Variable String in a UDT question (SOLVED)

[leopardpm]

here is the UDT:

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'given:
type thisType
    as ushort a
    as string s
    as ushort b
end type

dim as thisType Ary(1 to 3)

as far as actual memory/byte layout, it should look like this:
Array(1): 4 bytes for a, 1? byte for s, 4 bytes for b
(I don't know if a NULL string is 1 byte or how it initializes the array)

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Ary(1)   Ary(2)   Ary(3)
aaaasbbbbaaaasbbbbaaaasbbbb

so what happens when I do this?
Ary(2).s = "Test String" ' a string of 10 chars

Does it 'make space' in the array in memory by moving the righthand side over 10 bytes and insert the string? or is the variable string portion actually a pointer to the string somewhere else?

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Ary(1)   Ary(2)   Ary(3)
aaaasbbbbaaaaTest Stringsbbbbaaaasbbbb

Basically, I am wondering if arrays of variable strings are repeatedly moved around as strings are changed within them....

[MrSwiss]

Generally speaking: a FB var-len String, is a Type (in and of itself),
similar to: FixLenStr (using the same layout as FB-String) so, the
allocated memory for the effective String is outside of your Type,
which only contains the Type's header (1 x Ptr + 2 x Integer).

12 bytes = FBC 32 / 24 bytes = FBC 64

testing code:

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type thisType
    as string s
    as ushort a, b
end type

Print "Type size: "; Str(SizeOf(thisType))
Print "FBC x"; Str(SizeOf(Any Ptr) * 8) 

Sleep

[leopardpm]

ok... so the array data in memory is not physically moved around, only the pointer is possibly changed, whenever a string is changed in a variable sized string array... right?

[MrSwiss]

Yes, correct. The real string-memory is allocated to the Ptr ...
(len(String) / memory allocated, stored in the two Integers)

[leopardpm]

Thank you, Mr. Swiss!

[fxm]

This is the same principle for a var-len array declared as UDT field:
- Only the array descriptor is in the UDT data, with a constant length for a declared array, because only depending on the number of dimensions of the array (number of 'Any' in the declaration).
- The array data are allocated elsewhere in the heap memory, referenced by this descriptor.

For a fixed-len array declared as UDT field, the array data are directly in the UDT data (in the same way as for a UDT's fix-len string).