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//---------------------------------------------------------------------------
//
// <copyright file="ManagedIStream.cs" company="Microsoft">
// Copyright (C) Microsoft Corporation. All rights reserved.
// </copyright>
//
// Description:
// Implements an IStream component initialized from an
// object of type System.IO.Stream.
//
// History:
// 03/28/2004: JohnLarc: Initial implementation
//---------------------------------------------------------------------------
using System;
using System.IO;
using System.Diagnostics; // for Assert
using System.IO.Packaging; // for native APIs
using System.Runtime.InteropServices; // for Marshal, COMException, etc.
using System.Runtime.InteropServices.ComTypes; // for IStream
using System.Windows; // for ExceptionStringTable
using System.Security; // for SecurityCritical
using MS.Win32; // for NativeMethods
namespace MS.Internal.IO.Packaging
{
// The class ManagedIStream is not COM-visible. Its purpose is to be able to invoke COM interfaces
// from managed code rather than the contrary.
internal class ManagedIStream : IStream
{
/// <summary>
/// Constructor
/// </summary>
internal ManagedIStream(Stream ioStream)
{
if (ioStream == null)
{
throw new ArgumentNullException("ioStream");
}
_ioStream = ioStream;
}
/// <summary>
/// Read at most bufferSize bytes into buffer and return the effective
/// number of bytes read in bytesReadPtr (unless null).
/// </summary>
/// <remarks>
/// mscorlib disassembly shows the following MarshalAs parameters
/// void Read([Out, MarshalAs(UnmanagedType.LPArray, SizeParamIndex=1)] byte[] pv, int cb, IntPtr pcbRead);
/// This means marshaling code will have found the size of the array buffer in the parameter bufferSize.
/// </remarks>
///<SecurityNote>
/// Critical: calls Marshal.WriteInt32 which LinkDemands, takes pointers as input
///</SecurityNote>
[SecurityCritical]
void IStream.Read(Byte[] buffer, Int32 bufferSize, IntPtr bytesReadPtr)
{
Int32 bytesRead = _ioStream.Read(buffer, 0, (int) bufferSize);
if (bytesReadPtr != IntPtr.Zero)
{
Marshal.WriteInt32(bytesReadPtr, bytesRead);
}
}
/// <summary>
/// Move the stream pointer to the specified position.
/// </summary>
/// <remarks>
/// System.IO.stream supports searching past the end of the stream, like
/// OLE streams.
/// newPositionPtr is not an out parameter because the method is required
/// to accept NULL pointers.
/// </remarks>
///<SecurityNote>
/// Critical: calls Marshal.WriteInt64 which LinkDemands, takes pointers as input
///</SecurityNote>
[SecurityCritical]
void IStream.Seek(Int64 offset, Int32 origin, IntPtr newPositionPtr)
{
SeekOrigin seekOrigin;
// The operation will generally be I/O bound, so there is no point in
// eliminating the following switch by playing on the fact that
// System.IO uses the same integer values as IStream for SeekOrigin.
switch(origin)
{
case NativeMethods.STREAM_SEEK_SET:
seekOrigin = SeekOrigin.Begin;
break;
case NativeMethods.STREAM_SEEK_CUR:
seekOrigin = SeekOrigin.Current;
break;
case NativeMethods.STREAM_SEEK_END:
seekOrigin = SeekOrigin.End;
break;
default:
throw new ArgumentOutOfRangeException("origin");
}
long position = _ioStream.Seek(offset, seekOrigin);
// Dereference newPositionPtr and assign to the pointed location.
if (newPositionPtr != IntPtr.Zero)
{
Marshal.WriteInt64(newPositionPtr, position);
}
}
/// <summary>
/// Sets stream's size.
/// </summary>
void IStream.SetSize(Int64 libNewSize)
{
_ioStream.SetLength(libNewSize);
}
/// <summary>
/// Obtain stream stats.
