NetCoreServer/source/NetCoreServer/FileCache.cs at master · bubdm/NetCoreServer · GitHub

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using System;

using System.Collections.Generic;

using System.IO;

using System.Text;

using System.Threading;

using System.Web;

namespace NetCoreServer

{

/// <summary>

/// File cache is used to cache files in memory with optional timeouts.

/// FileSystemWatcher is used to monitor file system changes in cached

/// directories.

/// </summary>

/// <remarks>Thread-safe.</remarks>

public class FileCache : IDisposable

{

public delegate bool InsertHandler(FileCache cache, string key, byte[] value, TimeSpan timeout);

#region Cache items access

/// <summary>

/// Is the file cache empty?

/// </summary>

public bool Empty => _entriesByKey.Count == 0;

/// <summary>

/// Get the file cache size

/// </summary>

public int Size => _entriesByKey.Count;

/// <summary>

/// Add a new cache value with the given timeout into the file cache

/// </summary>

/// <param name="key">Key to add</param>

/// <param name="value">Value to add</param>

/// <param name="timeout">Cache timeout (default is 0 - no timeout)</param>

/// <returns>'true' if the cache value was added, 'false' if the given key was not added</returns>

public bool Add(string key, byte[] value, TimeSpan timeout = new TimeSpan())

{

using (new WriteLock(_lockEx))

{

// Try to find and remove the previous key

_entriesByKey.Remove(key);

// Update the cache entry

_entriesByKey.Add(key, new MemCacheEntry(value, timeout));

return true;

}

/// <summary>

/// Try to find the cache value by the given key

/// </summary>

/// <param name="key">Key to find</param>

/// <returns>'true' and cache value if the cache value was found, 'false' if the given key was not found</returns>

public (bool, byte[]) Find(string key)

{

using (new ReadLock(_lockEx))

{

// Try to find the given key

if (!_entriesByKey.TryGetValue(key, out var cacheValue))

return (false, new byte[0]);

return (true, cacheValue.Value);

}

/// <summary>

/// Remove the cache value with the given key from the file cache

/// </summary>

/// <param name="key">Key to remove</param>

/// <returns>'true' if the cache value was removed, 'false' if the given key was not found</returns>

public bool Remove(string key)

{

using (new WriteLock(_lockEx))

{

return _entriesByKey.Remove(key);

}

#endregion

#region Cache management methods

/// <summary>

/// Insert a new cache path with the given timeout into the file cache

/// </summary>

/// <param name="path">Path to insert</param>

/// <param name="prefix">Cache prefix (default is "/")</param>

/// <param name="filter">Cache filter (default is "*.*")</param>

/// <param name="timeout">Cache timeout (default is 0 - no timeout)</param>

/// <param name="handler">Cache insert handler (default is 'return cache.Add(key, value, timeout)')</param>

/// <returns>'true' if the cache path was setup, 'false' if failed to setup the cache path</returns>

public bool InsertPath(string path, string prefix = "/", string filter = "*.*", TimeSpan timeout = new TimeSpan(), InsertHandler handler = null)

{

handler ??= (FileCache cache, string key, byte[] value, TimeSpan timespan) => cache.Add(key, value, timespan);

// Try to find and remove the previous path

RemovePathInternal(path);

using (new WriteLock(_lockEx))

{

// Add the given path to the cache

_pathsByKey.Add(path, new FileCacheEntry(this, prefix, path, filter, handler, timeout));

// Create entries by path map

_entriesByPath[path] = new HashSet<string>();

}

// Insert the cache path

if (!InsertPathInternal(path, path, prefix, timeout, handler))

return false;

return true;

}

/// <summary>

/// Try to find the cache path

/// </summary>

/// <param name="path">Path to find</param>

/// <returns>'true' if the cache path was found, 'false' if the given path was not found</returns>

public bool FindPath(string path)

{

using (new ReadLock(_lockEx))

{

// Try to find the given key

return _pathsByKey.ContainsKey(path);

}

/// <summary>

/// Remove the cache path from the file cache

/// </summary>

/// <param name="path">Path to remove</param>

/// <returns>'true' if the cache path was removed, 'false' if the given path was not found</returns>

public bool RemovePath(string path)

{

return RemovePathInternal(path);

}

/// <summary>

/// Clear the memory cache

/// </summary>

public void Clear()

{

using (new WriteLock(_lockEx))

