/// <summary>
/// Tries to acquire a shared read lock
/// for the resource, and specifies a timeout for the lock. If this operation
/// succeeds, the lock must be released as soon
/// as possible through the <see cref="ReleaseReadLock"/>
/// method.
/// </summary>
/// <returns>A lock that corresponds to the request. If the lock was denied, the
/// returned item's <see cref="LockItem.LockType"/>
/// is <see cref="ResourceLockType.Denied"/>.</returns>
/// <param name="timeout">The timeout of the lock.
/// A null value requests a lock that doesn't time out.</param>
/// <returns>True if the lock was granted.</returns>
/// <exception cref="ArgumentOutOfRangeException">In case of a negative
/// timeout.</exception>
public LockItem TryGetReadLock(TimeSpan?timeout)
{
lock (this)
{
if (HasWriteLock)
{
return(LockItem.CreateDenied(ResourceId));
}
//clean up inactive locks from time to time
Cleanup();
var item = LockItem.CreateRead(ResourceId, timeout);
readLocks.Add(item);
return(item);
}
}
/// <summary>
/// Tries to acquire an exclusive write lock for the resource
/// which expires after a given time span in order not to block
/// the resource indefinitely.
/// If this operation succeeds, the lock must be released as soon
/// as possible through the <see cref="IResourceLockRepository.ReleaseReadLock"/>
/// method.
/// </summary>
/// <param name="resourceId">Identifies the locked resource.</param>
/// <param name="timeout">The specified expiration timeout from now.
/// Allowed values are null for indefinite locking, or any positive value.</param>
/// <returns>True if the lock was granted.</returns>
/// <exception cref="ArgumentOutOfRangeException">In case of a negative
/// timeout.</exception>
public LockItem TryGetReadLock(string resourceId, TimeSpan?timeout)
{
return(LockItem.CreateRead(resourceId, timeout));
}
/// <summary>
/// Tries to acquire a shared read lock for a given resource
/// which never expires.
/// If this operation succeeds, the lock must be released as soon
/// as possible through the <see cref="IResourceLockRepository.ReleaseReadLock"/>
/// method.
/// </summary>
/// <returns>A <see cref="LockItem"/> instance which represents
/// the acquired lock, if any. If no lock was granted, the
/// returned item's <see cref="LockItem.LockType"/> property
/// returns <see cref="ResourceLockType.Denied"/>.</returns>
public LockItem TryGetReadLock(string resourceId)
{
return(LockItem.CreateRead(resourceId, null));
}
/// <summary>
/// Gets a guard that can be used with a <c>using</c>
/// statement, which tries to get a read lock and
/// ensures the lock is being released as soon as
/// the using block is being exited. Check the
/// guard's <see cref="ResourceLockGuard.IsLockEnabled"/>
/// property to verify whether the lock was granted
/// or not.
/// </summary>
/// <returns>A guard that handles management of the
/// acquired read lock.</returns>
public ResourceLockGuard GetReadGuard(string resourceId)
{
return(new ResourceLockGuard(LockItem.CreateRead(resourceId, null), this));
}