V3R6 APIs Turn ILE *SRVPGMs into DLLs

The following is an excerpt from today's NEWSWire/400


V3R6 APIs TURN ILE *SRVPGMs INTO DLLs
V3R6 has two new APIs that turn ordinary ILE service programs 
(*SRVPGMs) into AS/400 dynamic link libraries (DLLs). DLLs let 
you skip activating code you rarely need or delay activating code 
until later, says Scott Gerard, an AS/400 Division senior 
programmer. Rather than hard-coding *SRVPGM and procedure names 
at compile time, you can use the two new DLL APIs -- QleActBndPgm 
(Activate Bound Program) and QleGetExp (Get Export) -- to compute 
the names at runtime. Postponing these decisions from compile 
time to runtime gives your ILE programs more control and 
flexibility.

To see how powerful the DLL APIs can be, consider the following 
example: A main program starts up and displays a screen that has 
three input fields. The first two fields are the library name and 
object name of a *SRVPGM; the third field is a procedure name. 
The application dynamically activates the *SRVPGM, looks up the 
procedure by name in the *SRVPGM, and then calls it. This 
application would be impossible to write without the DLL APIs, 
Gerard notes.

The APIs let you 1) dynamically activate or load a *SRVPGM and 2) 
get pointers to procedures and data items in the activated 
*SRVPGM. Calling procedures in a DLL is the same as calling 
producedures using a procedure pointer. API QleActBndPgm 
activates the appropriate service program and all service 
programs that are bound to it. The API does this by returning a 
value called an activation mark, which is an integer that 
uniquely identifies the *SRVPGM's activation. The second DLL API, 
QleGetExp, finds an exported symbol in a *SRVPGM. The API returns 
a value that indicates whether the symbol was found, whether the 
symbol is a procedure or a variable, and a procedure pointer or 
space pointer. The two DLL APIs are fully described in OS/400 
Program and CL Command APIs (SC41-4870-00).



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