Low Level Functions¶

In this chapter we will learn about the low level functions provided by Ring

callgc()
varptr()
space()
nullpointer()
object2pointer()
pointer2object()
ptrcmp()
ringvm_cfunctionslist()
ringvm_functionslist()
ringvm_classeslist()
ringvm_packageslist()
ringvm_memorylist()
ringvm_calllist()
ringvm_fileslist()
ringvm_settrace()
ringvm_tracedata()
ringvm_traceevent()
ringvm_tracefunc()
ringvm_scopescount()
ringvm_evalinscope()
ringvm_passerror()
ringvm_hideerrorMsg()
ringvm_callfunc()
ringvm_see()
ringvm_give()

callgc() function¶

Use this function to force calling the garbage collector during function execution when you use a loop that create temp. variables that you don’t free using the assignment operation.

It’s very rare to need this function but it’s useful when you create something like event-loop for your game engine and start creating lists on the fly when you call functions.

Example

While True

        # process events
        # call functions using temp. lists like myfunc(["temp list"])

        # call the garbage collector
        callgc()
End

Tip

In Ring the garbage collector works automatically in the end of function execution or when you use the assignment statement.

varptr() function¶

Use the varptr() function when you need to pass a pointer to a C/C++ function.

Syntax:

varptr(cVariableName,cPointerType) —> Low Level Object (C Pointer)

example:

r = 10
z = 20
see r + nl
see varptr("r","int")
see varptr("z","int")

Output:

10
00E3C740
int
2
00E3BEC0
int
2

Note

the low level object is a list contains three items (The Pointer, The Type, The Status)

space() function¶

Use the space function to allocate a specific number of bytes in Memory.

Syntax:

Space(nBytesCount) ---> String

Example:

mystring = space(200)
See "String Size : " + len(mystring) + nl
See "String : " + mystring + nl
See "String Pointer : "
See varptr("mystring","char *")

Output:

String Size : 200
String :
String Pointer : 00FF8FE8
char *
2

Note

You may need the space() and VarPtr() functions to pass buffers to C functions.

nullpointer() function¶

You may need to pass the NULL pointer to a C function that may expect a pointer as parameter and accept NULL pointers for optional parameters.

Example:

The next example uses the SDL_BlitSurface() function from the LibSDL Library through RingSDL The function accept SDL_Rect pointers in the second and the last parameter. Also the function accept NULL pointers, so we can pass them using the NULLPointer() Function.

SDL_BlitSurface(text, nullpointer(), surface, nullpointer())

Note

The previous code doesn’t work alone, you need to learn how to use RingSDL first.

Tip

We can pass NULL as parameter instead of using NULLPointer()

object2pointer() function¶

Use this function to get a C pointer for Ring lists and objects

Syntax:

object2pointer(List|Object) --> Low Level Object ( C Pointer )

pointer2object() function¶

Use this function to get the Ring list and/or object from the low level object (C Pointer)

Syntax:

pointer2object(Low Level Object) ---> List|Object

Example:

# Create the list
mylist = 1:5

# Create pointer to the list
x = object2pointer(mylist)
see x

see nl

# Add items to the list
mylist + "welcome"

# print the list items
y = pointer2object(x)
see y

Output:

0069A5D8
OBJECTPOINTER
0

1
2
3
4
5
welcome

Note

In Ring the assignment operator copy lists and objects by value, to copy by reference Just use the object2pointer() and pointer2object() functions.

Tip

The object2pointer() and pointer2object() are used in the stdlib - Tree Class implementation to create a reference for the parent node (object) in the child node (another object).

ptrcmp() function¶

We can compare between two pointers (C Objects) using the ptrcmp() function.

Syntax:

ptrcmp(oObject1,oObject2) ---> value = 1 if oObject1 = oObject2
                               value = 0 if oObject1 != oObject2

Example:

fp = fopen("ptrcmp.ring","r")
fp2 = fp
fp3 = fopen("ptrcmp.ring","r")

see ptrcmp(fp,fp2) + nl
see ptrcmp(fp,fp3) + nl

fclose(fp)
fclose(fp3)

Output:

1
0

ringvm_cfunctionslist() function¶

The Function return a list of functions written in C.

