1 files changed, 616 insertions, 0 deletions
diff --git a/lib/private/Preview/Generator.php b/lib/private/Preview/Generator.php
new file mode 100644
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+++ b/lib/private/Preview/Generator.php
@@ -0,0 +1,616 @@
+<?php
+
+/**
+ * SPDX-FileCopyrightText: 2016 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+namespace OC\Preview;
+
+use OCP\EventDispatcher\IEventDispatcher;
+use OCP\Files\File;
+use OCP\Files\IAppData;
+use OCP\Files\InvalidPathException;
+use OCP\Files\NotFoundException;
+use OCP\Files\NotPermittedException;
+use OCP\Files\SimpleFS\InMemoryFile;
+use OCP\Files\SimpleFS\ISimpleFile;
+use OCP\Files\SimpleFS\ISimpleFolder;
+use OCP\IConfig;
+use OCP\IImage;
+use OCP\IPreview;
+use OCP\IStreamImage;
+use OCP\Preview\BeforePreviewFetchedEvent;
+use OCP\Preview\IProviderV2;
+use OCP\Preview\IVersionedPreviewFile;
+use Psr\Log\LoggerInterface;
+
+class Generator {
+	public const SEMAPHORE_ID_ALL = 0x0a11;
+	public const SEMAPHORE_ID_NEW = 0x07ea;
+
+	public function __construct(
+		private IConfig $config,
+		private IPreview $previewManager,
+		private IAppData $appData,
+		private GeneratorHelper $helper,
+		private IEventDispatcher $eventDispatcher,
+		private LoggerInterface $logger,
+	) {
+	}
+
+	/**
+	 * Returns a preview of a file
+	 *
+	 * The cache is searched first and if nothing usable was found then a preview is
+	 * generated by one of the providers
+	 *
+	 * @return ISimpleFile
+	 * @throws NotFoundException
+	 * @throws \InvalidArgumentException if the preview would be invalid (in case the original image is invalid)
+	 */
+	public function getPreview(
+		File $file,
+		int $width = -1,
+		int $height = -1,
+		bool $crop = false,
+		string $mode = IPreview::MODE_FILL,
+		?string $mimeType = null,
+		bool $cacheResult = true,
+	): ISimpleFile {
+		$specification = [
+			'width' => $width,
+			'height' => $height,
+			'crop' => $crop,
+			'mode' => $mode,
+		];
+
+		$this->eventDispatcher->dispatchTyped(new BeforePreviewFetchedEvent(
+			$file,
+			$width,
+			$height,
+			$crop,
+			$mode,
+			$mimeType,
+		));
+
+		$this->logger->debug('Requesting preview for {path} with width={width}, height={height}, crop={crop}, mode={mode}, mimeType={mimeType}', [
+			'path' => $file->getPath(),
+			'width' => $width,
+			'height' => $height,
+			'crop' => $crop,
+			'mode' => $mode,
+			'mimeType' => $mimeType,
+		]);
+
+
+		// since we only ask for one preview, and the generate method return the last one it created, it returns the one we want
+		return $this->generatePreviews($file, [$specification], $mimeType, $cacheResult);
+	}
+
+	/**
+	 * Generates previews of a file
+	 *
+	 * @throws NotFoundException
+	 * @throws \InvalidArgumentException if the preview would be invalid (in case the original image is invalid)
+	 */
+	public function generatePreviews(File $file, array $specifications, ?string $mimeType = null, bool $cacheResult = true): ISimpleFile {
+		//Make sure that we can read the file
+		if (!$file->isReadable()) {
+			$this->logger->warning('Cannot read file: {path}, skipping preview generation.', ['path' => $file->getPath()]);
+			throw new NotFoundException('Cannot read file');
+		}
+
+		if ($mimeType === null) {
+			$mimeType = $file->getMimeType();
+		}
+
+		$previewFolder = $this->getPreviewFolder($file);
+		// List every existing preview first instead of trying to find them one by one
+		$previewFiles = $previewFolder->getDirectoryListing();
+
+		$previewVersion = '';
+		if ($file instanceof IVersionedPreviewFile) {
+			$previewVersion = $file->getPreviewVersion() . '-';
+		}
+
+		// Get the max preview and infer the max preview sizes from that
+		$maxPreview = $this->getMaxPreview($previewFolder, $previewFiles, $file, $mimeType, $previewVersion);
+		$maxPreviewImage = null; // only load the image when we need it
