===================================
Extension using the C/C++ languages
===================================

We can extend the Ring Virtual Machine (RingVM) by adding new functions written in the C programming language or C++. 
The RingVM comes with many functions written in C that we can call like any Ring function.

We can extend the language by writing new functions then rebuilding the RingVM again, or we can create shared 
library (DLL/So) file to extend the RingVM without the need to rebuild it.

The Ring language source code comes with two files to add new modules to the RingVM, ring_ext.h and ring_ext.c

.. index:: 
	pair: Extension; ring_ext.h

ring_ext.h
==========

The file ring_ext.h contains constants that we can change to include/exclude modules during the build process.

.. code-block:: C

	#ifndef ringext_h
	#define ringext_h
	/* Constants */
	#define RING_VM_LISTFUNCS 	1
	#define RING_VM_REFMETA 	1
	#define RING_VM_MATH		1
	#define RING_VM_FILE 		1
	#define RING_VM_OS 		1
	#define RING_VM_MYSQL 		1
	#define RING_VM_ODBC 		1
	#define RING_VM_OPENSSL		1
	#define RING_VM_CURL 		1
	#define RING_VM_DLL 		1
	#endif


.. index:: 
	pair: Extension; ring_ext.c

ring_ext.c
==========

The file ring_ext.c check constants defined in ring_ext.h before calling the start-up function in each module.

Each module contains a function that register the module functions in the RingVM.

.. code-block:: C

	#include "ring.h"

	void ring_vm_extension ( RingState *pRingState )
	{
		/* Reflection and Meta-programming */
		#if RING_VM_REFMETA
			ring_vm_refmeta_loadfunctions(pRingState);
		#endif
		/* List Functions */
		#if RING_VM_LISTFUNCS
			ring_vm_listfuncs_loadfunctions(pRingState);
		#endif
		/* Math */
		#if RING_VM_MATH
			ring_vm_math_loadfunctions(pRingState);
		#endif
		/* File */
		#if RING_VM_FILE
			ring_vm_file_loadfunctions(pRingState);
		#endif
		/* OS */
		#if RING_VM_OS
			ring_vm_os_loadfunctions(pRingState);
		#endif
		/* MySQL */
		#if RING_VM_MYSQL
			ring_vm_mysql_loadfunctions(pRingState);
		#endif
		/* ODBC */
		#if RING_VM_ODBC
			ring_vm_odbc_loadfunctions(pRingState);
		#endif
		/* OPENSSL */
		#if RING_VM_OPENSSL
			ring_vm_openssl_loadfunctions(pRingState);
		#endif
		/* CURL */
		#if RING_VM_CURL
			ring_vm_curl_loadfunctions(pRingState);
		#endif
		/* DLL */
		#if RING_VM_DLL
			ring_vm_dll_loadfunctions(pRingState);
		#endif
	}

.. index:: 
	pair: Extension; Module Organization

Module Organization
===================

Each module starts by include the ring header file (ring.h).
This files contains the Ring API that we can use to extend the RingVM.

Each module comes with a function to register the module functions in the RingVM 
The registration is done by using ring_vm_funcregister() function.


The ring_vm_funcregister() function takes two parameters, the first is the function name
that will be used by Ring programs to call the function. The second parameter is the 
function pointer in the C program.

for example, the ring_vmmath.c module contains the next code to register the module functions

.. code-block:: C

	#include "ring.h"

	void ring_vm_math_loadfunctions ( RingState *pRingState )
	{
		ring_vm_funcregister("sin",ring_vm_math_sin);
		ring_vm_funcregister("cos",ring_vm_math_cos);
		ring_vm_funcregister("tan",ring_vm_math_tan);
		ring_vm_funcregister("asin",ring_vm_math_asin);
		ring_vm_funcregister("acos",ring_vm_math_acos);
		ring_vm_funcregister("atan",ring_vm_math_atan);
		ring_vm_funcregister("atan2",ring_vm_math_atan2);
		ring_vm_funcregister("sinh",ring_vm_math_sinh);
		ring_vm_funcregister("cosh",ring_vm_math_cosh);
		ring_vm_funcregister("tanh",ring_vm_math_tanh);
		ring_vm_funcregister("exp",ring_vm_math_exp);
		ring_vm_funcregister("log",ring_vm_math_log);
		ring_vm_funcregister("log10",ring_vm_math_log10);
		ring_vm_funcregister("ceil",ring_vm_math_ceil);
		ring_vm_funcregister("floor",ring_vm_math_floor);
		ring_vm_funcregister("fabs",ring_vm_math_fabs);
		ring_vm_funcregister("pow",ring_vm_math_pow);
		ring_vm_funcregister("sqrt",ring_vm_math_sqrt);
		ring_vm_funcregister("unsigned",ring_vm_math_unsigned);
		ring_vm_funcregister("decimals",ring_vm_math_decimals);
		ring_vm_funcregister("murmur3hash",ring_vm_math_murmur3hash);
	}