Syntax:

RingVM_CFunctionsList() ---> List

Example:

See RingVM_CFunctionsList()

ringvm_functionslist() function¶

The Function return a list of functions written in Ring.

Each List Member is a list contains the next items

Function Name
Program Counter (PC) - Function Position in Byte Code.
Source Code File Name
Private Flag (For Private Methods in Classes)

Syntax:

RingVM_FunctionsList() ---> List

Example:

test()

func test
        see ringvm_functionslist()

Output:

test
8
B:/ring/tests/scripts/functionslist.ring
0

ringvm_classeslist() function¶

The Function return a list of Classes.

Each List Member is a list contains the next items

Class Name
Program Counter (PC) - Class Position in Byte Code.
Parent Class Name
Methods List
Flag (Is parent class information collected)
Pointer to the package (or NULL if no package is used)

Syntax:

RingVM_ClassesList() ---> List

Example:

see ringvm_classeslist()

class class1
        func f1
class class2 from class1
class class3 from class1

Output:

class1
9

f1
13
B:/ring/tests/scripts/classeslist.ring
0
0
00000000
class2
16
class1
0
00000000
class3
20
class1
0
00000000

ringvm_packageslist() function¶

The Function return a list of Packages.

Each List Member is a list contains the next items

Package Name
Classes List

Syntax:

RingVM_PackagesList() ---> List

Example:

see ringvm_packageslist()

package package1
        class class1

package package2
        class class1

package package3
        class class1

Output:

package1
class1
11

0
00FEF838
package2
class1
17

0
00FEF978
package3
class1
23

0
00FEFF68

ringvm_memorylist() function¶

The Function return a list of Memory Scopes and Variables.

Each List Member is a list contains variables in a different scope.

Each Item in the scope list is a list contains the next items

Variable Name
Variable Type
Variable Value
Pointer Type (List/Item) if the value is a list
Private Flag (if the variable is an attribute in a Class)

Syntax:

RingVM_MemoryList() ---> List

Example:

x = 10
test()
func test
        y = 20
        see ringvm_memorylist()

Output:

true
2
1
0
0
false
2
0
0
0
nl
1


0
0
null
1

0
0
ring_gettemp_var
4
00000000
0
0
ccatcherror
1
NULL
0
0
ring_settemp_var
4
00000000
0
0
ring_tempflag_var
2
0
0
0
stdin
3
50512DB8
file
0
0
0
stdout
3
50512DD8
file
0
0
0
stderr
3
50512DF8
file
0
0
0
this
4
00000000
0
0
sysargv
3
B:\ring\bin/ring
B:/ring/tests/scripts/memorylist.ring
0
0
x
2
10
0
0
y
2
20
0
0

ringvm_calllist() function¶

The Function return a list of the functions call list.

Each List Member is a list contains the next items

Function Type
Function Name
Program Counter (PC)
Stack Pointer (SP)
Temp. Memory List
Method or Function Flag
Caller PC
FuncExec Flag
ListStart Flag
Nested Lists Pointer
State List

Syntax:

RingVM_CallList() ---> List

Example:

hello()
func hello
        test()

func test
        mylist = ringvm_calllist()
        for t in mylist see t[2] + nl next

Output:

function hello() in file B:/ring/tests/scripts/calllist.ring
called from line 1
function test() in file B:/ring/tests/scripts/calllist.ring
called from line 3
ringvm_calllist

ringvm_fileslist() function¶

Function return a list of the Ring Files.

