SDK Shared Library Functions

'C' functions defined in shared libraries can be used with the following Recital products:

Product	Executables
Recital Terminal Developer for Linux	<path>/db.exe
Recital Terminal Developer for UNIX	<path>/db.exe
Recital Terminal Developer for Windows	<path>/db.exe
Recital Server for Linux	<path>/db_netserver <path>/db_recserver
Recital Server for UNIX	<path>/db_netserver <path>/db_recserver

Defining the C functions

Samples to demonstrate the usage of shared libraries are included in the following directories:

Product	Default API Linked Directory
Recital Terminal Developer for Linux	<path>/sdk/api/shared
Recital Terminal Developer for UNIX	<path>/sdk/api/shared
Recital Terminal Developer for Windows	<path>/sdk/api/shared
Recital Server for Linux	<path>/api/shared
Recital Server for UNIX	<path>/api/shared

The shared library must include the following four elements:

The include file "dbapi.h"

#include "dbapi.h"

The API_SHARED_FUNCTION_TABLE structure

Used to define the 'C' functions and objects included in the library:

// Recital API function address table 
static		struct 	API_FUNCTION_ADDRESS_TABLE	*api_function_address_table = NULL;
 
// Add all functions and objects  to this structure as follows:
//	Recital Name,	C Function Name		Type 
//
// Make sure the last entry is NULL.
//
static		struct	API_SHARED_FUNCTION_TABLE	api_function_table[7] = {
			{"schar",		"fnSamplesCharacter",	API_FUNCTION},
			{"stype",		"fnSamplesType",		API_FUNCTION},
			{"slog",		"fnSamplesLogical",	API_FUNCTION},
			{"snum",		"fnSamplesNumeric",	API_FUNCTION},
			{"sopen",	"fnSamplesOpen",		API_FUNCTION},
			{"myclass", 	"clsMyClass",		API_CLASS},
			{NULL,		NULL,				-1}
} ;

The initAPI() function

// This function is used to define function addresses for API calls.
int	initAPI(struct	API_FUNCTION_ADDRESS_TABLE	*function_address_table)
{
    api_function_address_table = function_address_table;
    return 0;
}

The getFunctions() function

// This function is used to return the function names of the API.
struct	API_SHARED_FUNCTION_TABLE	*getFunctions(void)
{
	return api_function_table;
}

Using the 'C' functions and classes:

Shared libraries are loaded using the SET LIBRARY TO <library> [ADDITIVE] command. By default library files are accessed from the directory defined by the DB_LIBDIR environment variable. This is set in the 'profile' file of the Recital product:

Product	Profile
Recital Terminal Developer for Linux	<path>/profile.db
Recital Terminal Developer for UNIX	<path>/profile.db
Recital Terminal Developer for Windows	<path>/profile.db
Recital Server for Linux	<path>/profile.uas
Recital Server for UNIX	<path>/profile.uas

By default, DB_LIBDIR is set to the sharedlib sub-directory of the recital root. If full path information is specified, the shared library files can be loaded from other directories, e.g.

// pdf.so is in the DB_LIBDIR directory
set library to pdf
 
//mylib.so is in /usr/recital/myapplibs
set library to /usr/recital/myapplibs/mylib

The Recital/4GL function LOADLIBRARY(<library>) can also be used to load additional shared libraries. The name of the shared library file including the full path and file extension must be specified.

The SET LIBRARY TO or RELEASE LIBRARY <library> commands are used to close all or specified shared libraries.

The Recital/4GL LIST PROCEDURE and DISPLAY PROCEDURE commands include loaded shared library function names in their listings and the Recital/4GL LIST CLASSES and DISPLAY CLASSES commands include loaded shared library class names in their listings.

Loaded shared library functions can be used in the same way as an internal Recital function. Loaded shared library classes can be used in the same way as Recital system classes.