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//------------------------------------------------------------------------------
// <copyright file="Win32Exception.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//------------------------------------------------------------------------------
/*
*/
namespace System.ComponentModel {
using Microsoft.Win32;
using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Runtime.Remoting;
using System.Runtime.Serialization;
using System.Security;
using System.Security.Permissions;
using System.Text;
/// <devdoc>
/// <para>The exception that is thrown for a Win32 error code.</para>
/// </devdoc>
// Code already shipped - safe to place link demand on derived class constructor when base doesn't have it - Suppress message.
[HostProtection(SharedState = true)]
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Security", "CA2123:OverrideLinkDemandsShouldBeIdenticalToBase")]
[Serializable]
[SuppressUnmanagedCodeSecurity]
public class Win32Exception : ExternalException, ISerializable {
/// <devdoc>
/// <para>Represents the Win32 error code associated with this exception. This
/// field is read-only.</para>
/// </devdoc>
private readonly int nativeErrorCode;
/// <devdoc>
/// <para>Initializes a new instance of the <see cref='System.ComponentModel.Win32Exception'/> class with the last Win32 error
/// that occured.</para>
/// </devdoc>
[SecurityPermission(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)]
public Win32Exception() : this(Marshal.GetLastWin32Error()) {
}
/// <devdoc>
/// <para>Initializes a new instance of the <see cref='System.ComponentModel.Win32Exception'/> class with the specified error.</para>
/// </devdoc>
[SecurityPermission(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)]
public Win32Exception(int error) : this(error, GetErrorMessage(error)) {
}
/// <devdoc>
/// <para>Initializes a new instance of the <see cref='System.ComponentModel.Win32Exception'/> class with the specified error and the
/// specified detailed description.</para>
/// </devdoc>
[SecurityPermission(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)]
public Win32Exception(int error, string message)
: base(message) {
nativeErrorCode = error;
}
/// <devdoc>
/// Initializes a new instance of the Exception class with a specified error message.
/// FxCop CA1032: Multiple constructors are required to correctly implement a custom exception.
/// </devdoc>
[SecurityPermission(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)]
public Win32Exception( string message ) : this(Marshal.GetLastWin32Error(), message) {
}
/// <devdoc>
/// Initializes a new instance of the Exception class with a specified error message and a
/// reference to the inner exception that is the cause of this exception.
/// FxCop CA1032: Multiple constructors are required to correctly implement a custom exception.
/// </devdoc>
[SecurityPermission(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)]
public Win32Exception( string message, Exception innerException ) : base(message, innerException) {
nativeErrorCode = Marshal.GetLastWin32Error();
}
protected Win32Exception(SerializationInfo info, StreamingContext context) : base (info, context) {
IntSecurity.UnmanagedCode.Demand();
nativeErrorCode = info.GetInt32("NativeErrorCode");
}
/// <devdoc>
/// <para>Represents the Win32 error code associated with this exception. This
/// field is read-only.</para>
/// </devdoc>
public int NativeErrorCode {
get {
return nativeErrorCode;
}
}
private static bool TryGetErrorMessage(int error, StringBuilder sb, out string errorMsg)
{
errorMsg = "";
int result = SafeNativeMethods.FormatMessage(
SafeNativeMethods.FORMAT_MESSAGE_IGNORE_INSERTS |
SafeNativeMethods.FORMAT_MESSAGE_FROM_SYSTEM |
SafeNativeMethods.FORMAT_MESSAGE_ARGUMENT_ARRAY,
IntPtr.Zero, (uint) error, 0, sb, sb.Capacity + 1,
null);
if (result != 0) {
int i = sb.Length;
while (i > 0) {
char ch = sb[i - 1];
if (ch > 32 && ch != '.') break;
i--;
}
errorMsg = sb.ToString(0, i);
}
else if (Marshal.GetLastWin32Error() == SafeNativeMethods.ERROR_INSUFFICIENT_BUFFER) {
return false;
}
else {
errorMsg ="Unknown error (0x" + Convert.ToString(error, 16) + ")";
}
return true;
}
// Windows API FormatMessage lets you format a message string given an errocode.
// Unlike other APIs this API does not support a way to query it for the total message size.
//
// So the API can only be used in one of these two ways.
// a. You pass a buffer of appropriate size and get the resource.
// b. Windows creates a buffer and passes the address back and the onus of releasing the bugffer lies on the caller.
//
// Since the error code is coming from the user, it is not possible to know the size in advance.
// Unfortunately we can't use option b. since the buffer can only be freed using LocalFree and it is a private API on onecore.
// Also, using option b is ugly for the manged code and could cause memory leak in situations where freeing is unsuccessful.
//
// As a result we use the following approach.
// We initially call the API with a buffer size of 256 and then gradually increase the size in case of failure until we reach the max allowed size of 65K bytes.
private const int MaxAllowedBufferSize = 65 * 1024;
private static string GetErrorMessage(int error) {
string errorMsg;
StringBuilder sb = new StringBuilder(256);
do {
if (TryGetErrorMessage(error, sb, out errorMsg))
return errorMsg;
else {
// increase the capacity of the StringBuilder by 4 times.
sb.Capacity *= 4;
}
}
while (sb.Capacity < MaxAllowedBufferSize);
// If you come here then a size as large as 65K is also not sufficient and so we give the generic errorMsg.
return "Unknown error (0x" + Convert.ToString(error, 16) + ")";
}
// Even though all we're exposing is the nativeErrorCode (which is also available via public property)
// it's not a bad idea to have this in place. Later, if more fields are added to this exception,
// we won't need to worry about accidentaly exposing them through this interface.
[SecurityPermissionAttribute(SecurityAction.Demand,SerializationFormatter=true)]
public override void GetObjectData(SerializationInfo info, StreamingContext context) {
if (info==null) {
throw new ArgumentNullException("info");
}
info.AddValue("NativeErrorCode", nativeErrorCode);
base.GetObjectData(info, context);
}
}
}
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