In this article Barry Mavin, CEO and Chief Software Architect for Recital details how to Build C Extension Libraries to use with Recital.
Overview
It is possible to extend the functionaliy of Recital products using "Extension libraries" that can be written in C. These extension libraries, written using the Recital/SDK API, are dynamically loadable from all Recital 9 products. This includes:
- Recital
- Recital Server
- Recital Web
Building C Extension Libraries
You can create C wrappers for virtually any native operating system function and access these from the Recital 4GL. Unlike traditional APIs which only handle the development of C functions that are callable from the 4GL, the Recital/SDK allows you to build Classes that are accessible from all Recital products. e.g. You could create a GUI framework for Linux that handles VFP system classes!
To deploy your C Extension Libraries, copy them to the following location:
Windows:
\Program Files\Recital\extensions
Linux/Unix:
/opt/recital/extensions
Please see the Recital/SDK API Reference documentation for further details.
Sample code
Listed below is the complete example of a C Extension Library.:
////////////////////////////////////////////////////////////////////////////////
#include "mirage_demo.h"
////////////////////////////////////////////////////////////////////////////////
// Declare your functions and classes below as follows:
//
// Recital Function Name, C Function Name, Type (Function or Class)
//
#define MAX_ELEMENTS 7
static struct API_SHARED_FUNCTION_TABLE api_function_table[MAX_ELEMENTS] = {
{"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}
};
////////////////////////////////////////////////////////////////////////////////
// Recital API initialization. This should be in only ONE of your C files
// **IT SHOULD NEVER BE EDITED OR REMOVED**
INIT_API;
///////////////////////////////////////////////////////////////////////
// This is an example of passing a character parameter and returning one.
RECITAL_FUNCTION fnSamplesCharacter(void)
{
char *arg1;
if (!_parse_parameters(PCOUNT, "C", &arg1)) {
ERROR(-1, "Incorrect parameters");
}
_retc(arg1);
}
///////////////////////////////////////////////////////////////////////
// This is an example of passing a numeric parameter and returning one.
RECITAL_FUNCTION fnSamplesNumeric(void)
{
int arg1;
if (!_parse_parameters(PCOUNT, "N", &arg1)) {
ERROR(-1, "Incorrect parameters");
}
_retni(arg1);
}
///////////////////////////////////////////////////////////////////////
// This is an example returns the data type of the parameter passed.
RECITAL_FUNCTION fnSamplesType(void)
{
char result[10];
if (PCOUNT != 1) {
ERROR(-1, "Incorrect parameters");
}
switch (_parinfo(1)) {
case API_CTYPE:
strcpy(result, "Character");
break;
case API_NTYPE:
strcpy(result, "Numeric");
break;
case API_LTYPE:
strcpy(result, "Logical");
break;
case API_DTYPE:
strcpy(result, "Date");
break;
case API_TTYPE:
strcpy(result, "DateTime");
break;
case API_YTYPE:
strcpy(result, "Currency");
break;
case API_ATYPE:
strcpy(result, "Array");
break;
default:
strcpy(result, "Unkown");
break;
}
_retc(result);
}
///////////////////////////////////////////////////////////////////////
// This is an example returns "True" or False.
RECITAL_FUNCTION fnSamplesLogical(void)
{
char result[10];
int arg1;
if (!_parse_parameters(PCOUNT, "L", &arg1)) {
ERROR(-1, "Incorrect parameters");
}
if (arg1) strcpy(result, "True");
else strcpy(result, "False");
_retc(result);
}
///////////////////////////////////////////////////////////////////////
// This example opens a table.
