ResourcePool.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / xsp / System / Web / Util / ResourcePool.cs / 1 / ResourcePool.cs
                        

                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Web.Util { 
    using System.Collections; 
    using System.Threading;
 
    /*
     * ResourcePool provides a place to store expensive resources,
     * such as network connections, that you want to dispose of when
     * they are underused. A resource pool can be configured to timeout 
     * resources at a given interval, and to have a max limit of resources.
     */ 
    class ResourcePool : IDisposable { 
        ArrayList       _resources;     // the resources
        int             _iDisposable;   // resources below this index are candidates for disposal 
        int             _max;           // max number of resources
        Timer           _timer;         // periodic timer
        TimerCallback   _callback;      // callback delegate
        TimeSpan        _interval;      // callback interval 
        bool            _disposed;
 
        internal ResourcePool(TimeSpan interval, int max) { 
            _interval = interval;
            _resources = new ArrayList(4); 
            _max = max;
            _callback = new TimerCallback(this.TimerProc);

            Debug.Validate("ResourcePool", this); 
        }
 
        ~ResourcePool() { 
            Dispose(false);
        } 

        public void Dispose() {
            Dispose(true);
        } 

        void Dispose(bool disposing) { 
            lock (this) { 
                if (!_disposed) {
                    if (_resources != null) { 
                        foreach (IDisposable resource in _resources) {
                            resource.Dispose();
                        }
 
                        _resources.Clear();
                    } 
 
                    if (_timer != null) {
                        _timer.Dispose(); 
                    }

                    Debug.Trace("ResourcePool", "Disposed");
                    _disposed = true; 

                    // Suppress finalization of this disposed instance. 
                    if (disposing) 
                    {
                        GC.SuppressFinalize(this); 
                    }
                }
            }
        } 

        internal object RetrieveResource() { 
            object result = null; 

            // avoid lock in common case 
            if (_resources.Count != 0) {
                lock (this) {
                    Debug.Validate("ResourcePool", this);
 
                    if (!_disposed) {
                        if (_resources.Count == 0) { 
                            result = null; 
                            Debug.Trace("ResourcePool", "RetrieveResource returned null");
                        } else { 
                            result = _resources[_resources.Count-1];
                            _resources.RemoveAt(_resources.Count-1);
                            if (_resources.Count < _iDisposable) {
                                _iDisposable = _resources.Count; 
                            }
                        } 
 
                        Debug.Validate("ResourcePool", this);
                    } 
                }
            }

            return result; 
        }
 
        internal void StoreResource(IDisposable o) { 

            lock (this) { 
                Debug.Validate("ResourcePool", this);

                if (!_disposed) {
                    if (_resources.Count < _max) { 
                        _resources.Add(o);
                        o = null; 
                        if (_timer == null) { 

#if DBG 
                            if (!Debug.IsTagPresent("Timer") || Debug.IsTagEnabled("Timer"))
#endif
                            {
                                _timer = new Timer(_callback, null, _interval, _interval); 
                            }
                        } 
                    } 

                    Debug.Validate("ResourcePool", this); 
                }
            }

            if (o != null) { 
                Debug.Trace("ResourcePool", "StoreResource reached max=" + _max);
                o.Dispose(); 
            } 
        }
 
        void TimerProc(Object userData) {
            IDisposable[] a = null;

            lock (this) { 
                Debug.Validate("ResourcePool", this);
 
                if (!_disposed) { 
                    if (_resources.Count == 0) {
                        if (_timer != null) { 
                            _timer.Dispose();
                            _timer = null;
                        }
 
                        Debug.Validate("ResourcePool", this);
                        return; 
                    } 

                    a = new IDisposable[_iDisposable]; 
                    _resources.CopyTo(0, a, 0, _iDisposable);
                    _resources.RemoveRange(0, _iDisposable);

                    // It means that whatever remain in _resources will be disposed 
                    // next time the timer proc is called.
                    _iDisposable = _resources.Count; 
 
                    Debug.Trace("ResourcePool", "Timer disposing " + a.Length + "; remaining=" + _resources.Count);
                    Debug.Validate("ResourcePool", this); 
                }
            }

            if (a != null) { 
                for (int i = 0; i < a.Length; i++) {
                    try { 
                        a[i].Dispose(); 
                    }
                    catch { 
                        // ignore all errors
                    }
                }
            } 
        }
 
#if DBG 
        internal void DebugValidate() {
            Debug.CheckValid(_resources != null, "_resources != null"); 

            Debug.CheckValid(0 <= _iDisposable && _iDisposable <= _resources.Count,
                             "0 <= _iDisposable && _iDisposable <= _resources.Count" +
                             ";_iDisposable=" + _iDisposable + 
                             ";_resources.Count=" + _resources.Count);
 
            Debug.CheckValid(_interval > TimeSpan.Zero, "_interval > TimeSpan.Zero" + 
                             ";_interval=" + _interval);
        } 
#endif
    }
}

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