Vienna buchan calling the notes c-api from lotus_script

Calling the Notes
C API from
LotusScript

Bill Buchan
HADSL

© 2006 Wellesley Information Services. All rights reserved.

What We’ll Cover …

• Introduction
• Architectures
• The LotusScript eXtension toolkit
• Platform differences
• Calling simple Notes C API
• Complex Notes C API
• Wrap-up

2

Target and Purpose

• Who is the target audience?
Advanced Lotus Notes Developers
Developers who have a little experience in C API
• What is this about?
This talk aims to demonstrate advanced LotusScript, showing:
The Notes C API interface
The LSX interface
Pros and cons of each

3

Notes C API

• Why Notes C API?
900+ Supported Methods
Many complex tasks can be called via API
• Who am I?
Bill Buchan
Dual PCLP in v3, v4, v5, v6, v7
Ten+ years senior development consultancy for
Enterprise customers
Learn from my pain!
Five+ years code auditing
CEO of HADSL — developing best-practice tools

4

Notes C API Programming Toolkit

• Where can you find information on the C API?
The Lotus Notes C Programming toolkit
• The toolkit contains:
Contains two documentation databases
Each function and structure is documented
A large number of sample C programs are included
Compile time libraries for all platforms
• Generally speaking, backward compatibility is good:
For instance, if you have v6 and v7 servers, creating the
program using v6 of the API toolkit means that it will run
on v6 and v7 servers

Note
5


• Introduction
• Architectures
• Wrap-up

6

Notes/Domino Architectures

• Domino is a multi-platform server product
• Notes now supports four clients:
Windows, Mac (Power PC), Mac (Intel), and Linux
• LotusScript supported from v4.x of Notes, on all server
and client platforms
Rich set of APIs for general business logic
Robust, supported environment for general business
applications
Amazing level of multi-platform support
• What if you want to go further?
Exploit a piece of Notes C API interface? Don't
Forget
Call a platform specific DLL?
7

But Surely

• Currently, something like:
90% of all Domino servers run on Windows
95% of all Notes clients run on Windows
• Why not write platform code for that and that alone?
A short sighted decision. Your environment may start
supporting more platforms.
Windows 64-bit coming over the horizon
Treat it as a separate platform
As was 16-bit Windows GOTCHA!
• Corporate push to centralize and consolidate
Especially on medium-high level platforms
Linux, Solaris, AIX, HP/UX
8

Be Pragmatic — The Skills Triangle

Few Code Examples
Harder

C-API

LotusScript, Java

Easier
Many Code Examples
9

Be Pragmatic

• Call the Notes C API from LotusScript if:
You cannot find a supported architectural solution
You have the skills to support LSX and/or Notes C API coding
You might possibly require multi-platform code
You accept that this code will be harder to write, harder to
maintain, and harder to support

10

Architectures — Conclusion

• If you have to step outside the comfort zone,
you have two choices:
LotusScript eXtension Toolkit — LSX
This builds a library — on windows, a DLL — which
allows you to extend LotusScript with custom C code
Fairly straightforward
A different version for each platform
LotusScript calling the Notes C API interface directly
Not straightforward
One code base can cover all platforms

11


• Introduction
• Architectures
• Pros and cons

12

What Is the LSX Toolkit?

• A C-based API for Lotus Notes
• Interfaces with LotusScript
• Allows you to build platform-specific libraries
• Pros
Straightforward for a competent C Programmer
• Cons
Platform — and sometimes version(!) — specific
You have to produce a version (from the same source code)
for each platform
Lack of support
Last release — March 2001
Note Visual Studio 2005 not supported
13

What Can You Use the LSX Toolkit for?

• Used to use it for Notes Database work
We have a Notes Database installer which unpacks,
design refreshes, sets ACLs, etc.
Initially coded that as LSX
Now use LotusScript calls to Notes C API directly
Deployment of LSXs is non-trivial
Especially updating LSXs that are in use!
• Still use it for Active Directory Integration
AD integration possible using LotusScript/COM
interface — but unreliable
Coded Active Directory Services Interface (ADSI) to manage
objects within AD — from within LotusScript!

14

How Can You Create an LSX With the Toolkit?

