indexingfiltermarshaler.cs source code in C# .NET

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Code:

/ Net / Net / 3.5.50727.3053 / DEVDIV / depot / DevDiv / releases / Orcas / SP / wpf / src / Framework / MS / Internal / IO / Packaging / indexingfiltermarshaler.cs / 1 / indexingfiltermarshaler.cs

                            //------------------------------------------------------------------------------ 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// Description: 
//   Class which acts as adaptor between IManagedFilter and IFilter. 
//   Used by PackageFilter for XamlFilter and CorePropertiesFilter.
//   Used by EncryptedPackageFilter for CorePropertiesFilter. 
//
// History:
//  02/25/2004: JohnLarc: Creation, using BruceMac's code from XamlFilter, ContainerFilter, and ManagedFilterMarshalingHelper.
//  08/26/2004: JohnLarc: Removed access to indexing filters from managed code. 
//  07/18/2005: ArindamB: Removed IPersistStream and IPersistFile interfaces.
// 
//----------------------------------------------------------------------------- 

using System.Diagnostics; 
using System;
using System.Runtime.InteropServices;
using System.Collections;
using System.Windows;                     // for ExceptionStringTable 
using System.Security;                    // for SecurityCritical
 
using MS.Internal.Interop;                // for STAT_CHUNK, etc. 
using MS.Internal;                        // for Invariant
using MS.Internal.PresentationFramework;  // for SecurityHelper 
using MS.Win32;

namespace MS.Internal.IO.Packaging
{ 
    #region IndexingFilterMarshaler
    ///  
    /// Adapter for IManagedFilter. Used to obtain an IFilter interface from an IManagedFilter. 
    /// 
    ///  
    /// IManagedFilter is supported by filters which have purely managed implementation and don't work
    /// with interop entities. Callers like PackageFilter and EncryptedPackageFilter which support
    /// IFilter interfaces interact with IManagedFilters like XamlFilter, PackageCorePropertiesFilter
    /// and EncryptedPackageCorePropertiesFilter through IndexingFilterMarshaler. 
    /// 
    internal class IndexingFilterMarshaler : IFilter 
    { 
        #region Static members.
        ///  
        /// pre-defined GUID for storage properties on file system files (as per MSDN)
        /// 
        internal static Guid PSGUID_STORAGE = new Guid(0xb725f130, 0x47ef, 0x101a, 0xa5, 0xf1, 0x02, 0x60, 0x8c, 0x9e, 0xeb, 0xac);
 
        /// Cache frequently used size values to incur reflection cost just once.
        internal static readonly Int32 _int16Size = SecurityHelper.SizeOf(typeof(Int16)); 
 
        /// 
        /// Constructor. 
        /// 
        /// IManagedFilter implementation
        internal IndexingFilterMarshaler(IManagedFilter managedFilter)
        { 
            if (managedFilter == null)
            { 
                throw new ArgumentNullException("managedFilter"); 
            }
 
            _implementation = managedFilter;
        }

        ///  
        /// Init
        ///  
        /// length of aAttributes 
        /// array of FULLPROPSPEC structs
        /// managed array 
        internal static ManagedFullPropSpec[] MarshalFullPropSpecArray(
            uint cAttributes,    // length of aAttributes
            FULLPROPSPEC[] aAttributes)
        { 
            // If there are attributes, these override the flags
            if (cAttributes > 0) 
            { 
                // Attributes count and array should match.
                // This has already been checked for by XpsFilter. 
                Invariant.Assert(aAttributes != null);

                ManagedFullPropSpec[] initAttributes = new ManagedFullPropSpec[checked((int)cAttributes)];
 
                // convert to managed equivalents to isolate the marshaling effort
                for (int i = 0; i < cAttributes; i++) 
                { 
                    // convert and add to local list
                    initAttributes[i] = new ManagedFullPropSpec(aAttributes[i]); 
                }

                return initAttributes;
            } 
            else
                return null; 
        } 

