11using System ;
22using System . Collections ;
33using System . Collections . Generic ;
4- using System . Linq ;
4+ using System . Runtime . InteropServices ;
5+ using ComTypes = System . Runtime . InteropServices . ComTypes ;
56
67namespace Rubberduck . VBEditor . SafeComWrappers
78{
9+ // The CLR automagically handles COM enumeration by custom marshalling IEnumVARIANT to a managed class (see EnumeratorToEnumVariantMarshaler)
10+ // But as we need explicit control over all COM objects in RD, this is unacceptable. We need to obtain the explicit IEnumVARIANT interface
11+ // and ensure this RCW is destroyed in a timely fashion, using Marshal.ReleaseComObject.
12+ // The automatic custom marshalling of the enumeration getter method (DISPID_ENUM) prohibits access to the underlying IEnumVARIANT interface.
13+ // To work around it, we must call the IDispatch:::Invoke method directly (instead of using CLRs normal late-bound method calling ability).
14+
15+ [ ComImport ( ) , Guid ( "00020400-0000-0000-C000-000000000046" ) ]
16+ [ InterfaceType ( ComInterfaceType . InterfaceIsIUnknown ) ]
17+ interface IDispatch
18+ {
19+ [ PreserveSig ] int GetTypeInfoCount ( [ Out ] out uint pctinfo ) ;
20+ [ PreserveSig ] int GetTypeInfo ( [ In ] uint iTInfo , [ In ] uint lcid , [ Out ] out ComTypes . ITypeInfo pTypeInfo ) ;
21+ [ PreserveSig ] int GetIDsOfNames ( [ In ] ref Guid riid , [ In ] string [ ] rgszNames , [ In ] uint cNames , [ In ] uint lcid , [ Out ] out int [ ] rgDispId ) ;
22+
23+ [ PreserveSig ]
24+ int Invoke ( [ In ] int dispIdMember ,
25+ [ In ] ref Guid riid ,
26+ [ In ] uint lcid ,
27+ [ In ] uint dwFlags ,
28+ [ In , Out ] ref ComTypes . DISPPARAMS pDispParams ,
29+ [ Out ] out Object pVarResult ,
30+ [ In , Out ] ref ComTypes . EXCEPINFO pExcepInfo ,
31+ [ Out ] out uint pArgErr ) ;
32+ }
33+
34+ class IDispatchHelper
35+ {
36+ public enum StandardDispIds : int
37+ {
38+ DISPID_ENUM = - 4
39+ }
40+
41+ public enum InvokeKind : int
42+ {
43+ DISPATCH_METHOD = 1 ,
44+ DISPATCH_PROPERTYGET = 2 ,
45+ DISPATCH_PROPERTYPUT = 4 ,
46+ DISPATCH_PROPERTYPUTREF = 8 ,
47+ }
48+
49+ public static object PropertyGet_NoArgs ( IDispatch obj , int memberId )
50+ {
51+ var pDispParams = new ComTypes . DISPPARAMS ( ) ;
52+ object pVarResult ;
53+ var pExcepInfo = new ComTypes . EXCEPINFO ( ) ;
54+ uint ErrArg ;
55+ Guid guid = new Guid ( ) ;
56+
57+ int hr = obj . Invoke ( memberId , ref guid , 0 , ( uint ) ( InvokeKind . DISPATCH_METHOD | InvokeKind . DISPATCH_PROPERTYGET ) ,
58+ ref pDispParams , out pVarResult , ref pExcepInfo , out ErrArg ) ;
59+
60+ if ( hr < 0 )
61+ {
62+ // could expand this to better handle DISP_E_EXCEPTION
63+ throw Marshal . GetExceptionForHR ( hr ) ;
64+ }
65+
66+ return pVarResult ;
67+ }
68+ }
69+
70+ [ ComImport ( ) , Guid ( "00020404-0000-0000-C000-000000000046" ) ]
71+ [ InterfaceType ( ComInterfaceType . InterfaceIsIUnknown ) ]
72+ public interface IEnumVARIANT
73+ {
74+ // rgVar is technically an unmanaged array here, but we only ever call with celt=1, so this is compatible.
