/// <summary>
/// Ensures that the cache is not expired.
/// </summary>
private void EnsureExpiration()
{
bool cacheExpired = false;
long maxAge = -1,
expires = -1;
string key = "HttpCache:EnsureExpiration";
if (!TemporaryStorage.Contains(key))
{
cacheExpired = !CanCache();
if (!cacheExpired)
{
if (Flags.ContainsKey("max-age") && long.TryParse(Flags["max-age"], out maxAge) && maxAge > 0)
{
cacheExpired = new DateTime(Created + maxAge).Ticks < DateTime.UtcNow.Ticks;
}
else if (Flags.ContainsKey("expires") && long.TryParse(Flags["expires"], out expires))
{
cacheExpired = new DateTime(expires).Ticks < DateTime.UtcNow.Ticks;
}
}
if (cacheExpired)
{
ClearItems();
}
TemporaryStorage.Set(key, true);
}
}
/// <summary>
/// Returns value indicating whether items can be added or updated.
/// </summary>
/// <returns>Value indicating whether items can be added or updated.</returns>
private bool CanCache()
{
bool ret = true;
string key = "HttpCache:CanCache";
if (!TemporaryStorage.Contains(key))
{
TemporaryStorage.Set(key, !Flags.ContainsKey("no-cache") && !Flags.ContainsKey("no-store"));
}
ret = TemporaryStorage.Get <bool>(key);
return(ret);
}
/// <summary>
/// Ensures that flags are loaded.
/// </summary>
private void EnsureFlags()
{
string[] v = null;
string expires = string.Empty;
string cacheControl = string.Empty;
string key = "HttpCache:EnsureFlags";
DateTime expiresDate = DateTime.MinValue;
if (!TemporaryStorage.Contains(key))
{
expires = HttpContext.Current.Request.Headers["Expires"];
cacheControl = HttpContext.Current.Request.Headers["Cache-Control"];
Flags = new Dictionary <string, string>();
if (!string.IsNullOrEmpty(cacheControl))
{
foreach (string pair in cacheControl.Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries))
{
v = pair.ToLowerInvariant().Split(new char[] { '=' }, StringSplitOptions.RemoveEmptyEntries);
if (v.Any())
{
if (!Flags.ContainsKey(v[0]))
{
Flags.Add(v[0], v.Length > 1 ? v[1] : string.Empty);
}
else
{
Flags[v[0]] = v[1];
}
}
}
}
if (!Flags.ContainsKey("expires") && !string.IsNullOrEmpty(expires) && DateTime.TryParseExact(expires, "ddd, dd MMM yyyy HH:mm:ss 'GMT'", CultureInfo.InvariantCulture, DateTimeStyles.None, out expiresDate))
{
Flags.Add("expires", expiresDate.Ticks.ToString());
}
TemporaryStorage.Set(key, true);
}
}
/// <summary>
/// Returns value indicating whether the item with the given key is currently in the cache.
/// </summary>
/// <param name="key">Item key.</param>
/// <returns>Value indicating whether the item with the given key is currently in the cache.</returns>
protected override bool ContainsItem(string key)
{
EnsureExpiration();
return(base.ContainsItem(key) || TemporaryStorage.Contains(key));
}