Key features of the Recital scripting language include:
What are the key feature of the Recital database?
- High performance database application scripting language
- Modern object-oriented language features
- Easy to learn, easy to use
- Fast, just-in-time compiled
- Develop desktop or web applications
- Cross-platform support
- Extensive built-in functions
- Superb built-in SQL command integration
- Navigational data access for the most demanding applications
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);
} Opening SSH to the outside world is a security risk. Here is how to restrict SSH access to certain IP addresses on a machine.
- Edit the /etc/hosts.allow file to include these lines, assuming your machine is on the 192.168.2.x nonrouting IP block, and you want to enable an external address of 217.40.111.121 IP block: Remember to add the period on the end of each incomplete IP number. If you have another complete IP address or range, add a space and that range on the end.
sshd,sshdfwd-X11: 192.168.2. 217.40.111.121
- Edit your /etc/hosts.deny file to include this line:
sshd,sshdfwd-X11:ALL
- These lines refuse SSH connections from anyone not in the IP address blocks listed.
Additionally you can restrict SSH access by username.
- Edit the /etc/ssh/sshd_config file and add the following lines
PermitRootLogin no
AllowUsers user1 user2 user3 etc
PasswordAuthentication yes
Now restart the ssh daemon for these changes to take effect
service sshd restart
DirectoryIndex default.rsp index.html
lslk lists information about locks held on files with local inodes on systems running linux.
Install it with:
yum install lslk
http://kbala.com/ie-9-supports-corner-radius/
try
open database southwind
catch
die("Cannot open database, please try later.")
endtry
- edit the .vmx file and add the following line
uuid.action = "keep"
- set the virtual machine to power off when vmware is stopped. Do not set this to "suspend" or it will not restart on the backup machine.
It would appear that gigabit LAN is not! In fact it often runs at the same speed as 100Mbps LAN. Let's look at why exactly.
After configuring your network you can use the ifconfig command to see what speeds the LAN is connected. Even though 1000Mbps is reported by the card, the reality is that the overall throughtput may well be ~100Mpbs. You can try copying a large file using scp to demonstrate this.
As it turns out, in order to use a gigabit LAN you need to use CAT6 cables. CAT5 and CAT5E are not good enough. End result, the ethernet cards throttle back the speed to reduce dropped packets and errors.
You can find a good article here titled Squeeze Your Gigabit NIC for Top Performance. After tuning up the TCP parameters i found that it made no dfifference. The principal reasons behind low gigabit ethernet performance can be summed up as follows.
- Need to use CAT6 cables
- Slow Disk speed
- Limitations of the PCI bus which the gigabit ethernet cards use
You can get an idea about the disk speed using the hdparm command:
Display the disk partitions and choose the main linux partition which has the / filesystem.
# fdisk -l
Then get disk cache and disk read statistics:
# hdparm -Tt /dev/sda0
On my desktop system the sata disk perfomance is a limiting factor. These were the results:
/dev/sda1:
Timing cached reads: 9984 MB in 2.00 seconds = 4996.41 MB/sec
Timing buffered disk reads: 84 MB in 3.13 seconds = 58.49 MB/sec
Well, that equates to a raw disk read speed of 58.49 * 8 = 467Mbps which is half the speed of a gigabit LAN.
So.. NAS storage with lots of memory looks to be the way to go... If you use the right cables!
On entry to the .rsp page.
IF type( _session["state"] ) != "U"m_state = _session["state"]RESTORE DATASESSION FROM m_state
ELSE
// open up your tables for the first timeENDIF
SAVE DATASESSION TO m_state_SESSION["state"] = m_state