Syntax:

RingVM_FilesList() ---> List

Example:

load "stdlib.ring"
see ringvm_fileslist()

Output:

B:/ring/tests/scripts/fileslist.ring
B:\ring\bin\stdlib.ring
eval
stdlib.ring
stdlib.rh
stdclasses.ring
stdfunctions.ring
stdbase.ring
stdstring.ring
stdlist.ring
stdstack.ring
stdqueue.ring
stdmath.ring
stddatetime.ring
stdfile.ring
stdsystem.ring
stddebug.ring
stddatatype.ring
stdconversion.ring
stdodbc.ring
stdmysql.ring
stdsecurity.ring
stdinternet.ring
stdhashtable.ring
stdtree.ring

ringvm_settrace()¶

The function ringvm_settrace() determine the Trace function name

The trace function is a Ring function that will be called for each event

Syntax:

RingVM_SetTrace(cCode)

ringvm_tracedata()¶

Inside the function that we will use for tracing events

We can use the ringvm_tracedata() function to get the event data.

The event data is a list contains the next items

The Source Code Line Number
The Source File Name
The Function/Method Name
Method or Function (Bool : True=Method, False=Function/File)

Syntax:

RingVM_TraceData() ---> aDataList

ringvm_traceevent()¶

Inside the function that we will use for tracing events

We can use ringvm_traceevent() to know the event type

New Line
Before Function
After Function
Runtime Error
Before C Function
After C Function

Syntax:

RingVM_TraceEvent() ---> nTraceEvent

ringvm_tracefunc()¶

The function return the name of the function that we are using for tracing events.

Syntax:

RingVM_TraceEvent() ---> cCode

ringvm_scopescount()¶

We can use the RingVM_ScopesCount() function to know the number of scopes used in the application.

In the start of the program, We have the (global scope only)

When we call a function, A new scope is created.

When the function execution is done, the function scope is deleted.

Syntax:

RingVM_ScopesCount() ---> nScopes

ringvm_evalinscope()¶

The function ringvm_evalinscope() is similar to the eval() function

Unlike eval() which execute the code in the current scope

Using RingVM_EvalInScope() we can execute the scope in a specific scope.

Syntax:

RingVM_EvalInScope(nScope,cCode)

ringvm_passerror()¶

When we have runtime error, After printing the Error message, Ring will end the execution of the program.

Using ringvm_passerror() we can avoid that, and continue the execution of our program.

Syntax:

RingVM_PassError()

ringvm_hideerrormsg()¶

We can disable/enable displaying the runtime error messages using the RingVM_HideErrorMsg() function.

Syntax:

RingVM_HideErrorMsg(lStatus)

ringvm_callfunc()¶

We can call a function from a string without using eval() using the ringvm_callfunc()

Syntax:

RingVM_CallFunc(cFuncName)

Example - Using the Trace Functions¶

The next example use the Trace Functions to trace the program Events!

In practical, We will use the Trace Library instead of these low level functions!

load "tracelib.ring"

ringvm_settrace("mytrace()")

see "Hello, world!" + nl
see "Welcome" + nl
see "How are you?" +nl
mytest()
new myclass { mymethod() }

func mytest
        see "Message from mytest" + nl

func mytrace
        see "====== The Trace function is Active ======" + nl +
                "Trace Function Name : " + ringvm_TraceFunc() + nl +
                "Trace Event : "
        switch ringvm_TraceEvent()
                on TRACEEVENT_NEWLINE           see "New Line"
                on TRACEEVENT_NEWFUNC           see "New Function"
                on TRACEEVENT_RETURN            see "Return"
                on TRACEEVENT_ERROR             see "Error"
                on TRACEEVENT_BEFORECFUNC       see "Before C Function"
                on TRACEEVENT_AFTERCFUNC        see "After C Function"
        off
        see nl +
                "Line Number : " + ringvm_tracedata()[TRACEDATA_LINENUMBER] + nl +
                "File Name   : " + ringvm_tracedata()[TRACEDATA_FILENAME] + nl +
                "Function Name : " + ringvm_tracedata()[TRACEDATA_FUNCNAME] + nl +
                "Method or Function : "
                if ringvm_tracedata()[TRACEDATA_METHODORFUNC] =
                                 TRACEDATA_METHODORFUNC_METHOD
                        see "Method"
                else
                        if ringvm_tracedata()[TRACEDATA_FUNCNAME] = NULL
                                see "Command"
                        else
                                see "Function"
                        ok
                ok
                see nl + Copy("=",42) + nl

class myclass
        func mymethod
                see "Message from mymethod" + nl

