mono/mcs/class/referencesource/System.Data/System/Data/OleDb/PropertyIDSet.cs

//------------------------------------------------------------------------------
// <copyright file="PropertyIDSet.cs" company="Microsoft">
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
// <owner current="true" primary="true">[....]</owner>
// <owner current="true" primary="false">[....]</owner>
//------------------------------------------------------------------------------

using System;
using System.Data;
using System.Data.Common;
using System.Data.ProviderBase;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;
using System.Security;
using System.Security.Permissions;

namespace System.Data.OleDb {

    internal sealed class PropertyIDSet : DbBuffer {
    
        static private readonly int PropertyIDSetAndValueSize = ODB.SizeOf_tagDBPROPIDSET + ADP.PtrSize; // sizeof(tagDBPROPIDSET) + sizeof(int)
        static private readonly int PropertyIDSetSize = ODB.SizeOf_tagDBPROPIDSET;

        private int _count;

        // the PropertyID is stored at the end of the tagDBPROPIDSET structure
        // this way only a single memory allocation is required instead of two
        internal PropertyIDSet(Guid propertySet, int propertyID) : base(PropertyIDSetAndValueSize) {
            _count = 1;

            // rgPropertyIDs references where that PropertyID is stored
            // depending on IntPtr.Size, tagDBPROPIDSET is either 24 or 28 bytes long
            IntPtr ptr = ADP.IntPtrOffset(base.handle, PropertyIDSetSize);
            Marshal.WriteIntPtr(base.handle, 0, ptr);

            Marshal.WriteInt32(base.handle, ADP.PtrSize, /*propertyid count*/1);

            ptr = ADP.IntPtrOffset(base.handle, ODB.OffsetOf_tagDBPROPIDSET_PropertySet);
            Marshal.StructureToPtr(propertySet, ptr, false/*deleteold*/);

            // write the propertyID at the same offset
            Marshal.WriteInt32(base.handle, PropertyIDSetSize, propertyID);
        }

        // no propertyIDs, just the propertyset guids
        internal PropertyIDSet(Guid[] propertySets) : base(PropertyIDSetSize * propertySets.Length) {
            _count = propertySets.Length;
            for(int i = 0; i < propertySets.Length; ++i) {
                IntPtr ptr = ADP.IntPtrOffset(base.handle, (i * PropertyIDSetSize) + ODB.OffsetOf_tagDBPROPIDSET_PropertySet);
                Marshal.StructureToPtr(propertySets[i], ptr, false/*deleteold*/);
            }
        }

        internal int Count {
            get {
                return _count;
            }
        }
    }
}