// Based on code by 'Scott Mitchell' <[email protected]>
// http://www.4guysfromrolla.com/articles/061610-1.aspx
// Add the following to Web.config
// Use the cacheFolder attribute to specify the disk location for the cache
//
// <system.web>
// <caching>
// <outputCache enableOutputCache="true" defaultProvider="disk">
// <providers>
// <add name="disk" type="DiskOutputCache.DiskOutputCacheProvider, DiskOutputCache" cacheFolder="~/App_Data/OutputCache" />
// </providers>
// </outputCache>
// </caching>
// </system.web>
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.IO;
using System.Linq;
using System.Runtime.Serialization.Formatters.Binary;
using System.Text;
using System.Web;
using System.Web.Caching;
namespace DiskOutputCache {
/// <summary>
/// An <see cref="OutputCacheProvider"/> that uses the file system for storage.
/// </summary>
public class DiskOutputCacheProvider : OutputCacheProvider {
readonly IDictionary<string, CacheItem> cacheItems = new ConcurrentDictionary<string, CacheItem>();
string cacheFolder;
public override void Initialize(string name, NameValueCollection config) {
HttpServerUtility serverUtil = HttpContext.Current.Server;
const string cacheFolderKey = "cacheFolder";
string cacheFolderValue = config[cacheFolderKey];
string folder;
if (!String.IsNullOrEmpty(cacheFolderValue)) {
folder = serverUtil.MapPath(cacheFolderValue);
config.Remove(cacheFolderKey);
} else {
throw new ArgumentException(String.Format("The attribute '{0}' is missing in the configuration of the '{1}' provider.", cacheFolderKey, name));
}
if (folder[folder.Length - 1] != Path.DirectorySeparatorChar)
folder += Path.DirectorySeparatorChar;
if (!Directory.Exists(folder))
Directory.CreateDirectory(folder);
this.cacheFolder = folder;
base.Initialize(name, config);
}
public override object Add(string key, object entry, DateTime utcExpiry) {
// See if this key already exists in the cache. If so, we need to return it and NOT overwrite it!
object results = Get(key);
if (results != null)
return results;
// If the item is NOT in the cache, then save it!
Set(key, entry, utcExpiry);
return entry;
}
public override object Get(string key) {
CacheItem item;
if (!this.cacheItems.TryGetValue(key, out item))
return null;
if (item.UtcExpiry < DateTime.UtcNow) {
// Item has expired
Remove(key, item);
return null;
}
return GetCacheData(item);
}
object GetCacheData(CacheItem item) {
string fileToRetrieve = GetFilePath(item);
BinaryFormatter formatter = new BinaryFormatter();
Stream source = null;
try {
source = new FileStream(fileToRetrieve, FileMode.Open, FileAccess.Read, FileShare.Read);
return formatter.Deserialize(source);
} catch (IOException) {
} finally {
if (source != null)
source.Dispose();
}
return null;
}
public override void Remove(string key) {
CacheItem item;
if (this.cacheItems.TryGetValue(key, out item))
Remove(key, item);
}
void Remove(string key, CacheItem item) {
RemoveCacheData(item);
this.cacheItems.Remove(key);
}
void RemoveCacheData(CacheItem item) {
string fileToDelete = GetFilePath(item);
try {
File.Delete(fileToDelete);
} catch (IOException) { }
}
public override void Set(string key, object entry, DateTime utcExpiry) {
// Create a DiskOutputCacheItem object
CacheItem item = new CacheItem(key, utcExpiry);
WriteCacheData(item, entry);
// Add item to CacheItems, if needed, or update the existing key, if it already exists
this.cacheItems[key] = item;
}
void WriteCacheData(CacheItem item, object entry) {
string fileToWrite = GetFilePath(item);
BinaryFormatter formatter = new BinaryFormatter();
Stream destination = null;
try {
destination = new FileStream(fileToWrite, FileMode.OpenOrCreate, FileAccess.Write, FileShare.None);
formatter.Serialize(destination, entry);
} catch (IOException) {
} finally {
if (destination != null)
destination.Dispose();
}
}
string GetFilePath(CacheItem item) {
return this.cacheFolder + item.FileName;
}
class CacheItem {
static readonly char[] invalidFileNameChars = Path.GetInvalidFileNameChars();
public string FileName { get; private set; }
public DateTime UtcExpiry { get; private set; }
public CacheItem(string key, DateTime utcExpiry) {
this.FileName = GetSafeFileName(key);
this.UtcExpiry = utcExpiry;
}
string GetSafeFileName(string unsafeFileName) {
char[] invalid = unsafeFileName.ToCharArray()
.Where(c => invalidFileNameChars.Contains(c))
.ToArray();
if (invalid.Length > 0) {
var sb = new StringBuilder(unsafeFileName, unsafeFileName.Length);
for (int i = 0; i < invalid.Length; i++)
sb.Replace(invalid[i], '_');
return sb.ToString();
}
return unsafeFileName;
}
}
}
}
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