.. tip:: Remember that the function ring_vm_math_loadfunctions() will be called by the 
		 ring_vm_extension() function (in the ring_ext.c file). 

.. index:: 
	pair: Extension; Function Structure

Function Structure
==================

Each module function may contains the next steps

1 - Check Parameters Count

2 - Check Parameters Type

3 - Get Parameters Values

4 - Execute Code/Call Functions

5 - Return Value

The structure is very similar to any function (Input - Process - Output)
But here we will use the Ring API for the steps 1,2,3 and 5.


.. index:: 
	pair: Extension; Check Parameters Count

Check Parameters Count
======================

We can check the parameters count using the RING_API_PARACOUNT macro.

We can compare RING_API_PARACOUNT with any numeric value using == or != operators.


Example:

.. code-block:: C

	if ( RING_API_PARACOUNT != 1 ) {
		/* code */
	}

	
Example:

.. code-block:: C

	if ( RING_API_PARACOUNT == 1 ) {
		/* code */
	}

.. index:: 
	pair: Extension; Display Error Message

Display Error Message
=====================

We can display error messages using the RING_API_ERROR() function.

The function will display the error and end the execution of the program.

.. note:: the behaviour of this function can be changed by the Ring code 
		  using Try/Catch/Done statements, so in your C code, use Return after this function.
		  

Syntax:

.. code-block:: C

	RING_API_ERROR(const char *cErrorMsg);
	

The Ring API comes with some of predefined error messages that we can use

.. code-block:: C

	#define RING_API_MISS1PARA "Bad parameters count, the function expect one parameter"
	#define RING_API_MISS2PARA "Bad parameters count, the function expect two parameters"
	#define RING_API_MISS3PARA "Bad parameters count, the function expect three parameters"
	#define RING_API_MISS4PARA "Bad parameters count, the function expect four parameters"
	#define RING_API_BADPARATYPE 	"Bad parameter type!"
	#define RING_API_BADPARACOUNT 	"Bad parameters count!"
	#define RING_API_BADPARARANGE 	"Bad parameters value, error in range!"
	#define RING_API_NOTPOINTER 	"Error in parameter, not pointer!"
	#define RING_API_NULLPOINTER	"Error in parameter, NULL pointer!"
	#define RING_API_EMPTYLIST 	"Bad parameter, empty list!"

.. index:: 
	pair: Extension; Check Parameters Type

Check Parameters Type
=====================

We can check the parameter type using the next functions

.. code-block:: C

	int RING_API_ISNUMBER(int nParameterNumber);
	int RING_API_ISSTRING(int nParameterNumber);
	int RING_API_ISLIST(int nParameterNumber);
	int RING_API_ISPOINTER(int nParameterNumber);

The output of these functions will be 1 (True) or 0 (False).	

.. index:: 
	pair: Extension; Get Parameters Values

Get Parameters Values
=====================

We can get paramters values using the next functions

.. code-block:: C

	double RING_API_GETNUMBER(int nParameterNumber);
	const char *RING_API_GETSTRING(int nParameterNumber);
	int RING_API_GETSTRINGSIZE(int nParameterNumber);
	List *RING_API_GETLIST(int nParameterNumber);
	void *RING_API_GETCPOINTER(int nParameterNumber, const char *cPoinerType);
	int RING_API_GETPOINTERTYPE(int nParameterNumber);

	
.. index:: 
	pair: Extension; Return Value

Return Value
============

We can return values from our function using the next functions.

