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Diffstat (limited to 'indra/llfilesystem/lldiskcache.h')
| -rw-r--r-- | indra/llfilesystem/lldiskcache.h | 183 |
1 files changed, 0 insertions, 183 deletions
diff --git a/indra/llfilesystem/lldiskcache.h b/indra/llfilesystem/lldiskcache.h deleted file mode 100644 index 997884da31..0000000000 --- a/indra/llfilesystem/lldiskcache.h +++ /dev/null @@ -1,183 +0,0 @@ -/** - * @file lldiskcache.h - * @brief The disk cache implementation declarations. - * - * @Description: - * This code implements a disk cache using the following ideas: - * 1/ The metadata for a file can be encapsulated in the filename. - The filenames will be composed of the following fields: - Prefix: Used to identify the file as a part of the cache. - An additional reason for using a prefix is that it - might be possible, either accidentally or maliciously - to end up with the cache dir set to a non-cache - location such as your OS system dir or a work folder. - Purging files from that would obviously be a disaster - so this is an extra step to help avoid that scenario. - ID: Typically the asset ID (UUID) of the asset being - saved but can be anything valid for a filename - Extra Info: A field for use in the future that can be used - to store extra identifiers - e.g. the discard - level of a JPEG2000 file - Asset Type: A text string created from the LLAssetType enum - that identifies the type of asset being stored. - .asset A file extension of .asset is used to help - identify this as a Viewer asset file - * 2/ The time of last access for a file can be updated instantly - * for file reads and automatically as part of the file writes. - * 3/ The purge algorithm collects a list of all files in the - * directory, sorts them by date of last access (write) and then - * deletes any files based on age until the total size of all - * the files is less than the maximum size specified. - * 4/ An LLSingleton idiom is used since there will only ever be - * a single cache and we want to access it from numerous places. - * 5/ Performance on my modest system seems very acceptable. For - * example, in testing, I was able to purge a directory of - * 10,000 files, deleting about half of them in ~ 1700ms. For - * the same sized directory of files, writing the last updated - * time to each took less than 600ms indicating that this - * important part of the mechanism has almost no overhead. - * - * $LicenseInfo:firstyear=2009&license=viewerlgpl$ - * Second Life Viewer Source Code - * Copyright (C) 2020, Linden Research, Inc. - * - * This library is free software; you can redistribute it and/or - * modify it under the terms of the GNU Lesser General Public - * License as published by the Free Software Foundation; - * version 2.1 of the License only. - * - * This library 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 - * Lesser General Public License for more details. - * - * You should have received a copy of the GNU Lesser General Public - * License along with this library; if not, write to the Free Software - * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA - * - * Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA - * $/LicenseInfo$ - */ - -#ifndef _LLDISKCACHE -#define _LLDISKCACHE - -#include "llsingleton.h" - -class LLDiskCache : - public LLParamSingleton<LLDiskCache> -{ - public: - /** - * Since this is using the LLSingleton pattern but we - * want to allow the constructor to be called first - * with various parameters, we also invoke the - * LLParamSingleton idiom and use it to initialize - * the class via a call in LLAppViewer. - */ - LLSINGLETON(LLDiskCache, - /** - * The full name of the cache folder - typically a - * a child of the main Viewer cache directory. Defined - * by the setting at 'DiskCacheDirName' - */ - const std::string cache_dir, - /** - * The maximum size of the cache in bytes - Based on the - * setting at 'CacheSize' and 'DiskCachePercentOfTotal' - */ - const int max_size_bytes, - /** - * A flag that enables extra cache debugging so that - * if there are bugs, we can ask uses to enable this - * setting and send us their logs - */ - const bool enable_cache_debug_info); - - virtual ~LLDiskCache() = default; - - public: - /** - * Construct a filename and path to it based on the file meta data - * (id, asset type, additional 'extra' info like discard level perhaps) - * Worth pointing out that this function used to be in LLFileSystem but - * so many things had to be pushed back there to accomodate it, that I - * decided to move it here. Still not sure that's completely right. - */ - const std::string metaDataToFilepath(const std::string id, - LLAssetType::EType at, - const std::string extra_info); - - /** - * Update the "last write time" of a file to "now". This must be called whenever a - * file in the cache is read (not written) so that the last time the file was - * accessed is up to date (This is used in the mechanism for purging the cache) - */ - void updateFileAccessTime(const std::string file_path); - - /** - * Purge the oldest items in the cache so that the combined size of all files - * is no bigger than mMaxSizeBytes. - */ - void purge(); - - /** - * Clear the cache by removing all the files in the specified cache - * directory individually. Only the files that contain a prefix defined - * by mCacheFilenamePrefix will be removed. - */ - void clearCache(); - - /** - * Return some information about the cache for use in About Box etc. - */ - const std::string getCacheInfo(); - - private: - /** - * Utility function to gather the total size the files in a given - * directory. Primarily used here to determine the directory size - * before and after the cache purge - */ - uintmax_t dirFileSize(const std::string dir); - - /** - * Utility function to convert an LLAssetType enum into a - * string that we use as part of the cache file filename - */ - const std::string assetTypeToString(LLAssetType::EType at); - - private: - /** - * The maximum size of the cache in bytes. After purge is called, the - * total size of the cache files in the cache directory will be - * less than this value - */ - uintmax_t mMaxSizeBytes; - - /** - * The folder that holds the cached files. The consumer of this - * class must avoid letting the user set this location as a malicious - * setting could potentially point it at a non-cache directory (for example, - * the Windows System dir) with disastrous results. - */ - std::string mCacheDir; - - /** - * The prefix inserted at the start of a cache file filename to - * help identify it as a cache file. It's probably not required - * (just the presence in the cache folder is enough) but I am - * paranoid about the cache folder being set to something bad - * like the users' OS system dir by mistake or maliciously and - * this will help to offset any damage if that happens. - */ - std::string mCacheFilenamePrefix; - - /** - * When enabled, displays additional debugging information in - * various parts of the code - */ - bool mEnableCacheDebugInfo; -}; - -#endif // _LLDISKCACHE |