{

// Stop all file system watchers

foreach (var fileCacheEntry in _pathsByKey)

fileCacheEntry.Value.StopWatcher();

// Clear all cache entries

_entriesByKey.Clear();

_entriesByPath.Clear();

_pathsByKey.Clear();

}

#endregion

#region Cache implementation

private readonly ReaderWriterLockSlim _lockEx = new ReaderWriterLockSlim();

private Dictionary<string, MemCacheEntry> _entriesByKey = new Dictionary<string, MemCacheEntry>();

private Dictionary<string, HashSet<string>> _entriesByPath = new Dictionary<string, HashSet<string>>();

private Dictionary<string, FileCacheEntry> _pathsByKey = new Dictionary<string, FileCacheEntry>();

private class MemCacheEntry

{

private readonly byte[] _value;

private readonly TimeSpan _timespan;

public byte[] Value => _value;

public TimeSpan Timespan => _timespan;

public MemCacheEntry(byte[] value, TimeSpan timespan = new TimeSpan())

{

_value = value;

_timespan = timespan;

}

public MemCacheEntry(string value, TimeSpan timespan = new TimeSpan())

{

_value = Encoding.UTF8.GetBytes(value);

_timespan = timespan;

}

};

private class FileCacheEntry

{

private readonly string _prefix;

private readonly string _path;

private readonly InsertHandler _handler;

private readonly TimeSpan _timespan;

private readonly FileSystemWatcher _watcher;

public FileCacheEntry(FileCache cache, string prefix, string path, string filter, InsertHandler handler, TimeSpan timespan)

{

_prefix = prefix;

_path = path;

_handler = handler;

_timespan = timespan;

_watcher = new FileSystemWatcher();

// Start the filesystem watcher

StartWatcher(cache, path, filter);

}

private void StartWatcher(FileCache cache, string path, string filter)

{

FileCacheEntry entry = this;

// Initialize a new filesystem watcher

_watcher.Created += (sender, e) => OnCreated(sender, e, cache, entry);

_watcher.Changed += (sender, e) => OnChanged(sender, e, cache, entry);

_watcher.Deleted += (sender, e) => OnDeleted(sender, e, cache, entry);

_watcher.Renamed += (sender, e) => OnRenamed(sender, e, cache, entry);

_watcher.Path = path;

_watcher.IncludeSubdirectories = true;

_watcher.Filter = filter;

_watcher.NotifyFilter = NotifyFilters.FileName | NotifyFilters.LastWrite;

_watcher.EnableRaisingEvents = true;

}

public void StopWatcher()

{

_watcher.Dispose();

}

private static bool IsDirectory(string path)

{

try

{

// Skip directory updates

if (File.GetAttributes(path).HasFlag(FileAttributes.Directory))

return true;

}

catch (Exception) {}

return false;

}

private static void OnCreated(object sender, FileSystemEventArgs e, FileCache cache, FileCacheEntry entry)

{

var key = e.FullPath.Replace(entry._path, entry._prefix);

var file = e.FullPath;

// Skip missing files

if (!File.Exists(file))

return;

// Skip directory updates

if (IsDirectory(file))

return;

cache.InsertFileInternal(entry._path, file, key, entry._timespan, entry._handler);

}

private static void OnChanged(object sender, FileSystemEventArgs e, FileCache cache, FileCacheEntry entry)

{

if (e.ChangeType != WatcherChangeTypes.Changed)

return;

var key = e.FullPath.Replace(entry._path, entry._prefix);

var file = e.FullPath;

// Skip missing files

if (!File.Exists(file))

return;

// Skip directory updates

if (IsDirectory(file))

return;

cache.InsertFileInternal(entry._path, file, key, entry._timespan, entry._handler);

}

private static void OnDeleted(object sender, FileSystemEventArgs e, FileCache cache, FileCacheEntry entry)

{

var key = e.FullPath.Replace(entry._path, entry._prefix);

var file = e.FullPath;

cache.RemoveFileInternal(entry._path, key);

}

private static void OnRenamed(object sender, RenamedEventArgs e, FileCache cache, FileCacheEntry entry)

{

var oldKey = e.OldFullPath.Replace(entry._path, entry._prefix);

var oldFile = e.OldFullPath;

var newKey = e.FullPath.Replace(entry._path, entry._prefix);

var newFile = e.FullPath;

// Skip missing files

if (!File.Exists(newFile))

return;