+		if ($maxPreview->getSize() === 0) {
+			$maxPreview->delete();
+			$this->logger->error('Max preview generated for file {path} has size 0, deleting and throwing exception.', ['path' => $file->getPath()]);
+			throw new NotFoundException('Max preview size 0, invalid!');
+		}
+
+		[$maxWidth, $maxHeight] = $this->getPreviewSize($maxPreview, $previewVersion);
+
+		if ($maxWidth <= 0 || $maxHeight <= 0) {
+			throw new NotFoundException('The maximum preview sizes are zero or less pixels');
+		}
+
+		$preview = null;
+
+		foreach ($specifications as $specification) {
+			$width = $specification['width'] ?? -1;
+			$height = $specification['height'] ?? -1;
+			$crop = $specification['crop'] ?? false;
+			$mode = $specification['mode'] ?? IPreview::MODE_FILL;
+
+			// If both width and height are -1 we just want the max preview
+			if ($width === -1 && $height === -1) {
+				$width = $maxWidth;
+				$height = $maxHeight;
+			}
+
+			// Calculate the preview size
+			[$width, $height] = $this->calculateSize($width, $height, $crop, $mode, $maxWidth, $maxHeight);
+
+			// No need to generate a preview that is just the max preview
+			if ($width === $maxWidth && $height === $maxHeight) {
+				// ensure correct return value if this was the last one
+				$preview = $maxPreview;
+				continue;
+			}
+
+			// Try to get a cached preview. Else generate (and store) one
+			try {
+				try {
+					$preview = $this->getCachedPreview($previewFiles, $width, $height, $crop, $maxPreview->getMimeType(), $previewVersion);
+				} catch (NotFoundException $e) {
+					if (!$this->previewManager->isMimeSupported($mimeType)) {
+						throw new NotFoundException();
+					}
+
+					if ($maxPreviewImage === null) {
+						$maxPreviewImage = $this->helper->getImage($maxPreview);
+					}
+
+					$this->logger->debug('Cached preview not found for file {path}, generating a new preview.', ['path' => $file->getPath()]);
+					$preview = $this->generatePreview($previewFolder, $maxPreviewImage, $width, $height, $crop, $maxWidth, $maxHeight, $previewVersion, $cacheResult);
+					// New file, augment our array
+					$previewFiles[] = $preview;
+				}
+			} catch (\InvalidArgumentException $e) {
+				throw new NotFoundException('', 0, $e);
+			}
+
+			if ($preview->getSize() === 0) {
+				$preview->delete();
+				throw new NotFoundException('Cached preview size 0, invalid!');
+			}
+		}
+		assert($preview !== null);
+
+		// Free memory being used by the embedded image resource.  Without this the image is kept in memory indefinitely.
+		// Garbage Collection does NOT free this memory.  We have to do it ourselves.
+		if ($maxPreviewImage instanceof \OCP\Image) {
+			$maxPreviewImage->destroy();
+		}
+
+		return $preview;
+	}
+
+	/**
+	 * Acquire a semaphore of the specified id and concurrency, blocking if necessary.
+	 * Return an identifier of the semaphore on success, which can be used to release it via
+	 * {@see Generator::unguardWithSemaphore()}.
+	 *
+	 * @param int $semId
+	 * @param int $concurrency
+	 * @return false|\SysvSemaphore the semaphore on success or false on failure
+	 */
+	public static function guardWithSemaphore(int $semId, int $concurrency) {
+		if (!extension_loaded('sysvsem')) {
+			return false;
+		}
+		$sem = sem_get($semId, $concurrency);
+		if ($sem === false) {
+			return false;
+		}
+		if (!sem_acquire($sem)) {
+			return false;
+		}
+		return $sem;
+	}
+
+	/**
+	 * Releases the semaphore acquired from {@see Generator::guardWithSemaphore()}.
+	 *
+	 * @param false|\SysvSemaphore $semId the semaphore identifier returned by guardWithSemaphore
+	 * @return bool
+	 */
+	public static function unguardWithSemaphore(false|\SysvSemaphore $semId): bool {
+		if ($semId === false || !($semId instanceof \SysvSemaphore)) {
+			return false;
+		}
+		return sem_release($semId);
+	}
+
+	/**
+	 * Get the number of concurrent threads supported by the host.
