
if (!$this->has($key)) {
return false;
}
}
return true;
}
/**
* Returns true if the store contains records for any of the given keys.
*
* @param array $keys
* @return bool
*/
public function has_any(array $keys) {
foreach ($keys as $key) {
if ($this->has($key)) {
return true;
}
}
return false;
}
/**
* Purges the cache definition deleting all the items within it.
*
* @return boolean True on success. False otherwise.
*/
public function purge() {
if ($this->isready) {
$files = glob($this->glob_keys_pattern(), GLOB_MARK | GLOB_NOSORT);
if (is_array($files)) {
foreach ($files as $filename) {
@unlink($filename);
}
}
$this->keys = array();
}
return true;
}
/**
* Purges all the cache definitions deleting all items within them.
*
* @return boolean True on success. False otherwise.
*/
protected function purge_all_definitions() {
// Warning: limit the deletion to what file store is actually able
// to create using the internal {@link purge()} providing the
// {@link $path} with a wildcard to perform a purge action over all the definitions.
$currpath = $this->path;
$this->path = $this->filestorepath.'/*';
$result = $this->purge();
$this->path = $currpath;
return $result;
}
/**
* Given the data from the add instance form this function creates a configuration array.
*
* @param stdClass $data
* @return array
*/
public static function config_get_configuration_array($data) {
$config = array();
if (isset($data->path)) {
$config['path'] = $data->path;
}
if (isset($data->autocreate)) {
$config['autocreate'] = $data->autocreate;
}
if (isset($data->singledirectory)) {
$config['singledirectory'] = $data->singledirectory;
}
if (isset($data->prescan)) {
$config['prescan'] = $data->prescan;
}
return $config;
}
/**
* Allows the cache store to set its data against the edit form before it is shown to the user.
*
* @param moodleform $editform
* @param array $config
*/
public static function config_set_edit_form_data(moodleform $editform, array $config) {
$data = array();
if (!empty($config['path'])) {
$data['path'] = $config['path'];
}
if (isset($config['autocreate'])) {
$data['autocreate'] = (bool)$config['autocreate'];
}
if (isset($config['singledirectory'])) {
$data['singledirectory'] = (bool)$config['singledirectory'];
}
if (isset($config['prescan'])) {
$data['prescan'] = (bool)$config['prescan'];
}
$editform->set_data($data);
}
/**
* Checks to make sure that the path for the file cache exists.
*
* @return bool
* @throws coding_exception
*/
protected function ensure_path_exists() {
global $CFG;
if (!is_writable($this->path)) {
if ($this->custompath && !$this->autocreate) {
throw new coding_exception('File store path does not exist. It must exist and be writable by the web server.');
}
$createdcfg = false;
if (!isset($CFG)) {
// This can only happen during destruction of objects.
// A cache is being used within a destructor, php is ending a request and $CFG has
// already being cleaned up.
// Rebuild $CFG with directory permissions just to complete this write.
$CFG = $this->cfg;
$createdcfg = true;
}
if (!make_writable_directory($this->path, false)) {
throw new coding_exception('File store path does not exist and can not be created.');
}
if ($createdcfg) {
// We re-created it so we'll clean it up.
unset($CFG);
}
}
return true;
}
/**
* Performs any necessary clean up when the file store instance is being deleted.
*
* 1. Purges the cache directory.
* 2. Deletes the directory we created for the given definition.
*/
public function instance_deleted() {
$this->purge_all_definitions();
@rmdir($this->filestorepath);
}
/**
* Generates an instance of the cache store that can be used for testing.
*
* Returns an instance of the cache store, or false if one cannot be created.
*
* @param cache_definition $definition
* @return cachestore_file
*/
public static function initialise_test_instance(cache_definition $definition) {
$name = 'File test';
$path = make_cache_directory('cachestore_file_test');
$cache = new cachestore_file($name, array('path' => $path));
if ($cache->is_ready()) {
$cache->initialise($definition);
}
return $cache;
}
/**
* Generates the appropriate configuration required for unit testing.
*
* @return array Array of unit test configuration data to be used by initialise().
*/
public static function unit_test_configuration() {
return array();
}
/**
* Writes your madness to a file.
*
* There are several things going on in this function to try to ensure what we don't end up with partial writes etc.
* 1. Files for writing are opened with the mode xb, the file must be created and can not already exist.
* 2. Renaming, data is written to a temporary file, where it can be verified using md5 and is then renamed.
*
* @param string $file Absolute file path
* @param string $content The content to write.
* @return bool
*/
protected function write_file($file, $content) {
// Generate a temp file that is going to be unique. We'll rename it at the end to the desired file name.
// in this way we avoid partial writes.
$path = dirname($file);
while (true) {
$tempfile = $path.'/'.uniqid(sesskey().'.', true) . '.temp';
if (!file_exists($tempfile)) {
break;
}
}
// Open the file with mode=x. This acts to create and open the file for writing only.
// If the file already exists this will return false.
// We also force binary.
$handle = @fopen($tempfile, 'xb+');
if ($handle === false) {
// File already exists... lock already exists, return false.
return false;
}
fwrite($handle, $content);
fflush($handle);
// Close the handle, we're done.
fclose($handle);
if (md5_file($tempfile) !== md5($content)) {
// The md5 of the content of the file must match the md5 of the content given to be written.
@unlink($tempfile);
return false;
}
// Finally rename the temp file to the desired file, returning the true|false result.
$result = rename($tempfile, $file);
@chmod($file, $this->cfg->filepermissions);
if (!$result) {
// Failed to rename, don't leave files lying around.
@unlink($tempfile);
}
return $result;
}
/**
* Returns the name of this instance.
* @return string
*/
public function my_name() {
return $this->name;
}
/**
* Finds all of the keys being used by this cache store instance.
*
* @return array
*/
public function find_all() {
$this->ensure_path_exists();
$files = glob($this->glob_keys_pattern(), GLOB_MARK | GLOB_NOSORT);
$return = array();
if ($files === false) {
return $return;
}
foreach ($files as $file) {
$return[] = substr(basename($file), 0, -6);
}
return $return;
}
/**
* Finds all of the keys whose keys start with the given prefix.
*
* @param string $prefix
*/
public function find_by_prefix($prefix) {
$this->ensure_path_exists();
$prefix = preg_replace('#(\*|\?|\[)#', '[$1]', $prefix);
$files = glob($this->glob_keys_pattern($prefix), GLOB_MARK | GLOB_NOSORT);
$return = array();
if ($files === false) {
return $return;
}
foreach ($files as $file) {
// Trim off ".cache" from the end.
$return[] = substr(basename($file), 0, -6);
}
return $return;
}
}