Output:

====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : After C Function
Line Number : 3
File Name   : test1.ring
Function Name : ringvm_settrace
Method or Function : Function
==========================================
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : New Line
Line Number : 5
File Name   : test1.ring
Function Name :
Method or Function : Command
==========================================
Hello, world!
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : New Line
Line Number : 6
File Name   : test1.ring
Function Name :
Method or Function : Command
==========================================
Welcome
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : New Line
Line Number : 7
File Name   : test1.ring
Function Name :
Method or Function : Command
==========================================
How are you?
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : New Line
Line Number : 8
File Name   : test1.ring
Function Name :
Method or Function : Command
==========================================
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : New Function
Line Number : 8
File Name   : test1.ring
Function Name : mytest
Method or Function : Function
==========================================
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : New Line
Line Number : 12
File Name   : test1.ring
Function Name : mytest
Method or Function : Function
==========================================
Message from mytest
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : New Line
Line Number : 14
File Name   : test1.ring
Function Name : mytest
Method or Function : Function
==========================================
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : Return
Line Number : 8
File Name   : test1.ring
Function Name :
Method or Function : Command
==========================================
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : New Line
Line Number : 9
File Name   : test1.ring
Function Name :
Method or Function : Command
==========================================
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : New Line
Line Number : 43
File Name   : test1.ring
Function Name :
Method or Function : Command
==========================================
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : Before C Function
Line Number : 9
File Name   : test1.ring
Function Name : ismethod
Method or Function : Function
==========================================
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : After C Function
Line Number : 9
File Name   : test1.ring
Function Name : ismethod
Method or Function : Function
==========================================
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : New Function
Line Number : 9
File Name   : test1.ring
Function Name : mymethod
Method or Function : Method
==========================================
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : New Line
Line Number : 44
File Name   : test1.ring
Function Name : mymethod
Method or Function : Method
==========================================
Message from mymethod
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : Return
Line Number : 9
File Name   : test1.ring
Function Name :
Method or Function : Command
==========================================
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : Before C Function
Line Number : 9
File Name   : test1.ring
Function Name : ismethod
Method or Function : Function
==========================================
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : After C Function
Line Number : 9
File Name   : test1.ring
Function Name : ismethod
Method or Function : Function
==========================================
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : Before C Function
Line Number : 9
File Name   : test1.ring
Function Name : ismethod
Method or Function : Function
==========================================
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : After C Function
Line Number : 9
File Name   : test1.ring
Function Name : ismethod
Method or Function : Function
==========================================
====== The Trace function is Active ======
Trace Function Name : mytrace()
Trace Event : New Line
Line Number : 11
File Name   : test1.ring
Function Name :
Method or Function : Command
==========================================

Example - The Trace Library¶

The next example uses the Trace functions provided by the Ring language to create the Trace library.

Using the Trace library we have nice Tracing tools and Interaction debugger too.

# Trace Events
TRACEEVENT_NEWLINE      = 1
TRACEEVENT_NEWFUNC      = 2
TRACEEVENT_RETURN       = 3
TRACEEVENT_ERROR        = 4
TRACEEVENT_BEFORECFUNC  = 5
TRACEEVENT_AFTERCFUNC   = 6

# Trace Data
TRACEDATA_LINENUMBER    = 1
TRACEDATA_FILENAME      = 2
TRACEDATA_FUNCNAME      = 3
TRACEDATA_METHODORFUNC  = 4

