Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Data/System/Data/ProviderBase/TimeoutTimer.cs

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+//------------------------------------------------------------------------------
+// <copyright file="TimeoutTimer.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+//
+//  Class used to manage timeouts in complex system operations.
+//
+// <owner current="true" primary="true">[....]</owner>
+// <owner current="true" primary="false">[....]</owner>
+//------------------------------------------------------------------------------
+
+namespace System.Data.ProviderBase
+{
+    using System;
+    using System.Data.Common;
+    using System.Diagnostics;
+
+// Purpose:
+//   Manages determining and tracking timeouts
+//
+// Intended use:
+//   Call StartXXXXTimeout() to get a timer with the given expiration point
+//   Get remaining time in appropriate format to pass to subsystem timeouts
+//   Check for timeout via IsExpired for checks in managed code.
+//   Simply abandon to GC when done.
+internal class TimeoutTimer
+{
+    //-------------------
+    // Fields
+    //-------------------
+    private long _timerExpire;
+    private bool _isInfiniteTimeout;
+
+    //-------------------
+    // Timeout-setting methods
+    //-------------------
+
+    // Get a new timer that will expire in the given number of seconds
+    //  For input, a value of zero seconds indicates infinite timeout
+    internal static TimeoutTimer StartSecondsTimeout(int seconds)
+    {
+        //--------------------
+        // Preconditions: None (seconds must conform to SetTimeoutSeconds requirements)
+
+        //--------------------
+        // Method body
+        var timeout = new TimeoutTimer();
+        timeout.SetTimeoutSeconds(seconds);
+
+        //---------------------
+        // Postconditions
+        Debug.Assert(timeout != null); // Need a valid timeouttimer if no error
+
+        return timeout;
+    }
+
+    // Get a new timer that will expire in the given number of milliseconds
+    //  No current need to support infinite milliseconds timeout
+    internal static TimeoutTimer StartMillisecondsTimeout(long milliseconds)
+    {
+        //--------------------
+        // Preconditions
+        Debug.Assert(0 <= milliseconds);
+
+        //--------------------
+        // Method body
+        var timeout = new TimeoutTimer();
+        timeout._timerExpire = checked(ADP.TimerCurrent() + (milliseconds * TimeSpan.TicksPerMillisecond));
+        timeout._isInfiniteTimeout = false;
+
+        //---------------------
+        // Postconditions
+        Debug.Assert(timeout != null); // Need a valid timeouttimer if no error
+
+        return timeout;
+    }
+
+    //-------------------
+    // Methods for changing timeout
+    //-------------------
+
+    internal void SetTimeoutSeconds(int seconds)
+    {
+        //--------------------
+        // Preconditions
+        Debug.Assert(0 <= seconds || InfiniteTimeout == seconds);  // no need to support negative seconds at present
+
+        //--------------------
+        // Method body
+        if (InfiniteTimeout == seconds)
+        {
+            _isInfiniteTimeout = true;
+        }
+        else
+        {
+            // Stash current time + timeout
+            _timerExpire = checked(ADP.TimerCurrent() + ADP.TimerFromSeconds(seconds));
+            _isInfiniteTimeout = false;
+        }
+
+        //---------------------
+        // Postconditions:None
+    }
+
+    //-------------------
+    // Timeout info properties
+    //-------------------
+
+    // Indicator for infinite timeout when starting a timer
+    internal static readonly long InfiniteTimeout = 0;
+
+    // Is this timer in an expired state?
+    internal bool IsExpired 
+    {
+        get 
+        {
+            return !IsInfinite && ADP.TimerHasExpired(_timerExpire);
+        }
+    }
+
+    // is this an infinite-timeout timer?
+    internal bool IsInfinite
+    {
+        get
+        {
+            return _isInfiniteTimeout;
+        }
+    }
+
+    // Special accessor for TimerExpire for use when thunking to legacy timeout methods.
+    internal long LegacyTimerExpire
+    {
+        get
+        {
+            return (_isInfiniteTimeout) ? Int64.MaxValue : _timerExpire;
+        }
+    }
+
+    // Returns milliseconds remaining trimmed to zero for none remaining
+    //  and long.MaxValue for infinite
+    // This method should be prefered for internal calculations that are not
+    //  yet common enough to code into the TimeoutTimer class itself.
+    internal long MillisecondsRemaining
+    {
+        get 
+        {
+            //-------------------
+            // Preconditions: None
+
+            //-------------------
+            // Method Body
+            long milliseconds;
+            if (_isInfiniteTimeout)
+            {
+                milliseconds = long.MaxValue;
+            }
+            else
+            {
+                milliseconds = ADP.TimerRemainingMilliseconds(_timerExpire);
+                if (0 > milliseconds)
+                {
+                    milliseconds = 0;
+                }
+            }
+
+            //--------------------
+            // Postconditions
+            Debug.Assert(0<=milliseconds); // This property guarantees no negative return values
+
+            return milliseconds;
+        }
+    }
+
+}
+
+}
+