• Design a data structure you wish to expose
in LotusScript
• Use the LSX Wizard to create a relevant LSX project
• Use a supported C-Compiler for your platform(s) to
create code to fill in the blanks
• Run Do_It to compile your library
Windows produces a .DLL file
*nix produces a .so file
• Place that library in the executable code directory
of your server and/or client
• Test, test, test! 16-bit
15

LSX Wizard (1)

• Create a new Project

16

LSX Wizard (2)
• Now add a class to the project

17

LSX Wizard (3)
• Override the Constructor

18

LSX Wizard (4)
• Add a “Close” Sub

19

LSX Wizard (5)

• Add a Getter and Setter

20

LSX Wizard (6)

• You should now see this:

21

LSX Wizard (7)
• Now generate code

22

LSX Wizard (8)
• Now fill in the code in the LSX source files

//{{LSX_AUTHOR_CODE_Include_1
//}}

#include "DbReplicaFlags.hpp"
// includes for the objects defined in your LSX
//{{LSX_AUTHOR_CODE_Include_2
//}}

23

LSX Wizard (9)
• Now fill in the code in the LSX source files
DbReplicaFlags:: DbReplicaFlags(
LSPTR(LSXLsiSession) pContainer, LSXString&
Server, LSXString& Database)
: LSXBase((LSPLTSTR)"DbReplicaFlags",
pContainer->LSXGetInstance(),
CDBREPLICAFLAGS_DBREPLICAFLAGS_ID,
pContainer)

//{{LSX_AUTHOR_CODE_Additional_Base_Class_Init1
//}}

//{{LSX_AUTHOR_CODE_Internal_Member_Init1
//}}
{
//{{LSX_AUTHOR_CODE_Constructor1
//}}
}
24

LSX Wizard (10)

• Run a command prompt
Go to the LSX directory
Run LSXSetup W32
Run cd DbReplicaFlags
Run Do_it
This will compile the DLL file
Copy the DLL from lsxbinw32DbReplicaFlags.dll to
your Notes Program Directory
• Note:
The Notes client (or server) usually holds onto the DLL
once loaded, so refreshing the LSX usually requires a
client (or server) restart

25

LSX Wizard (11)
• Create a LotusScript Agent
Uselsx “DbReplicaFlags.dll” ' in 'Options'

Sub Initialize
Dim DR As New DbReplicaFlags("", "names.nsf")
Dim value As Integer

If dr.GetDbReplicaFlag(REPLFLG_DISABLE, value) Then

If (value) Then
Print "Replica Disable is set to 'TRUE'"
Else
Print "Replica Disable is set to 'False'"
End If
Else
Print "I failed to get the replica flag "
End If

Call dr.NSFDbClose()
End Sub
26

LSX Wizard (12)

• As a side effect of loading the LSX
The LSX signature is now available in the designer

27

Demo

Demo

Overview
the LSX Toolkit

28

LSX Summary

• LSX Toolkit is fairly straightforward
• Since the LSX Toolkit supports multiple platforms
and the same source code is used on each:
You do have to recompile the LSX on multiple platforms
You don’t have to take account of many platform differences
• It’s really relevant for extending your Notes/Domino
code to new APIs
e.g., You can call Active Directory API calls in order
to integrate Domino with Active Directory

29


• Introduction
• Architectures
• Wrap-up

30

Platform Differences: Definitions

• In normal LotusScript, platform differences
are taken care of
Even in LSX programming most differences are taken care of
Not so in direct LotusScript to C API calls
• Each platform represents data in a subtly
different manner
For instance, the HANDLE datatype has different lengths
on different platforms:
32 bits long in Windows and OS/400
16 bits long on AIX, Macintosh, etc.
Memory alignment widths on iSeries are different
from other platforms

31

Platform Specific implementations

• In order to call the Notes library, you will have to link to
different library files on each platform:
Windows/32: nnotes.dll
Solaris, Linux: libnotes.so
AIX: lnotes_r.a
HPUX: libnotes.sl
MacOs, OS/X: NotesLib
OS/400: libnotes.srvpgm
OS/390 libnotes
OS/2: lnotes.dll
Windows Alpha: anotes.dll

32

Platform Differences: Endians

• Endians
Some platforms represent multi-byte numbers with the lowest
value bytes in the lower segments of memory — little endians
Macintosh (on PowerPC!) represents the larger value bytes in
the lower segments of memory — big endians

33

Coding for Platform Differences

• Our challenge is to construct a code sequence that:
Knows which platform it’s running on
Makes calls to the platform-specific library file
Understands platform differences in terms of alignment
and data item size
And most importantly — fails “safe” when presented with
a new platform that it cannot deal with
• This is not a trivial exercise
My estimate is that this exercise will take at least 5-10 times
more effort — development + testing — than a normal
LotusScript business function