.. code-block:: C

	RING_API_RETNUMBER(double nValue);
	RING_API_RETSTRING(const char *cString);
	RING_API_RETSTRING2(const char *cString,int nStringSize);
	RING_API_RETLIST(List *pList);
	RING_API_RETCPOINTER(void *pValue,const char *cPointerType);

.. index:: 
	pair: Extension; Function Prototype


Function Prototype
==================

When we define new function to be used for RingVM extension, we use the next prototype

.. code-block:: C

	void my_function_name( void *pPointer );
	
or we can use the RING_FUNC() Macro

.. code-block:: C

	RING_FUNC(my_function_name);

	
.. index:: 
	pair: Extension; Sin() Implementation

Sin() Function Implementation
=============================

The next code represents the sin() function implementation using the Ring API and 
the sin() C function.


.. code-block:: C

	void ring_vm_math_sin ( void *pPointer )
	{
		if ( RING_API_PARACOUNT != 1 ) {
			RING_API_ERROR(RING_API_MISS1PARA);
			return ;
		}
		if ( RING_API_ISNUMBER(1) ) {
			RING_API_RETNUMBER(sin(RING_API_GETNUMBER(1)));
		} else {
			RING_API_ERROR(RING_API_BADPARATYPE);
		}
	}


.. index:: 
	pair: Extension; Fopen() and Fclose() Implementation

Fopen() and Fclose() Functions Implementation
=============================================

The next code represents the fopen() function implementation 
using the Ring API and the fopen() C Function.

The function takes two parameters, the first parameter is the file name as string.
The second parameter is the mode as string.

In the file ring_vmfile.h we have some constants to use as the pointer type like

.. code-block:: C

	#define RING_VM_POINTER_FILE 	"file"
	#define RING_VM_POINTER_FILEPOS "filepos"

The function implementation in ring_vmfile.c

.. code-block:: C

	void ring_vm_file_fopen ( void *pPointer )
	{
		FILE *fp  ;
		if ( RING_API_PARACOUNT != 2 ) {
			RING_API_ERROR(RING_API_MISS2PARA);
			return ;
		}
		if ( RING_API_ISSTRING(1) && RING_API_ISSTRING(2) ) {
			fp = fopen(RING_API_GETSTRING(1),RING_API_GETSTRING(2));
			RING_API_RETCPOINTER(fp,RING_VM_POINTER_FILE);
		} else {
			RING_API_ERROR(RING_API_BADPARATYPE);
		}
	}


The next code represents the fclose() function implementation

.. code-block:: C

	void ring_vm_file_fclose ( void *pPointer )
	{
		FILE *fp  ;
		if ( RING_API_PARACOUNT != 1 ) {
			RING_API_ERROR(RING_API_MISS1PARA);
			return ;
		}
		if ( RING_API_ISPOINTER(1) ) {
			fp = (FILE *) RING_API_GETCPOINTER(1,RING_VM_POINTER_FILE) ;
			if ( fp != NULL ) {
				RING_API_RETNUMBER(fclose(fp));
				RING_API_SETNULLPOINTER(1);
			}
		} else {
			RING_API_ERROR(RING_API_BADPARATYPE);
		}
	}

From fopen() and fclose() implementation we learned

1 - how to return C pointer using RING_API_RETCPOINTER() function

2 - how to check if the parameter is a pointer using the RING_API_ISPOINTER() function

3 - how to get C pointer value using the RING_API_GETCPOINTER() function

4 - how to set the C pointer variable (in RingVM) to NULL using the RING_API_SETNULLPOINTER() function

.. index:: 
	pair: Extension; RING API - list Functions

Ring API - List Functions
=========================

In this section we will learn about the list functions provided by the Ring API to create new lists and 
manipulate the list items.

