Netscape Directory Server Plug-In Programmer's Guide: Chapter 9 Writing Entry Store/Fetch Plug-Ins

Plug-In Programmer's Guide
Netscape Directory Server

Chapter 9 Writing Entry Store/Fetch Plug-Ins

This chapter describes how to write entry store and entry fetch plug-ins. You can use these types of plug-ins to invoke functions before and after data is read from the default database.

The chapter contains the following sections:

How Entry Store/Fetch Plug-Ins Work

Writing Entry Store/Fetch Functions

Registering Entry Store/Fetch Functions

How Entry Store/Fetch Plug-Ins Work

Entry store plug-in functions are called before data is written to the database. Entry fetch plug-in functions are called after data is read from the default database. This processing is illustrated in Figure 9-1.

Figure 9-1    How the Server Calls Entry Store and Entry Fetch Plug-In Functions

Writing Entry Store/Fetch Functions

Unlike most other types of plug-in functions, entry store and entry fetch plug-in functions are not passed a parameter block when called. Instead, entry store and entry fetch plug-in functions must have the following prototype:

void function_name( char **entry, unsigned long *len );
On Windows platforms, use the following prototype and make sure to include the function in a .def file:

__declspec( dllexport ) \
  void function_name( char **entry, unsigned long *len );
The parameters are described below:

entry

Pointer to a string specifying the entry in LDIF format; for details on this format, see slapi_filter_free().

len

Pointer to the length of the entry string.

Since the text of the entry is passed in as an argument, you can modify the entry before it gets saved to disk and modify the entry after it is read from disk.

Note

For example entry store and entry fetch plug-in functions, check this source file in your installation: <server_root>/plugins/slapd/slapi/examples/testentry.c

Registering Entry Store/Fetch Functions

Unlike most other types of plug-in functions, you do not register an entry store or entry fetch plug-in function by setting the function name in the parameter block. Instead, you specify the function name directly in the server configuration file.

In Directory Server 6.x, shut down the server, add the plug-in parameters to the dse.ldif file, and restart the server (see Chapter 3 "Configuring Plug-Ins"). For example, your plug-in entry might look like this:

dn: cn=Test entry,cn=plugins,cn=config objectClass: top objectClass: nsSlapdPlugin objectClass: extensibleObject cn: Test entry nsslapd-pluginPath: /usr/netscape/servers/plugins/slapd/slapi/    examples/libtest-plugin.so nsslapd-pluginInitfunc: testentry_init nsslapd-pluginType: ldbmentryfetchstore nsslapd-pluginEnabled: on nsslapd-pluginId: test-entry

For example plug-in functions that implement entry store and entry fetch operations, take a look at this source file:

<server_root>/plugins/slapd/slapi/examples/testentry.c

In Directory Server 4.x, add a directive, to the slapd.ldbm.conf file, in the following form to specify the name and location of your plug-in function:

plugin entrystore [on|off] "<name of plugin>" \   <library_name> <function_name>

plugin entryfetch [on|off] "<name of plugin>" \   <library_name> <function_name>

<library_name> is the name and path to your shared library or dynamic link library, and <function_name> is the name of your plug-in function.

For example, the following directives register the function named my_store() as the entry store plug-in function and my_fetch() as the entry fetch plug-in function. Both functions are defined in the library /usr/nslib/myentry.so.

plugin entrystore on "my entrystore plugin" \
  /serverroot/myentry.so my_store
plugin entryfetch on "my entryfetch plugin" \
  /serverroot/myentry.so my_fetch
Each entry store and entry fetch plug-in is associated with the default ldbm back-end. Make sure that the plugin directive that registers the plug-in is within the database section for ldbm in the slapd.ldbm.conf file for Directory Server 4.x. The plugin directive should be after the database ldbm directive and before the next database directive, if any.

Last Updated October 30, 2003

entry	Pointer to a string specifying the entry in LDIF format; for details on this format, see slapi_filter_free().
`len`	Pointer to the length of the `entry` string.


Note	For example entry store and entry fetch plug-in functions, check this source file in your installation: `<server_root>/plugins/slapd/slapi/examples/testentry.c`