// Copyright (c) 2009, 2019, Oracle and/or its affiliates. All rights reserved.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License, version 2.0, as
// published by the Free Software Foundation.
//
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// with the separately licensed software that they have included with
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//
// Without limiting anything contained in the foregoing, this file,
// which is part of MySQL Connector/NET, is also subject to the
// Universal FOSS Exception, version 1.0, a copy of which can be found at
// http://oss.oracle.com/licenses/universal-foss-exception.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// See the GNU General Public License, version 2.0, for more details.
//
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using System;

namespace MySql.Data.Common
{
    /// <summary>
    /// This class is modeled after .NET Stopwatch. It provides better
    /// performance (no system calls).It is however less precise than
    /// .NET Stopwatch, measuring in milliseconds. It is adequate to use
    /// when high-precision is not required (e.g for measuring IO timeouts),
    /// but not for other tasks.
    /// </summary>
    internal class LowResolutionStopwatch
    {
        long _startTime;
        public static readonly long Frequency = 1000; // measure in milliseconds
        public static readonly bool IsHighResolution = false;

        public LowResolutionStopwatch()
        {
            this.ElapsedMilliseconds = 0;
        }

        public long ElapsedMilliseconds { get; private set; }

        public void Start()
        {
            this._startTime = Environment.TickCount;
        }

        public void Stop()
        {
            long now = Environment.TickCount;
            long elapsed;

            // Calculate time different, handle possible overflow
            if (now < this._startTime)
            {
                if (now < 0)
                {
                    elapsed = 1 + ((long)Int32.MaxValue - this._startTime) + (now - (long)Int32.MinValue);
                }
                else
                {
                    elapsed = Int32.MaxValue - this._startTime + now;
                }
            }
            else
            {
                elapsed = now - this._startTime;
            }

            this.ElapsedMilliseconds += elapsed;
        }

        public void Reset()
        {
            this.ElapsedMilliseconds = 0;
            this._startTime = 0;
        }

        public TimeSpan Elapsed => new TimeSpan(0, 0, 0, 0, (int)this.ElapsedMilliseconds);

        public static LowResolutionStopwatch StartNew()
        {
            LowResolutionStopwatch sw = new LowResolutionStopwatch();
            sw.Start();
            return sw;
        }

        public static long GetTimestamp()
        {
            return Environment.TickCount;
        }

        bool IsRunning()
        {
            return (this._startTime != 0);
        }
    }
}