        ///  
        /// StringToPtr
        /// 
        /// Converts a managed string into the format useful for IFilter.GetText
        /// string to convert 
        /// maximum number of characters to convert
        /// pointer to write to 
        ///  
        /// This method, if exposed to partially trusted callers, can lead to arbitrary memory writing.
        /// Critical    - This code could be used to attempt to build a string from arbitrary data. 
        ///   This code is not intended to be used from PT code.
        ///   Not designed to be accessible from public surface at all. Invoked (indirectly) by unmanaged client code.
        /// 
        [SecurityCritical] 
        internal static void MarshalStringToPtr(string s, ref uint bufCharacterCount, IntPtr p)
        { 
            // bufCharacterCount is never supposed to be zero at this level. 
            Invariant.Assert(bufCharacterCount != 0);
 
            // ensure the interface rules are followed
            // string must also be null terminated so we restrict the length to buf size - 1
            if ((uint)(s.Length) > bufCharacterCount - 1)
                throw new InvalidOperationException(SR.Get(SRID.FilterGetTextBufferOverflow)); 

            // Return the number of characters written, including the terminating null. 
            bufCharacterCount = (UInt32)s.Length + 1; 

            // convert string to unmanaged string and write into provided buffer 
            Marshal.Copy(s.ToCharArray(), 0, p, s.Length);

            // null terminate (16bit's of zero to replace one Unicode character)
            Marshal.WriteInt16(p, s.Length * _int16Size, 0); 
        }
 
        ///  
        /// Marshal Managed to Native PROPSPEC
        ///  
        /// 
        /// 
        ///
        ///     Critical: calls Marshal.StringToCoTaskMemUni which LinkDemands, and writes string into unmanaged memory. 
        ///
        [SecurityCritical] 
        internal static void MarshalPropSpec(ManagedPropSpec propSpec, ref PROPSPEC native) 
        {
            native.propType = (uint)propSpec.PropType; 
            switch (propSpec.PropType)
            {
                case PropSpecType.Id:
                    native.union.propId = (uint)propSpec.PropId; 
                    break;
 
                case PropSpecType.Name: 
                    native.union.name = Marshal.StringToCoTaskMemUni(propSpec.PropName);
                    break; 

                default:
                    Invariant.Assert(false); // propSpec.PropType is set by internal code in the filter logic.
                    break; 
            }
        } 
 
        /// 
        /// Marshal Managed to Native FULLPROPSPEC 
        /// 
        /// 
        /// 
        /// 
        ///     Critical: calls MarshalPropSpec which is Critical.  Returns a pointer to unmanaged memory.
        /// 
        [SecurityCritical] 
        internal static void MarshalFullPropSpec(ManagedFullPropSpec fullPropSpec, ref FULLPROPSPEC native)
        { 
            native.guid = fullPropSpec.Guid;
            MarshalPropSpec(fullPropSpec.Property, ref native.property);
        }
 
        /// 
        /// GetChunk 
        ///  
        /// An interop STAT_CHUNK from a ManagedChunk
        /// 
        ///     Critical: calls MarshalFullPropSpec which is Critical.  Returns a pointer to unmanaged memory.
        ///
        [SecurityCritical]
        internal static STAT_CHUNK MarshalChunk(ManagedChunk chunk) 
        {
            STAT_CHUNK native = new STAT_CHUNK(); 
 
            native.idChunk = chunk.ID;
            Invariant.Assert(chunk.BreakType >= CHUNK_BREAKTYPE.CHUNK_NO_BREAK && chunk.BreakType <= CHUNK_BREAKTYPE.CHUNK_EOC); 
            native.breakType = chunk.BreakType;
            Invariant.Assert(
                chunk.Flags >= 0
                && 
                chunk.Flags <= (CHUNKSTATE.CHUNK_TEXT | CHUNKSTATE.CHUNK_VALUE | CHUNKSTATE.CHUNK_FILTER_OWNED_VALUE));
            native.flags = chunk.Flags; 
            native.locale = chunk.Locale; 
            native.idChunkSource = chunk.ChunkSource;
            native.cwcStartSource = chunk.StartSource; 
            native.cwcLenSource = chunk.LenSource;
            MarshalFullPropSpec(chunk.Attribute, ref native.attribute);

