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