75+ [ PreserveSig ] int Next ( [ In ] uint celt , [ Out ] out object rgVar , [ Out ] out uint pceltFetched ) ;
76+
77+ [ PreserveSig ] int Skip ( [ In ] uint celt ) ;
78+ [ PreserveSig ] int Reset ( ) ;
79+ [ PreserveSig ] int Clone ( [ Out ] out IEnumVARIANT retval ) ;
80+ }
81+
882 public class ComWrapperEnumerator < TWrapperItem > : IEnumerator < TWrapperItem >
983 where TWrapperItem : class
1084 {
1185 private readonly Func < object , TWrapperItem > _itemWrapper ;
12- private readonly IEnumerator _internal ;
86+ private readonly IEnumVARIANT _enumeratorRCW ;
87+ private TWrapperItem _currentItem ;
1388
14- public ComWrapperEnumerator ( IEnumerable source , Func < object , TWrapperItem > itemWrapper )
89+ public ComWrapperEnumerator ( object source , Func < object , TWrapperItem > itemWrapper )
1590 {
1691 _itemWrapper = itemWrapper ;
17- _internal = source ? . GetEnumerator ( ) ?? Enumerable . Empty < TWrapperItem > ( ) . GetEnumerator ( ) ;
92+
93+ if ( source != null )
94+ {
95+ _enumeratorRCW = ( IEnumVARIANT ) IDispatchHelper . PropertyGet_NoArgs ( ( IDispatch ) source , ( int ) IDispatchHelper . StandardDispIds . DISPID_ENUM ) ;
96+ ( ( IEnumerator ) this ) . Reset ( ) ; // precaution
97+ }
1898 }
1999
20100 public void Dispose ( )
21101 {
22- // nothing to dispose here
102+ if ( ! IsWrappingNullReference ) Marshal . ReleaseComObject ( _enumeratorRCW ) ;
23103 }
24104
25- public bool MoveNext ( )
105+ void IEnumerator . Reset ( )
26106 {
27- return _internal . MoveNext ( ) ;
107+ if ( ! IsWrappingNullReference )
108+ {
109+ int hr = _enumeratorRCW . Reset ( ) ;
110+ if ( hr < 0 )
111+ {
112+ throw Marshal . GetExceptionForHR ( hr ) ;
113+ }
114+ }
28115 }
116+
117+ public bool IsWrappingNullReference => _enumeratorRCW == null ;
118+
119+ public TWrapperItem Current => _currentItem ;
120+ object IEnumerator . Current => _currentItem ;
29121
30- public void Reset ( )
122+ bool IEnumerator . MoveNext ( )
31123 {
32- _internal . Reset ( ) ;
33- }
124+ if ( IsWrappingNullReference ) return false ;
125+
126+ _currentItem = null ;
34127
35- public TWrapperItem Current => _itemWrapper . Invoke ( _internal . Current ) ;
128+ object currentItemRCW ;
129+ uint celtFetched ;
130+ int hr = _enumeratorRCW . Next ( 1 , out currentItemRCW , out celtFetched ) ;
131+ // hr == S_FALSE (1) or S_OK (0), or <0 means error
36132
37- object IEnumerator . Current => Current ;
133+ _currentItem = _itemWrapper . Invoke ( currentItemRCW ) ; // creates a null wrapped reference even on end/error, just as a precaution
134+
135+ if ( hr < 0 )
136+ {
137+ throw Marshal . GetExceptionForHR ( hr ) ;
138+ }
139+
140+ return ( celtFetched == 1 ) ; // celtFetched will be 0 when we reach the end of the collection
141+ }
38142 }
39143}
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