+	 *
+	 * @return int number of concurrent threads, or 0 if it cannot be determined
+	 */
+	public static function getHardwareConcurrency(): int {
+		static $width;
+
+		if (!isset($width)) {
+			if (function_exists('ini_get')) {
+				$openBasedir = ini_get('open_basedir');
+				if (empty($openBasedir) || strpos($openBasedir, '/proc/cpuinfo') !== false) {
+					$width = is_readable('/proc/cpuinfo') ? substr_count(file_get_contents('/proc/cpuinfo'), 'processor') : 0;
+				} else {
+					$width = 0;
+				}
+			} else {
+				$width = 0;
+			}
+		}
+		return $width;
+	}
+
+	/**
+	 * Get number of concurrent preview generations from system config
+	 *
+	 * Two config entries, `preview_concurrency_new` and `preview_concurrency_all`,
+	 * are available. If not set, the default values are determined with the hardware concurrency
+	 * of the host. In case the hardware concurrency cannot be determined, or the user sets an
+	 * invalid value, fallback values are:
+	 * For new images whose previews do not exist and need to be generated, 4;
+	 * For all preview generation requests, 8.
+	 * Value of `preview_concurrency_all` should be greater than or equal to that of
+	 * `preview_concurrency_new`, otherwise, the latter is returned.
+	 *
+	 * @param string $type either `preview_concurrency_new` or `preview_concurrency_all`
+	 * @return int number of concurrent preview generations, or -1 if $type is invalid
+	 */
+	public function getNumConcurrentPreviews(string $type): int {
+		static $cached = [];
+		if (array_key_exists($type, $cached)) {
+			return $cached[$type];
+		}
+
+		$hardwareConcurrency = self::getHardwareConcurrency();
+		switch ($type) {
+			case 'preview_concurrency_all':
+				$fallback = $hardwareConcurrency > 0 ? $hardwareConcurrency * 2 : 8;
+				$concurrency_all = $this->config->getSystemValueInt($type, $fallback);
+				$concurrency_new = $this->getNumConcurrentPreviews('preview_concurrency_new');
+				$cached[$type] = max($concurrency_all, $concurrency_new);
+				break;
+			case 'preview_concurrency_new':
+				$fallback = $hardwareConcurrency > 0 ? $hardwareConcurrency : 4;
+				$cached[$type] = $this->config->getSystemValueInt($type, $fallback);
+				break;
+			default:
+				return -1;
+		}
+		return $cached[$type];
+	}
+
+	/**
+	 * @param ISimpleFolder $previewFolder
+	 * @param ISimpleFile[] $previewFiles
+	 * @param File $file
+	 * @param string $mimeType
+	 * @param string $prefix
+	 * @return ISimpleFile
+	 * @throws NotFoundException
+	 */
+	private function getMaxPreview(ISimpleFolder $previewFolder, array $previewFiles, File $file, $mimeType, $prefix) {
+		// We don't know the max preview size, so we can't use getCachedPreview.
+		// It might have been generated with a higher resolution than the current value.
+		foreach ($previewFiles as $node) {
+			$name = $node->getName();
+			if (($prefix === '' || str_starts_with($name, $prefix)) && strpos($name, 'max')) {
+				return $node;
+			}
+		}
+
+		$maxWidth = $this->config->getSystemValueInt('preview_max_x', 4096);
+		$maxHeight = $this->config->getSystemValueInt('preview_max_y', 4096);
+
+		return $this->generateProviderPreview($previewFolder, $file, $maxWidth, $maxHeight, false, true, $mimeType, $prefix);
+	}
+
+	private function generateProviderPreview(ISimpleFolder $previewFolder, File $file, int $width, int $height, bool $crop, bool $max, string $mimeType, string $prefix) {
+		$previewProviders = $this->previewManager->getProviders();
+		foreach ($previewProviders as $supportedMimeType => $providers) {
+			// Filter out providers that does not support this mime
+			if (!preg_match($supportedMimeType, $mimeType)) {
+				continue;
+			}
+
+			foreach ($providers as $providerClosure) {
+				$provider = $this->helper->getProvider($providerClosure);