            return native; 
        }
 
        ///  
        /// MarshalPropVariant
        ///  
        /// Object to marshal, should be DateTime or String
        /// newly allocated PROPVARIANT structure
        ///
        ///     Critical: calls Marshal.StringToCoTaskMemAnsi which LinkDemands, and writes string into unmanaged memory. 
        ///
        [SecurityCritical] 
        internal static IntPtr MarshalPropVariant(Object obj) 
        {
            IntPtr pszVal = IntPtr.Zero; 
            IntPtr pNative = IntPtr.Zero;

            try
            { 
                PROPVARIANT v;
 
                if (obj is string) 
                {
                    pszVal = Marshal.StringToCoTaskMemAnsi((string)obj); 

                    v = new PROPVARIANT();
                    v.vt = VARTYPE.VT_LPSTR;
                    v.union.pszVal = pszVal; 
                }
                else if (obj is DateTime) 
                { 
                    v = new PROPVARIANT();
                    v.vt = VARTYPE.VT_FILETIME; 
                    long longFileTime = ((DateTime)obj).ToFileTime();
                    v.union.filetime.dwLowDateTime = (Int32)longFileTime;
                    v.union.filetime.dwHighDateTime = (Int32)((longFileTime >> 32) & 0xFFFFFFFF);
                } 
                else
                { 
                    throw new InvalidOperationException( 
                        SR.Get(SRID.FilterGetValueMustBeStringOrDateTime));
                } 

                // allocate an unmanaged PROPVARIANT to return
                pNative = Marshal.AllocCoTaskMem(Marshal.SizeOf(typeof(PROPVARIANT)));
                // Per MSDN, AllocCoTaskMem never returns null. One can't be too careful, though. 
                Invariant.Assert(pNative != null);
 
                // marshal the managed PROPVARIANT into the unmanaged block and return it 
                Marshal.StructureToPtr(v, pNative, false);
            } 
            catch
            {
                if (pszVal != IntPtr.Zero)
                { 
                    Marshal.FreeCoTaskMem(pszVal);
                } 
 
                if (pNative != IntPtr.Zero)
                { 
                    Marshal.FreeCoTaskMem(pNative);
                }

                throw; 
            }
 
            return pNative; 
        }
        #endregion Static members. 

        #region IFilter implementation
        /// 
        /// Init 
        /// 
        /// usage flags 
        /// length of aAttributes 
        /// array of FULLPROPSPEC structs
        /// flags 
        public IFILTER_FLAGS Init(IFILTER_INIT grfFlags,       // IFILTER_INIT value
            uint cAttributes,               // length of aAttributes
            FULLPROPSPEC[] aAttributes)     // restrict responses to the specified attributes
        { 
            ManagedFullPropSpec[] managedArray = MarshalFullPropSpecArray(
                                                 cAttributes, aAttributes); 
 
            return _implementation.Init(grfFlags, managedArray);
        } 

        /// 
        /// GetChunk
        ///  
        /// the next chunk
        /// 
        ///     Critical: calls MarshalChunk which is Critical.  Returns a pointer to unmanaged memory. 
        ///
        [SecurityCritical] 
        public STAT_CHUNK GetChunk()
        {
            // Get the managed chunk
            ManagedChunk managedChunk = _implementation.GetChunk(); 

            if (managedChunk == null) 
            { 
                // End of chunks.
 
                if (ThrowOnEndOfChunks)
                {
                    // Throw exception.
                    throw new COMException(SR.Get(SRID.FilterEndOfChunks), 
                        (int)FilterErrorCode.FILTER_E_END_OF_CHUNKS);
                } 
 
                // Return STAT_CHUNK with idChunk as 0.
 
                STAT_CHUNK chunk = new STAT_CHUNK();
                chunk.idChunk = 0;
                return chunk;
 
            }
 
            // Valid chunk. Return corresponding STAT_CHUNK. 
            return MarshalChunk(managedChunk);
        } 

        /// 
        ///    GetText
        ///  
        /// Buffer size in Unicode characters (not bytes)
        /// Pre-allocated buffer for us to write into.  String must be null-terminated. 
        ///  
        /// Critical    - Invokes the critical method MarshalStringToPtr, which could be used to attempt to build a string from arbitrary data.
        ///   This code is not intended to be called from PT code. 
        ///   Not designed to be accessible from public surface at all. Invoked (indirectly) by unmanaged client code.
        /// 
        [SecurityCritical]
        public void GetText(ref uint bufCharacterCount, IntPtr pBuffer) 
        {
            // NOTE: bufCharacterCount and pBuffer are already validated by XpsFilter. 
            // In future, if this class is exposed publicly or used in a way other than 
            // through XpsFilter, proper checks needs to be present either here or in the caller.
 