34

Decoding Signatures
• A “Signature” is:
The definition of a function calls' parameters and return value
These can be found in the Notes “C API 7.0 Reference for
Domino and Notes”, at www-10.lotus.com/ldd/notesua.nsf/0b
345eb9d127270b8525665d006bc355/6a92a658297e6baf852571
a3007143be?OpenDocument
Example signature:
STATUS LNPUBLIC NSFNoteLSCompile(
DBHANDLE hDb, NOTEHANDLE hNote, DWORD dwFlags);
In Windows:
Declare Function W32_NSFLSCompile Lib LIB_W32
Alias "NSFNoteLSCompile"
ByVal hdb As Long,
ByVal hNote As Long,
ByVal null1 As Long )
As Integer
35

Decoding Signatures (cont.)

C-API Win32 Linux AIX Solaris Mac
BYTE BYTE BYTE BYTE BYTE BYTE
BOOL Long Long Long Long Integer
Int Long Long Long Long Long
Long Int Long Long Long Long Long
WORD Integer Integer Integer Integer Integer
SWORD Integer Integer Integer Integer Integer
DWORD Long Long Long Long Long
LONG Int Long Long Long Long Long
HANDLE Long Integer Integer Integer Integer
NOTEHANDLE Long Integer Integer Integer Integer
DBHANDLE Long Integer Integer Integer Integer
MEMHANDLE Long Long Long Long Long
STATUS Integer Integer Integer Integer Integer
Char * String String String String String

36


• Introduction
• Architectures
• Wrap-up

37

Calling a Simple C API Function

• Let’s get our feet wet with some simple API
No complex sequence of calls handling a shared
memory resource
A single call with simple datatypes
A call that will not result in client memory corruption
should we get it wrong. Hopefully.
• Let’s call it from Windows and ignore other platforms
A function that tells you the network latency — in milliseconds
— between the current Notes instance and a target server
NSFGetServerLatency

38

NSFGetServerLatency() – API Reference

• We shall call:
NSFGetServerLatency()
This returns the network latency time described in
milliseconds for a call to a remote server
Useful to decide which server is closest in terms of
network response
Its signature from the C API reference is:
STATUS LNPUBLIC NSFGetServerLatency(
char far *ServerName,
DWORD Timeout,
DWORD far *retClientToServerMS,
DWORD far *retServerToClientMS,
WORD far *ServerVersion);

39

NSFGetServerLatency() – API Reference (cont.)
• From the C API Reference:
Input Parameters
ServerName — Null-terminated string containing the name
of the server to query
Timeout — Number of milliseconds to wait for a reply from the server.
A timeout of 0 indicates that the default timeout value is to be used.
Output Parameters
(routine) — Return status from this call:
NOERROR — Success
retClientToServerMS — Optional — If not NULL, the number of
milliseconds required to send the request to the server is
stored at this address
retServerToClientMS — Optional — If not NULL, the number of
milliseconds required for the reply to return from the server
is stored at this address
ServerVersion — Optional — If not NULL, the server version
(the Domino build number for the server) is stored at this address 40

Simple C API Calling
' This is a constant for our windows-based
' Library file:
Const LIB_W32 = "nnotes.dll"

' Declare our function for windows
Declare Function W32_NSFGetServerLatency _
Lib LIB_W32 Alias {NSFGetServerLatency} (_
Byval ServerName As Lmbcs String, _
Byval Timeout As Long, _
retClientToServerMS As Long, _
retServerToClientMS As Long, _
ServerVersion As Integer) As Integer

41

Simple C API Calling: Execution
' A function to get network latency time...
Public Function getServerLatency _
(strServer As String) As Long
Dim nnServer As New NotesName(strServer)
Dim ToServer As Long, fromServer As Long
Dim ver As Integer
Dim timeout As Long

timeout = 1000 ' 1000ms == 1 second

Call W32_NSFGetServerLatency(nnServer.Canonical,_
timeout, toServer, fromServer, ver)

' Return both directional latencies added together
getServerLatency = fromServer + ToServer
End Function

42

Simple C API Calling: Execution (cont.)
Sub initialise
Print “Calling function”
Print “Latency is: “ + _
cstr(getServerLatency(“domino-
90.hadsl.com/HADSL/US”))
Print “Finished calling”
end sub

43

Simple C API Calling: The Results

• Running the agent “Example1” in the database produces
the following runtime output:

• Now — this is not production code! It requires:
Error handling
Multi-platform support

44

What Can’t You Call?