# Method of Function
TRACEDATA_METHODORFUNC_METHOD           = TRUE
TRACEDATA_METHODORFUNC_NOTMETHOD        = FALSE

TRACE_BREAKPOINTS = TRUE

TRACE_TEMPLIST = []

func Trace cType
        switch trim(lower(cType))
        on :AllEvents
                ringvm_settrace("TraceLib_AllEvents()")
        on :Functions
                ringvm_settrace("TraceLib_Functions()")
        on :PassError
                ringvm_settrace("TraceLib_PassError()")
        on :Debugger
                ringvm_settrace("TraceLib_Debugger()")
        on :LineByLine
                ringvm_settrace("TraceLib_LineByLine()")
        off

func TraceLib_AllEvents
        if right(ringvm_tracedata()[TRACEDATA_FILENAME],13) = "tracelib.ring"
                return
        ok
        see "====== The Trace function is Active ======" + nl +
                "Trace Function Name : " + ringvm_TraceFunc() + nl +
                "Trace Event : "
        switch ringvm_TraceEvent()
                on TRACEEVENT_NEWLINE           see "New Line"
                on TRACEEVENT_NEWFUNC           see "New Function"
                on TRACEEVENT_RETURN            see "Return"
                on TRACEEVENT_ERROR             see "Error"
                on TRACEEVENT_BEFORECFUNC       see "Before C Function"
                on TRACEEVENT_AFTERCFUNC        see "After C Function"
        off
        see nl +
                "Line Number : " + ringvm_tracedata()[TRACEDATA_LINENUMBER] + nl +
                "File Name   : " + ringvm_tracedata()[TRACEDATA_FILENAME] + nl +
                "Function Name : " + ringvm_tracedata()[TRACEDATA_FUNCNAME] + nl +
                "Method or Function : "
                if ringvm_tracedata()[TRACEDATA_METHODORFUNC] =
                                 TRACEDATA_METHODORFUNC_METHOD
                        see "Method"
                else
                        if ringvm_tracedata()[TRACEDATA_FUNCNAME] = NULL
                                see "Command"
                        else
                                see "Function"
                        ok
                ok
                see nl + Copy("=",42) + nl

func TraceLib_Functions
        if right(ringvm_tracedata()[TRACEDATA_FILENAME],13) = "tracelib.ring"
                return
        ok
        switch ringvm_TraceEvent()
                on TRACEEVENT_NEWFUNC
                        see "Open Func : " +
                        ringvm_TraceData()[TRACEDATA_FUNCNAME] + nl
                on TRACEEVENT_RETURN
                        see "Return to Func : " +
                        ringvm_TraceData()[TRACEDATA_FUNCNAME] + nl
        off

func TraceLib_PassError
        if right(ringvm_tracedata()[TRACEDATA_FILENAME],13) = "tracelib.ring"
                return
        ok
        switch ringvm_TraceEvent()
                on  TRACEEVENT_ERROR
                        see nl
                        see "TraceLib : After Error !" + nl
                        ringvm_passerror()
        off

func TraceLib_Debugger
        if right(ringvm_tracedata()[TRACEDATA_FILENAME],13) = "tracelib.ring"
                return
        ok
        switch ringvm_TraceEvent()
                on  TRACEEVENT_ERROR
                        _BreakPoint()
        off

func TraceLib_LineByLine
        if right(ringvm_tracedata()[TRACEDATA_FILENAME],13) = "tracelib.ring" or
                ringvm_TraceEvent() != TRACEEVENT_NEWLINE
                return
        ok
        aList = ringvm_tracedata()
        see "Before Line : " + aList[TRACEDATA_LINENUMBER] + nl
        _BreakPoint()

func BreakPoint
        if not TRACE_BREAKPOINTS
                return
        ok
        _BreakPoint()