            // get the managed string and marshal
            MarshalStringToPtr(_implementation.GetText((int)bufCharacterCount - 1),
                ref bufCharacterCount, pBuffer);
        } 

        ///  
        /// GetValue 
        /// 
        /// newly allocated PROPVARIANT structure 
        ///
        ///     Critical: calls MarshalPropVariant which is Critical.  Returns a pointer to unmanaged memory.
        ///
        [SecurityCritical] 
        public IntPtr GetValue()
        { 
            return MarshalPropVariant(_implementation.GetValue()); 
        }
 
        /// 
        /// BindRegion
        /// 
        ///  
        /// 
        ///  
        /// The MSDN specification requires this function to return E_NOTIMPL for the time being. 
        /// 
        public IntPtr BindRegion(FILTERREGION origPos, ref Guid riid) 
        {
            // The following exception maps to E_NOTIMPL.
            throw new NotImplementedException(SR.Get(SRID.FilterBindRegionNotImplemented));
        } 
        #endregion IFilter implementation
 
        #region Properties 

        ///  
        /// If set to true, FILTER_E_END_OF_CHUNKS exception is thrown
        /// by IFilter.GetChunk() on end of chunks.
        /// If false, a STAT_CHUNK with idChunk as 0 is returned instead.
        ///  
        internal bool ThrowOnEndOfChunks
        { 
            get 
            {
                return _throwOnEndOfChunks; 
            }

            set
            { 
                _throwOnEndOfChunks = value;
            } 
        } 

        #endregion Properties 

        #region Fields

        private IManagedFilter _implementation; 
        private bool _throwOnEndOfChunks = true;
 
        #endregion Fields 
    }
    #endregion IndexingFilterMarshaler 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
//------------------------------------------------------------------------------ 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// Description: 
//   Class which acts as adaptor between IManagedFilter and IFilter. 
//   Used by PackageFilter for XamlFilter and CorePropertiesFilter.
//   Used by EncryptedPackageFilter for CorePropertiesFilter. 
//
// History:
//  02/25/2004: JohnLarc: Creation, using BruceMac's code from XamlFilter, ContainerFilter, and ManagedFilterMarshalingHelper.
//  08/26/2004: JohnLarc: Removed access to indexing filters from managed code. 
//  07/18/2005: ArindamB: Removed IPersistStream and IPersistFile interfaces.
// 
//----------------------------------------------------------------------------- 

using System.Diagnostics; 
using System;
using System.Runtime.InteropServices;
using System.Collections;
using System.Windows;                     // for ExceptionStringTable 
using System.Security;                    // for SecurityCritical
 
using MS.Internal.Interop;                // for STAT_CHUNK, etc. 
using MS.Internal;                        // for Invariant
using MS.Internal.PresentationFramework;  // for SecurityHelper 
using MS.Win32;

namespace MS.Internal.IO.Packaging
{ 
    #region IndexingFilterMarshaler
    ///  
    /// Adapter for IManagedFilter. Used to obtain an IFilter interface from an IManagedFilter. 
    /// 
    ///  
    /// IManagedFilter is supported by filters which have purely managed implementation and don't work
    /// with interop entities. Callers like PackageFilter and EncryptedPackageFilter which support
    /// IFilter interfaces interact with IManagedFilters like XamlFilter, PackageCorePropertiesFilter
    /// and EncryptedPackageCorePropertiesFilter through IndexingFilterMarshaler. 
    /// 
    internal class IndexingFilterMarshaler : IFilter 
    { 
        #region Static members.
        ///  
        /// pre-defined GUID for storage properties on file system files (as per MSDN)
        /// 
        internal static Guid PSGUID_STORAGE = new Guid(0xb725f130, 0x47ef, 0x101a, 0xa5, 0xf1, 0x02, 0x60, 0x8c, 0x9e, 0xeb, 0xac);
 
