The polymorphic -interface DLL

diff -r ebc84c812384 -r 46218c8b8afa Symbian3/PDK/Source/GUID-38CF8A8E-4778-5374-8AC6-5F9486A2B7FB.dita --- a/Symbian3/PDK/Source/GUID-38CF8A8E-4778-5374-8AC6-5F9486A2B7FB.dita Thu Mar 11 15:24:26 2010 +0000 +++ b/Symbian3/PDK/Source/GUID-38CF8A8E-4778-5374-8AC6-5F9486A2B7FB.dita Thu Mar 11 18:02:22 2010 +0000 @@ -1,38 +1,38 @@ - - - - - -The polymorphic -interface DLLA polymorphic interface DLL is one which is written to implement -a programming interface defined elsewhere; for example, a device driver, an -application or an OPL extension. -

The API is defined in terms of a single abstract class whose functions -are declared as pure virtual. The DLL implements the API by defining -and implementing a concrete class derived from that abstract class. The DLL -exports a single function whose sole purpose is to create an object of the -derived class type; this is always the function at ordinal 1 within the DLL. -All other functions in the DLL are called through the virtual table mechanism -(the pointer to the vtable is set up by the constructor in the normal C++ -way).

At compilation time, application code includes the header file(s) which -define(s) the API. At link time, the application includes the DLL's module -definition file, which allows the address of the DLL function to be accessed -by specifying its ordinal.

When the application's executable runs, it loads the DLL at the time it -is required. The address of the single function exported by the DLL is accessed -indirectly by specifying its ordinal.

For a given interface, there may be many DLLs which obey the protocol imposed -by that interface each of which provides a different implementation.

A DLL of this type is often referred to as a dynamically loaded DLL.

The user of a dynamically loaded DLL uses an RLibrary type -object to load the DLL. The RLibrary object encapsulates -a handle to the DLL and must remain in existence while the DLL is in use; -typically this is for the life of the object provided by the DLL.

+ + + + + +The polymorphic +interface DLLA polymorphic interface DLL is one which is written to implement +a programming interface defined elsewhere; for example, a device driver, an +application or an OPL extension. +

The API is defined in terms of a single abstract class whose functions +are declared as pure virtual. The DLL implements the API by defining +and implementing a concrete class derived from that abstract class. The DLL +exports a single function whose sole purpose is to create an object of the +derived class type; this is always the function at ordinal 1 within the DLL. +All other functions in the DLL are called through the virtual table mechanism +(the pointer to the vtable is set up by the constructor in the normal C++ +way).

At compilation time, application code includes the header file(s) which +define(s) the API. At link time, the application includes the DLL's module +definition file, which allows the address of the DLL function to be accessed +by specifying its ordinal.

When the application's executable runs, it loads the DLL at the time it +is required. The address of the single function exported by the DLL is accessed +indirectly by specifying its ordinal.

For a given interface, there may be many DLLs which obey the protocol imposed +by that interface each of which provides a different implementation.

A DLL of this type is often referred to as a dynamically loaded DLL.

The user of a dynamically loaded DLL uses an RLibrary type +object to load the DLL. The RLibrary object encapsulates +a handle to the DLL and must remain in existence while the DLL is in use; +typically this is for the life of the object provided by the DLL.

\ No newline at end of file