+				if (!($provider instanceof IProviderV2)) {
+					continue;
+				}
+
+				if (!$provider->isAvailable($file)) {
+					continue;
+				}
+
+				$previewConcurrency = $this->getNumConcurrentPreviews('preview_concurrency_new');
+				$sem = self::guardWithSemaphore(self::SEMAPHORE_ID_NEW, $previewConcurrency);
+				try {
+					$this->logger->debug('Calling preview provider for {mimeType} with width={width}, height={height}', [
+						'mimeType' => $mimeType,
+						'width' => $width,
+						'height' => $height,
+					]);
+					$preview = $this->helper->getThumbnail($provider, $file, $width, $height);
+				} finally {
+					self::unguardWithSemaphore($sem);
+				}
+
+				if (!($preview instanceof IImage)) {
+					continue;
+				}
+
+				$path = $this->generatePath($preview->width(), $preview->height(), $crop, $max, $preview->dataMimeType(), $prefix);
+				try {
+					if ($preview instanceof IStreamImage) {
+						return $previewFolder->newFile($path, $preview->resource());
+					} else {
+						return $previewFolder->newFile($path, $preview->data());
+					}
+				} catch (NotPermittedException $e) {
+					throw new NotFoundException();
+				}
+
+				return $file;
+			}
+		}
+
+		throw new NotFoundException('No provider successfully handled the preview generation');
+	}
+
+	/**
+	 * @param ISimpleFile $file
+	 * @param string $prefix
+	 * @return int[]
+	 */
+	private function getPreviewSize(ISimpleFile $file, string $prefix = '') {
+		$size = explode('-', substr($file->getName(), strlen($prefix)));
+		return [(int)$size[0], (int)$size[1]];
+	}
+
+	/**
+	 * @param int $width
+	 * @param int $height
+	 * @param bool $crop
+	 * @param bool $max
+	 * @param string $mimeType
+	 * @param string $prefix
+	 * @return string
+	 */
+	private function generatePath($width, $height, $crop, $max, $mimeType, $prefix) {
+		$path = $prefix . (string)$width . '-' . (string)$height;
+		if ($crop) {
+			$path .= '-crop';
+		}
+		if ($max) {
+			$path .= '-max';
+		}
+
+		$ext = $this->getExtension($mimeType);
+		$path .= '.' . $ext;
+		return $path;
+	}
+
+
+	/**
+	 * @param int $width
+	 * @param int $height
+	 * @param bool $crop
+	 * @param string $mode
+	 * @param int $maxWidth
+	 * @param int $maxHeight
+	 * @return int[]
+	 */
+	private function calculateSize($width, $height, $crop, $mode, $maxWidth, $maxHeight) {
+		/*
+		 * If we are not cropping we have to make sure the requested image
+		 * respects the aspect ratio of the original.
+		 */
+		if (!$crop) {
+			$ratio = $maxHeight / $maxWidth;
+
+			if ($width === -1) {
+				$width = $height / $ratio;
+			}
+			if ($height === -1) {
+				$height = $width * $ratio;
+			}
+
+			$ratioH = $height / $maxHeight;
+			$ratioW = $width / $maxWidth;
+
+			/*
+			 * Fill means that the $height and $width are the max
+			 * Cover means min.
+			 */
+			if ($mode === IPreview::MODE_FILL) {
+				if ($ratioH > $ratioW) {
+					$height = $width * $ratio;
+				} else {
+					$width = $height / $ratio;
+				}
+			} elseif ($mode === IPreview::MODE_COVER) {
+				if ($ratioH > $ratioW) {
+					$width = $height / $ratio;
+				} else {
+					$height = $width * $ratio;
+				}
+			}
+		}
+
+		if ($height !== $maxHeight && $width !== $maxWidth) {
+			/*
+			 * Scale to the nearest power of four
+			 */
+			$pow4height = 4 ** ceil(log($height) / log(4));
+			$pow4width = 4 ** ceil(log($width) / log(4));
+
+			// Minimum size is 64
+			$pow4height = max($pow4height, 64);
+			$pow4width = max($pow4width, 64);
+
+			$ratioH = $height / $pow4height;
+			$ratioW = $width / $pow4width;
+
+			if ($ratioH < $ratioW) {
+				$width = $pow4width;
+				$height /= $ratioW;
+			} else {
+				$height = $pow4height;
+				$width /= $ratioH;
+			}
+		}
+
+		/*
+		 * Make sure the requested height and width fall within the max
+		 * of the preview.