        /// Cache frequently used size values to incur reflection cost just once.
        internal static readonly Int32 _int16Size = SecurityHelper.SizeOf(typeof(Int16)); 
 
        /// 
        /// Constructor. 
        /// 
        /// IManagedFilter implementation
        internal IndexingFilterMarshaler(IManagedFilter managedFilter)
        { 
            if (managedFilter == null)
            { 
                throw new ArgumentNullException("managedFilter"); 
            }
 
            _implementation = managedFilter;
        }

        ///  
        /// Init
        ///  
        /// length of aAttributes 
        /// array of FULLPROPSPEC structs
        /// managed array 
        internal static ManagedFullPropSpec[] MarshalFullPropSpecArray(
            uint cAttributes,    // length of aAttributes
            FULLPROPSPEC[] aAttributes)
        { 
            // If there are attributes, these override the flags
            if (cAttributes > 0) 
            { 
                // Attributes count and array should match.
                // This has already been checked for by XpsFilter. 
                Invariant.Assert(aAttributes != null);

                ManagedFullPropSpec[] initAttributes = new ManagedFullPropSpec[checked((int)cAttributes)];
 
                // convert to managed equivalents to isolate the marshaling effort
                for (int i = 0; i < cAttributes; i++) 
                { 
                    // convert and add to local list
                    initAttributes[i] = new ManagedFullPropSpec(aAttributes[i]); 
                }

                return initAttributes;
            } 
            else
                return null; 
        } 

        ///  
        /// StringToPtr
        /// 
        /// Converts a managed string into the format useful for IFilter.GetText
        /// string to convert 
        /// maximum number of characters to convert
        /// pointer to write to 
        ///  
        /// This method, if exposed to partially trusted callers, can lead to arbitrary memory writing.
        /// Critical    - This code could be used to attempt to build a string from arbitrary data. 
        ///   This code is not intended to be used from PT code.
        ///   Not designed to be accessible from public surface at all. Invoked (indirectly) by unmanaged client code.
        /// 
        [SecurityCritical] 
        internal static void MarshalStringToPtr(string s, ref uint bufCharacterCount, IntPtr p)
        { 
            // bufCharacterCount is never supposed to be zero at this level. 
            Invariant.Assert(bufCharacterCount != 0);
 
            // ensure the interface rules are followed
            // string must also be null terminated so we restrict the length to buf size - 1
            if ((uint)(s.Length) > bufCharacterCount - 1)
                throw new InvalidOperationException(SR.Get(SRID.FilterGetTextBufferOverflow)); 

            // Return the number of characters written, including the terminating null. 
            bufCharacterCount = (UInt32)s.Length + 1; 

            // convert string to unmanaged string and write into provided buffer 
            Marshal.Copy(s.ToCharArray(), 0, p, s.Length);

            // null terminate (16bit's of zero to replace one Unicode character)
            Marshal.WriteInt16(p, s.Length * _int16Size, 0); 
        }
 
        ///  
        /// Marshal Managed to Native PROPSPEC
        ///  
        /// 
        /// 
        ///
        ///     Critical: calls Marshal.StringToCoTaskMemUni which LinkDemands, and writes string into unmanaged memory. 
        ///
        [SecurityCritical] 
        internal static void MarshalPropSpec(ManagedPropSpec propSpec, ref PROPSPEC native) 
        {
            native.propType = (uint)propSpec.PropType; 
            switch (propSpec.PropType)
            {
                case PropSpecType.Id:
                    native.union.propId = (uint)propSpec.PropId; 
                    break;
 
                case PropSpecType.Name: 
                    native.union.name = Marshal.StringToCoTaskMemUni(propSpec.PropName);
                    break; 

                default:
                    Invariant.Assert(false); // propSpec.PropType is set by internal code in the filter logic.
                    break; 
            }
        } 
 
