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<?php
namespace Box\Spout\Reader\XLSX\Helper\SharedStringsCaching;
use Box\Spout\Common\Helper\FileSystemHelper;
use Box\Spout\Common\Helper\GlobalFunctionsHelper;
use Box\Spout\Reader\Exception\SharedStringNotFoundException;
/**
* Class FileBasedStrategy
*
* This class implements the file-based caching strategy for shared strings.
* Shared strings are stored in small files (with a max number of strings per file).
* This strategy is slower than an in-memory strategy but is used to avoid out of memory crashes.
*
* @package Box\Spout\Reader\XLSX\Helper\SharedStringsCaching
*/
class FileBasedStrategy implements CachingStrategyInterface
{
/** Value to use to escape the line feed character ("\n") */
const ESCAPED_LINE_FEED_CHARACTER = '_x000A_';
/** @var \Box\Spout\Common\Helper\GlobalFunctionsHelper Helper to work with global functions */
protected $globalFunctionsHelper;
/** @var \Box\Spout\Common\Helper\FileSystemHelper Helper to perform file system operations */
protected $fileSystemHelper;
/** @var string Temporary folder where the temporary files will be created */
protected $tempFolder;
/**
* @var int Maximum number of strings that can be stored in one temp file
* @see CachingStrategyFactory::MAX_NUM_STRINGS_PER_TEMP_FILE
*/
protected $maxNumStringsPerTempFile;
/** @var resource Pointer to the last temp file a shared string was written to */
protected $tempFilePointer;
/**
* @var string Path of the temporary file whose contents is currently stored in memory
* @see CachingStrategyFactory::MAX_NUM_STRINGS_PER_TEMP_FILE
*/
protected $inMemoryTempFilePath;
/**
* @var array Contents of the temporary file that was last read
* @see CachingStrategyFactory::MAX_NUM_STRINGS_PER_TEMP_FILE
*/
protected $inMemoryTempFileContents;
/**
* @param string|null $tempFolder Temporary folder where the temporary files to store shared strings will be stored
* @param int $maxNumStringsPerTempFile Maximum number of strings that can be stored in one temp file
*/
public function __construct($tempFolder, $maxNumStringsPerTempFile)
{
$rootTempFolder = ($tempFolder) ?: sys_get_temp_dir();
$this->fileSystemHelper = new FileSystemHelper($rootTempFolder);
$this->tempFolder = $this->fileSystemHelper->createFolder($rootTempFolder, uniqid('sharedstrings'));
$this->maxNumStringsPerTempFile = $maxNumStringsPerTempFile;
$this->globalFunctionsHelper = new GlobalFunctionsHelper();
$this->tempFilePointer = null;
}
/**
* Adds the given string to the cache.
*
* @param string $sharedString The string to be added to the cache
* @param int $sharedStringIndex Index of the shared string in the sharedStrings.xml file
* @return void
*/
public function addStringForIndex($sharedString, $sharedStringIndex)
{
$tempFilePath = $this->getSharedStringTempFilePath($sharedStringIndex);
if (!$this->globalFunctionsHelper->file_exists($tempFilePath)) {
if ($this->tempFilePointer) {
$this->globalFunctionsHelper->fclose($this->tempFilePointer);
}
$this->tempFilePointer = $this->globalFunctionsHelper->fopen($tempFilePath, 'w');
}
// The shared string retrieval logic expects each cell data to be on one line only
// Encoding the line feed character allows to preserve this assumption
$lineFeedEncodedSharedString = $this->escapeLineFeed($sharedString);
$this->globalFunctionsHelper->fwrite($this->tempFilePointer, $lineFeedEncodedSharedString . PHP_EOL);
}
/**
* Returns the path for the temp file that should contain the string for the given index
*
* @param int $sharedStringIndex Index of the shared string in the sharedStrings.xml file
* @return string The temp file path for the given index
*/
protected function getSharedStringTempFilePath($sharedStringIndex)
{
$numTempFile = intval($sharedStringIndex / $this->maxNumStringsPerTempFile);
return $this->tempFolder . '/sharedstrings' . $numTempFile;
}
/**
* Closes the cache after the last shared string was added.
* This prevents any additional string from being added to the cache.
*
* @return void
*/
public function closeCache()
{
// close pointer to the last temp file that was written
if ($this->tempFilePointer) {
$this->globalFunctionsHelper->fclose($this->tempFilePointer);
}
}
/**
* Returns the string located at the given index from the cache.
*
* @param int $sharedStringIndex Index of the shared string in the sharedStrings.xml file
* @return string The shared string at the given index
* @throws \Box\Spout\Reader\Exception\SharedStringNotFoundException If no shared string found for the given index
*/
public function getStringAtIndex($sharedStringIndex)
{
$tempFilePath = $this->getSharedStringTempFilePath($sharedStringIndex);
$indexInFile = $sharedStringIndex % $this->maxNumStringsPerTempFile;
if (!$this->globalFunctionsHelper->file_exists($tempFilePath)) {
throw new SharedStringNotFoundException("Shared string temp file not found: $tempFilePath ; for index: $sharedStringIndex");
}
if ($this->inMemoryTempFilePath !== $tempFilePath) {
// free memory
unset($this->inMemoryTempFileContents);
$this->inMemoryTempFileContents = explode(PHP_EOL, $this->globalFunctionsHelper->file_get_contents($tempFilePath));
$this->inMemoryTempFilePath = $tempFilePath;
}
$sharedString = null;
// Using isset here because it is way faster than array_key_exists...
if (isset($this->inMemoryTempFileContents[$indexInFile])) {
$escapedSharedString = $this->inMemoryTempFileContents[$indexInFile];
$sharedString = $this->unescapeLineFeed($escapedSharedString);
}
if ($sharedString === null) {
throw new SharedStringNotFoundException("Shared string not found for index: $sharedStringIndex");
}
return rtrim($sharedString, PHP_EOL);
}
/**
* Escapes the line feed characters (\n)
*
* @param string $unescapedString
* @return string
*/
private function escapeLineFeed($unescapedString)
{
return str_replace("\n", self::ESCAPED_LINE_FEED_CHARACTER, $unescapedString);
}
/**
* Unescapes the line feed characters (\n)
*
* @param string $escapedString
* @return string
*/
private function unescapeLineFeed($escapedString)
{
return str_replace(self::ESCAPED_LINE_FEED_CHARACTER, "\n", $escapedString);
}
/**
* Destroys the cache, freeing memory and removing any created artifacts
*
* @return void
*/
public function clearCache()
{
if ($this->tempFolder) {
$this->fileSystemHelper->deleteFolderRecursively($this->tempFolder);
}
}
}