func _BreakPoint
        see nl+nl+Copy("=",60) + nl +
        Copy(" ",20)+"Interactive Debugger" + nl +
        Copy("=",60) + nl +
        "Command (Exit)        : End Program" + nl +
        "Command (Cont)        : Continue Execution" + nl +
        "Command (Locals)      : Print local variables names" + nl +
        "Command (LocalsData)  : Print local variables data" + nl +
        "Command (Globals)     : Print global variables names" + nl +
        "We can execute Ring code" + nl +
        Copy("=",60) + nl
        while true
                        see nl + "code:> "
                        give cCode
                cmd = trim(lower(cCode))
                if cmd = "exit" or cmd = "bye"
                        shutdown()
                ok
                nScope = ringvm_scopescount()-2
                switch cmd
                        on "locals"
                                ringvm_EvalInScope(nScope,"see locals() callgc()")
                                loop
                        on "localsdata"
                                PrintLocalsData(nScope)
                                loop
                        on "globals"
                                ringvm_EvalInScope(nScope,"see globals() callgc()")
                                loop
                        on "cont"
                                ringvm_passerror()
                                exit
                off
                Try
                        ringvm_EvalInScope(nScope,cCode)
                        catch
                                        see cCatchError
                        done
        end

func NoBreakPoints
        TRACE_BREAKPOINTS = FALSE


func PrintLocalsData nScope
        if nScope = 1   # Global
                ringvm_Evalinscope(nScope,'TRACE_TEMPLIST = globals()')
        else
                ringvm_Evalinscope(nScope,'TRACE_TEMPLIST = locals() callgc()')
        ok
        see nl
        aTempList = TRACE_TEMPLIST
        TRACE_TEMPLIST = []
        nSpaces = 5
        for TRACE_ITEM in aTempList
                if len(TRACE_ITEM) + 5 > nSpaces
                        nSpaces = len(TRACE_ITEM) + 5
                ok
        next
        for TRACE_ITEM in aTempList
                see "Variable : " +  TRACE_ITEM
                cVarName = TRACE_ITEM
                see copy(" ",nSpaces-len(cVarName)) + " Type : "
                ringvm_Evalinscope(nScope,"see type(" +  TRACE_ITEM +")")
                ringvm_Evalinscope(nScope,"see Copy(' ',fabs(15-len(type(" +
                                          TRACE_ITEM +"))))")
                see " Value : "
                ringvm_Evalinscope(nScope,"see " +  TRACE_ITEM)
                see nl
        next

ringvm_see() function¶

Using the ringvm_see() function we can redefine the behavior of the See command

Also we can use ring_see() to have the original behavior

Example:

see "Hello world" + nl
see 123 + nl
see ["one","two","three"]
see new point {x=10 y=20 z=30}

func ringvm_see t
        ring_see("We want to print: ")
        ring_See(t)

class point x y z

Output:

We want to print: Hello world
We want to print: 123
We want to print: one
two
three
We want to print: x: 10.000000
y: 20.000000
z: 30.000000

ringvm_give() function¶

Using the ringvm_give() function we can redefine the behavior of the Give command

Example:

see "Name: " give name
see "Hello " + name

func ringvm_give
        see "Mahmoud" + nl
        return "Mahmoud"

Output:

Name: Mahmoud
Hello Mahmoud

Low Level Functions¶

callgc() function¶

varptr() function¶

space() function¶

nullpointer() function¶

object2pointer() function¶

pointer2object() function¶

ptrcmp() function¶

ringvm_cfunctionslist() function¶

ringvm_functionslist() function¶

ringvm_classeslist() function¶

ringvm_packageslist() function¶

ringvm_memorylist() function¶

ringvm_calllist() function¶

ringvm_fileslist() function¶

ringvm_settrace()¶

ringvm_tracedata()¶

ringvm_traceevent()¶

ringvm_tracefunc()¶

ringvm_scopescount()¶

ringvm_evalinscope()¶

ringvm_passerror()¶

ringvm_hideerrormsg()¶

ringvm_callfunc()¶

Example - Using the Trace Functions¶

Example - The Trace Library¶

ringvm_see() function¶

ringvm_give() function¶

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