        /// 
        /// Marshal Managed to Native FULLPROPSPEC 
        /// 
        /// 
        /// 
        /// 
        ///     Critical: calls MarshalPropSpec which is Critical.  Returns a pointer to unmanaged memory.
        /// 
        [SecurityCritical] 
        internal static void MarshalFullPropSpec(ManagedFullPropSpec fullPropSpec, ref FULLPROPSPEC native)
        { 
            native.guid = fullPropSpec.Guid;
            MarshalPropSpec(fullPropSpec.Property, ref native.property);
        }
 
        /// 
        /// GetChunk 
        ///  
        /// An interop STAT_CHUNK from a ManagedChunk
        /// 
        ///     Critical: calls MarshalFullPropSpec which is Critical.  Returns a pointer to unmanaged memory.
        ///
        [SecurityCritical]
        internal static STAT_CHUNK MarshalChunk(ManagedChunk chunk) 
        {
            STAT_CHUNK native = new STAT_CHUNK(); 
 
            native.idChunk = chunk.ID;
            Invariant.Assert(chunk.BreakType >= CHUNK_BREAKTYPE.CHUNK_NO_BREAK && chunk.BreakType <= CHUNK_BREAKTYPE.CHUNK_EOC); 
            native.breakType = chunk.BreakType;
            Invariant.Assert(
                chunk.Flags >= 0
                && 
                chunk.Flags <= (CHUNKSTATE.CHUNK_TEXT | CHUNKSTATE.CHUNK_VALUE | CHUNKSTATE.CHUNK_FILTER_OWNED_VALUE));
            native.flags = chunk.Flags; 
            native.locale = chunk.Locale; 
            native.idChunkSource = chunk.ChunkSource;
            native.cwcStartSource = chunk.StartSource; 
            native.cwcLenSource = chunk.LenSource;
            MarshalFullPropSpec(chunk.Attribute, ref native.attribute);

            return native; 
        }
 
        ///  
        /// MarshalPropVariant
        ///  
        /// Object to marshal, should be DateTime or String
        /// newly allocated PROPVARIANT structure
        ///
        ///     Critical: calls Marshal.StringToCoTaskMemAnsi which LinkDemands, and writes string into unmanaged memory. 
        ///
        [SecurityCritical] 
        internal static IntPtr MarshalPropVariant(Object obj) 
        {
            IntPtr pszVal = IntPtr.Zero; 
            IntPtr pNative = IntPtr.Zero;

            try
            { 
                PROPVARIANT v;
 
                if (obj is string) 
                {
                    pszVal = Marshal.StringToCoTaskMemAnsi((string)obj); 

                    v = new PROPVARIANT();
                    v.vt = VARTYPE.VT_LPSTR;
                    v.union.pszVal = pszVal; 
                }
                else if (obj is DateTime) 
                { 
                    v = new PROPVARIANT();
                    v.vt = VARTYPE.VT_FILETIME; 
                    long longFileTime = ((DateTime)obj).ToFileTime();
                    v.union.filetime.dwLowDateTime = (Int32)longFileTime;
                    v.union.filetime.dwHighDateTime = (Int32)((longFileTime >> 32) & 0xFFFFFFFF);
                } 
                else
                { 
                    throw new InvalidOperationException( 
                        SR.Get(SRID.FilterGetValueMustBeStringOrDateTime));
                } 

                // allocate an unmanaged PROPVARIANT to return
                pNative = Marshal.AllocCoTaskMem(Marshal.SizeOf(typeof(PROPVARIANT)));
                // Per MSDN, AllocCoTaskMem never returns null. One can't be too careful, though. 
                Invariant.Assert(pNative != null);
 
                // marshal the managed PROPVARIANT into the unmanaged block and return it 
                Marshal.StructureToPtr(v, pNative, false);
            } 
            catch
            {
                if (pszVal != IntPtr.Zero)
                { 
                    Marshal.FreeCoTaskMem(pszVal);
                } 
 
                if (pNative != IntPtr.Zero)
                { 
                    Marshal.FreeCoTaskMem(pNative);
                }

                throw; 
            }
 
            return pNative; 
        }
        #endregion Static members. 

