78 lines
2.5 KiB
C#
78 lines
2.5 KiB
C#
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//-----------------------------------------------------------------------------
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// Copyright (c) Microsoft Corporation. All rights reserved.
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//-----------------------------------------------------------------------------
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namespace Microsoft.InfoCards
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{
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using System;
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using System.Runtime.InteropServices;
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using System.Runtime.CompilerServices;
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using System.Runtime.ConstrainedExecution;
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using System.Security;
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using Microsoft.InfoCards.Diagnostics;
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using IDT = Microsoft.InfoCards.Diagnostics.InfoCardTrace;
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//
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// Summary:
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// Provides a wrapper over memory allocated by GlobalAlloc
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// guaranteeing that it will be freed during rude thread / appdomain unloads.
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// Remarks:
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// There is a small ---- in the usage of this class, as it is used to wrap return parameters
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// immediatley following the function return.
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//
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internal class GlobalAllocSafeHandle : SafeHandle
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{
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[SuppressUnmanagedCodeSecurity]
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[ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
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[DllImport("Kernel32.dll", EntryPoint = "RtlZeroMemory", SetLastError = false)]
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public static extern void ZeroMemory(IntPtr dest, Int32 size);
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[SuppressUnmanagedCodeSecurity]
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[ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
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[DllImport("kernel32.dll", CallingConvention = CallingConvention.StdCall)]
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public static extern IntPtr GlobalFree(IntPtr hMem);
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//
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// How many bytes we currently wrap. This can be zero, as our usage allows for a valid handle
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// backed by 0 bytes of allocated memory - specificially TransformBlock and TransformFinalBlock
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// can return this by design.
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//
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private int m_bytes;
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private GlobalAllocSafeHandle() : base(IntPtr.Zero, true) { m_bytes = 0; }
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public int Length
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{
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set { m_bytes = value; }
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get { return m_bytes; }
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}
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public override bool IsInvalid
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{
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get
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{
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return (IntPtr.Zero == base.handle);
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}
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}
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//
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// Summary:
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// Clear the data held and release the memory.
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//
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protected override bool ReleaseHandle()
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{
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if (m_bytes > 0)
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{
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ZeroMemory(base.handle, m_bytes);
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GlobalFree(base.handle);
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m_bytes = 0;
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}
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return true;
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}
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}
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}
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