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/*++
Copyright (c) Microsoft Corporation
Module Name:
RequestCachePolicy.cs
Abstract:
The class implements caching policy paradigms that is used by all webrequest cache-aware clients
Author:
Alexei Vopilov 21-Dec-2002
Revision History:
4 Dec 2003 - Reworked as per design review.
30 Jul 2004 - Updated to accomodate FTP caching feature
--*/
namespace System.Net.Cache {
using System.Globalization;
// The enum describes cache settings applicable for any webrequest
public enum RequestCacheLevel
{
// Default cache behavior determined by the protocol class
Default = 0,
// Bypass the cache completely
BypassCache = 1,
// Only serve requests from cache, an exception is thrown if not found
CacheOnly = 2,
// Serve from the cache, but will sync up with the server if not found
CacheIfAvailable = 3,
// Attempt to revalidate cache with the server, reload if unable to
Revalidate = 4,
// Reload the data from the origin server
Reload = 5,
// Bypass the cache and removing existing entries in the cache
NoCacheNoStore = 6
}
//
// Common request cache policy used for caching of Http, FTP, etc.
//
public class RequestCachePolicy
{
private RequestCacheLevel m_Level;
//
// Public stuff
//
public RequestCachePolicy(): this (RequestCacheLevel.Default)
{
}
public RequestCachePolicy(RequestCacheLevel level)
{
if (level < RequestCacheLevel.Default || level > RequestCacheLevel.NoCacheNoStore)
throw new ArgumentOutOfRangeException("level");
m_Level = level;
}
//
public RequestCacheLevel Level
{
get {
return m_Level;
}
}
//
public override string ToString()
{
return "Level:" + m_Level.ToString();
}
//
// Internal stuff
//
//
#if TRAVE
/*
// Consider removing.
internal static string ToString(RequestCachePolicy Policy)
{
if (Policy == null) {
return "null";
}
return Policy.ToString();
}
*/
#endif
}
// The enum describes cache settings for http
public enum HttpRequestCacheLevel
{
// Default cache behavior, server fresh response fomr cache, otherwise attempt
// to revalidate with the server or reload
Default = 0,
// Bypass the cache completely
BypassCache = 1,
// Only serve requests from cache, an exception is thrown if not found
CacheOnly = 2,
// Serve from the cache, but will sync up with the server if not found
CacheIfAvailable = 3,
// Validate cached data with the server even if it looks fresh
Revalidate = 4,
// Reload the data from the origin server
Reload = 5,
// Bypass the cache and removing existing entries in the cache
NoCacheNoStore = 6,
// Serve from cache, or the next cache along the path
CacheOrNextCacheOnly= 7,
// Reload the data either from the origin server or from an uplevel cache
//This is equvalent to Cache-Control:MaxAge=0 HTTP semantic
Refresh = 8,
}
//
// CacheAgeControl is used to specify preferences with respect of cached item age and freshness.
//
public enum HttpCacheAgeControl {
// Invalid value. Indicates the enum is not initialized
None = 0x0,
// Cached item must be at least fresh for specified period since now
MinFresh = 0x1,
// Cached item must be fresh and it's age must not exceed specified period
MaxAge = 0x2,
// Cached item may be not fresh but it's expiration must not exceed specified period
MaxStale = 0x4,
// Cached item must fresh for some period in future and it's age must be less than specified
MaxAgeAndMinFresh = 0x3, // MaxAge|MinFresh,
// Cached item may be found as stale for some period but it's age must be less than specified
MaxAgeAndMaxStale = 0x6, // MaxAge|MaxStale,
}
//
// HTTP cache policy that expresses RFC2616 HTTP caching semantic
//
public class HttpRequestCachePolicy: RequestCachePolicy {
internal static readonly HttpRequestCachePolicy BypassCache = new HttpRequestCachePolicy(HttpRequestCacheLevel.BypassCache);
//Private members
private HttpRequestCacheLevel m_Level = HttpRequestCacheLevel.Default;
private DateTime m_LastSyncDateUtc = DateTime.MinValue;
