The relationships of the different structures are a little bit complex; we've written a lot of this kind of detail down in the book "Shared Source CLI Essentials" from O'Reilly that is now available. In particular, there is a map that shows the relationship of all of the various type and object headers that would probably be valuable to you. If I'm not mistaken, this map is also online, but I am on the road right now and can't remember the URL. Anyone else on this list able to jog my memory?
-- David > -----Original Message----- > From: Discussion of the Rotor Shared Source CLI > implementation [mailto:[EMAIL PROTECTED] On > Behalf Of Michael Cohen > Sent: Wednesday, April 02, 2003 7:50 AM > To: [EMAIL PROTECTED] > Subject: [DOTNET-ROTOR] types in the CLR > > > Hi, > > I've been doing some research on the shared source CLI > (Rotor), specifically looking at how types that are loaded in > the CLR are represented. From my current understanding, every > type that is loaded into an application domain by the > ClassLoader class is represented by an EEClass [class.h]. > Each EEClass has a pointer to a MethodTable class [class.h] > that stores the v-table and a map to interfaces that the > class inherits from. So the MethodTable is basically what > defines a type in memory. > > >From my understanding, when an instance of a type is instantiated, a > >new Object class [object.h] is created that represents the > instance of > >the type. This Object also contains a pointer to the MethodTable. > > To help further my understanding of how types are laid out in > memory I read Don Box's book "Essential .NET Volume 1: The > Common Language Runtime". On page 80, Box proceeds to explain > the CLR object header and a structure called the > CORINFO_CLASS_STRUCT. > > The object header contains a sync block, a handle > representing the object's type, and the object's fields. I > did find an ObjHeader class [syncblk.h] that contains a > member called m_SyncBlockValue, but it does not contain a > handle or array of fields. Does anyone know how the ObjHeader > class, Object class, and fields are actually laid out in > memory and also where this occurs in Rotor? My guess is that > the type handle is the pointer in the Object class pointing > back to the MethodTable. > > Box explains that the CORINFO_CLASS_STRUCT structure contains > several pieces of information that defines the type. The type > handle in the object header points to this structure. Within > Rotor, I found a COR_INFO_CLASS_HANDLE [corinfo.h] that is > typed defined as struct CORINFO_CLASS_STRUCT_*. Based on this > newfound knowledge, I've become a little confused about how > the CORINFO_CLASS_HANDLE and the MethodTable class are > related to each other. Does anyone know the details of how > the CORINFO_CLASS_HANDLE is used in the runtime and how it > relates to the MethodTable class? > > Finally, when there is a managed reference to an object in > the runtime's managed heap, is the reference wrapped in the > OBJECTREF class [vars.hpp]? The OBJECTREF class does contain > a pointer m_asObj that points to an Object class. > > Thanks in advance to anyone that can help me. > > Michael Cohen > > > -------------------------------------------------------------- > -------------- > This electronic message transmission contains information > that may be confidential or privileged. The information > contained herein is intended solely for the recipient and use > by any other party is not authorized. If you are not the > intended recipient (or otherwise authorized to receive this > message by the intended recipient), any disclosure, copying, > distribution or use of the contents of the information is > prohibited. If you have received this electronic message > transmission in error, please contact the sender by reply > email and delete all copies of this message. Cigital, Inc. > accepts no responsibility for any loss or damage resulting > directly or indirectly from the use of this email or its > contents. Thank You. > -------------------------------------------------------------- > -------------- > >