RECITAL_FUNCTION fnSamplesOpen(void)
{
char *arg1;
if (!_parse_parameters(PCOUNT, "C", &arg1)) {
ERROR(-1, "Incorrect parameters");
}
if (_parinfo(1) == API_CTYPE) {
_retni(COMMAND(arg1));
} else {
_retni(-1);
}
}
///////////////////////////////////////////////////////////////////////
// Define the MyClass CLASS using the API macros
///////////////////////////////////////////////////////////////////////
RECITAL_EXPORT int DEFINE_CLASS(clsMyClass)
{
/*-------------------------------------*/
/* Dispatch factory methods and return */
/*-------------------------------------*/
DISPATCH_FACTORY();
/*---------------------------------*/
/* Dispatch constructor and return */
/*---------------------------------*/
DISPATCH_METHOD(clsMyClass, Constructor);
/*--------------------------------*/
/* Dispatch destructor and return */
/*--------------------------------*/
DISPATCH_METHOD(clsMyClass, Destructor);
/*-----------------------------------*/
/* Dispatch DEFINE method and return */
/*-----------------------------------*/
DISPATCH_METHOD(clsMyClass, Define);
/*------------------------------*/
/* Dispatch SET or GET PROPERTY */
/* method for property NumValue */
/* then return. */
/*------------------------------*/
DISPATCH_PROPSET(clsMyClass, NumValue);
DISPATCH_PROPGET(clsMyClass, NumValue);
/*------------------------------*/
/* Dispatch SET or GET PROPERTY */
/* method for property LogValue */
/* then return. */
/*------------------------------*/
DISPATCH_PROPSET(clsMyClass, LogValue);
DISPATCH_PROPGET(clsMyClass, LogValue);
/*-------------------------------*/
/* Dispatch SET or GET PROPERTY */
/* method for property DateValue */
/* then return. */
/*-------------------------------*/
DISPATCH_PROPSET(clsMyClass, DateValue);
DISPATCH_PROPGET(clsMyClass, DateValue);
/*-------------------------------*/
/* Dispatch SET or GET PROPERTY */
/* method for property TimeValue */
/* then return. */
/*-------------------------------*/
DISPATCH_PROPSET(clsMyClass, TimeValue);
DISPATCH_PROPGET(clsMyClass, TimeValue);
/*-------------------------------*/
/* Dispatch SET or GET PROPERTY */
/* method for property CurrValue */
/* then return. */
/*-------------------------------*/
DISPATCH_PROPSET(clsMyClass, CurrValue);
DISPATCH_PROPGET(clsMyClass, CurrValue);
/*-------------------------------*/
/* Dispatch SET or GET PROPERTY */
/* method for property CharValue */
/* then return. */
/*-------------------------------*/
DISPATCH_PROPSET(clsMyClass, CharValue);
DISPATCH_PROPGET(clsMyClass, CharValue);
/*------------------------------*/
/* Dispatch SET or GET PROPERTY */
/* method for property ObjValue */
/* then return. */
/*------------------------------*/
DISPATCH_PROPSET(clsMyClass, ObjValue);
DISPATCH_PROPGET(clsMyClass, ObjValue);
/*-----------------------------------*/
/* If message not found return error */
/*-----------------------------------*/
OBJECT_RETERROR("Unknown message type");
}
////////////////////////////////////////////////////////////////////////////////
// Define METHOD handlers
////////////////////////////////////////////////////////////////////////////////
DEFINE_METHOD(clsMyClass, Constructor)
{
struct example_data *objectDataArea;
/* Allocate memory for objects objectData area */
objectDataArea = (struct example_data *)
malloc(sizeof(struct example_data));
if (objectDataArea == NULL) return(-1);
/* Assign the default property values */
strcpy(objectDataArea->prop_charvalue, "Test API object");
objectDataArea->prop_numvalue = 15.2827;
objectDataArea->prop_logvalue = 'F';
strcpy(objectDataArea->prop_datevalue, DATE_DATE());
strcpy(objectDataArea->prop_timevalue, DATE_DATETIME());
strcpy(objectDataArea->prop_currvalue, "15.2827");
strcpy(objectDataArea->object_name, "APIobject");
objectDataArea->prop_objvalue
= OBJECT_NEW(objectDataArea->object_name, "exception", NULL);
/* Set the object objectData area */
OBJECT_SETDATA((char *)objectDataArea);
return(0);
}
DEFINE_METHOD(clsMyClass, Destructor)
{
struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
if (objectData != NULL) {
if (objectData->prop_objvalue != NULL)
OBJECT_DELETE(objectData->prop_objvalue);
free(objectData);
objectData = NULL;
}
return(0);
}
DEFINE_METHOD(clsMyClass, Define)
{
struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
struct API_EXPRESSION result;
char buffer[512];
int rc;
/* Check the object class */
OBJECT_GETPROPERTY(objectData->prop_objvalue, "class", buffer);
rc = OBJECT_GETARG(buffer, &result);
if (result.errno == 0 && result.type == 'C'
&& strcmp(result.character, "Exception") == 0) {
switch (OBJECT_GETARGC()) {
case 1:
rc = OBJECT_GETPARAMETER(1, &result);
if (result.errno == 0 && result.type == 'C') {
OBJECT_SETARG(buffer, &result);
rc = OBJECT_SETPROPERTY(objectData->prop_objvalue,
"message", buffer);
}
break;
case 2:
rc = OBJECT_GETPARAMETER(2, &result);
if (result.errno == 0 && result.type == 'N') {
OBJECT_SETARG(buffer, &result);
rc = OBJECT_SETPROPERTY(objectData->prop_objvalue,
"errorno", buffer);
}
}
}
result.type = 'L';
result.logical = (rc == 0 ? 'T' : 'F');
OBJECT_RETRESULT(&result);
}
////////////////////////////////////////////////////////////////////////////////
// Define GET property handlers
////////////////////////////////////////////////////////////////////////////////
DEFINE_PROPERTYGET(clsMyClass, NumValue)
{
struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
if (objectData == NULL) return(-1);
OBJECT_RETPROPERTY('N', objectData->prop_numvalue);
}
DEFINE_PROPERTYGET(clsMyClass, LogValue)
{
struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
if (objectData == NULL) return(-1);
OBJECT_RETPROPERTY('L', objectData->prop_logvalue);
}
DEFINE_PROPERTYGET(clsMyClass, DateValue)
{
struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
if (objectData == NULL) return(-1);
OBJECT_RETPROPERTY('D', objectData->prop_datevalue);
}
DEFINE_PROPERTYGET(clsMyClass, TimeValue)
{
struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
if (objectData == NULL) return(-1);
OBJECT_RETPROPERTY('T', objectData->prop_timevalue);
}
DEFINE_PROPERTYGET(clsMyClass, CurrValue)
{
struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
if (objectData == NULL) return(-1);
OBJECT_RETPROPERTY('Y', objectData->prop_currvalue);
}
DEFINE_PROPERTYGET(clsMyClass, CharValue)
{
struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
if (objectData == NULL) return(-1);
OBJECT_RETPROPERTY('C', objectData->prop_charvalue);
}
DEFINE_PROPERTYGET(clsMyClass, ObjValue)
{
struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
if (objectData == NULL) return(-1);
OBJECT_RETPROPERTY('O', objectData->prop_objvalue);
}
////////////////////////////////////////////////////////////////////////////////
// Define SET property handlers
////////////////////////////////////////////////////////////////////////////////
DEFINE_PROPERTYSET(clsMyClass, NumValue)
{
struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
struct API_EXPRESSION result;
int rc = OBJECT_ERROR;
OBJECT_GETVALUE(&result);
if (result.errno == 0 && result.type == 'N') {
objectData->prop_numvalue = result.number;
rc = OBJECT_SUCCESS;
}
return(rc);
}
DEFINE_PROPERTYSET(clsMyClass, LogValue)
{
struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
struct API_EXPRESSION result;
int rc = OBJECT_ERROR;
OBJECT_GETVALUE(&result);
if (result.errno == 0 && result.type == 'L') {
objectData->prop_logvalue = result.logical;
rc = OBJECT_SUCCESS;
}
return(rc);
}
DEFINE_PROPERTYSET(clsMyClass, DateValue)
{
struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
struct API_EXPRESSION result;
int rc = OBJECT_ERROR;
OBJECT_GETVALUE(&result);
if (result.errno == 0 && result.type == 'D') {
strcpy(objectData->prop_datevalue, DATE_DTOS(result.date));
rc = OBJECT_SUCCESS;
}
return(rc);
}
DEFINE_PROPERTYSET(clsMyClass, TimeValue)
{
struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
struct API_EXPRESSION result;
int rc = OBJECT_ERROR;
OBJECT_GETVALUE(&result);
if (result.errno == 0 && result.type == 'T') {
strcpy(objectData->prop_timevalue, DATE_TTOS(result.datetime));
rc = OBJECT_SUCCESS;
}
return(rc);
}
DEFINE_PROPERTYSET(clsMyClass, CurrValue)
{
struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
struct API_EXPRESSION result;
int rc = OBJECT_ERROR;
OBJECT_GETVALUE(&result);
if (result.errno == 0 && result.type == 'Y') {
strcpy(objectData->prop_currvalue, CURR_YTOS(result.currency));
rc = OBJECT_SUCCESS;
}
return(rc);
}
DEFINE_PROPERTYSET(clsMyClass, CharValue)
{
struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
struct API_EXPRESSION result;
int rc = OBJECT_ERROR;
OBJECT_GETVALUE(&result);
if (result.errno == 0 && result.type == 'C') {
strcpy(objectData->prop_currvalue, result.character);
rc = OBJECT_SUCCESS;
}
return(rc);
}
DEFINE_PROPERTYSET(clsMyClass, ObjValue)
{
struct example_data *objectData = (struct example_data *)OBJECT_GETDATA();
OBJECT objvalue;
int rc = OBJECT_ERROR;
if (OBJECT_GETTYPE() == 'O') {
objvalue = OBJECT_GETOBJECT();
objectData->prop_objvalue = OBJECT_ASSIGN(objvalue, objectData->object_name);
rc = OBJECT_SUCCESS;
}
return(rc);
}
An extremely useful article that describes some firefox undocumented features that allow you to install Firefox XPI And JAR Firefox Add-ons And Themes.