+		 */
+		if ($height > $maxHeight) {
+			$ratio = $height / $maxHeight;
+			$height = $maxHeight;
+			$width /= $ratio;
+		}
+		if ($width > $maxWidth) {
+			$ratio = $width / $maxWidth;
+			$width = $maxWidth;
+			$height /= $ratio;
+		}
+
+		return [(int)round($width), (int)round($height)];
+	}
+
+	/**
+	 * @throws NotFoundException
+	 * @throws \InvalidArgumentException if the preview would be invalid (in case the original image is invalid)
+	 */
+	private function generatePreview(
+		ISimpleFolder $previewFolder,
+		IImage $maxPreview,
+		int $width,
+		int $height,
+		bool $crop,
+		int $maxWidth,
+		int $maxHeight,
+		string $prefix,
+		bool $cacheResult,
+	): ISimpleFile {
+		$preview = $maxPreview;
+		if (!$preview->valid()) {
+			throw new \InvalidArgumentException('Failed to generate preview, failed to load image');
+		}
+
+		$previewConcurrency = $this->getNumConcurrentPreviews('preview_concurrency_new');
+		$sem = self::guardWithSemaphore(self::SEMAPHORE_ID_NEW, $previewConcurrency);
+		try {
+			if ($crop) {
+				if ($height !== $preview->height() && $width !== $preview->width()) {
+					//Resize
+					$widthR = $preview->width() / $width;
+					$heightR = $preview->height() / $height;
+
+					if ($widthR > $heightR) {
+						$scaleH = $height;
+						$scaleW = $maxWidth / $heightR;
+					} else {
+						$scaleH = $maxHeight / $widthR;
+						$scaleW = $width;
+					}
+					$preview = $preview->preciseResizeCopy((int)round($scaleW), (int)round($scaleH));
+				}
+				$cropX = (int)floor(abs($width - $preview->width()) * 0.5);
+				$cropY = (int)floor(abs($height - $preview->height()) * 0.5);
+				$preview = $preview->cropCopy($cropX, $cropY, $width, $height);
+			} else {
+				$preview = $maxPreview->resizeCopy(max($width, $height));
+			}
+		} finally {
+			self::unguardWithSemaphore($sem);
+		}
+
+
+		$path = $this->generatePath($width, $height, $crop, false, $preview->dataMimeType(), $prefix);
+		try {
+			if ($cacheResult) {
+				return $previewFolder->newFile($path, $preview->data());
+			} else {
+				return new InMemoryFile($path, $preview->data());
+			}
+		} catch (NotPermittedException $e) {
+			throw new NotFoundException();
+		}
+		return $file;
+	}
+
+	/**
+	 * @param ISimpleFile[] $files Array of FileInfo, as the result of getDirectoryListing()
+	 * @param int $width
+	 * @param int $height
+	 * @param bool $crop
+	 * @param string $mimeType
+	 * @param string $prefix
+	 * @return ISimpleFile
+	 *
+	 * @throws NotFoundException
+	 */
+	private function getCachedPreview($files, $width, $height, $crop, $mimeType, $prefix) {
+		$path = $this->generatePath($width, $height, $crop, false, $mimeType, $prefix);
+		foreach ($files as $file) {
+			if ($file->getName() === $path) {
+				$this->logger->debug('Found cached preview: {path}', ['path' => $path]);
+				return $file;
+			}
+		}
+		throw new NotFoundException();
+	}
+
+	/**
+	 * Get the specific preview folder for this file
+	 *
+	 * @param File $file
+	 * @return ISimpleFolder
+	 *
+	 * @throws InvalidPathException
+	 * @throws NotFoundException
+	 * @throws NotPermittedException
+	 */
+	private function getPreviewFolder(File $file) {
+		// Obtain file id outside of try catch block to prevent the creation of an existing folder
+		$fileId = (string)$file->getId();
+
+		try {
+			$folder = $this->appData->getFolder($fileId);
+		} catch (NotFoundException $e) {
+			$folder = $this->appData->newFolder($fileId);
+		}
+
+		return $folder;
+	}
+
+	/**
+	 * @param string $mimeType
+	 * @return null|string
+	 * @throws \InvalidArgumentException
+	 */
+	private function getExtension($mimeType) {
+		switch ($mimeType) {
+			case 'image/png':
+				return 'png';
+			case 'image/jpeg':
+				return 'jpg';
+			case 'image/webp':
+				return 'webp';
+			case 'image/gif':
+				return 'gif';
+			default:
+				throw new \InvalidArgumentException('Not a valid mimetype: "' . $mimeType . '"');
+		}
+	}
+}