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//------------------------------------------------------------------------------
// <copyright file="PinnedArraySegment.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//------------------------------------------------------------------------------
namespace System.Web.Util {
using System;
using System.Diagnostics.CodeAnalysis;
using System.Runtime.InteropServices;
using System.Security.Permissions;
// Utility class for pinning an ArraySegment<T> so that it can be passed to unmanaged code.
//
// This type is not thread safe.
[SecurityPermission(SecurityAction.LinkDemand, UnmanagedCode = true)]
internal sealed class PinnedArraySegment<T> : IDisposable {
private int _count;
private GCHandle _gcHandle;
[SuppressMessage("Microsoft.Reliability", "CA2006:UseSafeHandleToEncapsulateNativeResources", Justification = @"This is a memory pointer, not a handle. The handle is in the _gcHandle field, and its lifetime is controlled by the caller.")]
private IntPtr _pointer;
internal unsafe PinnedArraySegment(ArraySegment<T> segment) {
// Structs - like ArraySegment<T> - can be "torn" by malicious users trying to take
// advantage of race conditions that occur as a result of their copy-by-value semantics.
// Since we'll pass the ArraySegment<T> to unmanaged code, we need to perform validation
// to make sure that this hasn't happened. The ArraySegment<T> constructor can be used
// to perform this validation. (MSRC 10170)
segment = new ArraySegment<T>(segment.Array, segment.Offset, segment.Count);
_gcHandle = GCHandle.Alloc(segment.Array, GCHandleType.Pinned); // pin the array so that unmanaged code can access it
_pointer = Marshal.UnsafeAddrOfPinnedArrayElement(segment.Array, segment.Offset);
_count = segment.Count;
}
public int Count {
get {
ThrowIfDisposed();
return _count;
}
}
public IntPtr Pointer {
get {
ThrowIfDisposed();
return _pointer;
}
}
[SuppressMessage("Microsoft.Usage", "CA2216:DisposableTypesShouldDeclareFinalizer", Justification = @"We don't own native resources.")]
public void Dispose() {
if (_pointer != IntPtr.Zero) {
// only free the GCHandle once
_pointer = IntPtr.Zero;
_gcHandle.Free();
}
}
private void ThrowIfDisposed() {
if (_pointer == IntPtr.Zero) {
throw new ObjectDisposedException(GetType().FullName);
}
}
}
}
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