• Callback routines
Some Notes C API functions require you to specify mandatory
callback routines — other pieces of C API that will get called
by the target C API routine
Issue
LotusScript does not (and IMHO never will) support this
This rules out Extension Manager Routines, Menu
Addin Routines
In terms of callback routines that allow you to specify optional
callbacks (progress status indicators, etc), you can pass in
NULL (or ZERO), and the callback function will be ignored

45


• Introduction
• Architectures
• Wrap-up

46

Defining Complex C API
• Complex C API is where:
More than one function call is required to perform a task
and/or
A HANDLE of some description is needed to
reference a data object

47

API Handles

• A handle is a numeric reference to a structure in memory
that the C API interface has created
For example, a handle to a Notes Database
• You do not deal with the memory structure itself —
you deal with the handle to the memory structure
Example: NSFDbOpen()creates a new memory structure
and gives you back the handle to that
You perform some work using NSFDInfoGet()
You close the database using NSFDbClose()

48

Some Rules on Handles

• There are different types of handles:
Document handle, database handle, etc.
Do not mix these handles up!
Doing so will crash the session/client/server
• Always properly close your handles
You have to properly trap all code branches
You have to keep track of the handle until you
specifically de-allocate it
Not doing so will crash the session/client/server
It may not crash immediately. It may crash when the
session, client or server closes.
• You cannot change the value of the handle
Doing so will crash the session/client/server 49

Coding Around Handles

• A really good way is to use a class
It performs the “open” part of the handle operation on
the class constructor
It performs the “close” part of the handle operation on
the class destructor
This means that no matter what happens, the handle
operation will be properly closed even if this is not
specifically coded in your LotusScript
All the code specific to this handle operation is
embedded in the class
And can include multi-platform code
All you see in your LotusScript is an operation with
this specific class
50

Database Handle Class – Introduction

Demo

Demo of
DbHandleManager

51

Handle Summary

• If you get a handle, you have to de-allocate it
• Only use handle data you know is valid
If a handle == NULLHANDLE (or ZERO), then it’s
not a valid handle
• Bonus:
NotesDocument.handle returns the current handle
You can easily use LotusScript to:
find a document
use direct calls to update information that the object
model does not support (at the moment)
e.g., Writing Notes Replica Items

52

Complex C API

• Where more than one function call is required to
perform a function, it is recommended that:
You use defensive coding techniques to understand and
make “safe” every single coding branch possible
Any handle information used during this sequence is kept
safe and its de-allocation specifically catered for
You use classes to ensure proper construction and
destruction of handle information

53


• Introduction
• Architectures
• Wrap-up

54

Know Your Battleground

• LotusScript coding is:
Fairly straightforward
Supported
Platform independent
• Stepping outside of this comfort zone is going to be hard
Take far more time in development and testing
Push development resources to the limit
Only do this if you have an absolute business need

55

LSX Versus Notes C API

• You need to establish, based on your requirements,
which is the best fit:
LS calling Notes C-
Feature LSX API directory
Requires code No Deployment
Deployment deployment required
Different LSX for each
Multi-platform platform Same code in Library
Very good integration –
C-API integration callbacks, etc Basic integration
Code Difficulty Medium Hard
Stability Extremely Stable Stable

56

Resources

• Normunds Kalnberzin, “LotusScript to Lotus C API
Programming Guide,” www.Ls2Capi.com
The ultimate reference
Ebook for €18, Book + shipping for €42
It pays for itself in a single hour
• Notes C API Reference, LSX Toolkit
http://www-
128.ibm.com/developerworks/lotus/downloads/toolkits.html
• Julian Robichaux, “Notes API Tips,”
www.nsftools.com/tips/APITips.htm
Lotus Notes API tips

57

7 Key Points to Take Home

• Calling Notes C API is hard
It has to be tested on all platforms
It can easily take out a client or server process
Only use it if absolutely required
Use defensive coding!
It’s the next stage beyond the well-regulated
LotusScript sandbox
It might be simpler to use LSX than Direct
LotusScript to C API calls
You certainly get more control and debugging
It gives you all possible Notes capability

58

Your Turn!

Questions?

How to Contact Me:
Bill Buchan
Bill@hadsl.com
59

Vienna buchan calling the notes c-api from lotus_script

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