private TimeSpan m_MaxAge = TimeSpan.MaxValue;
private TimeSpan m_MinFresh = TimeSpan.MinValue;
private TimeSpan m_MaxStale = TimeSpan.MinValue;
//
// Public stuff
//
public HttpRequestCachePolicy():this(HttpRequestCacheLevel.Default)
{
}
//
public HttpRequestCachePolicy(HttpRequestCacheLevel level): base(MapLevel(level))
{
m_Level = level;
}
//
// Creates an automatic cache policy that is bound to a simples age control
//
public HttpRequestCachePolicy(HttpCacheAgeControl cacheAgeControl, TimeSpan ageOrFreshOrStale):this(HttpRequestCacheLevel.Default)
{
switch(cacheAgeControl) {
case HttpCacheAgeControl.MinFresh:
m_MinFresh = ageOrFreshOrStale;
break;
case HttpCacheAgeControl.MaxAge:
m_MaxAge = ageOrFreshOrStale;
break;
case HttpCacheAgeControl.MaxStale:
m_MaxStale = ageOrFreshOrStale;
break;
default:
throw new ArgumentException(SR.GetString(SR.net_invalid_enum, "HttpCacheAgeControl"), "cacheAgeControl");
}
}
//
// Creates an automatic cache policy that is bound to a complex age control
//
public HttpRequestCachePolicy(HttpCacheAgeControl cacheAgeControl, TimeSpan maxAge, TimeSpan freshOrStale):this(HttpRequestCacheLevel.Default)
{
switch(cacheAgeControl) {
case HttpCacheAgeControl.MinFresh:
m_MinFresh = freshOrStale;
break;
case HttpCacheAgeControl.MaxAge:
m_MaxAge = maxAge;
break;
case HttpCacheAgeControl.MaxStale:
m_MaxStale = freshOrStale;
break;
case HttpCacheAgeControl.MaxAgeAndMinFresh:
m_MaxAge = maxAge;
m_MinFresh = freshOrStale;
break;
case HttpCacheAgeControl.MaxAgeAndMaxStale:
m_MaxAge = maxAge;
m_MaxStale = freshOrStale;
break;
default:
throw new ArgumentException(SR.GetString(SR.net_invalid_enum, "HttpCacheAgeControl"), "cacheAgeControl");
}
}
//
// Creates an automatic cache policy with the Date Synchronization requirement
//
public HttpRequestCachePolicy(DateTime cacheSyncDate):this(HttpRequestCacheLevel.Default)
{
m_LastSyncDateUtc = cacheSyncDate.ToUniversalTime();
}
//
//
//
public HttpRequestCachePolicy(HttpCacheAgeControl cacheAgeControl, TimeSpan maxAge, TimeSpan freshOrStale, DateTime cacheSyncDate)
:this(cacheAgeControl, maxAge, freshOrStale)
{
m_LastSyncDateUtc = cacheSyncDate.ToUniversalTime();
}
//
// Properties
//
public new HttpRequestCacheLevel Level
{
get {
return m_Level;
}
}
//
// Requires revalidation of items stored before lastSyncDate
//
public DateTime CacheSyncDate {
get {
if (m_LastSyncDateUtc == DateTime.MinValue || m_LastSyncDateUtc == DateTime.MaxValue) {
return m_LastSyncDateUtc;
}
return m_LastSyncDateUtc.ToLocalTime();}
}
//
internal DateTime InternalCacheSyncDateUtc {
get {return m_LastSyncDateUtc;}
}
//
// Specifies age policy according to HTTP 1.1 RFC caching semantic
//
public TimeSpan MaxAge {
get {return m_MaxAge;}
}
//
// Specifies age policy according to HTTP 1.1 RFC caching semantic
//
public TimeSpan MinFresh {
get {return m_MinFresh;}
}
//
// Specifies age policy according to HTTP 1.1 RFC caching semantic
//
public TimeSpan MaxStale {
get {return m_MaxStale;}
}
//
//
//
public override string ToString()
{
return "Level:" + m_Level.ToString() +
(m_MaxAge == TimeSpan.MaxValue? string.Empty: " MaxAge:" + m_MaxAge.ToString()) +
(m_MinFresh == TimeSpan.MinValue? string.Empty: " MinFresh:" + m_MinFresh.ToString()) +
(m_MaxStale == TimeSpan.MinValue? string.Empty: " MaxStale:" + m_MaxStale.ToString()) +
(CacheSyncDate==DateTime.MinValue? string.Empty: " CacheSyncDate:" + CacheSyncDate.ToString(CultureInfo.CurrentCulture));
}
//
//
//
private static RequestCacheLevel MapLevel(HttpRequestCacheLevel level)
{
if (level <= HttpRequestCacheLevel.NoCacheNoStore)
return (RequestCacheLevel) level;
if (level == HttpRequestCacheLevel.CacheOrNextCacheOnly)
return RequestCacheLevel.CacheOnly;
if (level == HttpRequestCacheLevel.Refresh)
return RequestCacheLevel.Reload;
throw new ArgumentOutOfRangeException("level");
}
}
}
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