/// </summary>
/// <remarks>
/// STATSG has to be qualified because it is defined both in System.Runtime.InteropServices and
/// System.Runtime.InteropServices.ComTypes.
/// The STATSTG structure is shared by streams, storages and byte arrays. Members irrelevant to streams
/// or not available from System.IO.Stream are not returned, which leaves only cbSize and grfMode as
/// meaningful and available pieces of information.
/// grfStatFlag is used to indicate whether the stream name should be returned and is ignored because
/// this information is unavailable.
/// </remarks>
void IStream.Stat(out System.Runtime.InteropServices.ComTypes.STATSTG streamStats, int grfStatFlag)
{
streamStats = new System.Runtime.InteropServices.ComTypes.STATSTG();
streamStats.type = NativeMethods.STGTY_STREAM;
streamStats.cbSize = _ioStream.Length;
// Return access information in grfMode.
streamStats.grfMode = 0; // default value for each flag will be false
if (_ioStream.CanRead && _ioStream.CanWrite)
{
streamStats.grfMode |= NativeMethods.STGM_READWRITE;
}
else if (_ioStream.CanRead)
{
streamStats.grfMode |= NativeMethods.STGM_READ;
}
else if (_ioStream.CanWrite)
{
streamStats.grfMode |= NativeMethods.STGM_WRITE;
}
else
{
// A stream that is neither readable nor writable is a closed stream.
// Note the use of an exception that is known to the interop marshaller
// (unlike ObjectDisposedException).
throw new IOException(SR.Get(SRID.StreamObjectDisposed));
}
}
/// <summary>
/// Write at most bufferSize bytes from buffer.
/// </summary>
///<SecurityNote>
/// Critical: calls Marshal.WriteInt32 which LinkDemands, takes pointers as input
///</SecurityNote>
[SecurityCritical]
void IStream.Write(Byte[] buffer, Int32 bufferSize, IntPtr bytesWrittenPtr)
{
_ioStream.Write(buffer, 0, bufferSize);
if (bytesWrittenPtr != IntPtr.Zero)
{
// If fewer than bufferSize bytes had been written, an exception would
// have been thrown, so it can be assumed we wrote bufferSize bytes.
Marshal.WriteInt32(bytesWrittenPtr, bufferSize);
}
}
#region Unimplemented methods
/// <summary>
/// Create a clone.
/// </summary>
/// <remarks>
/// Not implemented.
/// </remarks>
void IStream.Clone(out IStream streamCopy)
{
streamCopy = null;
throw new NotSupportedException();
}
/// <summary>
/// Read at most bufferSize bytes from the receiver and write them to targetStream.
/// </summary>
/// <remarks>
/// Not implemented.
/// </remarks>
void IStream.CopyTo(IStream targetStream, Int64 bufferSize, IntPtr buffer, IntPtr bytesWrittenPtr)
{
throw new NotSupportedException();
}
/// <summary>
/// Commit changes.
/// </summary>
/// <remarks>
/// Only relevant to transacted streams.
/// </remarks>
void IStream.Commit(Int32 flags)
{
throw new NotSupportedException();
}
/// <summary>
/// Lock at most byteCount bytes starting at offset.
/// </summary>
/// <remarks>
/// Not supported by System.IO.Stream.
/// </remarks>
void IStream.LockRegion(Int64 offset, Int64 byteCount, Int32 lockType)
{
throw new NotSupportedException();
}
/// <summary>
/// Undo writes performed since last Commit.
/// </summary>
/// <remarks>
/// Relevant only to transacted streams.
/// </remarks>
void IStream.Revert()
{
throw new NotSupportedException();
}
/// <summary>
/// Unlock the specified region.
/// </summary>
/// <remarks>
/// Not supported by System.IO.Stream.
/// </remarks>
void IStream.UnlockRegion(Int64 offset, Int64 byteCount, Int32 lockType)
{
throw new NotSupportedException();
}
#endregion Unimplemented methods
#region Fields
private Stream _ioStream;
#endregion Fields
}
}
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