GC.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / FXUpdate3074 / FXUpdate3074 / 1.1 / untmp / whidbey / QFE / ndp / clr / src / BCL / System / GC.cs / 5 / GC.cs
                        

                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
/*============================================================
** 
** Class:  GC 
**
** 
** Purpose: Exposes features of the Garbage Collector through
** the class libraries.  This is a class which cannot be
** instantiated.
** 
**
===========================================================*/ 
namespace System { 
    //This class only static members and doesn't require the serializable keyword.
 
    using System;
    using System.Security.Permissions;
    using System.Reflection;
    using System.Security; 
    using System.Threading;
    using System.Runtime.CompilerServices; 
    using System.Runtime.ConstrainedExecution; 
    using System.Reflection.Cache;
    using System.Globalization; 

    // !!!!!!!!!!!!!!!!!!!!!!!
    // make sure you change the def in vm\gc.h
    // if you change this! 
    [Serializable]
    public enum GCCollectionMode 
    { 
        Default = 0,
        Forced = 1, 
        Optimized = 2
    }

    // !!!!!!!!!!!!!!!!!!!!!!! 
    // make sure you change the def in vm\gc.h
    // if you change this! 
    [Serializable] 
    public enum GCNotificationStatus
    { 
        Succeeded = 0,
        Failed = 1,
        Canceled = 2,
        Timeout = 3, 
        NotApplicable = 4
    } 
 
    public static class GC
    { 

        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        internal static extern int nativeGetGCLatencyMode();
 
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        internal static extern void nativeSetGCLatencyMode(int newLatencyMode); 
 
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private static extern int GetGenerationWR(IntPtr handle); 

        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private static extern long nativeGetTotalMemory();
 
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private static extern void nativeCollectGeneration(int generation, int mode); 
 
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private static extern int nativeGetMaxGeneration(); 

        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        private static extern int nativeCollectionCount (int generation); 

        [MethodImplAttribute(MethodImplOptions.InternalCall)] 
        internal static extern bool nativeIsServerGC(); 

        [MethodImplAttribute(MethodImplOptions.InternalCall)] 
        internal static extern void nativeAddMemoryPressure(UInt64 bytesAllocated);

        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        internal static extern void nativeRemoveMemoryPressure(UInt64 bytesAllocated); 

        [SecurityPermission(SecurityAction.LinkDemand, UnmanagedCode=true)] 
        public static void AddMemoryPressure (long bytesAllocated) { 
            if( bytesAllocated <= 0) {
                throw new ArgumentOutOfRangeException("bytesAllocated", 
                        Environment.GetResourceString("ArgumentOutOfRange_NeedPosNum"));
            }

            if( (4 == IntPtr.Size) && (bytesAllocated > Int32.MaxValue) ) { 
                throw new ArgumentOutOfRangeException("pressure",
                        Environment.GetResourceString("ArgumentOutOfRange_MustBeNonNegInt32")); 
            } 

            nativeAddMemoryPressure((ulong)bytesAllocated); 
        }

        [SecurityPermission(SecurityAction.LinkDemand, UnmanagedCode=true)]
        public static void RemoveMemoryPressure (long bytesAllocated) { 
            if( bytesAllocated <= 0) {
                throw new ArgumentOutOfRangeException("bytesAllocated", 
                        Environment.GetResourceString("ArgumentOutOfRange_NeedPosNum")); 
            }
 
            if( (4 == IntPtr.Size)  && (bytesAllocated > Int32.MaxValue) ) {
                throw new ArgumentOutOfRangeException("bytesAllocated",
                        Environment.GetResourceString("ArgumentOutOfRange_MustBeNonNegInt32"));
            } 

            nativeRemoveMemoryPressure((ulong) bytesAllocated); 
        } 

 
        // Returns the generation that obj is currently in.
        //
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        public static extern int GetGeneration(Object obj); 

 
        // Forces a collection of all generations from 0 through Generation. 
        //
        public static void Collect(int generation) { 
            Collect(generation, GCCollectionMode.Default);
        }

        // Garbage Collect all generations. 
        //
        public static void Collect() { 
            //-1 says to GC all generations. 
            nativeCollectGeneration(-1, (int)GCCollectionMode.Default);
        } 

        public static void Collect(int generation, GCCollectionMode mode)
        {
            if (generation<0) 
            {
                throw new ArgumentOutOfRangeException("generation", Environment.GetResourceString("ArgumentOutOfRange_GenericPositive")); 
            } 
            if ((mode < GCCollectionMode.Default) || (mode > GCCollectionMode.Optimized))
            { 
                throw new ArgumentOutOfRangeException(Environment.GetResourceString("ArgumentOutOfRange_Enum"));
            }

            nativeCollectGeneration(generation, (int)mode); 
        }
 
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] 
        public static int CollectionCount (int generation) {
            if (generation<0) { 
                throw new ArgumentOutOfRangeException("generation", Environment.GetResourceString("ArgumentOutOfRange_GenericPositive"));
            }
            return nativeCollectionCount(generation);
 