.. code-block:: C

	List * ring_list_new ( int nSize ) ;
	void ring_list_newitem ( List *pList ) ;
	Item * ring_list_getitem ( List *pList,int index ) ;
	List * ring_list_delete ( List *pList ) ;
	void ring_list_deleteitem ( List *pList,int index ) ;
	void ring_list_print ( List *pList ) ;
	int ring_list_gettype ( List *pList, int index ) ;
	void ring_list_setint ( List *pList, int index ,int number ) ;
	void ring_list_addint ( List *pList,int x ) ;
	void ring_list_setpointer ( List *pList, int index ,void *pValue ) ;
	void ring_list_addpointer ( List *pList,void *pValue ) ;
	void ring_list_setfuncpointer ( List *pList, int index ,void (*pFunc)(void *) ) ;
	void ring_list_addfuncpointer ( List *pList,void (*pFunc)(void *) ) ;
	int ring_list_isfuncpointer ( List *pList, int index ) ;
	void ring_list_setdouble ( List *pList, int index ,double number ) ;
	void ring_list_adddouble ( List *pList,double x ) ;
	void ring_list_setstring ( List *pList, int index ,const char *str ) ;
	void ring_list_setstring2 ( List *pList, int index ,const char *str,int nStrSize ) ;
	void ring_list_addstring ( List *pList,const char *str ) ;
	void ring_list_addstring2 ( List *pList,const char *str,int nStrSize ) ;
	List * ring_list_newlist ( List *pList ) ;
	List * ring_list_getlist ( List *pList, int index ) ;
	void ring_list_setlist ( List *pList, int index ) ;
	void ring_list_setactiveitem ( List *pList, Items *pItems, int index ) ;
	void ring_list_copy ( List *pNewList, List *pList ) ;
	int ring_list_isnumber ( List *pList, int index ) ;
	int ring_list_isstring ( List *pList, int index ) ;
	int ring_list_islist ( List *pList, int index ) ;
	int ring_list_ispointer ( List *pList, int index ) ;
	void ring_list_deleteallitems ( List *pList ) ;
	void ring_list_insertitem ( List *pList,int x ) ;
	void ring_list_insertint ( List *pList,int nPos,int x ) ;
	void ring_list_insertdouble ( List *pList,int nPos,double x ) ;
	void ring_list_insertpointer ( List *pList,int nPos,void *pValue ) ;
	void ring_list_insertstring ( List *pList,int nPos,const char *str ) ;
	void ring_list_insertstring2 ( List *pList,int nPos,const char *str,int nStrSize ) ;
	void ring_list_insertfuncpointer ( List *pList,int nPos,void (*pFunc)(void *) ) ;
	List * ring_list_insertlist ( List *pList,int nPos ) ;
	int ring_list_isiteminsidelist ( List *pList,Item *pItem ) ;
	int ring_list_findstring ( List *pList,const char *str,int nColumn ) ;
	int ring_list_finddouble ( List *pList,double nNum1,int nColumn ) ;
	void ring_list_sortnum ( List *pList,int left,int right,int nColumn ) ;
	void ring_list_sortstr ( List *pList,int left,int right,int nColumn ) ;
	int ring_list_binarysearchnum ( List *pList,double nNum1,int nColumn ) ;
	int ring_list_binarysearchstr ( List *pList,const char *cFind,int nColumn ) ;
	void ring_list_swap ( List *pList,int x,int y ) ;
	double ring_list_getdoublecolumn ( List *pList,int nIndex,int nColumn ) ;
	char * ring_list_getstringcolumn ( List *pList,int nIndex,int nColumn ) ;
	void ring_list_genarray ( List *pList ) ;
	void ring_list_deletearray ( List *pList ) ;
	void ring_list_genhashtable ( List *pList ) ;
	void ring_list_genhashtable2 ( List *pList ) ;
	void ring_list_refcopy ( List *pNewList, List *pList ) ;
	void ring_list_clear ( List *pList ) ;
	/* Macro */
	ring_list_isdouble(pList,index)
	ring_list_isint(pList,index) 
	ring_list_deletelastitem(x)
	ring_list_gethashtable(x) 
	ring_list_getint(pList,index)
	ring_list_getpointer(pList,index)
	ring_list_getfuncpointer(pList,index)
	ring_list_callfuncpointer(pList,index,x)
	ring_list_getdouble(pList,index) 
	ring_list_getstring(pList,index) 
	ring_list_getstringobject(pList,index) 
	ring_list_getstringsize(pList,index)
	ring_list_getsize(x) (x->nSize)

.. index:: 
	pair: Extension; RING API - String Functions

Ring API - String Functions
===========================

In this section we will learn about the string functions provided by the Ring API to create new string and 
manipulate the string content.