        #region IFilter implementation
        /// 
        /// Init 
        /// 
        /// usage flags 
        /// length of aAttributes 
        /// array of FULLPROPSPEC structs
        /// flags 
        public IFILTER_FLAGS Init(IFILTER_INIT grfFlags,       // IFILTER_INIT value
            uint cAttributes,               // length of aAttributes
            FULLPROPSPEC[] aAttributes)     // restrict responses to the specified attributes
        { 
            ManagedFullPropSpec[] managedArray = MarshalFullPropSpecArray(
                                                 cAttributes, aAttributes); 
 
            return _implementation.Init(grfFlags, managedArray);
        } 

        /// 
        /// GetChunk
        ///  
        /// the next chunk
        /// 
        ///     Critical: calls MarshalChunk which is Critical.  Returns a pointer to unmanaged memory. 
        ///
        [SecurityCritical] 
        public STAT_CHUNK GetChunk()
        {
            // Get the managed chunk
            ManagedChunk managedChunk = _implementation.GetChunk(); 

            if (managedChunk == null) 
            { 
                // End of chunks.
 
                if (ThrowOnEndOfChunks)
                {
                    // Throw exception.
                    throw new COMException(SR.Get(SRID.FilterEndOfChunks), 
                        (int)FilterErrorCode.FILTER_E_END_OF_CHUNKS);
                } 
 
                // Return STAT_CHUNK with idChunk as 0.
 
                STAT_CHUNK chunk = new STAT_CHUNK();
                chunk.idChunk = 0;
                return chunk;
 
            }
 
            // Valid chunk. Return corresponding STAT_CHUNK. 
            return MarshalChunk(managedChunk);
        } 

        /// 
        ///    GetText
        ///  
        /// Buffer size in Unicode characters (not bytes)
        /// Pre-allocated buffer for us to write into.  String must be null-terminated. 
        ///  
        /// Critical    - Invokes the critical method MarshalStringToPtr, which could be used to attempt to build a string from arbitrary data.
        ///   This code is not intended to be called from PT code. 
        ///   Not designed to be accessible from public surface at all. Invoked (indirectly) by unmanaged client code.
        /// 
        [SecurityCritical]
        public void GetText(ref uint bufCharacterCount, IntPtr pBuffer) 
        {
            // NOTE: bufCharacterCount and pBuffer are already validated by XpsFilter. 
            // In future, if this class is exposed publicly or used in a way other than 
            // through XpsFilter, proper checks needs to be present either here or in the caller.
 
            // get the managed string and marshal
            MarshalStringToPtr(_implementation.GetText((int)bufCharacterCount - 1),
                ref bufCharacterCount, pBuffer);
        } 

        ///  
        /// GetValue 
        /// 
        /// newly allocated PROPVARIANT structure 
        ///
        ///     Critical: calls MarshalPropVariant which is Critical.  Returns a pointer to unmanaged memory.
        ///
        [SecurityCritical] 
        public IntPtr GetValue()
        { 
            return MarshalPropVariant(_implementation.GetValue()); 
        }
 
        /// 
        /// BindRegion
        /// 
        ///  
        /// 
        ///  
        /// The MSDN specification requires this function to return E_NOTIMPL for the time being. 
        /// 
        public IntPtr BindRegion(FILTERREGION origPos, ref Guid riid) 
        {
            // The following exception maps to E_NOTIMPL.
            throw new NotImplementedException(SR.Get(SRID.FilterBindRegionNotImplemented));
        } 
        #endregion IFilter implementation
 
        #region Properties 

        ///  
        /// If set to true, FILTER_E_END_OF_CHUNKS exception is thrown
        /// by IFilter.GetChunk() on end of chunks.
        /// If false, a STAT_CHUNK with idChunk as 0 is returned instead.
        ///  
        internal bool ThrowOnEndOfChunks
        { 
            get 
            {
                return _throwOnEndOfChunks; 
            }

            set
            { 
                _throwOnEndOfChunks = value;
            } 
        } 

        #endregion Properties 

        #region Fields

        private IManagedFilter _implementation; 
        private bool _throwOnEndOfChunks = true;
 
        #endregion Fields 
    }
    #endregion IndexingFilterMarshaler 
}

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

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