http://www.universefirefox.com/how-to/how-to-install-xpi-and-jar-firefox-add-ons-and-themes
I am pleased to finally report that the Centos release of Redhats 5.3 has been built and is available for download from http://www.centos.org/
The highlights of this release can be found at the following URL: http://www.redhat.com
The main areas of interest in my opinion excluding critical secirty fixes are:
- Updated hardwaresupport support for the new Intel Core i7 (Nehalem) chips
- Beefed up virtualiseation support increasing CPU and Ram limits of Virtual machines.
- Inclusion of the fully open sourced OpenJDK. This makes Red Hat Enterprise Linux 5.3 the first enterprise-ready solution with a fully open source Java stack when combined with JBoss Enterprise Application Platform.
For those who already have Centos 5.2 installed you can simply receive the update via Yum.
Before you do the following, check that you do not have 3rd party repo's and the Centos-testing repo enabled.
You can display the currently enabled repo's using the following command.
$ yum repolist
Then as root at the prompt type:
$ yum update
There is a good article here this describes agile software development techniques. This is what we have always been doing but it's nice to see it defined formally.
We use this technique ourselves on our development portal.
This guide will assist you in setting up an rsnapshot backup server on your network. rsnapshot uses rsync via ssh to perform unattended backups of multiple systems in your network. The guide can be found on the centos website here.
Recital 10 enhances the APPEND FROM command. The enhancement was added to the following syntax ;
APPEND FROM <table-name>Before when appending into a shared Recital table each new row was locked along with the table header, then unlocked after it was inserted. This operation has now been enhanced to lock the table once, complete inserting all the rows from the table and then unlock the table. The performance of this operation has been increased by using this method. All the database and table constraints are still enforced.
Usually, you do not need to setup an email server under Linux. Most GUI email clients support Gmail POP3 and IMAP configurations. But, how do you send mail via the standard /usr/bin/mail user agents in a shell script? Programs such as sendmail / postfix / exim can be configured as a gmail smarthost but they are largely overkill for this use. The ssmtp program is a neat utility that does just that for you via gmail.
Recital 10 introduced the ARRAY( ) functions. This function operates in the same way as the PHP ARRAY( ) function. It can be used to declare a dynamic or associative array and optionally initialize it with elements.
// declare an empty dynamic array
a = array()
// declare a simple dynamic array
a = array("barry", "recital", "boston")
foreach a as value
echo value
endfor
// declare an associative array
a = array("name" => "barry", "company" => "recital", "location" => "boston")
echo "length of a is " + len(a)
foreach a as key => value
echo "key=" + key + ", value=" + value
endfor
When using Eclipse CDT on Fedora 7 I was unable to build anything from inside Eclipse Ganymede.
As it turns out, you need to do this:
cp /usr/bin/ld /usr/libexec/gcc/i386-redhat-linux/4.1.2/real-ld
This is because gcc does not look in /usr/bin for ld which results in the following error when building:
collect2: cannot find ld
You can see where gcc looks for other programs with this command:
gcc -print-search-dirs