.. code-block:: C

	String * ring_string_new ( const char *str ) ;
	String * ring_string_new2 ( const char *str,int nStrSize ) ;
	String * ring_string_delete ( String *pString ) ;
	int ring_string_size ( String *pString ) ;
	void ring_string_set ( String *pString,const char *str ) ;
	void ring_string_set2 ( String *pString,const char *str,int nStrSize ) ;
	void ring_string_add ( String *pString,const char *str ) ;
	void ring_string_add2 ( String *pString,const char *str,int nStrSize ) ;
	void ring_string_print ( String *pString ) ;
	void ring_string_setfromint ( String *pString,int x ) ;
	char * ring_string_lower ( char *cStr ) ;
	char * ring_string_upper ( char *cStr ) ;
	char * ring_string_lower2 ( char *cStr,int nStrSize ) ;
	char * ring_string_upper2 ( char *cStr,int nStrSize ) ;
	char * ring_string_find ( char *cStr1,char *cStr2 ) ;
	char * ring_string_find2 ( char *cStr1,int nStrSize1,char *cStr2,int nStrSize2 ) ;
	/* Macro */
	ring_string_tolower(x)
	ring_string_toupper(x)
	ring_string_get(x)


.. index:: 
	pair: Extension; MySQL_Columns() Implementation

MySQL_Columns() Function Implementation
=======================================

The next code presents the MySQL_Columns() function implementation.

This function returns table columns information.

.. code-block:: C

	void ring_vm_mysql_columns ( void *pPointer )
	{
		MYSQL *con  ;
		MYSQL_RES *result  ;
		int nColumns,x  ;
		MYSQL_ROW row  ;
		MYSQL_FIELD *field  ;
		List *pList, *pList2  ;
		if ( RING_API_PARACOUNT != 1 ) {
			RING_API_ERROR(RING_API_MISS1PARA);
			return ;
		}
		if ( RING_API_ISPOINTER(1) ) {
			con = (MYSQL *) RING_API_GETCPOINTER(1,RING_VM_POINTER_MYSQL) ;
			if ( con == NULL ) {
				return ;
			}
			result = mysql_store_result(con);
			if ( result == NULL ) {
				RING_API_RETNUMBER(0);
				return ;
			}
			pList = RING_API_NEWLIST ;
			nColumns = mysql_num_fields(result);
			if ( row = mysql_fetch_row(result) ) {
				while ( field = mysql_fetch_field(result) ) {
					pList2 = ring_list_newlist(pList);
					ring_list_addstring(pList2,field->name);
					ring_list_adddouble(pList2,field->length);
					ring_list_adddouble(pList2,field->type);
					ring_list_adddouble(pList2,field->flags);
				}
			}
			mysql_free_result(result);
			RING_API_RETLIST(pList);
		} else {
			RING_API_ERROR(RING_API_BADPARATYPE);
		}
	}

Lists are of type List, in the previoud function we declared two pointers of type List
using List *pList, *pList2;
	
.. note:: The function uses RING_API_NEWLIST to create new list instead of ring_list_new()
		  to create the list in Temp. Memory related to the function scope. This way we can
		  return the list from the function. Also we don't delete the list, if it's stored in 
		  a variable by Ring Code it will be saved, if not it will be automatically deleted by RingVM.
		  

The list can contains sub lists, we used the function ring_list_newlist() to create a sublist.

The function ring_list_addstring() is used to add string items to the list/sublist.

The function ring_list_adddouble() is used to add numeric items to the list/sublist.

.. note:: All numeric items in lists returned from RingVM extension functions must be of type double
          and added to the list using ring_list_adddouble() function.
		  

We return the list from the extension function using the RING_API_RETLIST() function.

.. index:: 
	pair: Extension; Shared Libraries

Dynamic/Shared Libraries (DLL/So) and LoadLib() function
========================================================

Instead of rebuilding the RingVM after writing new functions using C/C++ and the Ring API, we can create
a DLL/So file and dynamically use the functions provided by this file in the runtime using the LoadLib() function.

Dynamic library example in C

.. code-block:: C

	#include "ring.h"

	RING_DLL __declspec(dllexport) 

	RING_FUNC(ring_ringlib_dlfunc)
	{
		printf("Message from dlfunc");
	}

	RING_DLL void ringlib_init(RingState *pRingState)
	{
		ring_vm_funcregister("dlfunc",ring_ringlib_dlfunc); 
	}

the idea is to create the ringlib_init() function, this function will be called by the RingVM when we use the generated DLL 
file though the LoadLib() function.

Inside the ringlib_init() function we can register the module function or call a function that do the registration process
for all of the module functions.

The next Ring code demonstrates how to use the DLL library during the runtime.

.. code-block:: none

	See "Dynamic DLL" + NL
	LoadLib("ringlib.dll")
	dlfunc()

Output:

.. code-block:: none

	Dynamic DLL
	Message from dlfunc





