Array of Pointers of Strings

[wbtcpip]

i have to pass to a c library an "Array of Pointers of Strings"

for exemple in c:

char *arr[] = { "Geek", "Geeks", "Geekfor" };

how i can create it in GB32?

the classic Dim x(3) as string create a classic array of strings not an array of Pointers

 

[(X)]

What happens if you pass an array of string pointers?

Dim a$(3)
a$(0) = "Geek0"
a$(1) = "Geek1"
a$(2) = "Geek2"
Dim x(3) As Long
x(V:a$(0))
x(V:a$(1))
x(V:a$(2))

and pass *x(), the pointer to the x() array...

[wbtcpip]

it works like this.

dim comando(10) As String, comandov(10) As Int

comando(0) = "loadfile"

comandov(0) = V:comando(0)

comando(1) = "av://dshow:video=Full HD 1080P PC Camera"

comandov(1) = V:comando(1)

and passing v:comandov(0) to the c library

i was looking for a less coding solution like in c

[Roger Cabo]

Not really sure what you like to do.

This is a unsafe behavior to use Pointers to Strings in GB32 and can cause to fatal crash or data corruption.
I cannot recommended this behavior. Because through a GB Memory Collection update, it could be possible that old pointers locate silently to undefined memory.

There is only one use case for this. If you have a static memory allocation of all strings in a row.
Then you should take care that these memory block is write protected, unless you update all pointers based on /0 each time you access them.

[dragonjim]

To make it a bit less clumsy, you could always use functions like in the example below.

Dim s$(), pt%()
PtrArrayCreate(s$(), "Entry 1", "Entry 2", "Entry 3", "Entry 4")
PtrArrayAdd(s$(), "Entry 5", "Entry 6", "Entry 7", "")
PtrArrayPointers(s$(), pt%())
Local n%
For n% = 0 To UBound(s$())
 Debug pt%(n%),s$(n%)
Next n%
Debug.Show

Procedure PtrArrayCreate(ByRef a$(), ParamArray p())
 Local n%
 ReDim a$(0 To UBound(p()))
 For n% = 0 To UBound(p())
   a$(n%) = p(n%)
 Next n%
EndProcedure
Procedure PtrArrayAdd(ByRef a$(), ParamArray p())
 Local ct%, lb% = UBound(a$()) + 1, n%, ub% = UBound(a$()) + UBound(p()) + 1
 ReDim a$(0 To ub%)
 For n% = lb% To ub%
   a$(n%) = p(ct%) : Inc ct%
 Next n%
EndProcedure
Procedure PtrArrayPointers(ByRef a$(), ByRef p%())
 Local n%
 ReDim p%(LBound(a$()) To UBound(a$()))
 For n% = LBound(a$()) To UBound(a$())
   p%(n%) = V:a$(n%)
 Next n%
EndProcedure

I have purposely kept the pointer creation separate as, sometimes, changing the content of an array element can change the pointer, so a pointer array created upon the creation of the string array may no longer be valid.