        }
 
 
        // This method DOES NOT DO ANYTHING in and of itself.  It's used to
        // prevent a finalizable object from losing any outstanding references 
        // a touch too early.  The JIT is very aggressive about keeping an
        // object's lifetime to as small a window as possible, to the point
        // where a 'this' pointer isn't considered live in an instance method
        // unless you read a value from the instance.  So for finalizable 
        // objects that store a handle or pointer and provide a finalizer that
        // cleans them up, this can cause subtle races with the finalizer 
        // thread.  This isn't just about handles - it can happen with just 
        // about any finalizable resource.
        // 
        // Users should insert a call to this method near the end of a
        // method where they must keep an object alive for the duration of that
        // method, up until this method is called.  Here is an example:
        // 
        // "...all you really need is one object with a Finalize method, and a
        // second object with a Close/Dispose/Done method.  Such as the following 
        // contrived example: 
        //
        // class Foo { 
        //    Stream stream = ...;
        //    protected void Finalize() { stream.Close(); }
        //    void Problem() { stream.MethodThatSpansGCs(); }
        //    static void Main() { new Foo().Problem(); } 
        // }
        // 
        // 
        // In this code, Foo will be finalized in the middle of
        // stream.MethodThatSpansGCs, thus closing a stream still in use." 
        //
        // If we insert a call to GC.KeepAlive(this) at the end of Problem(), then
        // Foo doesn't get finalized and the stream says open.
        [MethodImplAttribute(MethodImplOptions.InternalCall)] 
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        public static extern void KeepAlive(Object obj); 
 
        // Returns the generation in which wo currently resides.
        // 
        public static int GetGeneration(WeakReference wo) {
            int result = GetGenerationWR(wo.m_handle);
            KeepAlive(wo);
            return result; 
        }
 
        // Returns the maximum GC generation.  Currently assumes only 1 heap. 
        //
        public static int MaxGeneration { 
            get { return nativeGetMaxGeneration(); }
        }

        [MethodImplAttribute(MethodImplOptions.InternalCall)] 
        public static extern void WaitForPendingFinalizers();
 
        // Indicates that the system should not call the Finalize() method on 
        // an object that would normally require this call.
        // Has the DynamicSecurityMethodAttribute custom attribute to prevent 
        // inlining of the caller.
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        internal static extern void nativeSuppressFinalize(Object o); 

        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)] 
        public static void SuppressFinalize(Object obj) { 
            if (obj == null)
                throw new ArgumentNullException("obj"); 
            nativeSuppressFinalize(obj);
        }

        // Indicates that the system should call the Finalize() method on an object 
        // for which SuppressFinalize has already been called. The other situation
        // where calling ReRegisterForFinalize is useful is inside a finalizer that 
        // needs to resurrect itself or an object that it references. 
        // Has the DynamicSecurityMethodAttribute custom attribute to prevent
        // inlining of the caller. 
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private static extern void nativeReRegisterForFinalize(Object o);

        public static void ReRegisterForFinalize(Object obj) { 
            if (obj == null)
                throw new ArgumentNullException("obj"); 
            nativeReRegisterForFinalize(obj); 
        }
 
        // Returns the total number of bytes currently in use by live objects in
        // the GC heap.  This does not return the total size of the GC heap, but
        // only the live objects in the GC heap.
        // 
        public static long GetTotalMemory(bool forceFullCollection) {
            long size = nativeGetTotalMemory(); 
            if (!forceFullCollection) 
                return size;
            // If we force a full collection, we will run the finalizers on all 
            // existing objects and do a collection until the value stabilizes.
            // The value is "stable" when either the value is within 5% of the
            // previous call to nativeGetTotalMemory, or if we have been sitting
            // here for more than x times (we don't want to loop forever here). 
            int reps = 20;  // Number of iterations
            long newSize = size; 
            float diff; 
            do {
                GC.WaitForPendingFinalizers(); 
                GC.Collect();
                size = newSize;
                newSize = nativeGetTotalMemory();
                diff = ((float)(newSize - size)) / size; 
            } while (reps-- > 0 && !(-.05 < diff && diff < .05));
            return newSize; 
        } 

