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//------------------------------------------------------------------------------
// <copyright file="DbConnectionPoolAuthenticationContext.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
// <owner current="true" primary="true">harsudan</owner>
// <owner current="true" primary="false">yuronhe</owner>
//------------------------------------------------------------------------------
using System;
using System.Diagnostics;
using System.Runtime.ConstrainedExecution;
using System.Threading;
namespace System.Data.ProviderBase
{
/// <summary>
/// Represents the context of an authentication attempt when using the new active directory based authentication mechanisms.
/// All data members, except_isUpdateInProgressCounter, should be immutable.
/// </summary>
sealed internal class DbConnectionPoolAuthenticationContext
{
/// <summary>
/// The value expected in _isUpdateInProgress if a thread has taken a lock on this context,
/// to perform the update on the context.
/// </summary>
private const int STATUS_LOCKED = 1;
/// <summary>
/// The value expected in _isUpdateInProgress if no thread has taken a lock on this context.
/// </summary>
private const int STATUS_UNLOCKED = 0;
/// <summary>
/// Access Token, which is obtained from Active Directory Authentication Library for SQL Server, and needs to be sent to SQL Server
/// as part of TDS Token type Federated Authentication Token.
/// </summary>
private readonly byte[] _accessToken;
/// <summary>
/// Expiration time of the above access token.
/// </summary>
private readonly DateTime _expirationTime;
/// <summary>
/// A member which is used to achieve a lock to control refresh attempt on this context.
/// </summary>
private int _isUpdateInProgress;
/// <summary>
/// Constructor.
/// </summary>
/// <param name="accessToken">Access Token that will be used to connect to SQL Server. Carries identity information about a user.</param>
/// <param name="expirationTime">The expiration time in UTC for the above accessToken.</param>
internal DbConnectionPoolAuthenticationContext(byte[] accessToken, DateTime expirationTime) {
Debug.Assert(accessToken != null && accessToken.Length > 0);
Debug.Assert(expirationTime > DateTime.MinValue && expirationTime < DateTime.MaxValue);
_accessToken = accessToken;
_expirationTime = expirationTime;
_isUpdateInProgress = STATUS_UNLOCKED;
}
/// <summary>
/// Static Method.
/// Given two contexts, choose one to update in the cache. Chooses based on expiration time.
/// </summary>
/// <param name="context1">Context1</param>
/// <param name="context2">Context2</param>
internal static DbConnectionPoolAuthenticationContext ChooseAuthenticationContextToUpdate(DbConnectionPoolAuthenticationContext context1, DbConnectionPoolAuthenticationContext context2) {
Debug.Assert(context1 != null, "context1 should not be null.");
Debug.Assert(context2 != null, "context2 should not be null.");
return context1.ExpirationTime > context2.ExpirationTime ? context1 : context2;
}
internal byte[] AccessToken {
get {
return _accessToken;
}
}
internal DateTime ExpirationTime {
get {
return _expirationTime;
}
}
/// <summary>
/// Try locking the variable _isUpdateInProgressCounter and return if this thread got the lock to update.
/// Whichever thread got the chance to update this variable to 1 wins the lock.
/// </summary>
internal bool LockToUpdate() {
int oldValue = Interlocked.CompareExchange(ref _isUpdateInProgress, STATUS_LOCKED, STATUS_UNLOCKED);
return (oldValue == STATUS_UNLOCKED);
}
/// <summary>
/// Release the lock which was obtained through LockToUpdate.
/// </summary>
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
internal void ReleaseLockToUpdate() {
int oldValue = Interlocked.CompareExchange(ref _isUpdateInProgress, STATUS_UNLOCKED, STATUS_LOCKED);
Debug.Assert(oldValue == STATUS_LOCKED);
}
}
}
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