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/**
* @file lldiskcache.h
* @brief The disk cache implementation.
*
* $LicenseInfo:firstyear=2009&license=viewerlgpl$
* 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:
LLSINGLETON(LLDiskCache,
const std::string cache_dir,
const int max_size_bytes,
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 which is used in the mechanism for purging the cache, is up to date.
*/
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 the files in the cache directory individually
*/
void clearCache(const std::string cache_dir);
/**
* 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
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