        [MethodImplAttribute(MethodImplOptions.InternalCall)] 
        private static extern bool nativeRegisterForFullGCNotification(int maxGenerationPercentage, int largeObjectHeapPercentage);

        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private static extern bool nativeCancelFullGCNotification(); 

        [MethodImplAttribute(MethodImplOptions.InternalCall)] 
        private static extern int nativeWaitForFullGCApproach(int millisecondsTimeout); 

        [MethodImplAttribute(MethodImplOptions.InternalCall)] 
        private static extern int nativeWaitForFullGCComplete(int millisecondsTimeout);

        [PermissionSetAttribute(SecurityAction.LinkDemand, Name="FullTrust")]
        public static void RegisterForFullGCNotification(int maxGenerationThreshold, int largeObjectHeapThreshold) 
        {
            if ((maxGenerationThreshold <= 0) || (maxGenerationThreshold >= 100)) 
            { 
                throw new ArgumentOutOfRangeException("maxGenerationThreshold",
                                                      String.Format( 
                                                          CultureInfo.CurrentCulture,
                                                          Environment.GetResourceString("ArgumentOutOfRange_Bounds_Lower_Upper"),
                                                          1,
                                                          99)); 
            }
 
            if ((largeObjectHeapThreshold <= 0) || (largeObjectHeapThreshold >= 100)) 
            {
                throw new ArgumentOutOfRangeException("largeObjectHeapThreshold", 
                                                      String.Format(
                                                          CultureInfo.CurrentCulture,
                                                          Environment.GetResourceString("ArgumentOutOfRange_Bounds_Lower_Upper"),
                                                          1, 
                                                          99));
} 
 
            if (!nativeRegisterForFullGCNotification(maxGenerationThreshold, largeObjectHeapThreshold))
            { 
                throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_NotWithConcurrentGC"));
            }
        }
 
        [PermissionSetAttribute(SecurityAction.LinkDemand, Name="FullTrust")]
        public static void CancelFullGCNotification() 
        { 
            if (!nativeCancelFullGCNotification())
            { 
                throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_NotWithConcurrentGC"));
            }
        }
 
        [PermissionSetAttribute(SecurityAction.LinkDemand, Name="FullTrust")]
        public static GCNotificationStatus WaitForFullGCApproach() 
        { 
            return (GCNotificationStatus)nativeWaitForFullGCApproach(-1);
        } 

        [PermissionSetAttribute(SecurityAction.LinkDemand, Name="FullTrust")]
        public static GCNotificationStatus WaitForFullGCApproach(int millisecondsTimeout)
        { 
            if (millisecondsTimeout < -1)
                throw new ArgumentOutOfRangeException("millisecondsTimeout", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegOrNegative1")); 
 
            return (GCNotificationStatus)nativeWaitForFullGCApproach(millisecondsTimeout);
        } 

        [PermissionSetAttribute(SecurityAction.LinkDemand, Name="FullTrust")]
        public static GCNotificationStatus WaitForFullGCComplete()
        { 
            return (GCNotificationStatus)nativeWaitForFullGCComplete(-1);
        } 
 
        [PermissionSetAttribute(SecurityAction.LinkDemand, Name="FullTrust")]
        public static GCNotificationStatus WaitForFullGCComplete(int millisecondsTimeout) 
        {
            if (millisecondsTimeout < -1)
                throw new ArgumentOutOfRangeException("millisecondsTimeout", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegOrNegative1"));
            return (GCNotificationStatus)nativeWaitForFullGCComplete(millisecondsTimeout); 
        }
 
        [MethodImplAttribute(MethodImplOptions.InternalCall)] 
        private static extern void SetCleanupCache();
 
        private static ClearCacheHandler m_cacheHandler;
        private static readonly Object locker = new Object();

        internal static event ClearCacheHandler ClearCache { 
            add {
                lock (locker) { 
                    m_cacheHandler+=value; 
                    SetCleanupCache();
                } 
            }
            remove {
                lock (locker)
                    m_cacheHandler-=value; 
            }
        } 
 
        //This method is called from native code.  If you update the signature, please also update
        //mscorlib.h and COMUtilNative.cpp 
        internal static void FireCacheEvent() {
            BCLDebug.Trace("CACHE", "Called FileCacheEvent");
            ClearCacheHandler handler = Interlocked.Exchange(ref m_cacheHandler, null);
            if (handler!=null) { 
                handler(null, null);
            } 
        } 
    }
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.

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