// Skip directory updates

if (IsDirectory(newFile))

return;

cache.RemoveFileInternal(entry._path, oldKey);

cache.InsertFileInternal(entry._path, newFile, newKey, entry._timespan, entry._handler);

}

};

private bool InsertFileInternal(string path, string file, string key, TimeSpan timeout, InsertHandler handler)

{

try

{

key = key.Replace('\\', '/');

file = file.Replace('\\', '/');

// Load the cache file content

var content = File.ReadAllBytes(file);

if (!handler(this, key, content, timeout))

return false;

using (new WriteLock(_lockEx))

{

// Update entries by path map

_entriesByPath[path].Add(key);

}

return true;

}

catch (Exception) { return false; }

}

private bool RemoveFileInternal(string path, string key)

{

try

{

key = key.Replace('\\', '/');

using (new WriteLock(_lockEx))

{

// Update entries by path map

_entriesByPath[path].Remove(key);

}

return Remove(key);

}

catch (Exception) { return false; }

}

private bool InsertPathInternal(string root, string path, string prefix, TimeSpan timeout, InsertHandler handler)

{

try

{

string keyPrefix = (string.IsNullOrEmpty(prefix) || (prefix == "/")) ? "/" : (prefix + "/");

// Iterate through all directory entries

foreach (var item in Directory.GetDirectories(path))

{

string key = keyPrefix + HttpUtility.UrlDecode(Path.GetFileName(item));

// Recursively insert sub-directory

if (!InsertPathInternal(root, item, key, timeout, handler))

return false;

}

foreach (var item in Directory.GetFiles(path))

{

string key = keyPrefix + HttpUtility.UrlDecode(Path.GetFileName(item));

// Insert file into the cache

if (!InsertFileInternal(root, item, key, timeout, handler))

return false;

}

return true;

}

catch (Exception) { return false; }

}

private bool RemovePathInternal(string path)

{

using (new WriteLock(_lockEx))

{

// Try to find the given path

if (!_pathsByKey.TryGetValue(path, out var cacheValue))

return false;

// Stop the file system watcher

cacheValue.StopWatcher();

// Remove path entries

foreach (var entryKey in _entriesByPath[path])

_entriesByKey.Remove(entryKey);

_entriesByPath.Remove(path);

// Remove cache path

_pathsByKey.Remove(path);

return true;

}

#endregion

#region IDisposable implementation

// Disposed flag.

private bool _disposed;

// Implement IDisposable.

public void Dispose()

{

Dispose(true);

GC.SuppressFinalize(this);

}

protected virtual void Dispose(bool disposingManagedResources)

{

// The idea here is that Dispose(Boolean) knows whether it is

// being called to do explicit cleanup (the Boolean is true)

// versus being called due to a garbage collection (the Boolean

// is false). This distinction is useful because, when being

// disposed explicitly, the Dispose(Boolean) method can safely

// execute code using reference type fields that refer to other

// objects knowing for sure that these other objects have not been

// finalized or disposed of yet. When the Boolean is false,

// the Dispose(Boolean) method should not execute code that

// refer to reference type fields because those objects may

// have already been finalized."

if (!_disposed)

{

if (disposingManagedResources)

{

// Dispose managed resources here...

Clear();

}

// Dispose unmanaged resources here...

// Set large fields to null here...

// Mark as disposed.

_disposed = true;

}

// Use C# destructor syntax for finalization code.

~FileCache()

{

// Simply call Dispose(false).

Dispose(false);

}

#endregion

}

/// <summary>

/// Disposable lock class performs exit action on dispose operation.

/// </summary>

public class DisposableLock : IDisposable

{

private readonly Action _exitLock;

public DisposableLock(Action exitLock)

{

_exitLock = exitLock;

}

public void Dispose()

{

_exitLock();

}

/// <summary>

/// Read lock class enters read lock on construction and performs exit read lock on dispose.

/// </summary>

public class ReadLock : DisposableLock

{

public ReadLock(ReaderWriterLockSlim locker) : base(locker.ExitReadLock)

{

locker.EnterReadLock();

}

/// <summary>

/// Write lock class enters write lock on construction and performs exit write lock on dispose.

/// </summary>

public class WriteLock : DisposableLock

{

public WriteLock(ReaderWriterLockSlim locker) : base(locker.ExitWriteLock)

{

locker.EnterWriteLock();

}

NetCoreServer/source/NetCoreServer/FileCache.cs at master · bubdm/NetCoreServer · GitHub

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