using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 
using System.Web.Caching; 
using System.Xml.Serialization; 
using System.IO; 
using System.Runtime.Serialization.Formatters.Binary; 
  
namespace OutputCacheTest.Caching 
{ 
    /// <summary> 
    /// OutputCache精灵,如果缓存时间小于设置时间时则缓存到内存，否则缓存到文件 
    /// </summary> 
    public class SmartOutputCacheProvider : OutputCacheProvider 
    { 
        private const string KEY_PREFIX = "__outputCache_"; 
  
        /// <summary> 
        /// 初始化SmartOutputCacheProvider，读取配置文件中配置的MemoryCacheLimit和FileCacheRoot的值 
        /// </summary> 
        /// <param name="name">provider名字</param> 
        /// <param name="config">配置</param> 
        public override void Initialize(string name, System.Collections.Specialized.NameValueCollection config) 
        { 
            string memoryLimit = config["memoryCacheLimit"]; 
            if (memoryLimit == null) 
            { 
                MemoryCacheLimit = new TimeSpan(0, 30, 0); 
            } 
            else
            { 
                MemoryCacheLimit = TimeSpan.Parse(memoryLimit); 
            } 
  
            string fileCacheRoot = config["fileCa oot"]; 
            if (string.IsNullOrEmpty(fileCacheRoot)) 
            { 
                fileCacheRoot = AppDomain.CurrentDomain.BaseDirectory + "cache\\"; 
            } 
            this.FileCacheRoot = fileCacheRoot; 
            base.Initialize(name, config); 
        } 
  
        /// <summary> 
        /// 添加缓存 
        /// </summary> 
        /// <param name="key">缓存的键，key的值是有asp.net内部生成的</param> 
        /// <param name="entry">缓存的对象</param> 
        /// <param name="utcExpiry">过期时间</param> 
        /// <returns>返回缓存值</returns> 
        public override object Add(string key, object entry, DateTime utcExpiry) 
        { 
            Set(key, entry, utcExpiry); 
            return entry; 
        } 
  
        /// <summary> 
        /// 处理缓存键值，防止在文件缓存时出现文件路径不允许的字符 
        /// </summary> 
        /// <param name="key">缓存键</param> 
        /// <returns>处理后的键</returns> 
        private string ProcessKey(string key) 
        { 
            return KEY_PREFIX + System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(key, "MD5"); 
        } 
  
        /// <summary> 
        /// 返回缓存文件的物理路径 
        /// </summary> 
        /// <param name="processedKey">处理后的键</param> 
        /// <returns>物理路径</returns> 
        private string GetFilePath(string processedKey) 
        { 
            return Path.Combine(FileCacheRoot, processedKey + ".data"); 
        } 
  
        /// <summary> 
        /// 获得缓存值，如果在HttpRuntime.Cache中有则直接读取内存中的值，否则从文件读取 
        /// </summary> 
        /// <param name="key">缓存键</param> 
        /// <returns>缓存值</returns> 
        public override object Get(string key) 
        { 
            string processedKey = ProcessKey(key); 
  
            CacheDataWithExpiryTimeUtc result = HttpRuntime.Cache[processedKey] as CacheDataWithExpiryTimeUtc; 
            if (result == null) 
            { 
                string path = GetFilePath(processedKey); 
                if (!File.Exists(path)) 
                    return null; 
  
                using (FileStream file = File.OpenRead(path)) 
                { 
                    var formatter = new BinaryFormatter(); 
                    result = (CacheDataWithExpiryTimeUtc)formatter.Deserialize(file); 
                } 
            } 
  
            if (result == null || result.ExpiryTimeUtc <= DateTime.UtcNow) 
            { 
                Remove(key); 
                return null; 
            } 
            return result.Data; 
        } 
  
        /// <summary> 
        /// 根据键移除缓存 
        /// </summary> 
        /// <param name="key">缓存键</param> 
        public override void Remove(string key) 
        { 
            string processedKey = ProcessKey(key); 
            HttpRuntime.Cache.Remove(processedKey); 
            string path = GetFilePath(processedKey); 
            if (!File.Exists(path)) 
                File. (path); 
        } 
  
        /// <summary> 
        /// 设置缓存 
        /// </summary> 
        /// <param name="key">缓存键</param> 
        /// <param name="entry">缓存内容</param> 
        /// <param name="utcExpiry">过期时间</param> 
        public override void Set(string key, object entry, DateTime utcExpiry) 
        { 
            TimeSpan ts = utcExpiry - DateTime.UtcNow; 
            string processedKey = ProcessKey(key); 
  
            CacheDataWithExpiryTimeUtc cacheItem = new CacheDataWithExpiryTimeUtc 
            { 
                Data = entry, 
                ExpiryTimeUtc = utcExpiry 
            }; 
  
            if (ts <= MemoryCacheLimit) 
            { 
                HttpRuntime.Cache. (processedKey, cacheItem, null, utcExpiry.ToLocalTime(), TimeSpan.Zero); 
            } 
            else
            { 
                string cacheFilePath = GetFilePath(processedKey); 
                  
                using (var fs = new FileStream(cacheFilePath,FileMode.OpenOrCreate,FileAccess.ReadWrite)) 
                { 
                    var formatter = new BinaryFormatter(); 
                    formatter.Serialize(fs, cacheItem); 
                } 
            } 
        } 
  
        /// <summary> 
        /// 如果缓存设定的时间超过此值则缓存到文件中，否则在HttpRuntime.Cache中做缓存 
        /// </summary> 
        [XmlAttribute("memoryCacheLimit")] 
        public TimeSpan MemoryCacheLimit { get; set; } 
  
  
        /// <summary> 
        /// 文件缓存的根目录，可以指定任何可访问目录 
        /// </summary> 
        [XmlAttribute("fileCacheRoot")] 
        public string FileCacheRoot { get; set; } 
    } 
  
    /// <summary> 
    /// 对缓存数据和缓存的过期时间的封装 
    /// </summary> 
    [Serializable] 
    internal class CacheDataWithExpiryTimeUtc 
    { 
        public object Data { get; set; } 
  
        public DateTime ExpiryTimeUtc { get; set; } 
    } 
}